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Biomedical subjects

W T Roth

Publications and source records attributed to W T Roth.

At least 91 records · Page 5Linked to original sources
PubMed1980

Age differences in P3-reaction time associations.

Eight healthy old and 12 healthy young women had event-related potentials (ERPs) recorded during the performance of a memory retrieval task. For each subject the single trial data recorded at Pz were analyzed using Woody's adaptive filter technique. The old subjects differed from the young in several respects: P3 amplitude at Pz was smaller, P3 latency and reaction time (RT) were greater, the relationship between P3 latency and RT was considerably altered. The adaptive filter increased the amplitude of P3 but the age-related amplitude difference persisted, suggesting that this difference is not due to increased latency variability with age. The old subjects had lower single trial P3-RT correlations and longer elapsed time from P3 peak to the response than did the young subjects. Both groups had greater RTs for outset items ('negative' responses) than for inset items ('positive' responses). For the young subjects P3 latency was also greater for the outset compared to the inset items but the difference was not found for the old subjects. Thus, the relationship between P3 latency and RT is altered in the aged--P3 and RT are less tightly coupled than in the young.

Adult↗
PubMed1980

Age-related changes in auditory event-related potentials.

Twelve elderly and 12 young women were subjects in a reaction-time task designed to elicit middle and late event-related potentials (ERP). The aged subjects differed from the young in respect to the later occurring ERP components: P2 was larger and later; P3 was later and had a different scalp distribution; the slow wave (SW) was smaller. In contrast, no age-related differences were found for N1 amplitude or latency. It is suggested that the diminution in SW amplitude contributes to the change in scalp distribution of P3 amplitude seen with age. The relationship of reaction time and P3 latency of single trials was examined by the adaptive filter technique. There was no difference between the old and young subjects as both groups revealed signficant, positive P3 latency-reaction time correlations.

Adult↗
PubMed1980

Event-related potentials in schizophrenics.

Fifteen schizophrenics and 15 age-matched controls were compared on 3 auditory event-related potential (ERP) paradigms that elicited a variety of components. In one paradigm, tones were given at 0.75, 2.25 and 6.75 sec interstimulus intervals; in another, infrequently occurring targets in a reaction-time task were interspersed with frequent background stimuli; and, in a third, noise bursts or tones were delivered in a random sequence at either 70 or 100 dB SPL. The sensitivity of some of the ERP components in distinguishing schizophrenics from controls depended on the conditions under which the component was elicited. N1 amplitude was smaller in the schizophrenics than in the controls after longer interstimulus intervals. P2 amplitude was smaller in the schizophrenics than in the controls after longer interstimulus intervals. P2 amplitude was smaller in the schizophrenics only at higher stimulus intensities. P2 latency was shorter in schizophrenics except in the paradigm that varied interstimulus intervals. P3 amplitude, however, was much smaller in schizophrenics than controls ragardless of whether P3 was elicited by targets in a task or was elicited by 100 dB SPL stimuli. The loud stimuli also elicited blink reflexes that coincided with N1, but these reflexes did not vary by clinical group. Neither the amplitude of the slow wave following targets nor the sustained potential that accompanies prolonged auditory stimuli differed between schizophrenics and controls.

Adult↗
PubMed1980

P3 reduction in auditory evoked potentials of schizophrenics.

Fifteen schizophrenics and 15 age-matched controls performed a reaction time (RT) task. A Bernoulli sequence of 85 dB SPL, 50 msec, 800 c/sec (P = 0.85) and 1200 c/sec (P = 0.15) tones was presented with an interstimulus interval of 1 sec. Subjects were instructed to press a button quickly upon hearing the 1200 c/sec tone. If a subject failed to respond within 650 msec, a 50 msec white noise burst occurred. In averages synchronized with target tones and computed without respect to RT, P3 was maximal at PZ with a mean latency of 330 msec for both schizophrenics and controls. P3 amplitude at PZ, however, averaged 6 muV in schizophrenics and 14 muV in controls (P < 0.001). Both mean RT and mean within-subject variance were greater in schizophrenices than controls. Other kinds of averages were computed to investigate the possibility that the amplitude differences were associated with different RTs or with differences in P3 latency variability in underlying trails. Averages of trials associated with short RTs (100--286 msec) had larger P3s than averages associated with long RTs (287--600 msec) (P < 0.01). Within each RT range, however, schizophrenic P3s were smaller than control P3s. Neither response-synchronized averaging nor adaptive filtering eliminated P3 amplitude differences between groups, indicating that P3 latency variability cannot account for these differences. We hypothesize that the smaller P3s in schizophrenics represent a deficit in reactivity to unexpected stimuli that is compatible with normal RT performance.

Adult↗
PubMed1980

Sensitivity of some human cognitive functions to effects of methamphetamine and secobarbital.

Sternberg's memory scanning task, Buschke's selective reminding task, and a time production task were given to 18 male subjects after they had received 10 mg of methamphetamine, 100 mg of secobarbital and placebo on separate days. Time production and learning that involved storage and retrieval of information in long-term memory were most sensitive to drug effects. Other measures of learning and memory scanning performance were not affected by either drug.

Adult↗
PubMed1980

Auditory brain stem and cortical evoked potentials in schizophrenia.

Auditory brain stem and cortical evoked potentials were recorded from 15 schizophrenics and 15 controls. There were significant cortical evoked potential differences between the two groups. However, brain stem evoked potentials were almost identical, suggesting that the cortical evoked potential differences are not due to peripheral factors such as inability to match sensory thresholds or defects in auditory acuity.

Adult↗
PubMed1979

Event-related potential changes in healthy aged females.

Neurophysiological changes in the central nervous system were demonstrated with EEG even-related potentials in healthy, aged women. Compared to young women, the aged women showed decreased amplitude of the late sustained potential (SP), increased P2 latency, disruption of the normal stimulus intensity-response amplitude function of P2 and increased amplitude of the P1 component. These age-related changes are interpreted as neurophysiological reflections of CNS deterioration found in non-senile elderly persons.

Adult↗
PubMed1979

Event-related potentials recorded from young and old adults during a memory retrieval task.

Six healthy old and 8 healthy young subjects each received a series of trials in a memory retrieval task devised by Sternberg (1966). On each trials, the subject received a memory set of 1-4 digits and was then shown a test digit. The subject's task was to press one of two response buttons indicating whether the test digit was a member of the memory set for that trial. Response time (RT) was found to be an increasing, linear function of the number of items held in memory. The slope of the RT function was a composite measure of the time necessary to process each additional item in memory while the intercept was a measure of stimulus encoding and response processes that do not depend on memory set size (see Sternberg 1966, 1969, 1975). We found that the latency of P3 to the test stimulus also increased with increases in memory set size, although the slope of the P3 was less than that for RT. We have suggested that the intercept of the P3 slope reflects the time it takes to encode the test stimulus before the evaluation of the stimulus starts, while the slope reflects the amount of time per digit needed to evaluate the set. We have suggested that the difference between RT and P3 slopes represents the additional time per digit which the subjects waits before making a response, due to low confidence occurring with more difficult task conditions (i.e., when set size = 4). We further suggest that the intercept of the RT-P3 latency slope is a reflection of pure response processes. Time estimates of these processes are made for young and old subjects.

Adult↗
PubMed1979

Event-related potential changes in chronic alcoholics.

Ten chronic alcoholics (10+ year alcoholic drinking history) and ten age and sex matched controls were tested on an ERP paradigm which elicited a large P3 component. The N1 and P2 sensory evoked potential components did not differ in amplitude or latency between the two groups. The latency of the P3 was significantly longer for the alcoholics than the controls for both a response and non-response stimulus. This finding is consistent with the results seen in a variety of dementias and is offered as evidence of the dementing effects of prolonged alcoholism in this group of subjects. While the P3 latencies were prolonged for the alcoholics, their reaction times were not different from the controls. Single trial analysis using Woody's adaptive filter also demonstrated that the single trial estimates for the 3 latency were significantly prolonged for the alcoholics. The single trial correlation between the P3 latency and each trial's corresponding reaction time was significantly greater for the alcoholics than for the controls.

Acoustic Stimulation↗
PubMed1979

The effects of ethanol and meperidine on auditory evoked potentials.

The effects of ethanol and meperidine on the auditory evoked potential (AEP) to stimuli of different intensities were investigated. Sixteen normal male volunteers received ethanol, 0.8 ml/kg, 100 mg meperidine, and a placebo on different days in a double-blind study. AEPs were recorded from Fz, Cz and Pz electrode placements. The stimuli were 500 msec 1000 Hz tones at 50, 60, 70 and 80 dB sound pressure level presented in a pseudo-random sequence. Meperidine had no significant effect on AEP variables. Ethanol reduced AEP activity between 24 and 250 msec but had no effect on the sustained potential measured between 300 and 450 msec.

Adult↗
PubMed1979

Age effects on event-related potentials in a selective attention task.

We used an event-related brain potential (ERP) technique developed by Hillyard et al. (1973) to test abilities to attenuate irrelevant stimuli and to detect target stimuli. Subjects, 12 healthy old (80.3 years) and 12 healthy young adults (22.0 years), heard 1500 Hz tones in one ear and 800 Hz tones in the other ear. Infrequently, the pitch of either tone was raised. During one run, infrequent tones in the right ear were targets, and in the other run those in the left ear were targets. Subjects counted targets. For both groups, an early component of the ERP (N1) was larger to tones in the attended ear than in the unattended ear, and a later component (P3) was largest to the target. This suggests that both groups can attenuate irrelevant stimuli and can use stimulus probability information in this task. That P3 was later for old subjects suggests that they take longer to decide stimulus relevance.

Acoustic Stimulation↗
PubMed1978

Methamphetamine and diphenhydramine effects on the rate of cognitive processing.

Three cognitive tasks in which performance depends primarily on the rate of cognitive processing were given to 24 male subjects before and after oral doses of methamphetamine (10 mg), diphenhydramine hydrochloride (100 mg), and placebo. Each subject was tested on Monday, Wednesday, and Friday of one week with drug orders balanced across subjects. Compared with placebo and diphenhydramine, methamphetamine increased the rate at which a visual display was scanned for a target stimulus. Methamphetamine affected neither a time-production task nor a divided attention task that required the subject to perform two cognitive tasks in a limited amount of time. This suggests that methamphetamine can increase cognitive processing speed on tasks involving familiar cognitive operations but that an increase is not likely in tasks involving more complicated decision processes. Compared with placebo and methamphetamine, diphenhydramine caused subjects no experience geophysical time as passing more slowly, but the drug had no significant effects on the visual search or divided-attention tasks. This suggests that time perception is more likely to be altered by diphenhydramine than is performance on tasks requiring short periods of rapid cognitive processing.

Adolescent↗