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Biomedical subjects

G R Marsh

Publications and source records attributed to G R Marsh.

33 records · Page 2Linked to original sources
PubMed1989

Polysomnographic assessment of DIMS: empirical evaluation of its diagnostic value.

This investigation examined the diagnostic value of polysomnography (PSG) for evaluating disorders of initiating and maintaining sleep (DIMS). The sample consisted of 100 outpatients who presented to the Duke Sleep Disorders Center with a complaint of chronic insomnia. All patients were given comprehensive medical, psychiatric, behavioral, and ambulatory PSG evaluations. Sleep disorder diagnoses were assigned using the criteria of the Association of Sleep Disorders Centers. Overall, PSG yielded important diagnostic information in 65% of the sample: 34% were given a primary sleep disorder diagnosis that was heavily dependent on PSG data [periodic movements of sleep (PMS) = 25%, apnea = 3%, and subjective insomnia = 6%]; 15% were given a secondary diagnosis of one of these three disorders; and PSG ruled out suspected PMS in 9% and sleep apnea in 7% of the sample. Patients greater than 40 years of age had a significantly higher rate of positive PSG findings than younger patients. Using only the clinical exam, two experienced sleep clinicians were able to predict only 14 of 25 PMS cases and one of three cases of sleep apnea. Based on these data, we suggest using PSG routinely with older insomniacs and with younger patients who fail initial treatment.

Adult↗
PubMed1985

Prediction and evaluation of memory performance by young and old adults.

Does the poorer performance of older people in laboratory tests of episodic memory result from metamemory problems? Memory of 20 young and 20 old adults for 60 "unrelated" paired associates was measured by an associative matching task. Two metamemory measures also were taken: Each pair was rated at the time of study for the likelihood that the person would recall it (prediction measure) and on the matching task each response pairing was judged as to its correctness (response evaluation measure). Young adults were correct on 50% of the associative matches, old only 30%. The two groups did not differ in the predictive metamemory measure: Both were able to predict relative memorability. Old persons, however, underestimated task difficulty (i.e., they overestimated the number of correct associative matches they would make, whereas the young did not). Both groups were quite accurate in the response evaluation measure.

Adolescent↗
PubMed1984

Differences in the late components of the event-related potential due to age and to semantic and non-semantic tasks.

Recent work in event-related potentials (ERPs) has revealed differences between ERPs elicited during the performance of semantic and nonsemantic tasks. This experiment examined age differences in the late components of the ERP as a function of these tasks. Young and elderly males were presented with 5-word strings on each trial. The subject's task was to decide whether or not the fifth word matched the other four. In one condition, the first 4 words were identical to one another and the fifth word was either the same or different. In the other condition, the first 4 words were different from one another but were drawn from from the same semantic category. The fifth word was either from the category or from a different category. Matches occurred in 15% of the trials and mismatches in 85%. The ERP to the fifth word was analyzed. All ERPs evidenced a late positive component (LPC), the latency of which was greater for the Category task and for mismatches. LPC amplitude was greater in the Identity task. In addition, young subjects' LPC amplitudes were greater for matches than for mismatches, whereas the reverse was true for the elderly. In agreement with previous research, our results indicated that an N400 wave is evident only in response to semantic incongruity and that variables affecting late positive activity seem to be independent of those producing N400. The N400 wave was seen at a greater latency in the elderly. Our results extend previous work (e.g., Kutas and Hillyard 1980) by finding an N400 in a semantic context other than sentences, and in concluding that this component is relatively insensitive to stimulus frequency.

Adult↗
PubMed1979

The effects of deanol on cognitive performance and electrophysiology in elderly humans.

Deanol (900 mg/day for 21 days) had no effect on learning a list of words when tested at weekly intervals. Tests of simple and complex reaction time and a test of continuous serial decoding of digits showed no enhancement with the drug. Several components of evoked potentials recorded from several scalp sites did show enhanced amplitude under drug treatment. These changes were not accompanied by changes in the EEG spectrum as are seen with some other psychoactive drugs. Deanol seems to be an ineffective treatment for the normal slowing of cognitive function seen in the normal elderly person or those elderly with only minimal cognitive decline and free of symptoms of dementia. Contrary to earlier reports, elderly persons were found to be able to benefit from warning signals in a complex reaction time task.

Aged↗
PubMed1979

Changes in event related potentials during processing of Stroop stimuli.

In a simplified Stroop test, subjects responded with a button press to either the color or word dimension of Stroop stimuli. Response times were analyzed as a function of condition (color or word), stimulus type (congruent or noncongruent color-word pairing) and visual field of presentation (left or right). Changes in the stimulus evoked potential (Experiment I) and the preresponse (premotor) potential (Experiment II) were measured as a function of the independent variables and hemisphere of recording site. Stimulus type had the expected Stroop effect on response time, with noncongruent stimuli associated with longer RTs. The pattern of changes in the event related potentials suggested that the typical Stroop interference effect (color condition) is localized in the response selection stage of processing. However, the less common reverse Stroop effect (word condition) probably results from more complex processing interactions during encoding of the color and word dimensions.

Brain↗
PubMed1975

Changes in alpha rhythm asymmetry during learning of verbal and visuospatial tasks.

Alpha activity in the two cortical hemispheres was examined during learning and overlearning of a verbal and a visuospatial task. Compared to a pretask baseline condition, the amount of alpha activity during the tasks was decreased. An increase in alpha activity was found from learning to overlearning in both tasks. A greater amount of alpha was found in the right hemisphere for both tasks. In addition, no difference in the degree of alpha asymmetry was found between the tasks. This was discussed in light of prior contrary findings. A significant positive correlation was found between change in learning rate and change in alpha asymmetry during the verbal task. An interpretation of this finding was offered in terms of the level of hemispheric activation reflecting the degree of task engagement.

Alpha Rhythm↗
PubMed1975

Age differences in evoked potential correlates of a memory scanning process.

Elderly subjects when compared to young, mature subjects in a memory-scanning task were shown to have longer response times (RT). A late positive component (LPC) of the average evoked potential did not reflect this difference between groups. However, in both groups, the LPC was seen to occur with longer latency at RT increased. LPC amplitudes also declined with increasing RT. There were greater differences between left- and right-hemisphere LPC amplitude and between LPC recorded along the midline scalp in the younger group than in the older subjects.

Adult↗
PubMed1975

Age-dependent changes in hippocampal theta.

The hippocampal theta rhythm in rats exhibited an age-dependent slowing in modal frequency. However, the theta rhythm of young rats with chronic respiratory infections showed a similar slowing. Respiratory disease-free hamsters also exhibited an age-dependent slowing of modal frequencies. These findings emphasize that the health status of the animal must be examined carefully in order to establish an age-dependent slowing in hippocampal rhythm.

Age Factors↗
PubMed1975

Age differences in the speed of a spatial cognitive process.

Older subjects responded slower than younger subjects on a spatial task which required them to rotate mentally a perspectively drawn figure in order to judge whether it was congruent with a second figure. Decision time was partitioned into two components: (1) the time taken for the "mental rotation" process, (2) the time taken for the remaining processes such as stimulus encoding and motor output. Both components required more time in the elderly group. The increase with age in the component of decision time representing rotational processes was similar to those increases seen by other investigators examining age-dependent differences in time required for memory-scanning processes using verbal stimuli.

Adolescent↗
PubMedDate not supplied

Slow-wave sleep and waking cognitive performance II: Findings among middle-aged adults with and without insomnia complaints.

Previous studies showing a relationship between nocturnal slow-wave sleep (SWS) and subsequent diurnal performance among young normal sleepers and older insomnia sufferers have provided limited support for the notion that this sleep stage serves a restorative role for neurocognitive functioning. The current study, which examined the relationship between SWS and reaction time performance among middle-aged adults with and without insomnia complaints, was conducted to further explore this possibility. A sample of 31 noncomplaining middle-aged (ages 40 to 59 years) normal sleepers and a like-aged sample of 27 insomnia sufferers, provided data for the current investigation. All participants underwent nocturnal sleep monitoring immediately prior to undergoing a battery of daytime tests that measured simple reaction time, vigilance/signal detection, and complex reaction time. Results showed relationships between reaction time performances on some tasks and some SWS measures among both the normal sleepers and insomnia sufferers. Findings supported our prediction that the presence of sleep pathology (e.g., insomnia) alters the SWS-performance relationship observed, but the results failed to show a consistent relationship between SWS and subsequent performance within either sample. The findings suggest that the specific performance demands of the task in question as well as physiological parameters other than SWS may determine performance as well. Findings for this and previous studies do provide some support for the contention that the neurocognitive restorative value of SWS may change across the lifespan. Possible implications of the study's findings are discussed and directions for future research are considered.

Adult↗