Depressive Deficits in Memory: Implications for Memory Improvement Following Traumatic Brain Injury Paula T. Hertel, PhD Trinity University, San Antonio, TX Experimental findings of memory impairment in depression are reviewed, and implications for rehabilitation are discussed. Impairments typically occur when the structure ofthe task is insufficient to constrain the nature of the procedures to be used. When such constraint is provided, or when the task is not particularly sensitive to strategic processing, depression-related impairments are rarely observed. Keywords: Memory; depression; attention; strategies; control
Head injuries and strokes produce a variety of psychological problems, including memory difficulties and depression. Neuropsychological evidence suggests that damage to the frontal lobes, in particular, is associated with both affective and cognitive disturbances. The types of cognitive difficulties include impaired attention, limited skills in monitoring, and other strategy-related deficits.l Traumatically brain-injured (TBI) clients quite understandably feel depressed, not only because they cannot function as before, but because the injury has damaged areas of the brain that directly mediate mood. 2,3 Although people with brain injuries typically experience cognitive deficits associated with depressed moods at some point in their recovery, there is little research that systematically investigates relationships between depression and memory in organically impaired populations. Such investigations with nonimpaired populations, however, are numerous. 4 Because depression and memory impairment are common outcomes ofTBI, and because their relationship in TBI clients has received little experAcknowledgment: The author is grateful to Doug Herrmann and Rick Parente for discussions concerning implications of her work for rehabilitation.
imental attention, theory and research performed with uninjured populations provide reasonable directions for investigating aids to rehabilitation. My intent in this article is to briefly review the research I have conducted on the nature of depression-related impairments in memory and to discuss its implications for cognitive rehabilitation. The link between depressed moods and memory is typically understood to be mediated by attentional capacity.5.6 The notion is that depressed moods somehow reduce the amount of attention that could be otherwise paid to ongoing experiences. When the depressed person later tries to remember the earlier experience, performance is impaired. (In the clinical setting, those who work with head-injured clients often notice a level of preoccupation with personal problems that is sufficient to render therapy ineffective.) Initially, this attentional-resource theory of depressive memory was supported by a variety of experimental findings. For example, Ellis, Thomas, and Rodriguez 7 used a mood-induction procedure to establish sad moods in college students and then asked them to make decisions about the "fit" of words in accompanying sentence frames. On some trials the word was the obvious choice for the missing element in the frame (e.g., dream for NeuroRehabill994; 4(3):143-150 Copyright © 1994 by Butterworth-Heinemann
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the frame, "She was awakened by her frightening _ _"). On other trials, the word was just one of several words that might fit the frame (e.g., dream for "He was alarmed by the frightening _ _"). In the former case, each word could be easily integrated with its sentence frame to provide an elaboration that would subsequently help subjects to remember the word; in the latter case, such elaborations presumably would be more difficult. Ellis and his colleagues presented 12 words in easy contexts, and another 12 words in difficult contexts. Then they surprised the subjects with a request for free recall of all the words. On that test, the subjects who had been induced to feel sad recalled as many words from the easy contexts as did control subjects, but fewer words from the difficult contexts. One possible interpretation of these results is that depressed moods reduced the amount of attentional resources available for the task at hand; sufficient resources were available for elaboration on the easy trials, but not on the difficult ones. 8 This interpretation relies on the assumption that depressed or sad people pervasively allocate resources to their mood states; they cannot concentrate on the task at hand because they are thinking about themselves. 9 To some extent, this state of mind might also characterize patients with neurological impairments. For all patients suffering depressed moods, the hope for rehabilitation seems to rest on mood repair; only when affect is neutralized would attentional resources be freed to allocate to the ongoing task. The hope for rehabilitation is therefore not as good as it could be, given the implications that arise from the following experimental findings. In collaboration with Stephanie Rude,10 I recruited clinically depressed outpatients and nondepressed controls to participate in an experiment that was similar to the one just described. In fact, half of the subjects in both groups made decisions about words in both easy and difficult contexts under conditions that were very similar to those used by Ellis and his colleagues. That is, they could make the decision whenever they chose to do so during the 8-second trial, and let their minds wander until the next word was presented. On the subsequent test, the depressed subjects recalled fewer words from the difficult contexts
than did the nondepressed subjects, just as one would expect if the results from the moodinduced students could be generalized to a clinical population. The more interesting finding, however, was produced by the other half of the subjects, who had been instructed to wait until the end of each trial to report their decisions and repeat the word. These instructions were designed to focus and sustain subjects' attention on the task at hand. The issue, of course, was whether such instructions would be sufficiently successful to overcome the recall impairment observed in the unfocused groups. In fact, the depressed subjects in the focused group recalled words from the difficult contexts at slighter higher levels (although not reliably so) than did the nondepressed subjects. These instructions sustained subjects' attention to the task and thereby facilitated elaborations that were important in preventing depression-related impairments. Depressed subjects were clearly capable of such attention and needed only some environmental support for reallocation. The message for rehabilitation, then, is subtly but importantly different: Mood repair is not a requisite for successful performance; rather successful performance through environmentally supported attention might even aid in mood repair. 11 This message is particularly optimistic for clients with TBI, because mood repair after head injury can require years of intensive therapy. In the theoretical realm, our findings led us to propose a framework for understanding depressive impairments in memory that emphasizes the control of attention, rather than its availability. The main proposition of the framework is that depression inhibits cognitive initiative. The typical cognitive task-in the laboratory and in everyday life-is loosely structured. By that I mean that there are a number of options for attending, organizing, elaborating, integrating, monitoring, constructing, and so on. Specific processes are not completely specified by the overt requirements of the task. For example, in the unfocused groups in the experiment described above, the subjects could choose to make quick decisions about the fit of the word in the frame and then think about something else, or they could continue to attend to the word in the context of the sentence and
Depression and Memory
further elaborate its meaning. Under these typically unstructured conditions, people who are not depressed are more likely to sustain attention to the task and process strategically, whereas depressed subjects are inclined to do mainly what is required and nothing else. In that sense, depression inhibits cognitive initiative. Impaired cognitive initiative is frequently observed with TBI clients in unstructured situations, but the provision of structured goals or incentives, for example, can raise their performance to near-average levels. 12 In formulating the initiative framework 13 we identified three categories of task conditions under which the initiation of cognitive strategies would or would not play a role in producing depressed-related differences in performance. Tasks either (1) permit the spontaneous initiation of strategies (such as sustained attention) through lack of structure, (2) direct the use of such strategies, or (3) bypass the benefits of strategic processing. In tasks that permit spontaneously initiated strategies, we predict depression-related deficits in performance. To the extent that tasks are well structured and leave little or no room for individual variation in the type of processing, we predict that such deficits will not be found. Finally, some tests of performance do not profit from the prior use of strategies and therefore should not reveal depressive impairments. Each of these categories has implications for rehabilitation. The first two categories are described next and followed by a description of tasks that bypass the advantages of prior initiative.
ATTENTIONAL AND STRATEGIC CONTROL Tests of Recall The experiment described above illustrates the importance of strategies that sustain attention to the task. lO When the initial task was loosely constrained, the non depressed participants seemed to sustain attention on their own initiative, whereas the depressed participants seemed to let their minds wander. But when the task was designed to focus everyone's attention on the task, depressed and nondepressed participants per-
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formed equally well. These conclusions were reached by examining performance on a subsequent test of free recall (i.e., remembering the words from the previous list, without hints or cues), which has frequently been used in experiments that provide evidence of depressed-related impairment. An early experiment concerning depression and free recall conducted by Weingartner and his colleagues provides a good example. 14 Clinically depressed patients were exposed to a list of words that were inherently organized but presented in a random order; later they did not recall as many of those words as did the nondepressed controls. Organizational strategies clearly benefit performance on tests of free recall, and in this situation organizational strategies were not overtly instructed when the subjects first learned the list; the impairment is therefore consistent with our initiative framework. The question is whether the provision of the organizational structure would reduce the impairment, and indeed the impairment was minimal when the words were presented with their organization intact. The question for rehabilitation, furthermore, is whether clinically depressed patients can be taught to anticipate the need for such organizational strategies,14 or whether the environment itself must be structured in order to repair performance.
Recognition Memory Instances of remembering sometimes require recall (e.g., names of people, places, or things, episodes from the past), but not always. We are often in situations where the name or the episode is provided and we are asked if we recognize it as having occurred previously (e.g., did we meet soand-so last year at the conference). In the laboratory, recognition tests sometimes show depression-related impairments and sometimes do not. 15 This is because recognition decisions are based on multiple sources of information. Jacoby's research on recognition suggests that these decisions sometimes are based primarily on feelings of familiarity, and sometimes on controlled recollection of the past. 16 A feeling that something is familiar is by nature not a strategic or thoughtful memory experience, and therefore
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cognitive initiative is not an important factor. In contrast, conscious recollection of specific past occurrences is a matter of attentional control; the su~ject can use retrieval strategies t.hat are focused on the detailed nature of those past events. Therefore the recollective component of recognition, rather than its basis in familiarity, should be impaired during episodes of depression. These were the predictions for results recently obtained in our laboratory. 17 Subjects who were in depressed or non depressed moods participated in a recognition experiment. Initially, they were exposed to a long list of words, each of which was briefly presented on a computer monitor and rated for meaning. The important aspect of the experiment was the nature of instructions for a later test of recognition. Half of the previously rated words (and other old and new words) were evaluated under standard recognition instructions. Subjects were required to judge whether each was old or new. Again, such a judgment can be based on a sense that the word is familiar, on controlled recollection of the list, or (more likely) on a mixture of both types of processes. As is often the case, performance under these instructions failed to show a depressionrelated impairment. However, a second set of instructions was used to judge the remaining half of the previously rated words (and other old and new words). Under these inst.ructions, subjects were asked to reserve the judgment of "old" for words from a different phase of the experiment and to call all previously rated words "new," along with the truly new words. The rationale for these inst.ructions was the following: If subjects judge the rated words to be old, they must not be recollecting in a controlled sense (otherwise, they would say "new"), but instead relying on a feeling of familiarity to make the judgment. According to procedures established by Jacoby,16 we were able to estimate each of the two components of recognition performance-familiarity and recollection-for each subject. Then we determined whether depressed and non depressed subjects differed in their feelings of familiarity or their recollection. The results showed no reliable difference in the estimates of familiarity; both groups relied on familiarity to a similar degree in trying to
make recogmtlOn decisions. More importantly, however, a depression-related impairment in estimates of controlled recollection was found. In short, depressed subjects relied on familiarity because recollection was impaired. What are the implications of these results for rehabilitation? They depend on the development of procedures for training controlled recollective strategies. In training clients to recognize information from specific contexts, for example, the clinician might guide them to use memory for aspects of that original context in making the decision and not to trust their sense offamiliarity. Some evidence from our previous research on recognition tentatively suggests that such training could be effective. In a series of experiments,!3 subjects in depressed or nondepressed moods performed three tasks. First, we asked them simple questions, such as, "What are the days of the week?" Some of the questions, including the example just given, contained homophones (words that sound the same but have different meanings and spellings). The second task they performed was a spelling test; we read a list of words aloud, at a fairly rapid pace, and r.equested their spelling. Some of the words on the spelling test were homophones and some of the homophones were taken from the first task. The final task was a recognition test. Again we read a list of words aloud and asked the subjects to tell us whether each was from the first (question) task. The nondepressed subjects recognized those words more accurately. Moreover, their decisions clearly depended on how they had spelled the old homophones in the second task. If they had spelled them in line with the meaning established by the question (e.g., "w-e-e-k" instead ofthe more frequent spelling of "w-e-a-k"), then they were more likely to recognize them. This association between recognition and spelling was not produced by the depressed subjects, who were just as likely to recognize homophones that they had spelled in line with the questions as those they had spelled in other forms. It seemed to us, therefore, that non depressed subjects had devised a strategy for performing the recognition task. We characterized that strategy as a series of questions the subjects might have posed to themselves: Was the word on the spelling test? How did I spell it? Was
Depression and Memory
that word part of one of the questions I had been asked earlier? Then we conducted another experiment in which we structured the recognition test according to those questions. The results were that the depressed subjects now recognized as many homophones as did nondepressed subjects and, moreover, their recognition performance depended on how they had spelled. In short, the provision of a strategy eliminated the impairment. Clinicians may therefore need to devise specific questions that could guide recognition and serve as models for the sort of strategies clients might later learn to establish on their own.
THE IRRELEVANCE OF CONTROL Implicit Memory In a different vein, other results from the homophone experiment were perhaps the first to show that depression is irrelevant to performance on tests of implicit memory. Implicit merrwry is a term used by some memory researchers 18 to refer to the influence of prior experience on current tasks in which the subject is not deliberately trying to remember the prior experience. It is assumed by these researchers that the subject'S attention is focused on the task at hand, rather than on past events, but that nevertheless those past events can influence performance. Another way to express this idea is to say that subjects are remembering without awareness that they are remembering. (Traditionally, such performance has been understood simply as evidence for learning.) Although it is probably true that all tests of memory tap both conscious and unaware memory processes, 19 certain tests arguably tap unaware processes to a greater extent than conscious ones. The spelling test described is one such test. On that test, the proportion of old homophones that were spelled in line with the question ("w-e-e-k" instead of "w-e-a-k") was compared to the proportion of new homophones on the test that were spelled in the same way (the less common way). The extent to which old homophones were spelled in the less common way more frequendy than new ones serves as a measure of implicit memory. Subjects are showing that they are influenced by the pre-
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vious questions, but they are not trying to remember. Recall that the subject's task was to spell the words quickly; not much time was given for initiating recollective processes. Also, the actual purpose of the spelling test (which was to assess memory) was concealed by the inclusion of a large number of new words to be spelled along with the old words. The upshot of all these methods was the observation that depressed and nondepressed subjects showed comparable levels of implicit memory. The field of implicit-memory research has its roots in research on neuropsychological impairment. Studies by Warrington and Weiskrantz 20 were the first to show that amnesics perform quite well on implicit tests, even though their recognition memory is severely impaired. Since then, a host of investigations have shown similar results by using quite different implicit tests. 21 ,22 Similarly, research on depressive impairment has been extended to clinically depressed patients and continues to show that depressed suqjects perform "normally" on various implicit tests. 23 ,24 When the memory-oriented nature of the test is appropriately concealed, nondepressed subjects often fail to take the initiative to monitor the relevance of the past. The benefits of initiating strategies are therefure bypassed, so depression-related impairments should not be expected and have not been fuund. One of the interesting conclusions to emerge from tests of implicit memory is that they seem to be litde affected by how much or what kind of attention was paid during initial exposure to the materials. Whether subjects make semantic connections between words or merely read them, doesn't seem to affect performance on implicit tests,25 even though we have known for a long time that explicit memory (e.g., recall and recognition) is improved by elaborations of meaning. A recent experiment performed with clinically depressed outpatients and nondepressed controls illustrates the point about the effects of semantic elaboration. 26 In the first phase of the experiment, subjects were asked to perform two ratings tasks on separate lists of words. Some of the words were rated according to their emotional value to the subject, and the others were rated on purely perceptual features (the degree of angularity or
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curvature in the computer-displayed word). The last phase of the experiment was a test of free recall of the words from the first phase. As expected, words that were meaningfully processed were recalled more frequently than the others. Furthermore, the depressed subjects recalled fewer words from both rating tasks than did the nondepressed subjects. Elaborative processing benefits deliberate recollection, and depression probably inhibited the degree of initial elaboration. All of this was old news; the interesting outcome was provided by the second task. Nested between the rating tasks and the test of free recall was a test of word identification. Here, all of the rated words and as many new words were each flashed very briefly (typically less than 100 ms) on the computer monitor and followed by a perceptual mask; the subjects' task was to read each word aloud. On this test, the difference between the percentages of old (rated) and new words identified serves as the measure of implicit memory. Nondepressed subjects showed the typical finding of similar implicit memory, regardless of the type of rating that had been made in the first phase. In the depressed sample, implicit memory fur words from the semantic rating task was comparable to performance by nondepressed subjects. However, words that were rated for their perceptual features showed reduced implicit memory. The subjects were not required to treat those materials as units of meaning as they rated perceptual features; the nondepressed subjects appeared to do so on their own initiative (as one might expect), but the depressed subjects were clearly less inclined to do so. This finding might be the first evidence of a depression-related impairment on a test of implicit memory. It can be understood by realizing that reading a briefly flashed word on the test will benefit from having read it previously; the word must indeed be processed as a lexical unit. To the extent that the "mind" of the depressed person is "elsewhere," the lack of environmental control of attention can lead to depression-related impairments, even on so-called implicit tests. Research on implicit memory provides good news for people who are depressed. Their lack of
cognitive initiative would not seem to be a detriment, as long as they are not required to remember deliberately and as long as they have attended to the basic meaning of the event to be remembered. In the real world, much of the influence of the past occurs without our deliberate invocation of the past. To be able to take comfort in this claim, however, the depressed person must devote some minimal degree of attention to ongoing events on other than a purely perceptual level.
Problem Solving by Analogy One final line of research in my laboratory might provide even better news than does research on implicit memory.27 The line follows up on previous work by Needham and Begg on the conditions for obtaining spontaneous transfer of prior training in solving insight problems. 28 For our purposes, the relevant conditions of their experiments involved the following steps: First, subjects either tried to solve or tried to memorize a series of word problems and were taught the correct solution after each attempt. Second, they were given a second set of problems, each of which was analogous to one of the training problems; the problem structure was the same, but the setting, actors, and details differed. Importantly, no mention was made of the analogies; all suqjects were simply asked to try to solve each problem. Needham and Begg found that solutions to the second set were improved by problem-oriented training. Compared to trying to memorize training problems, trying to solve them, even with little success, was a more transfer-appropriate approach. 29 Our research was designed to determine whether depression would impair this process. We reasoned that the "effect" of depression should depend on the nature of the procedures used during the transfer phase. If subjects deliberately think back to the training problems and consciously notice and apply the methods of the analogous ones, then depressed subjects should be impaired. The lack of initiative in monitoring the relevance of the past would be responsible for this impairment. If, however, the use of prior experience with similar problems was less deliberate,
Depression and Memory
with the similar structures more or less automatically cueing the appropriate strategies, then transfer performance by depressed subjects should not be impaired. In order to discover the primary basis for transfer (deliberate or nondeliberate) by nondepressed subjects, we performed the following experiment. All subjects were given problem-oriented training; they tried to solve each training problem before being taught its solution. Then prior to each problem in the transfer phase, some of the subjects were asked to clear their minds and get ready for the next problem, whereas the others were given an explicit hint about the appropriate analogy for the next problem. The outcome of this manipulation for the nondepressed subjects was that those who were not given hints solved more accurately than did those who were. If subjects without hints had been deliberately trying to remember training problems, they would have performed no better than did those where were given hints to remember. We thereby concluded that the basis of spontaneous (no-hint) transfer was the nondeliberate use of the analogies and cueing by similar problem structures. Therefore, we expected depressed subjects in the no-hint condition to perform as well as the nondepressed subjects, and they did. The surprising outcome was obtained from the depressed subjects who were given hints during the transfer phase. These subjects solved reliably more accurately than did the nondepressed subjects! On a tentative basis, we suggested that they were able to avoid the pitfulls of monitoring the past. When cognitive control turns out to be disadvantageous, depression is not a bad state to be in. The implication of this finding for clients with TBI is threefold. First, problem-solving strategies should be well trained in a problem-oriented manner, rather than learned more passively through observation. Further, training examples should be very similar to real world situations. Then, in those situations where the strategies should come into play, the client should not be concerned about remembering his or her training, but instead focus on the task at hand and allow the training to take effect.
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SUMMARY Evidence from the research I have described might be useful in establishing practical guidelines for memory rehabilitation when the client is depressed. First, improvement in focused attention and recollection might depend on improvement in mood, especially when tasks are unstructured. Therapists who work with severely depressed clients must therefore ask whether their treatment is even feasible. Medication might be necessary in order to reduce the depression sufficiently to facilitate attention. The clients' energies might be better spent in directly attacking the causes of the depression through environmental, legal, or social intervention. Second, depression will impair memory most often when the task requires conscious attempts to remember. In these situations perhaps the best approach is to facilitate performance through environmental control. Such control can eliminate the clients' need to initiate beneficial procedures on their own, either during their initial exposure to the materials to be remembered or during the episode of remembering. Explicit help in structuring their more important or frequent tasks requiring conscious attention and recollection is recommended, as is the use of prosthetic cueing devices. These measures can potentially ensure not only competent performance, but mood repair through practical accomplishments. Third, on those much more frequent occasions when memory is used largely without deliberation or awareness, impairments should typically not be expected. Clients who are depressed are sometimes obsessed by their memory difficulties, which they notice when they fail during deliberate attempts to remember. In situations where deliberate memory is not required but rather relevant past experience, perhaps the most important advice to give depressed clients who are concerned about their ability to remember is to relax and not make memory an issue. Then the relevant experiences of the past can be better trusted to guide their performance on the task at hand.
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REFERENCES 1. Schacter DL. Memory, amnesia, and frontal lobe dysfunction. Psychobiology 1987;15. 2. Resnick SM. Positron emission tomography in psychiatric illness. Current Directions in Psychological Science 1992;1:92-98. 3. Mayes AR. Human organic memory disorders. New York: Cambridge University Press, 1988. 4. Hartlage S, Alloy LB, Vazquez C, Dykman B. Automatic and effortful processing in depression. Psychological Bulletin 1993;113:247-278. 5. Williams JMG, Watts FN, MacLeod C, Mathews· A. Cognitive psychology and emotional disorders. New York: John Wiley & Sons, 1988. 6. Ellis HC, Hertel PT. Cognition, emotion, and memory: Some applications and issues. In Izawa C, ed. Cognitive psychology applied. Hillsdale, NJ: Erlbaum, 1993:199-215. 7. Ellis HC, Thomas RI, Rodriguez IA. Emotional mood states and memory: Elaborative encoding, semantic processing, and cognitive effort. Journal of Experimental Psychology: Learning, Memory, and Cognition 1984; 10:470-482. 8. Ellis HC, Ashbrook pw. Resource allocation model of the effects of depressed mood states on memory. In Fiedler K, Forgas J, eds. Affect, cognition, and social behavior. Toronto: Hogrefe, 1988:25-43. 9. Ingram RE. Self-focused attention in clinical disorders: Review and a conceptual model. Psychological Bulletin 1990;107: 156-176. 10. Hertel PT, Rude SS. Depressive deficits in memory: Focusing attention improves subsequent recall. Journal of Experimental Psychology: General 1991a;120:301-309. 11. Hertel PT. Improving mood and memory through automatic and controlled procedures of mind. In Herrmann D, Weingartner H, Searleman A, McEvoy C eds. Memory improvement: Implications for memory theory. New York: SpringerVerlag, 1992b:47-65. 12. Parente R, Anderson-Parente J. Retraining memory. Houston: CSY Publishing, 1991. 13. Hertel PT, Hardin TS. Remembering with and without awareness in a depressed mood: Evidence of deficits in intiative. Journal of Experimental Psychology: General 1990; 119:45-49. 14. Weingartner H, Cohen RM, Murphy DL, Martello J, Gerdt C. Cognitive processes in depression. Archives of General Psychiatry 1981 ;38:42-47. 15. Watts FN, Morris L, MacLeod AK. Recognition memory in depression. Journal of Abnormal Psychology 1987;96:273-275.
16. Jacoby LL. A process dissociation framework: Separating automatic from intentional uses of memory. Journal of Memory and Language 1991 ;30:513-541. 17. Hertel PT, Milan S, Lyman BL, Terrell C. Depressive deficits in recollective components of recognition. Paper presented at the annual meeting of the Psychonomic Society, Washington DC, Nov. 1993. 18. Roediger HL, III. Implicit memory: Retention without remembering. American Psychologist 1990;45: 1043-1056. 19. Jacoby LL, Toth JP, Yonelinas AP. Separating conscious and unconscious influences of memory: Measuring recollection. Journal ofExperimental Psychology: General 1993;122:139-154. 20. Warrington EK, Weiskrantz L. Amnesic syndrome: Consolidation or retrieval. Nature 1970; 228:628-630. 21. Jacoby LL, Kelley CM. Unconscious influences of memory: Dissociations and automaticity. In Milner AD, Rugg MD, eds. The neuropsychology of consciousnesss. New York: Academic Press, 1991: 201-233. 22. Squire LR, Butters N. The neuropsychology ofmemory. New York: Guilford, 1984. 23. Denny EB, Hunt RR. Affective valence and memory in depression: Dissociation of recall and fragment completion.Journal ofAbnormal Psychology 1991;101:575-580. 24. Watkins PC, Mathews A, Williamson DA, Fuller RD. Mood-congruent memory in depression: Emotional priming or elaboration? Journal of Abnormal Psychology 1992; 10 1:581-586. 25. Jacoby LL, Dallas M. On the relationship between autobiographical memory and perceptual learning. Journal of Experimental Psychology: GeneraI1981;110:306-340. 26. Hertel PT. Depressive deficits in word identification and recall. Cognition and Emotion, in press. 27. Hertel PT, Knoedler AJ. The spontaneous and directed uses of analogies in problem solving: Do depressed moods help or hurt? Unpublished manuscript, 1994. 28. Needham DR, Begg 1M. Problem-oriented training promotes spontaneous analogical transfer: Memory-oriented training promotes memory for training. Memory & Cognition 1991;19:543-557. 29. Morris CD, Bransford JD, Franks JJ. Levels of processing versus transfer appropriate processing. Journal of Verbal Learning and Verbal Behavior 1977;16:519-533.
Head injuries and strokes produce a variety of psychological problems, including memory difficulties and depression. Neuropsychological evidence suggests that damage to the frontal lobes, in particular, is associated with both affective and cognitive disturbances. The types of cognitive difficulties include impaired attention, limited skills in monitoring, and other strategy-related deficits.l Traumatically brain-injured (TBI) clients quite understandably feel depressed, not only because they cannot function as before, but because the injury has damaged areas of the brain that directly mediate mood. 2,3 Although people with brain injuries typically experience cognitive deficits associated with depressed moods at some point in their recovery, there is little research that systematically investigates relationships between depression and memory in organically impaired populations. Such investigations with nonimpaired populations, however, are numerous. 4 Because depression and memory impairment are common outcomes ofTBI, and because their relationship in TBI clients has received little experAcknowledgment: The author is grateful to Doug Herrmann and Rick Parente for discussions concerning implications of her work for rehabilitation.
imental attention, theory and research performed with uninjured populations provide reasonable directions for investigating aids to rehabilitation. My intent in this article is to briefly review the research I have conducted on the nature of depression-related impairments in memory and to discuss its implications for cognitive rehabilitation. The link between depressed moods and memory is typically understood to be mediated by attentional capacity.5.6 The notion is that depressed moods somehow reduce the amount of attention that could be otherwise paid to ongoing experiences. When the depressed person later tries to remember the earlier experience, performance is impaired. (In the clinical setting, those who work with head-injured clients often notice a level of preoccupation with personal problems that is sufficient to render therapy ineffective.) Initially, this attentional-resource theory of depressive memory was supported by a variety of experimental findings. For example, Ellis, Thomas, and Rodriguez 7 used a mood-induction procedure to establish sad moods in college students and then asked them to make decisions about the "fit" of words in accompanying sentence frames. On some trials the word was the obvious choice for the missing element in the frame (e.g., dream for NeuroRehabill994; 4(3):143-150 Copyright © 1994 by Butterworth-Heinemann
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the frame, "She was awakened by her frightening _ _"). On other trials, the word was just one of several words that might fit the frame (e.g., dream for "He was alarmed by the frightening _ _"). In the former case, each word could be easily integrated with its sentence frame to provide an elaboration that would subsequently help subjects to remember the word; in the latter case, such elaborations presumably would be more difficult. Ellis and his colleagues presented 12 words in easy contexts, and another 12 words in difficult contexts. Then they surprised the subjects with a request for free recall of all the words. On that test, the subjects who had been induced to feel sad recalled as many words from the easy contexts as did control subjects, but fewer words from the difficult contexts. One possible interpretation of these results is that depressed moods reduced the amount of attentional resources available for the task at hand; sufficient resources were available for elaboration on the easy trials, but not on the difficult ones. 8 This interpretation relies on the assumption that depressed or sad people pervasively allocate resources to their mood states; they cannot concentrate on the task at hand because they are thinking about themselves. 9 To some extent, this state of mind might also characterize patients with neurological impairments. For all patients suffering depressed moods, the hope for rehabilitation seems to rest on mood repair; only when affect is neutralized would attentional resources be freed to allocate to the ongoing task. The hope for rehabilitation is therefore not as good as it could be, given the implications that arise from the following experimental findings. In collaboration with Stephanie Rude,10 I recruited clinically depressed outpatients and nondepressed controls to participate in an experiment that was similar to the one just described. In fact, half of the subjects in both groups made decisions about words in both easy and difficult contexts under conditions that were very similar to those used by Ellis and his colleagues. That is, they could make the decision whenever they chose to do so during the 8-second trial, and let their minds wander until the next word was presented. On the subsequent test, the depressed subjects recalled fewer words from the difficult contexts
than did the nondepressed subjects, just as one would expect if the results from the moodinduced students could be generalized to a clinical population. The more interesting finding, however, was produced by the other half of the subjects, who had been instructed to wait until the end of each trial to report their decisions and repeat the word. These instructions were designed to focus and sustain subjects' attention on the task at hand. The issue, of course, was whether such instructions would be sufficiently successful to overcome the recall impairment observed in the unfocused groups. In fact, the depressed subjects in the focused group recalled words from the difficult contexts at slighter higher levels (although not reliably so) than did the nondepressed subjects. These instructions sustained subjects' attention to the task and thereby facilitated elaborations that were important in preventing depression-related impairments. Depressed subjects were clearly capable of such attention and needed only some environmental support for reallocation. The message for rehabilitation, then, is subtly but importantly different: Mood repair is not a requisite for successful performance; rather successful performance through environmentally supported attention might even aid in mood repair. 11 This message is particularly optimistic for clients with TBI, because mood repair after head injury can require years of intensive therapy. In the theoretical realm, our findings led us to propose a framework for understanding depressive impairments in memory that emphasizes the control of attention, rather than its availability. The main proposition of the framework is that depression inhibits cognitive initiative. The typical cognitive task-in the laboratory and in everyday life-is loosely structured. By that I mean that there are a number of options for attending, organizing, elaborating, integrating, monitoring, constructing, and so on. Specific processes are not completely specified by the overt requirements of the task. For example, in the unfocused groups in the experiment described above, the subjects could choose to make quick decisions about the fit of the word in the frame and then think about something else, or they could continue to attend to the word in the context of the sentence and
Depression and Memory
further elaborate its meaning. Under these typically unstructured conditions, people who are not depressed are more likely to sustain attention to the task and process strategically, whereas depressed subjects are inclined to do mainly what is required and nothing else. In that sense, depression inhibits cognitive initiative. Impaired cognitive initiative is frequently observed with TBI clients in unstructured situations, but the provision of structured goals or incentives, for example, can raise their performance to near-average levels. 12 In formulating the initiative framework 13 we identified three categories of task conditions under which the initiation of cognitive strategies would or would not play a role in producing depressed-related differences in performance. Tasks either (1) permit the spontaneous initiation of strategies (such as sustained attention) through lack of structure, (2) direct the use of such strategies, or (3) bypass the benefits of strategic processing. In tasks that permit spontaneously initiated strategies, we predict depression-related deficits in performance. To the extent that tasks are well structured and leave little or no room for individual variation in the type of processing, we predict that such deficits will not be found. Finally, some tests of performance do not profit from the prior use of strategies and therefore should not reveal depressive impairments. Each of these categories has implications for rehabilitation. The first two categories are described next and followed by a description of tasks that bypass the advantages of prior initiative.
ATTENTIONAL AND STRATEGIC CONTROL Tests of Recall The experiment described above illustrates the importance of strategies that sustain attention to the task. lO When the initial task was loosely constrained, the non depressed participants seemed to sustain attention on their own initiative, whereas the depressed participants seemed to let their minds wander. But when the task was designed to focus everyone's attention on the task, depressed and nondepressed participants per-
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formed equally well. These conclusions were reached by examining performance on a subsequent test of free recall (i.e., remembering the words from the previous list, without hints or cues), which has frequently been used in experiments that provide evidence of depressed-related impairment. An early experiment concerning depression and free recall conducted by Weingartner and his colleagues provides a good example. 14 Clinically depressed patients were exposed to a list of words that were inherently organized but presented in a random order; later they did not recall as many of those words as did the nondepressed controls. Organizational strategies clearly benefit performance on tests of free recall, and in this situation organizational strategies were not overtly instructed when the subjects first learned the list; the impairment is therefore consistent with our initiative framework. The question is whether the provision of the organizational structure would reduce the impairment, and indeed the impairment was minimal when the words were presented with their organization intact. The question for rehabilitation, furthermore, is whether clinically depressed patients can be taught to anticipate the need for such organizational strategies,14 or whether the environment itself must be structured in order to repair performance.
Recognition Memory Instances of remembering sometimes require recall (e.g., names of people, places, or things, episodes from the past), but not always. We are often in situations where the name or the episode is provided and we are asked if we recognize it as having occurred previously (e.g., did we meet soand-so last year at the conference). In the laboratory, recognition tests sometimes show depression-related impairments and sometimes do not. 15 This is because recognition decisions are based on multiple sources of information. Jacoby's research on recognition suggests that these decisions sometimes are based primarily on feelings of familiarity, and sometimes on controlled recollection of the past. 16 A feeling that something is familiar is by nature not a strategic or thoughtful memory experience, and therefore
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cognitive initiative is not an important factor. In contrast, conscious recollection of specific past occurrences is a matter of attentional control; the su~ject can use retrieval strategies t.hat are focused on the detailed nature of those past events. Therefore the recollective component of recognition, rather than its basis in familiarity, should be impaired during episodes of depression. These were the predictions for results recently obtained in our laboratory. 17 Subjects who were in depressed or non depressed moods participated in a recognition experiment. Initially, they were exposed to a long list of words, each of which was briefly presented on a computer monitor and rated for meaning. The important aspect of the experiment was the nature of instructions for a later test of recognition. Half of the previously rated words (and other old and new words) were evaluated under standard recognition instructions. Subjects were required to judge whether each was old or new. Again, such a judgment can be based on a sense that the word is familiar, on controlled recollection of the list, or (more likely) on a mixture of both types of processes. As is often the case, performance under these instructions failed to show a depressionrelated impairment. However, a second set of instructions was used to judge the remaining half of the previously rated words (and other old and new words). Under these inst.ructions, subjects were asked to reserve the judgment of "old" for words from a different phase of the experiment and to call all previously rated words "new," along with the truly new words. The rationale for these inst.ructions was the following: If subjects judge the rated words to be old, they must not be recollecting in a controlled sense (otherwise, they would say "new"), but instead relying on a feeling of familiarity to make the judgment. According to procedures established by Jacoby,16 we were able to estimate each of the two components of recognition performance-familiarity and recollection-for each subject. Then we determined whether depressed and non depressed subjects differed in their feelings of familiarity or their recollection. The results showed no reliable difference in the estimates of familiarity; both groups relied on familiarity to a similar degree in trying to
make recogmtlOn decisions. More importantly, however, a depression-related impairment in estimates of controlled recollection was found. In short, depressed subjects relied on familiarity because recollection was impaired. What are the implications of these results for rehabilitation? They depend on the development of procedures for training controlled recollective strategies. In training clients to recognize information from specific contexts, for example, the clinician might guide them to use memory for aspects of that original context in making the decision and not to trust their sense offamiliarity. Some evidence from our previous research on recognition tentatively suggests that such training could be effective. In a series of experiments,!3 subjects in depressed or nondepressed moods performed three tasks. First, we asked them simple questions, such as, "What are the days of the week?" Some of the questions, including the example just given, contained homophones (words that sound the same but have different meanings and spellings). The second task they performed was a spelling test; we read a list of words aloud, at a fairly rapid pace, and r.equested their spelling. Some of the words on the spelling test were homophones and some of the homophones were taken from the first task. The final task was a recognition test. Again we read a list of words aloud and asked the subjects to tell us whether each was from the first (question) task. The nondepressed subjects recognized those words more accurately. Moreover, their decisions clearly depended on how they had spelled the old homophones in the second task. If they had spelled them in line with the meaning established by the question (e.g., "w-e-e-k" instead ofthe more frequent spelling of "w-e-a-k"), then they were more likely to recognize them. This association between recognition and spelling was not produced by the depressed subjects, who were just as likely to recognize homophones that they had spelled in line with the questions as those they had spelled in other forms. It seemed to us, therefore, that non depressed subjects had devised a strategy for performing the recognition task. We characterized that strategy as a series of questions the subjects might have posed to themselves: Was the word on the spelling test? How did I spell it? Was
Depression and Memory
that word part of one of the questions I had been asked earlier? Then we conducted another experiment in which we structured the recognition test according to those questions. The results were that the depressed subjects now recognized as many homophones as did nondepressed subjects and, moreover, their recognition performance depended on how they had spelled. In short, the provision of a strategy eliminated the impairment. Clinicians may therefore need to devise specific questions that could guide recognition and serve as models for the sort of strategies clients might later learn to establish on their own.
THE IRRELEVANCE OF CONTROL Implicit Memory In a different vein, other results from the homophone experiment were perhaps the first to show that depression is irrelevant to performance on tests of implicit memory. Implicit merrwry is a term used by some memory researchers 18 to refer to the influence of prior experience on current tasks in which the subject is not deliberately trying to remember the prior experience. It is assumed by these researchers that the subject'S attention is focused on the task at hand, rather than on past events, but that nevertheless those past events can influence performance. Another way to express this idea is to say that subjects are remembering without awareness that they are remembering. (Traditionally, such performance has been understood simply as evidence for learning.) Although it is probably true that all tests of memory tap both conscious and unaware memory processes, 19 certain tests arguably tap unaware processes to a greater extent than conscious ones. The spelling test described is one such test. On that test, the proportion of old homophones that were spelled in line with the question ("w-e-e-k" instead of "w-e-a-k") was compared to the proportion of new homophones on the test that were spelled in the same way (the less common way). The extent to which old homophones were spelled in the less common way more frequendy than new ones serves as a measure of implicit memory. Subjects are showing that they are influenced by the pre-
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vious questions, but they are not trying to remember. Recall that the subject's task was to spell the words quickly; not much time was given for initiating recollective processes. Also, the actual purpose of the spelling test (which was to assess memory) was concealed by the inclusion of a large number of new words to be spelled along with the old words. The upshot of all these methods was the observation that depressed and nondepressed subjects showed comparable levels of implicit memory. The field of implicit-memory research has its roots in research on neuropsychological impairment. Studies by Warrington and Weiskrantz 20 were the first to show that amnesics perform quite well on implicit tests, even though their recognition memory is severely impaired. Since then, a host of investigations have shown similar results by using quite different implicit tests. 21 ,22 Similarly, research on depressive impairment has been extended to clinically depressed patients and continues to show that depressed suqjects perform "normally" on various implicit tests. 23 ,24 When the memory-oriented nature of the test is appropriately concealed, nondepressed subjects often fail to take the initiative to monitor the relevance of the past. The benefits of initiating strategies are therefure bypassed, so depression-related impairments should not be expected and have not been fuund. One of the interesting conclusions to emerge from tests of implicit memory is that they seem to be litde affected by how much or what kind of attention was paid during initial exposure to the materials. Whether subjects make semantic connections between words or merely read them, doesn't seem to affect performance on implicit tests,25 even though we have known for a long time that explicit memory (e.g., recall and recognition) is improved by elaborations of meaning. A recent experiment performed with clinically depressed outpatients and nondepressed controls illustrates the point about the effects of semantic elaboration. 26 In the first phase of the experiment, subjects were asked to perform two ratings tasks on separate lists of words. Some of the words were rated according to their emotional value to the subject, and the others were rated on purely perceptual features (the degree of angularity or
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curvature in the computer-displayed word). The last phase of the experiment was a test of free recall of the words from the first phase. As expected, words that were meaningfully processed were recalled more frequently than the others. Furthermore, the depressed subjects recalled fewer words from both rating tasks than did the nondepressed subjects. Elaborative processing benefits deliberate recollection, and depression probably inhibited the degree of initial elaboration. All of this was old news; the interesting outcome was provided by the second task. Nested between the rating tasks and the test of free recall was a test of word identification. Here, all of the rated words and as many new words were each flashed very briefly (typically less than 100 ms) on the computer monitor and followed by a perceptual mask; the subjects' task was to read each word aloud. On this test, the difference between the percentages of old (rated) and new words identified serves as the measure of implicit memory. Nondepressed subjects showed the typical finding of similar implicit memory, regardless of the type of rating that had been made in the first phase. In the depressed sample, implicit memory fur words from the semantic rating task was comparable to performance by nondepressed subjects. However, words that were rated for their perceptual features showed reduced implicit memory. The subjects were not required to treat those materials as units of meaning as they rated perceptual features; the nondepressed subjects appeared to do so on their own initiative (as one might expect), but the depressed subjects were clearly less inclined to do so. This finding might be the first evidence of a depression-related impairment on a test of implicit memory. It can be understood by realizing that reading a briefly flashed word on the test will benefit from having read it previously; the word must indeed be processed as a lexical unit. To the extent that the "mind" of the depressed person is "elsewhere," the lack of environmental control of attention can lead to depression-related impairments, even on so-called implicit tests. Research on implicit memory provides good news for people who are depressed. Their lack of
cognitive initiative would not seem to be a detriment, as long as they are not required to remember deliberately and as long as they have attended to the basic meaning of the event to be remembered. In the real world, much of the influence of the past occurs without our deliberate invocation of the past. To be able to take comfort in this claim, however, the depressed person must devote some minimal degree of attention to ongoing events on other than a purely perceptual level.
Problem Solving by Analogy One final line of research in my laboratory might provide even better news than does research on implicit memory.27 The line follows up on previous work by Needham and Begg on the conditions for obtaining spontaneous transfer of prior training in solving insight problems. 28 For our purposes, the relevant conditions of their experiments involved the following steps: First, subjects either tried to solve or tried to memorize a series of word problems and were taught the correct solution after each attempt. Second, they were given a second set of problems, each of which was analogous to one of the training problems; the problem structure was the same, but the setting, actors, and details differed. Importantly, no mention was made of the analogies; all suqjects were simply asked to try to solve each problem. Needham and Begg found that solutions to the second set were improved by problem-oriented training. Compared to trying to memorize training problems, trying to solve them, even with little success, was a more transfer-appropriate approach. 29 Our research was designed to determine whether depression would impair this process. We reasoned that the "effect" of depression should depend on the nature of the procedures used during the transfer phase. If subjects deliberately think back to the training problems and consciously notice and apply the methods of the analogous ones, then depressed subjects should be impaired. The lack of initiative in monitoring the relevance of the past would be responsible for this impairment. If, however, the use of prior experience with similar problems was less deliberate,
Depression and Memory
with the similar structures more or less automatically cueing the appropriate strategies, then transfer performance by depressed subjects should not be impaired. In order to discover the primary basis for transfer (deliberate or nondeliberate) by nondepressed subjects, we performed the following experiment. All subjects were given problem-oriented training; they tried to solve each training problem before being taught its solution. Then prior to each problem in the transfer phase, some of the subjects were asked to clear their minds and get ready for the next problem, whereas the others were given an explicit hint about the appropriate analogy for the next problem. The outcome of this manipulation for the nondepressed subjects was that those who were not given hints solved more accurately than did those who were. If subjects without hints had been deliberately trying to remember training problems, they would have performed no better than did those where were given hints to remember. We thereby concluded that the basis of spontaneous (no-hint) transfer was the nondeliberate use of the analogies and cueing by similar problem structures. Therefore, we expected depressed subjects in the no-hint condition to perform as well as the nondepressed subjects, and they did. The surprising outcome was obtained from the depressed subjects who were given hints during the transfer phase. These subjects solved reliably more accurately than did the nondepressed subjects! On a tentative basis, we suggested that they were able to avoid the pitfulls of monitoring the past. When cognitive control turns out to be disadvantageous, depression is not a bad state to be in. The implication of this finding for clients with TBI is threefold. First, problem-solving strategies should be well trained in a problem-oriented manner, rather than learned more passively through observation. Further, training examples should be very similar to real world situations. Then, in those situations where the strategies should come into play, the client should not be concerned about remembering his or her training, but instead focus on the task at hand and allow the training to take effect.
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SUMMARY Evidence from the research I have described might be useful in establishing practical guidelines for memory rehabilitation when the client is depressed. First, improvement in focused attention and recollection might depend on improvement in mood, especially when tasks are unstructured. Therapists who work with severely depressed clients must therefore ask whether their treatment is even feasible. Medication might be necessary in order to reduce the depression sufficiently to facilitate attention. The clients' energies might be better spent in directly attacking the causes of the depression through environmental, legal, or social intervention. Second, depression will impair memory most often when the task requires conscious attempts to remember. In these situations perhaps the best approach is to facilitate performance through environmental control. Such control can eliminate the clients' need to initiate beneficial procedures on their own, either during their initial exposure to the materials to be remembered or during the episode of remembering. Explicit help in structuring their more important or frequent tasks requiring conscious attention and recollection is recommended, as is the use of prosthetic cueing devices. These measures can potentially ensure not only competent performance, but mood repair through practical accomplishments. Third, on those much more frequent occasions when memory is used largely without deliberation or awareness, impairments should typically not be expected. Clients who are depressed are sometimes obsessed by their memory difficulties, which they notice when they fail during deliberate attempts to remember. In situations where deliberate memory is not required but rather relevant past experience, perhaps the most important advice to give depressed clients who are concerned about their ability to remember is to relax and not make memory an issue. Then the relevant experiences of the past can be better trusted to guide their performance on the task at hand.
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REFERENCES 1. Schacter DL. Memory, amnesia, and frontal lobe dysfunction. Psychobiology 1987;15. 2. Resnick SM. Positron emission tomography in psychiatric illness. Current Directions in Psychological Science 1992;1:92-98. 3. Mayes AR. Human organic memory disorders. New York: Cambridge University Press, 1988. 4. Hartlage S, Alloy LB, Vazquez C, Dykman B. Automatic and effortful processing in depression. Psychological Bulletin 1993;113:247-278. 5. Williams JMG, Watts FN, MacLeod C, Mathews· A. Cognitive psychology and emotional disorders. New York: John Wiley & Sons, 1988. 6. Ellis HC, Hertel PT. Cognition, emotion, and memory: Some applications and issues. In Izawa C, ed. Cognitive psychology applied. Hillsdale, NJ: Erlbaum, 1993:199-215. 7. Ellis HC, Thomas RI, Rodriguez IA. Emotional mood states and memory: Elaborative encoding, semantic processing, and cognitive effort. Journal of Experimental Psychology: Learning, Memory, and Cognition 1984; 10:470-482. 8. Ellis HC, Ashbrook pw. Resource allocation model of the effects of depressed mood states on memory. In Fiedler K, Forgas J, eds. Affect, cognition, and social behavior. Toronto: Hogrefe, 1988:25-43. 9. Ingram RE. Self-focused attention in clinical disorders: Review and a conceptual model. Psychological Bulletin 1990;107: 156-176. 10. Hertel PT, Rude SS. Depressive deficits in memory: Focusing attention improves subsequent recall. Journal of Experimental Psychology: General 1991a;120:301-309. 11. Hertel PT. Improving mood and memory through automatic and controlled procedures of mind. In Herrmann D, Weingartner H, Searleman A, McEvoy C eds. Memory improvement: Implications for memory theory. New York: SpringerVerlag, 1992b:47-65. 12. Parente R, Anderson-Parente J. Retraining memory. Houston: CSY Publishing, 1991. 13. Hertel PT, Hardin TS. Remembering with and without awareness in a depressed mood: Evidence of deficits in intiative. Journal of Experimental Psychology: General 1990; 119:45-49. 14. Weingartner H, Cohen RM, Murphy DL, Martello J, Gerdt C. Cognitive processes in depression. Archives of General Psychiatry 1981 ;38:42-47. 15. Watts FN, Morris L, MacLeod AK. Recognition memory in depression. Journal of Abnormal Psychology 1987;96:273-275.
16. Jacoby LL. A process dissociation framework: Separating automatic from intentional uses of memory. Journal of Memory and Language 1991 ;30:513-541. 17. Hertel PT, Milan S, Lyman BL, Terrell C. Depressive deficits in recollective components of recognition. Paper presented at the annual meeting of the Psychonomic Society, Washington DC, Nov. 1993. 18. Roediger HL, III. Implicit memory: Retention without remembering. American Psychologist 1990;45: 1043-1056. 19. Jacoby LL, Toth JP, Yonelinas AP. Separating conscious and unconscious influences of memory: Measuring recollection. Journal ofExperimental Psychology: General 1993;122:139-154. 20. Warrington EK, Weiskrantz L. Amnesic syndrome: Consolidation or retrieval. Nature 1970; 228:628-630. 21. Jacoby LL, Kelley CM. Unconscious influences of memory: Dissociations and automaticity. In Milner AD, Rugg MD, eds. The neuropsychology of consciousnesss. New York: Academic Press, 1991: 201-233. 22. Squire LR, Butters N. The neuropsychology ofmemory. New York: Guilford, 1984. 23. Denny EB, Hunt RR. Affective valence and memory in depression: Dissociation of recall and fragment completion.Journal ofAbnormal Psychology 1991;101:575-580. 24. Watkins PC, Mathews A, Williamson DA, Fuller RD. Mood-congruent memory in depression: Emotional priming or elaboration? Journal of Abnormal Psychology 1992; 10 1:581-586. 25. Jacoby LL, Dallas M. On the relationship between autobiographical memory and perceptual learning. Journal of Experimental Psychology: GeneraI1981;110:306-340. 26. Hertel PT. Depressive deficits in word identification and recall. Cognition and Emotion, in press. 27. Hertel PT, Knoedler AJ. The spontaneous and directed uses of analogies in problem solving: Do depressed moods help or hurt? Unpublished manuscript, 1994. 28. Needham DR, Begg 1M. Problem-oriented training promotes spontaneous analogical transfer: Memory-oriented training promotes memory for training. Memory & Cognition 1991;19:543-557. 29. Morris CD, Bransford JD, Franks JJ. Levels of processing versus transfer appropriate processing. Journal of Verbal Learning and Verbal Behavior 1977;16:519-533.
