Perceptualand Motor Skills, 1991, 72, 820-822. O Perceptual and Motor Skills 1991
LATENCY OF AUDITORY EVENT-RELATED POTENTIAL P 3 CORRELATES W I T H FORWARD D I G I T SPAN IN AN ALASKAN SUBARCTIC SAMPLE ' ANITA M. BUSH AND CHARLES R. GEIST University of Alaska-Fairbanks SCOTT EMERY Fairbanks Neurologic and Psycbiahic Clinic Summary.-16 normal women (ages 25 to 80 years) who could remember more numbers on the Wechsler Adult Intelligence Scale Forward Digit Span subtest had significantly longer mean latency for the auditory event-related potential P3 waveform than those persons who could remember fewer numbers.
A digit-repetition task, such as the Digit Span subtest of the Wechsler Adult Intelligence Scale (WAIS), is used as a quantifiable measure of a person's basic level of attention (Strub & Black, 1989). Similarly, the P3 component of the event-related potential, ERP, appears on a person's electroencephalogram (EEG) when that person is attending to a stimulus during an attentional performance task. This P3 component of the event-related potential, when elicited by auditory stimuli in an oddball detection task, has been recommended for use as an objective test of organically determined dementia (Goodin, Squires, & Starr, 1978; Pfefferbaum, Horvath, Roth, & Kopell, 1979). Polich, Howard, and Starr (1983) tested 96 neurologically normal subjects (men and women, ages 50 to 87 years) using both the WAIS Digit Span subtest and the auditory event-related potential (AERP). The results suggested that the latency of P3 is related to memory capacity in normal subjects, since relatively short latencies were obtained from those subjects who could remember larger numbers of digits. Three elements of that study confound interpretation of the data. First, P3 latency has been reported to vary with age (Brown, Marsh, & LaRue, 1983; Pfefferbaum, Ford, Roth, & Kopell, 1980). Second, Picton, Stuss, Champagne, and Nelson (1984) reported gender-related differences in P3 latency of the AERP. Third, a Norwegian study (Anderson, Chambers, Myhre, Nicholson, & Stone, 1984) conducted at 69ON latitude reported changes in the electroencephalogram related to season. I t should also be mentioned, as Polich, et al. (1983) do, that their subjects had an over-all
'Address correspondence to C. R. Geist, Department of Behavioral Sciences and Human Services, University of Alaska-Fairbanks, Fairbanks, Alaska 99775-0900.
LATENCY P3 CORRELATES OF DIGIT SPAN
82 1
adult mean Digit Span score significantly larger than the normative value typically observed. I n light of these considerations, in the present study the correlation between AERP P3 latency and forward Digit Span was estimated. Subjects were 16 women, ages 25 to 8 1 years (mean age = 35.5 yr.), neurologically normal, residents of the Alaskan subarctic (64.5 1°N, 147.73 W). The women were uncompensated volunteers, and each was naive to the ERP auditory oddball detection task on the first trial. Each woman was tested twice, and both trials were used in the subsequent analysis. A forward Digit Span test was conducted in the customary manner (Strub & Black, 1989, pp. 57-58). Presentation of digits was discontinued when the subject failed to repeat the sequence correctly. The typical person of average intelligence can repeat five to seven digits without difficulty (Strub & Black, 1989, pp. 57-58). The auditory event-related ~ o t e n t i a lwas recorded using an oddball detection (Bush & Emery, 1987). The subject's task was to maintain a silent running count of "higher-pitched" tones (the oddball, p = .15) counted from amid a stream of "lower-pitched" tones presented at the rate of l/sec. The 16 women had a forward Digit Span of four to eight digits (M = 6.6, S D = 1.04, SEM = 0.185). The latency of P3 in these women ranged from 265 to 485 msec. (M = 325.78, SD = 39.54, SEM = 6.99). A least squares regression, where Y is P3 latency in milliseconds and X is the forward Digit Span, showed Y = 1.49X + 3 15.9, with an Y,,,,* = 0.0% (t,, = 6.85, p < .025) and a Pearson product-moment correlation of 0.039. These results are sirmlar to the positive correlation reported by Brown, Marsh, and LaRue (1982) for 15 elderly persons, ages 50 to 80 years (unreported gender mix). The results contradict the weak negative correlation described by Hansch, Syndulko, Cohen, Goldberg, Potvin, and Tourtellotte (1982) for 20 elderly persons (unreported gender mix). The results are also contradictory of the stronger negative correlation reported by Polich, et al. (1983), using men and women, from more southern latitudes. These results show that subjects who could remember a greater number of digits had significantly longer P3 latencies than those subjects who could remember fewer digits. This goes against the currently accepted neuropsychological view and raises the question as t.0 whether the P3 latency can be correlated with short-term memory behavior. If the latency of the auditory P3 ERP does assess variations of memory ability in cognitively normal subjects, as Polich, et al. (1983) and others suggest, then more careful control and reporting of the age and gender variables seems needed. Other factors, such as seasonal photoperiod changes, might also be examined for their contributions to normal ERP variability.
822
A. M. BUSH, ETAL.
REFERENCES H., CHAMBERS, M. C., MYHKE,G., NICHOLSON, A,, & STONE,B. M. (1984) Sleep ANDERSON, of shiftworkers withn the Arctic Circle. Auiation, Space and Environrnenful Medicine, 55, 1026-1030. W., MARSH,J., & LARUE,A. (1982) Cognitive performance and P300 latency correlaBROWN, tion in older normal adults. Psychophysiology, 19, 309. (Abstract) BROWN, W., MARSH, J . , & LARUE,A. (1983) Exponential electrophysiological aging: P3OO latency. Electroencephalography and Clinical Neurophysiology, 55, 277-285. BUSH, A., & EMERY,S. (1987) P300 AERP: objective measurement of attention4 fatigue in nurses working eight and twelve hour shifts. Heart & Lung: The Journal of Critical Care, 16, 337. (Abstract) Gooom, D., SQUIRES,K., & STAKR,A. (1978) Long-latency event-related components of the auditory evoked potential in dementia. Brain, 101, 635-648. HANSCH, E. D., SYNDLILKO, K., COHEN,N., GOLDBERG, Z. I., POTVIN,A. R., & TO~TELLOTTE, W W (1982) Cognition in Parkinson Disease: an event-related potential perspective. Annals of Neurology, 11, 599-606. PFEFFERBAUM. A,, FORD,J. M., Ron-I, W. T.,& KOPELL,B. S. (1980) Age-related changes in auhrory event-related potentials. Electroencephalography and Clinical Neurophysiology, 49, 266-276. PFEFFEKBAUM, A,, HORVATH, T., ROTH, W., & KOPELL,B. (1979) Event-related potential changes in chronic alcoholics. ElechoencephalograpLy and Clinical Neurophysiology, 47, 637-647. PICTON,T. W., STUSS,D. T., CHAMPAGNE, S. C., & NELSON,R. F. (1984) The effects of age on human event-related potentials. Psychophysiology, 21, 312-325. POLICH,J., HOWARD, L., & STARR, A. (1983) P3OO latency correlates with digit span. Rychopbysiology, 20, 665-669. STRID, R. L., & BLACK,F. W. (1989) Neurobehavioral disorders: a clinical approach. Philadelphia, PA: F. A. Davis Co.
Accepted ApriL 18, 197 I
LATENCY OF AUDITORY EVENT-RELATED POTENTIAL P 3 CORRELATES W I T H FORWARD D I G I T SPAN IN AN ALASKAN SUBARCTIC SAMPLE ' ANITA M. BUSH AND CHARLES R. GEIST University of Alaska-Fairbanks SCOTT EMERY Fairbanks Neurologic and Psycbiahic Clinic Summary.-16 normal women (ages 25 to 80 years) who could remember more numbers on the Wechsler Adult Intelligence Scale Forward Digit Span subtest had significantly longer mean latency for the auditory event-related potential P3 waveform than those persons who could remember fewer numbers.
A digit-repetition task, such as the Digit Span subtest of the Wechsler Adult Intelligence Scale (WAIS), is used as a quantifiable measure of a person's basic level of attention (Strub & Black, 1989). Similarly, the P3 component of the event-related potential, ERP, appears on a person's electroencephalogram (EEG) when that person is attending to a stimulus during an attentional performance task. This P3 component of the event-related potential, when elicited by auditory stimuli in an oddball detection task, has been recommended for use as an objective test of organically determined dementia (Goodin, Squires, & Starr, 1978; Pfefferbaum, Horvath, Roth, & Kopell, 1979). Polich, Howard, and Starr (1983) tested 96 neurologically normal subjects (men and women, ages 50 to 87 years) using both the WAIS Digit Span subtest and the auditory event-related potential (AERP). The results suggested that the latency of P3 is related to memory capacity in normal subjects, since relatively short latencies were obtained from those subjects who could remember larger numbers of digits. Three elements of that study confound interpretation of the data. First, P3 latency has been reported to vary with age (Brown, Marsh, & LaRue, 1983; Pfefferbaum, Ford, Roth, & Kopell, 1980). Second, Picton, Stuss, Champagne, and Nelson (1984) reported gender-related differences in P3 latency of the AERP. Third, a Norwegian study (Anderson, Chambers, Myhre, Nicholson, & Stone, 1984) conducted at 69ON latitude reported changes in the electroencephalogram related to season. I t should also be mentioned, as Polich, et al. (1983) do, that their subjects had an over-all
'Address correspondence to C. R. Geist, Department of Behavioral Sciences and Human Services, University of Alaska-Fairbanks, Fairbanks, Alaska 99775-0900.
LATENCY P3 CORRELATES OF DIGIT SPAN
82 1
adult mean Digit Span score significantly larger than the normative value typically observed. I n light of these considerations, in the present study the correlation between AERP P3 latency and forward Digit Span was estimated. Subjects were 16 women, ages 25 to 8 1 years (mean age = 35.5 yr.), neurologically normal, residents of the Alaskan subarctic (64.5 1°N, 147.73 W). The women were uncompensated volunteers, and each was naive to the ERP auditory oddball detection task on the first trial. Each woman was tested twice, and both trials were used in the subsequent analysis. A forward Digit Span test was conducted in the customary manner (Strub & Black, 1989, pp. 57-58). Presentation of digits was discontinued when the subject failed to repeat the sequence correctly. The typical person of average intelligence can repeat five to seven digits without difficulty (Strub & Black, 1989, pp. 57-58). The auditory event-related ~ o t e n t i a lwas recorded using an oddball detection (Bush & Emery, 1987). The subject's task was to maintain a silent running count of "higher-pitched" tones (the oddball, p = .15) counted from amid a stream of "lower-pitched" tones presented at the rate of l/sec. The 16 women had a forward Digit Span of four to eight digits (M = 6.6, S D = 1.04, SEM = 0.185). The latency of P3 in these women ranged from 265 to 485 msec. (M = 325.78, SD = 39.54, SEM = 6.99). A least squares regression, where Y is P3 latency in milliseconds and X is the forward Digit Span, showed Y = 1.49X + 3 15.9, with an Y,,,,* = 0.0% (t,, = 6.85, p < .025) and a Pearson product-moment correlation of 0.039. These results are sirmlar to the positive correlation reported by Brown, Marsh, and LaRue (1982) for 15 elderly persons, ages 50 to 80 years (unreported gender mix). The results contradict the weak negative correlation described by Hansch, Syndulko, Cohen, Goldberg, Potvin, and Tourtellotte (1982) for 20 elderly persons (unreported gender mix). The results are also contradictory of the stronger negative correlation reported by Polich, et al. (1983), using men and women, from more southern latitudes. These results show that subjects who could remember a greater number of digits had significantly longer P3 latencies than those subjects who could remember fewer digits. This goes against the currently accepted neuropsychological view and raises the question as t.0 whether the P3 latency can be correlated with short-term memory behavior. If the latency of the auditory P3 ERP does assess variations of memory ability in cognitively normal subjects, as Polich, et al. (1983) and others suggest, then more careful control and reporting of the age and gender variables seems needed. Other factors, such as seasonal photoperiod changes, might also be examined for their contributions to normal ERP variability.
822
A. M. BUSH, ETAL.
REFERENCES H., CHAMBERS, M. C., MYHKE,G., NICHOLSON, A,, & STONE,B. M. (1984) Sleep ANDERSON, of shiftworkers withn the Arctic Circle. Auiation, Space and Environrnenful Medicine, 55, 1026-1030. W., MARSH,J., & LARUE,A. (1982) Cognitive performance and P300 latency correlaBROWN, tion in older normal adults. Psychophysiology, 19, 309. (Abstract) BROWN, W., MARSH, J . , & LARUE,A. (1983) Exponential electrophysiological aging: P3OO latency. Electroencephalography and Clinical Neurophysiology, 55, 277-285. BUSH, A., & EMERY,S. (1987) P300 AERP: objective measurement of attention4 fatigue in nurses working eight and twelve hour shifts. Heart & Lung: The Journal of Critical Care, 16, 337. (Abstract) Gooom, D., SQUIRES,K., & STAKR,A. (1978) Long-latency event-related components of the auditory evoked potential in dementia. Brain, 101, 635-648. HANSCH, E. D., SYNDLILKO, K., COHEN,N., GOLDBERG, Z. I., POTVIN,A. R., & TO~TELLOTTE, W W (1982) Cognition in Parkinson Disease: an event-related potential perspective. Annals of Neurology, 11, 599-606. PFEFFERBAUM. A,, FORD,J. M., Ron-I, W. T.,& KOPELL,B. S. (1980) Age-related changes in auhrory event-related potentials. Electroencephalography and Clinical Neurophysiology, 49, 266-276. PFEFFEKBAUM, A,, HORVATH, T., ROTH, W., & KOPELL,B. (1979) Event-related potential changes in chronic alcoholics. ElechoencephalograpLy and Clinical Neurophysiology, 47, 637-647. PICTON,T. W., STUSS,D. T., CHAMPAGNE, S. C., & NELSON,R. F. (1984) The effects of age on human event-related potentials. Psychophysiology, 21, 312-325. POLICH,J., HOWARD, L., & STARR, A. (1983) P3OO latency correlates with digit span. Rychopbysiology, 20, 665-669. STRID, R. L., & BLACK,F. W. (1989) Neurobehavioral disorders: a clinical approach. Philadelphia, PA: F. A. Davis Co.
Accepted ApriL 18, 197 I
