This article was downloaded by: [LMU Muenchen] On: 27 December 2014, At: 16:59 Publisher: Routledge Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Experimental Aging Research: An International Journal Devoted to the Scientific Study of the Aging Process Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/uear20
Age differences in the temporal continuity of gratings as a function of their spatial frequency a
a
b
Donald W. Kline , Charles T. Scialfa , Brian J. Lyman & Frank Schieber a
University of Calgary
b
Monell Chemical Senses Center
c
c
Oakland University Published online: 27 Sep 2007.
To cite this article: Donald W. Kline , Charles T. Scialfa , Brian J. Lyman & Frank Schieber (1990) Age differences in the temporal continuity of gratings as a function of their spatial frequency, Experimental Aging Research: An International Journal Devoted to the Scientific Study of the Aging Process, 16:2, 61-65, DOI: 10.1080/07340669008251528 To link to this article: http://dx.doi.org/10.1080/07340669008251528
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
61
Experimental Aging Research, Volume 16, Number 2, 1990, ISSN 0734-0664 O1990 Beech Hill Enterprises Inc.
Age Differences in the Temporal Continuity of Gratings as a Function of Their Spatial Frequency DONALD W. KLINEAND CHARLES T. SCIALFA University of Calgary
Downloaded by [LMU Muenchen] at 16:59 27 December 2014
BRIANJ. LYMAN Monell Chemical Senses Center
FRANKSCHIEBER Oakland University
This study compared young and elderly observers on the continuity of sinusoidal grating-pairs as a function of interstimulus interval (1st) and spatial frequency (3,1.0, 2.0, 4.0, 8.0, and 12.0 c/deg). Consistent with prior research, the maximum IS1 over which pattern continuity was maintained increased with spatial frequency. In addition, among older observers, grating continuity occurred at significantly longer ISI’s at the two lowest spatial frequencies; no age difference was observed at the higher spatial frequencies. These results could not be attributed to an age difference in retinal illumination associated with pupillary miosis. However, they do indicate an age-related decline in detecting visual offset and are consistent with the hypothesis of a decline in the effectiveness of the transient visual channels.
0
ne of the most frequently observed changes in the senescent visual system is a decline in its resolution of temporally-contiguous events (cf. Kline, 1984; Kline & Schieber, 1982). It has been proposed that the temporal sluggishness of the senescent visual system is due to a greater decline with age in the effectiveness of the transient as opposed to the sustained channels (Kline & Schieber, 1981). The present study evaluated the degree to which age differences in the perceived continuity of interrupted sinusoidal gratings of varied spatial frequency were consistent with a hypothesis of disjunctive visual channel aging. The “channels” or subdivisions that compose the visual system appear to differ in their response characteristics and to serve different visual functions (e.g., Campbell & Robson, 1968; Kulikowski & Tolhurst, 1973; Lennie, 1980; Vassilev & Mitov, 1976). Based on physiological evidence of two distinct classes of ganglion cells (i.e., X and Y cells) (Enroth-Cugell& Robson, 1966), these channels were categorized into two general types: “sustained” and “transient.” Although the sustained and transient channels are no longer thought to reflect directly the properties of “X”and “Y”ganglion cells respectively, the two channel types can be distinguished in terms of their functional characteristics. Sustained channels are sensitive
to high spatial frequencies, respond in a slow and persistent manner and are characterized by an extended temporal integration period. As a result, they are well-suited to the perception of form. Conversely, the transient channels, which are sensitive to low spatial frequency stimuli, respond quickly and briefly to stimulus change. In addition, activation of the transient channels appears to inhibit persisting activity in the sustained channels (Breitmeyer & Ganz, 1976; Singer & Bedworth, 1973). Most studies of age differences on the contrast sensitivity function (CSF) report deficits in sensitivity, not at low spatial frequencies as would be suggested by an impairment of transient channels, but at the higher spatial frequencies to which the sustained channels respond (Arundale, 1978; Derefeldt, Lennerstrand, & Lundh, 1979; Kline, Schieber, Abusamra, & Coyne, 1983; Owsley, Sekuler, & Siemsen, 1983; Scialfa, Tyrrell, Garvey, Deering, Leibowitz, & Goebel, 1988). Such static tests, however, lack a temporally-modulated component and consequently, are unlikely to tap the transient channels effectively. When the display is temporally modulated, age differences do become apparent at low spatial frequencies. It has been shown, for example, that motion enhancement of contrast sensitivity to low spatial frequency gratings is greatly diminished in older adults, especially
This research was supported by a grant from the Alberta Senior Citizens Secretariat (No. 69-4922) to the first author and a University of Calgary grant (No. 69-2206) to the second author. Correspondence and reprint requests should be addressed to Donald W.Kline, Ph.D., Department of Psychology, The University of Calgary, Calgary, AB T2N 1N4, CANADA
KLINE/SCIALFA/LYMAN/SCHIEBER
Downloaded by [LMU Muenchen] at 16:59 27 December 2014
62
at fast movement rates (Abusamra, McCoy, Schieber, & Kline, 1984; Owsley et al., 1983). Relatedly, Sloane, Owsley, and Alvarez (1988) found a small but significant age deficit in the CSF at the lowest spatial frequency tested ( 3c/d), a result that they suggested might be due either to the relatively large (6”) target used and/or to the presentation of gratings in counterphase flicker. Sturr, Church, and Taub (1985) observed that elderly observers showed much slower early light adaptation functions than young and middle-aged observers, a loss they suggested was consistent with a transient channel decline. In addition, Sturr and his colleagues have reported older observers to have attenuated brightness increment thresholds on transient backgrounds at both threshold (Sturr, Church, Nuding, Van Orden, & Taub, 1986) and suprathreshold levels (Sturr, Van Orden, & Taub, 1987). The authors held these results to be consistent with a decline in transient channel functioning. More recently, however, when Sturr, Church, and Taub (1988) studied age differences in temporal contrast summation functions of low (.416 c/d) and high spatial frequency (7.5 c/d) gratings, they found no support for the extended temporal summation that might be the result of a shift from transient to greater sustained visual functioning. Nor did they see an age-related increase in the critical duration for summation to contrast threshold for a low spatial frequency grating. The authors concluded that there was no evidence in their summation functions of an age-related sensitivity shift from transient to sustained channels, nor for response slowing within a channel. The authors suggested some reasons for the difference between their results and those of previous research. Unlike the earlier studies that examined the temporal resolution of suprathreshold stimuli, Sturr et al. compared young and old observers on temporal contrast summation at threshold. The authors also noted that many of the earlier studies used “cerebral” rather than retinal tasks. This implies no age deficit in temporal discrimination at the retina, even though one may be evident at higher stages of visual processing. Even this possibility deserves examination. Although the difference was not significant, the older observes required higher mean contrast levels than the young to reach threshold for the low spatial frequency grating at all six stimulus durations tested (Experiments 1 and 2). It may have also been the case that the older observers in the Sturr et al. study were somewhat more visually-select than those in other studies; when they were optically corrected for the test distance (Experiment 3), the typical age-related reduction in contrast sensitivity at high spatial frequencies (e.g., Kline et al., 1983; Owsley et al., 1983) was not observed. Meyer and Maguire (1977) defined the “persistence” of high-contrast square-wave gratings as the maximum blank interstimulus interval (ISI) with which the gratings could be cyclically interrupted and still be reported as continuous. They found that persistence of the gratings inceased monotonically with their spatial frequency. Subsequent studies using this and similar methods (e.g., Bowling, Lovegrove, & Mapperson, 1979; Long & Sakitt,
1984; Lovegrove & Heddle, 1980; Meyer & Maguire, 1981; Parker & Dutch, 1987) have all found that per-
sistence, continuity or perceptual latency increases with spatial frequency, a result usually ascribed to a spatial frequency-induced shift from transient to sustained channel functioning. It now appears that these “quasi-flicker” assessments of grating continuity better measure cletection of target offset than the total persistence of a filding stimulus trace (Long & Gildea, 1981; Long & Sakitt, 1984). The present investigation used the quasi-flicker method to evaluate further the hypothesis that an age difference in the temporal effectiveness of the transient channels would be reflected in a deficit among older observers in detecting offset in gratings of low but not high spatial frequency. Method Participants Twelve young (M = 20.92 yrs, range = 18-24 yrs) and twelve old (A4 = 63.33 yrs, range = 56-72 yrs) adult volunteers participated in the study. There were eight men and four women in each age group. All participants were community residents, and by self-report, in good general and visual health, including freedom from any illnesses or drugs known to impair visual function. All participants possessed at least a high-school level education. Mean years of formal schooling were 19.33 yrs (SD = 1.16 yrs) for the young adults and 13.17 yrs (SD = 2.33 yrs) for the old, a difference that was sta.tistically significant, t (22) = 2.89, p = .009. Mean scores on the vocabulary subtest of the Wechsler Adult Intelligence Scale (WAIS-V) were comparable for the young, 58.92 (SD = 3.68) and old, 54.33 (SD = 5.47), p > .05. Participants were refracted to their best acuity at the test distance (79 cm). Resulting acuity levels were 1.03 minutes of arc (minarc) (SD = .07) for the young and .98 minarc (SD = .07) for the old (20/20 represents resolution of 1.O minarc). Consistent with previous findings (e.g., Birren, Casperson, & Botwinick, 1950; Sloane et al., 1988) mean pupillary diameter at the test luminance (64 cd/m2), measured using a hand-held lab-built pupillometer, was greater among young adults than older ones (6.29 mm, SD = .75 vs 5.21 mm, SD = .81).
Apparatus and Materials The stimuli were photographs of CRT-generated grayscale, vertical sinusoidal gratings of six spatial frequencies (3,1 .O, 2.0,4.0, 8.0, and 12.0 c/d). At the viewing distance of 79 cm the blank fixation field and grating patterns subtended a visual angle of 5” vertically x ’7O horizontally. Grating contrast (maximum luminance minus minimum luminance divided by their sum) was .a. Space-averaged luminance of the gratings, the uniform blank field exposed during fixation and interstimulus intervals (ISIs) and the ambient luminance were all maintained at 64 cd/m2.
63
GRATING CONTINUITY
Gratings were presented using a Gerbrands Model T-3B-1 three-field tachistoscope and G1159 Logic Interface. Refractions were carried out using an American Optical Master Phoropter and Nearpoint Rotochart. Optical corrections were implemented with a R.H. Burton Model TLS trial lens set and frame or lens clip. A Tektronix 516 photometer with a 56523 luminance probe was used to determine luminance/contrast levels.
Subjects were tested in a single session of approximately 60 min. Particpants were refracted to their best acuity at the test distance. If no correction was required, observers wore a lensless trial frame to control for possible discomfort associated with its use. Prior to testing, all participants were adapted for 10 min to the test luminance. Persistence estimates were determined using a staircase method in which participants first fixated the center of the steadily-illuminated homogeneous fixation field. When they were “ready,” participants received a pair of gratings interrupted by the blank interstimulus interval (ISI). During both the initial practice session as well as during the test trials, each grating composing the pair was of the same spatial frequency and was exposed for 100 ms. Grating-pairs rather than multi-flash trains were used avoid problems associated with the aggregation of negative after-images (Georgeson & Turner, 1985) and flicker adaptation (Green, 1981), both of which tend to elevate continuity thresholds (Georgeson & Georgeson, 1985). On descending trials, the IS1 between the grating pairs was decreased in 10 msec steps until the first report by the observer that the grating was “just continuous.” The IS1 was then increased and deceased in 5 msec steps until observers reported the ratings to be either “just discontinuous” or “just continuous,” respectively. After four response reversals, a similar ascending trial was initiated at the same spatial frequency. Pairs of ascending and descending trials were alternated to establish continuity thresholds for each of the six spatial frequencies. The entire process was then repeated. Half of each age by sex group received descending trials followed by ascending trials; half received the reverse order. Order of spatial frequency was randomized with the limitation that all six spatial frequencies were presented once each before any was repeated. The 16 reversals (8 ascending and 8 descending) of IS1 were averaged for each participant to establish a mean continuity threshold for each spatial frequency. After completion of the continuity task, participants received the Vocabulary Subtest of the WAIS. Results It can be seen (Figure 1) that, for both age groups, grating continuity increased monotonically with increasing spatial frequency. The older adults, however, exhibited greater ISIs than the young at the lower spatial frequencies.
-
450
-
T
a E
Y
-1
4 >
E
Design and Procedure
Downloaded by [LMU Muenchen] at 16:59 27 December 2014
n
500
2 a L:
t;;
400-
350-
300-
3
!i2 5 0 200
I 0.5
I 1.0
I 2.0
I 4.0
I
I
E.0 12.0
SPATIAL FREQUENCY ( d d )
FIGURE 1. Temporal continuity thresholds (ISls) as a function of age and spatial frequency. Vertical bars indicate + 1 SE.
These general observations were confirmed in a 2 (Age) x 6 (Grating Frequency) multivariate analysis of variance (MANOVA). MANOVA rather than ANOVA procedures were utilized here because of the sensitivity of the latter to violations of the compound symmetry assumption (Maxwell & Delaney, 1990). Grating spatial frequency yielded a large main effect, rnultivariateF(5,18) = 17.79, p < .001, but age was not significant (p = .303). Of most direct relevance to the present study, the Age x Spatial Frequency interaction was significant, multivariate F (5,18) = 3.53, p = .021. Trend tests indicated that only the linear trend of the Age x Grating Frequency interaction was significant, F (1,22) = 4.81, p = .039; age differences diminished as the grating frequency increased. Further evidence for a spatial frequency-dependent age effect can be seen in the pair-wise comparisons of age differences in continuity at each grating frequency. The continuity thresholds for the old group were significantly higher than for the young at both .5 c/d, t (22) = 2.61, p = .016 and at 1.0 c/d, t (22) = 2.45, p = .023. No other tests approached significance; the probabilities for 2.0,4.0, 8.0, and 12.0 c/d gratings were .26, .44,.89 and . I S , respectively. The significant a priori difference between the age groups in pupil size meant that the illuminance in trolands for the older adults was about 70% that of their younger counterparts, t (22) = 3.37, p = .003. The possibility that the observed pattern of results might be attributable to age differences in retinal luminance was examined using illuminance in trolands as a covariate in pair-wise
KLINE/SCIALFA/LYMAN/SCHIEBER
64
tests of age effects at each spatial frequency. In no case did the outcome of the significance test change. The statistically significant age differences at .5 and 1.0 c/d remained; no other effects were significant.
Downloaded by [LMU Muenchen] at 16:59 27 December 2014
Discussion
The present investigation replicates, and extends to older observers, prior studies showing that, among young observers, the continuity of temporally-interrupted patterns increases directly with their spatial frequency (e.g., Bowling et al., 1979; Long & Sakitt, 1984; Meyer & Maguire, 1977). Such increased temporal “bridging” at higher spatial frequencies has generally been ascribed to increased mediation by sustained channels. The lack of an age difference in grating continuity at the higher spatial frequencies suggests that visual aging has little effect on the temporal resolving properties of the sustained channels. Conversely, the significant age difference in detecting the offset of low spatial frequency gratings suggests a decline in the temporal effectiveness of the transient channels. At the two lowest spatial frequencies, .5 and 1 .O c/d, the older observers reported grating continuity at ISIs more than 50 msec greater than those of their younger counterparts. This result does not appear attributable to age differences in the optic media. The slight difference in acuity at the test distance actually favored the older participants. Also, age differences in optical blur would most affect high not low spatial frequencies. Further, although reduced luminance appears to foster the perceived continuity of gratings in quasi-flicker presentations (Long & Sakitt, 198 l ) , for several reasons, it is unlikely that age differences in retinal luminance due to senile miosis can account for grating continuity differences at low spatial frequencies. First, in terms of age differences in grating visibility, such an attenuation would be more likely to reveal itself at high spatial frequencies. Secondly, an analysis removing the effect of senile miosis by using illuminance in trolands as a covariate had no effect on the age differences observed. Lastly, the small age difference in effective luminance at the level of the pupil in this study was not sufficient to increase grating continuity to the extent that was observed; Long and Sakitt (1981) found that, even at low spatial frequencies, it took about a ten-fold intensity difference within the luminance range of the present study to elevate IS1 by 50 msec. For this reason, it is also unlikely that increased opacity in the ocular media could explain more than a small part of the age difference in continuity thresholds. Although it was not significant, the apparent crossover of the age groups from 8.0 to 12.0 c/d is a potentially interesting one. ISIs of the younger observers increased across the entire spatial frequency range tested; those of the older observers appeared to asymptote at 8.0 c/d. This suggests that the time-constant of the mechanisms that mediate temporal discrimination of 8.0 and 12.0 c/d targets is similar for older but not younger observers. At the least, the good acuity levels of the old subjects and
the high contrast of the gratings used would suggest that the crossover, if meaningful, is unlikely to reflect age differences in spatial resolution. In conclusion, the present data are consistent with prior research showing that the senescent visual syiitem is limited in its ability to detect target offsets (Schieber & Kline, 1982). That this deficit is prominent only for targets of low spatial frequency is consistent with a hypothesized decline with age in the temporal resolving capacity of the transient visual channels. Additional research will be needed, however, to determine why such a decline is more evident on some tasks (Sloane et al., 1988; Sturr et al., 1986, 1987) than others (Sturr et al., 1988). References
Abusamra, L.C., McCoy, L., Schieber, F., & Kline, D.W. (1984, May). Age sensitivity to static and moving gratings: A transient channel loss? Paper presented at the meeting of the Midwestern Psychological Association, Minneapolis, Minnesota. Arundale, K. (1978). An investigation into the variation of human contrast sensitivity with age and ocular pathology. British Journal of Ophthalmology, 152, 21 3-21 5. Birren, J.E., Casperson, R.C., & Botwinick, J . (1950). Age changes in pupil size. Journal of Gerontology, 5, 267-27 1 . Bowling, A., Lovegrove, W., & Mapperson, B. (1 97’9). The effect of spatial frequency and contrast on visual persistence. Perception, 8, 529-539. Breitmeyer, B.G., & Ganz, L. (1976). Implications of siistained and transient channels for theories of visual pattern masking, saccadic suppression, and information processing. Psychological Review, 83, 1-36. Campbell, F.W., & Robson, J.G. (1968). Applications of Fourier analysis to the visibility of gratings. Journal of Physiology, 197, 551-556. Derefeldt, G., Lennerstrand, G., & Lundh, B. (1974). Age variations in normal human contrast sensitivity. Acta Ophthalmologica, 57, 679-690. Enroth-Cugell, C., & Robson, J.G. (1966). The contrast sensitivity of retinal ganglion cells of the cat. Journtd of Physiology, 231, 517-552. Georgeson, M.A., & Georgeson, J.M. (1985). On seeing the temporal gaps between gratings: A criterion problem for the measurement of visible persistence. Vision Research, 25, 1729-1733. Georgeson, M.A., & Turner, R.S.E. (1985). Afterimages of sinusoidal, square-wave and compound gratings. Vision Research, 25, 1709- 1720. Green, M. (1981). Psychophysical relationships among mechanisms sensitive to pattern, motion, and flicker. Vision Research, 21, 97 1-983. Kline, D.W. (1987). Ageing and the spatiotemporal discrimination performance of the visual system. Eye, I, 323-329. Kline, D.W., & Schieber, F. (1981). Visual aging: a tram sient/sustained shift? Perception and Psychophysics,
Downloaded by [LMU Muenchen] at 16:59 27 December 2014
GRATING CONTINUITY
29, 181-182. Kline, D.W., & Schieber, F. (1982). Visual persistence and temporal resolution. In R. Sekuler, D. Kline, & K. Dismukes (Eds.), Aging and human visual function (pp. 231-244). New York: Alan R. Liss. Kline, D.W., Schieber, F., Abusamra, L.C., & Coyne, A.C. (1983). Age and visual channels: Contrast sensitivity and response speed. Journal of Gerontology, 38, 211-216. Kulikowski, J.J., & Tolhurst, D.J. (1973). Psychophysical evidence for sustained and transient detectors in human vision. Journal of Physiology, 232, 149-162. Lennie, P. (1980). Parallel visual pathways: A review. Vision Research, 20, 561-594. Long, G.M., & Gildea, T.J. (1981). Latency for the perceived offset of brief target gratings. Vision Research, 21, 1395-1399. Long, G.M., & Sakitt, B. (1984). Visual persistence from flickered and flashed gratings: Methodological considerations. Bulletin of the Psychonomic Society, 22, 1-4.
Lovegrove, W., & Heddle, M. (1980). Visual persistence as a function of spatial frequency and age. Perception, 9, 529-532. Maxwell, S.E., & Delaney, H.D. (1990). Designing experiments and analyzing data: A model comparison perspective. Belmont, CA: Wadsworth. Meyer, G.E., & Maguire, W. (1977). Spatial frequency and the mediation of short-term visual storage. Science, 198, 524-525. Meyer, G.E.,& Maguire, W. (1981). Effects of spatialfrequency specific adaptation and target duration on visual persistence. Journal of Experimental Psychology: Human Perception and Performance, 7, 15 1- 156. Owsley, C., Sekuler, R., & Siemsen, D. (1983). Contrast
65
sensitivity throughout adulthood. Vision Research, 23, 689-699.
Parker, D.M., & Dutch, S. (1987). Perceptual latency and spatial frequency. Vision Research, 27, 1279-1283. Schieber, F., & Kline, D.W. (1982). Age and the discrimination of visual successiveness. Experimental Aging Research, 8, 159- 161. Scialfa, C.T., Tyrrell, R.A., Gamey, P.M., Deering, L.M., Leibowitz, H.W., & Goebel, C.C. (1988). Age differences in Vistech near contrast sensitivity. American Journal of Ophthalmology and Physiological Optics, 65, 951-956. Singer, W., & Bedworth, N. (1973). Inhibitory interactions between X and Y units in the cat lateral geniculate nucleaus . Brain Research, 49, 29 1-307. Sloane, M.E., Owsley, C., &Alvarez, S.L. (1988). Aging, senile miosis and spatial contrast at low luminance. Vision Research, 28, 123 5 - 1246. Sturr, J.F., Church, K.L., Nuding, S.C., Van Orden, K., & Taub, H.A. (1986). Older observers have attenuated increment thresholds upon transient backgrounds. Journal of Gerontology, 41, 743-747. Sturr, J., Church, K.L., & Taub, H.A. (1985). Early light adaptation in young, middle-aged and older observers. Perception & Psychophysics, 37, 455-458. Sturr, J., Church, K.L., & Taub, H.A. (1988). Temporal summation functions for the detection of sine-wave gratings in young and older adults. Vision Research, 28, 1247-1253. Sturr, J., Van Orden, K., & Taub, H.A. (1987). Selective attenuation in brightness for brief stimuli and at low intensities supports age-related transient channel losses. Experimental Aging Research, 13, 145- 149. Vassilev, A., & Mitov, D. (1976). Perception time and spatial frequency. Vision Research, 16, 89-92.
Experimental Aging Research: An International Journal Devoted to the Scientific Study of the Aging Process Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/uear20
Age differences in the temporal continuity of gratings as a function of their spatial frequency a
a
b
Donald W. Kline , Charles T. Scialfa , Brian J. Lyman & Frank Schieber a
University of Calgary
b
Monell Chemical Senses Center
c
c
Oakland University Published online: 27 Sep 2007.
To cite this article: Donald W. Kline , Charles T. Scialfa , Brian J. Lyman & Frank Schieber (1990) Age differences in the temporal continuity of gratings as a function of their spatial frequency, Experimental Aging Research: An International Journal Devoted to the Scientific Study of the Aging Process, 16:2, 61-65, DOI: 10.1080/07340669008251528 To link to this article: http://dx.doi.org/10.1080/07340669008251528
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http:// www.tandfonline.com/page/terms-and-conditions
61
Experimental Aging Research, Volume 16, Number 2, 1990, ISSN 0734-0664 O1990 Beech Hill Enterprises Inc.
Age Differences in the Temporal Continuity of Gratings as a Function of Their Spatial Frequency DONALD W. KLINEAND CHARLES T. SCIALFA University of Calgary
Downloaded by [LMU Muenchen] at 16:59 27 December 2014
BRIANJ. LYMAN Monell Chemical Senses Center
FRANKSCHIEBER Oakland University
This study compared young and elderly observers on the continuity of sinusoidal grating-pairs as a function of interstimulus interval (1st) and spatial frequency (3,1.0, 2.0, 4.0, 8.0, and 12.0 c/deg). Consistent with prior research, the maximum IS1 over which pattern continuity was maintained increased with spatial frequency. In addition, among older observers, grating continuity occurred at significantly longer ISI’s at the two lowest spatial frequencies; no age difference was observed at the higher spatial frequencies. These results could not be attributed to an age difference in retinal illumination associated with pupillary miosis. However, they do indicate an age-related decline in detecting visual offset and are consistent with the hypothesis of a decline in the effectiveness of the transient visual channels.
0
ne of the most frequently observed changes in the senescent visual system is a decline in its resolution of temporally-contiguous events (cf. Kline, 1984; Kline & Schieber, 1982). It has been proposed that the temporal sluggishness of the senescent visual system is due to a greater decline with age in the effectiveness of the transient as opposed to the sustained channels (Kline & Schieber, 1981). The present study evaluated the degree to which age differences in the perceived continuity of interrupted sinusoidal gratings of varied spatial frequency were consistent with a hypothesis of disjunctive visual channel aging. The “channels” or subdivisions that compose the visual system appear to differ in their response characteristics and to serve different visual functions (e.g., Campbell & Robson, 1968; Kulikowski & Tolhurst, 1973; Lennie, 1980; Vassilev & Mitov, 1976). Based on physiological evidence of two distinct classes of ganglion cells (i.e., X and Y cells) (Enroth-Cugell& Robson, 1966), these channels were categorized into two general types: “sustained” and “transient.” Although the sustained and transient channels are no longer thought to reflect directly the properties of “X”and “Y”ganglion cells respectively, the two channel types can be distinguished in terms of their functional characteristics. Sustained channels are sensitive
to high spatial frequencies, respond in a slow and persistent manner and are characterized by an extended temporal integration period. As a result, they are well-suited to the perception of form. Conversely, the transient channels, which are sensitive to low spatial frequency stimuli, respond quickly and briefly to stimulus change. In addition, activation of the transient channels appears to inhibit persisting activity in the sustained channels (Breitmeyer & Ganz, 1976; Singer & Bedworth, 1973). Most studies of age differences on the contrast sensitivity function (CSF) report deficits in sensitivity, not at low spatial frequencies as would be suggested by an impairment of transient channels, but at the higher spatial frequencies to which the sustained channels respond (Arundale, 1978; Derefeldt, Lennerstrand, & Lundh, 1979; Kline, Schieber, Abusamra, & Coyne, 1983; Owsley, Sekuler, & Siemsen, 1983; Scialfa, Tyrrell, Garvey, Deering, Leibowitz, & Goebel, 1988). Such static tests, however, lack a temporally-modulated component and consequently, are unlikely to tap the transient channels effectively. When the display is temporally modulated, age differences do become apparent at low spatial frequencies. It has been shown, for example, that motion enhancement of contrast sensitivity to low spatial frequency gratings is greatly diminished in older adults, especially
This research was supported by a grant from the Alberta Senior Citizens Secretariat (No. 69-4922) to the first author and a University of Calgary grant (No. 69-2206) to the second author. Correspondence and reprint requests should be addressed to Donald W.Kline, Ph.D., Department of Psychology, The University of Calgary, Calgary, AB T2N 1N4, CANADA
KLINE/SCIALFA/LYMAN/SCHIEBER
Downloaded by [LMU Muenchen] at 16:59 27 December 2014
62
at fast movement rates (Abusamra, McCoy, Schieber, & Kline, 1984; Owsley et al., 1983). Relatedly, Sloane, Owsley, and Alvarez (1988) found a small but significant age deficit in the CSF at the lowest spatial frequency tested ( 3c/d), a result that they suggested might be due either to the relatively large (6”) target used and/or to the presentation of gratings in counterphase flicker. Sturr, Church, and Taub (1985) observed that elderly observers showed much slower early light adaptation functions than young and middle-aged observers, a loss they suggested was consistent with a transient channel decline. In addition, Sturr and his colleagues have reported older observers to have attenuated brightness increment thresholds on transient backgrounds at both threshold (Sturr, Church, Nuding, Van Orden, & Taub, 1986) and suprathreshold levels (Sturr, Van Orden, & Taub, 1987). The authors held these results to be consistent with a decline in transient channel functioning. More recently, however, when Sturr, Church, and Taub (1988) studied age differences in temporal contrast summation functions of low (.416 c/d) and high spatial frequency (7.5 c/d) gratings, they found no support for the extended temporal summation that might be the result of a shift from transient to greater sustained visual functioning. Nor did they see an age-related increase in the critical duration for summation to contrast threshold for a low spatial frequency grating. The authors concluded that there was no evidence in their summation functions of an age-related sensitivity shift from transient to sustained channels, nor for response slowing within a channel. The authors suggested some reasons for the difference between their results and those of previous research. Unlike the earlier studies that examined the temporal resolution of suprathreshold stimuli, Sturr et al. compared young and old observers on temporal contrast summation at threshold. The authors also noted that many of the earlier studies used “cerebral” rather than retinal tasks. This implies no age deficit in temporal discrimination at the retina, even though one may be evident at higher stages of visual processing. Even this possibility deserves examination. Although the difference was not significant, the older observes required higher mean contrast levels than the young to reach threshold for the low spatial frequency grating at all six stimulus durations tested (Experiments 1 and 2). It may have also been the case that the older observers in the Sturr et al. study were somewhat more visually-select than those in other studies; when they were optically corrected for the test distance (Experiment 3), the typical age-related reduction in contrast sensitivity at high spatial frequencies (e.g., Kline et al., 1983; Owsley et al., 1983) was not observed. Meyer and Maguire (1977) defined the “persistence” of high-contrast square-wave gratings as the maximum blank interstimulus interval (ISI) with which the gratings could be cyclically interrupted and still be reported as continuous. They found that persistence of the gratings inceased monotonically with their spatial frequency. Subsequent studies using this and similar methods (e.g., Bowling, Lovegrove, & Mapperson, 1979; Long & Sakitt,
1984; Lovegrove & Heddle, 1980; Meyer & Maguire, 1981; Parker & Dutch, 1987) have all found that per-
sistence, continuity or perceptual latency increases with spatial frequency, a result usually ascribed to a spatial frequency-induced shift from transient to sustained channel functioning. It now appears that these “quasi-flicker” assessments of grating continuity better measure cletection of target offset than the total persistence of a filding stimulus trace (Long & Gildea, 1981; Long & Sakitt, 1984). The present investigation used the quasi-flicker method to evaluate further the hypothesis that an age difference in the temporal effectiveness of the transient channels would be reflected in a deficit among older observers in detecting offset in gratings of low but not high spatial frequency. Method Participants Twelve young (M = 20.92 yrs, range = 18-24 yrs) and twelve old (A4 = 63.33 yrs, range = 56-72 yrs) adult volunteers participated in the study. There were eight men and four women in each age group. All participants were community residents, and by self-report, in good general and visual health, including freedom from any illnesses or drugs known to impair visual function. All participants possessed at least a high-school level education. Mean years of formal schooling were 19.33 yrs (SD = 1.16 yrs) for the young adults and 13.17 yrs (SD = 2.33 yrs) for the old, a difference that was sta.tistically significant, t (22) = 2.89, p = .009. Mean scores on the vocabulary subtest of the Wechsler Adult Intelligence Scale (WAIS-V) were comparable for the young, 58.92 (SD = 3.68) and old, 54.33 (SD = 5.47), p > .05. Participants were refracted to their best acuity at the test distance (79 cm). Resulting acuity levels were 1.03 minutes of arc (minarc) (SD = .07) for the young and .98 minarc (SD = .07) for the old (20/20 represents resolution of 1.O minarc). Consistent with previous findings (e.g., Birren, Casperson, & Botwinick, 1950; Sloane et al., 1988) mean pupillary diameter at the test luminance (64 cd/m2), measured using a hand-held lab-built pupillometer, was greater among young adults than older ones (6.29 mm, SD = .75 vs 5.21 mm, SD = .81).
Apparatus and Materials The stimuli were photographs of CRT-generated grayscale, vertical sinusoidal gratings of six spatial frequencies (3,1 .O, 2.0,4.0, 8.0, and 12.0 c/d). At the viewing distance of 79 cm the blank fixation field and grating patterns subtended a visual angle of 5” vertically x ’7O horizontally. Grating contrast (maximum luminance minus minimum luminance divided by their sum) was .a. Space-averaged luminance of the gratings, the uniform blank field exposed during fixation and interstimulus intervals (ISIs) and the ambient luminance were all maintained at 64 cd/m2.
63
GRATING CONTINUITY
Gratings were presented using a Gerbrands Model T-3B-1 three-field tachistoscope and G1159 Logic Interface. Refractions were carried out using an American Optical Master Phoropter and Nearpoint Rotochart. Optical corrections were implemented with a R.H. Burton Model TLS trial lens set and frame or lens clip. A Tektronix 516 photometer with a 56523 luminance probe was used to determine luminance/contrast levels.
Subjects were tested in a single session of approximately 60 min. Particpants were refracted to their best acuity at the test distance. If no correction was required, observers wore a lensless trial frame to control for possible discomfort associated with its use. Prior to testing, all participants were adapted for 10 min to the test luminance. Persistence estimates were determined using a staircase method in which participants first fixated the center of the steadily-illuminated homogeneous fixation field. When they were “ready,” participants received a pair of gratings interrupted by the blank interstimulus interval (ISI). During both the initial practice session as well as during the test trials, each grating composing the pair was of the same spatial frequency and was exposed for 100 ms. Grating-pairs rather than multi-flash trains were used avoid problems associated with the aggregation of negative after-images (Georgeson & Turner, 1985) and flicker adaptation (Green, 1981), both of which tend to elevate continuity thresholds (Georgeson & Georgeson, 1985). On descending trials, the IS1 between the grating pairs was decreased in 10 msec steps until the first report by the observer that the grating was “just continuous.” The IS1 was then increased and deceased in 5 msec steps until observers reported the ratings to be either “just discontinuous” or “just continuous,” respectively. After four response reversals, a similar ascending trial was initiated at the same spatial frequency. Pairs of ascending and descending trials were alternated to establish continuity thresholds for each of the six spatial frequencies. The entire process was then repeated. Half of each age by sex group received descending trials followed by ascending trials; half received the reverse order. Order of spatial frequency was randomized with the limitation that all six spatial frequencies were presented once each before any was repeated. The 16 reversals (8 ascending and 8 descending) of IS1 were averaged for each participant to establish a mean continuity threshold for each spatial frequency. After completion of the continuity task, participants received the Vocabulary Subtest of the WAIS. Results It can be seen (Figure 1) that, for both age groups, grating continuity increased monotonically with increasing spatial frequency. The older adults, however, exhibited greater ISIs than the young at the lower spatial frequencies.
-
450
-
T
a E
Y
-1
4 >
E
Design and Procedure
Downloaded by [LMU Muenchen] at 16:59 27 December 2014
n
500
2 a L:
t;;
400-
350-
300-
3
!i2 5 0 200
I 0.5
I 1.0
I 2.0
I 4.0
I
I
E.0 12.0
SPATIAL FREQUENCY ( d d )
FIGURE 1. Temporal continuity thresholds (ISls) as a function of age and spatial frequency. Vertical bars indicate + 1 SE.
These general observations were confirmed in a 2 (Age) x 6 (Grating Frequency) multivariate analysis of variance (MANOVA). MANOVA rather than ANOVA procedures were utilized here because of the sensitivity of the latter to violations of the compound symmetry assumption (Maxwell & Delaney, 1990). Grating spatial frequency yielded a large main effect, rnultivariateF(5,18) = 17.79, p < .001, but age was not significant (p = .303). Of most direct relevance to the present study, the Age x Spatial Frequency interaction was significant, multivariate F (5,18) = 3.53, p = .021. Trend tests indicated that only the linear trend of the Age x Grating Frequency interaction was significant, F (1,22) = 4.81, p = .039; age differences diminished as the grating frequency increased. Further evidence for a spatial frequency-dependent age effect can be seen in the pair-wise comparisons of age differences in continuity at each grating frequency. The continuity thresholds for the old group were significantly higher than for the young at both .5 c/d, t (22) = 2.61, p = .016 and at 1.0 c/d, t (22) = 2.45, p = .023. No other tests approached significance; the probabilities for 2.0,4.0, 8.0, and 12.0 c/d gratings were .26, .44,.89 and . I S , respectively. The significant a priori difference between the age groups in pupil size meant that the illuminance in trolands for the older adults was about 70% that of their younger counterparts, t (22) = 3.37, p = .003. The possibility that the observed pattern of results might be attributable to age differences in retinal luminance was examined using illuminance in trolands as a covariate in pair-wise
KLINE/SCIALFA/LYMAN/SCHIEBER
64
tests of age effects at each spatial frequency. In no case did the outcome of the significance test change. The statistically significant age differences at .5 and 1.0 c/d remained; no other effects were significant.
Downloaded by [LMU Muenchen] at 16:59 27 December 2014
Discussion
The present investigation replicates, and extends to older observers, prior studies showing that, among young observers, the continuity of temporally-interrupted patterns increases directly with their spatial frequency (e.g., Bowling et al., 1979; Long & Sakitt, 1984; Meyer & Maguire, 1977). Such increased temporal “bridging” at higher spatial frequencies has generally been ascribed to increased mediation by sustained channels. The lack of an age difference in grating continuity at the higher spatial frequencies suggests that visual aging has little effect on the temporal resolving properties of the sustained channels. Conversely, the significant age difference in detecting the offset of low spatial frequency gratings suggests a decline in the temporal effectiveness of the transient channels. At the two lowest spatial frequencies, .5 and 1 .O c/d, the older observers reported grating continuity at ISIs more than 50 msec greater than those of their younger counterparts. This result does not appear attributable to age differences in the optic media. The slight difference in acuity at the test distance actually favored the older participants. Also, age differences in optical blur would most affect high not low spatial frequencies. Further, although reduced luminance appears to foster the perceived continuity of gratings in quasi-flicker presentations (Long & Sakitt, 198 l ) , for several reasons, it is unlikely that age differences in retinal luminance due to senile miosis can account for grating continuity differences at low spatial frequencies. First, in terms of age differences in grating visibility, such an attenuation would be more likely to reveal itself at high spatial frequencies. Secondly, an analysis removing the effect of senile miosis by using illuminance in trolands as a covariate had no effect on the age differences observed. Lastly, the small age difference in effective luminance at the level of the pupil in this study was not sufficient to increase grating continuity to the extent that was observed; Long and Sakitt (1981) found that, even at low spatial frequencies, it took about a ten-fold intensity difference within the luminance range of the present study to elevate IS1 by 50 msec. For this reason, it is also unlikely that increased opacity in the ocular media could explain more than a small part of the age difference in continuity thresholds. Although it was not significant, the apparent crossover of the age groups from 8.0 to 12.0 c/d is a potentially interesting one. ISIs of the younger observers increased across the entire spatial frequency range tested; those of the older observers appeared to asymptote at 8.0 c/d. This suggests that the time-constant of the mechanisms that mediate temporal discrimination of 8.0 and 12.0 c/d targets is similar for older but not younger observers. At the least, the good acuity levels of the old subjects and
the high contrast of the gratings used would suggest that the crossover, if meaningful, is unlikely to reflect age differences in spatial resolution. In conclusion, the present data are consistent with prior research showing that the senescent visual syiitem is limited in its ability to detect target offsets (Schieber & Kline, 1982). That this deficit is prominent only for targets of low spatial frequency is consistent with a hypothesized decline with age in the temporal resolving capacity of the transient visual channels. Additional research will be needed, however, to determine why such a decline is more evident on some tasks (Sloane et al., 1988; Sturr et al., 1986, 1987) than others (Sturr et al., 1988). References
Abusamra, L.C., McCoy, L., Schieber, F., & Kline, D.W. (1984, May). Age sensitivity to static and moving gratings: A transient channel loss? Paper presented at the meeting of the Midwestern Psychological Association, Minneapolis, Minnesota. Arundale, K. (1978). An investigation into the variation of human contrast sensitivity with age and ocular pathology. British Journal of Ophthalmology, 152, 21 3-21 5. Birren, J.E., Casperson, R.C., & Botwinick, J . (1950). Age changes in pupil size. Journal of Gerontology, 5, 267-27 1 . Bowling, A., Lovegrove, W., & Mapperson, B. (1 97’9). The effect of spatial frequency and contrast on visual persistence. Perception, 8, 529-539. Breitmeyer, B.G., & Ganz, L. (1976). Implications of siistained and transient channels for theories of visual pattern masking, saccadic suppression, and information processing. Psychological Review, 83, 1-36. Campbell, F.W., & Robson, J.G. (1968). Applications of Fourier analysis to the visibility of gratings. Journal of Physiology, 197, 551-556. Derefeldt, G., Lennerstrand, G., & Lundh, B. (1974). Age variations in normal human contrast sensitivity. Acta Ophthalmologica, 57, 679-690. Enroth-Cugell, C., & Robson, J.G. (1966). The contrast sensitivity of retinal ganglion cells of the cat. Journtd of Physiology, 231, 517-552. Georgeson, M.A., & Georgeson, J.M. (1985). On seeing the temporal gaps between gratings: A criterion problem for the measurement of visible persistence. Vision Research, 25, 1729-1733. Georgeson, M.A., & Turner, R.S.E. (1985). Afterimages of sinusoidal, square-wave and compound gratings. Vision Research, 25, 1709- 1720. Green, M. (1981). Psychophysical relationships among mechanisms sensitive to pattern, motion, and flicker. Vision Research, 21, 97 1-983. Kline, D.W. (1987). Ageing and the spatiotemporal discrimination performance of the visual system. Eye, I, 323-329. Kline, D.W., & Schieber, F. (1981). Visual aging: a tram sient/sustained shift? Perception and Psychophysics,
Downloaded by [LMU Muenchen] at 16:59 27 December 2014
GRATING CONTINUITY
29, 181-182. Kline, D.W., & Schieber, F. (1982). Visual persistence and temporal resolution. In R. Sekuler, D. Kline, & K. Dismukes (Eds.), Aging and human visual function (pp. 231-244). New York: Alan R. Liss. Kline, D.W., Schieber, F., Abusamra, L.C., & Coyne, A.C. (1983). Age and visual channels: Contrast sensitivity and response speed. Journal of Gerontology, 38, 211-216. Kulikowski, J.J., & Tolhurst, D.J. (1973). Psychophysical evidence for sustained and transient detectors in human vision. Journal of Physiology, 232, 149-162. Lennie, P. (1980). Parallel visual pathways: A review. Vision Research, 20, 561-594. Long, G.M., & Gildea, T.J. (1981). Latency for the perceived offset of brief target gratings. Vision Research, 21, 1395-1399. Long, G.M., & Sakitt, B. (1984). Visual persistence from flickered and flashed gratings: Methodological considerations. Bulletin of the Psychonomic Society, 22, 1-4.
Lovegrove, W., & Heddle, M. (1980). Visual persistence as a function of spatial frequency and age. Perception, 9, 529-532. Maxwell, S.E., & Delaney, H.D. (1990). Designing experiments and analyzing data: A model comparison perspective. Belmont, CA: Wadsworth. Meyer, G.E., & Maguire, W. (1977). Spatial frequency and the mediation of short-term visual storage. Science, 198, 524-525. Meyer, G.E.,& Maguire, W. (1981). Effects of spatialfrequency specific adaptation and target duration on visual persistence. Journal of Experimental Psychology: Human Perception and Performance, 7, 15 1- 156. Owsley, C., Sekuler, R., & Siemsen, D. (1983). Contrast
65
sensitivity throughout adulthood. Vision Research, 23, 689-699.
Parker, D.M., & Dutch, S. (1987). Perceptual latency and spatial frequency. Vision Research, 27, 1279-1283. Schieber, F., & Kline, D.W. (1982). Age and the discrimination of visual successiveness. Experimental Aging Research, 8, 159- 161. Scialfa, C.T., Tyrrell, R.A., Gamey, P.M., Deering, L.M., Leibowitz, H.W., & Goebel, C.C. (1988). Age differences in Vistech near contrast sensitivity. American Journal of Ophthalmology and Physiological Optics, 65, 951-956. Singer, W., & Bedworth, N. (1973). Inhibitory interactions between X and Y units in the cat lateral geniculate nucleaus . Brain Research, 49, 29 1-307. Sloane, M.E., Owsley, C., &Alvarez, S.L. (1988). Aging, senile miosis and spatial contrast at low luminance. Vision Research, 28, 123 5 - 1246. Sturr, J.F., Church, K.L., Nuding, S.C., Van Orden, K., & Taub, H.A. (1986). Older observers have attenuated increment thresholds upon transient backgrounds. Journal of Gerontology, 41, 743-747. Sturr, J., Church, K.L., & Taub, H.A. (1985). Early light adaptation in young, middle-aged and older observers. Perception & Psychophysics, 37, 455-458. Sturr, J., Church, K.L., & Taub, H.A. (1988). Temporal summation functions for the detection of sine-wave gratings in young and older adults. Vision Research, 28, 1247-1253. Sturr, J., Van Orden, K., & Taub, H.A. (1987). Selective attenuation in brightness for brief stimuli and at low intensities supports age-related transient channel losses. Experimental Aging Research, 13, 145- 149. Vassilev, A., & Mitov, D. (1976). Perception time and spatial frequency. Vision Research, 16, 89-92.
