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Biomedical subjects

R J Erwin

Publications and source records attributed to R J Erwin.

26 records · Page 2Linked to original sources
PubMed1986

Midlatency auditory evoked responses: differential recovery cycle characteristics.

Middle latency responses (MLRs), in the 10-100 msec latency range evoked by click stimuli, were examined in two sets of 7 adult subjects utilizing 5 randomly ordered rates of stimulus presentation: 0.5/sec, 1/sec, 5/sec, 8/sec and 10/sec. Evoked potentials were collected in 250 trial averages for each rate, and a replication across rates yielded 500 trial averages. Peak-to-peak measurements for Pa-Nb and P1-Nb components revealed that the P1 component was reduced in amplitude or absent at the faster rates, while the amplitude of the Pa component remained unchanged across rates. In addition, the latency of Pa was significantly longer for the faster rates of stimulation. These findings were similar across both mastoid and sternovertebral references. Taken together with previous work, these data suggest that the human Pa and P1 potentials reflect different generator systems. Moreover, the physiological similarities between the human P1 potential and the cat wave A suggest that in the human, as in the cat, this potential may be generated within the ascending reticular activating system, whereas the physiological similarities between the human Pa and the cat wave 7, as well as previous clinical data, suggest an auditory cortex origin of this component.

Adult↗
PubMed1986

Event-related potential indices of ambiguous sentence processing.

An event-related potential (ERP) probe was used to examine various models of ambiguous sentence processing. ERPs to light flashes were recorded during and immediately after auditorily presented ambiguous and unambiguous target sentences. Each target sentence was preceded by either a relevant or a neutral context sentence. Principal component analyses of the ERPs indicated that although certain components varied as a function of ambiguity, none of the components varied as a function of preceding context. These findings provided some support for a postdecision model of ambiguity processing which suggests that both meanings of an ambiguity are always processed, even when prior disambiguating context is available.

Adult↗
PubMed1986

Neuroelectrical correlates of categorical perception for place of articulation in normal and lead-treated rhesus monkeys.

Categorical perception of place of articulation contrasts was evaluated in rhesus monkeys. The monkeys had been chronically exposed to subclinical levels of lead, either from conception to birth, or for approximately 6 months beginning at birth, or were never exposed to lead. Auditory evoked responses were recorded from scalp electrodes placed over left and right hemispheres during stimulus presentation. The brain responses recorded from the right hemisphere of the normal control group of monkeys discriminated between the categories of [dae] and [gae]. Categorical discriminations were also noted for monkeys exposed to lead either prenatally or postnatally. These discriminations, in contrast, were found over only the left hemisphere. In additions, postnatal exposure resulted in categorical discrimination associated with slower latency components, suggesting a less mature pattern than that obtained for prenatally exposed monkeys. Finally, the brain responses of the animals in the normal control and postnatal exposure conditions evidenced reliable within-category, as well as between-category, discriminations. These results suggest that the neurocortical mechanisms associated with categorical perception of place information may differ between human and nonhuman primates and that early exposure to lead alters these processes.

Animals↗
PubMed1979

The effect of food and water deprivation and satiation on recognition.

Food and water deprived and satiated subjects, as well as control subjects, were shown words presented tachistoscopically for .01 sec until word recognition. Five food-relevant, five water-relevant, and five neutral (animal) words of high string frequency were matched for letter confusability and letter predictability. Analyses of the data, in terms of number of presentations until recognition as well as number of words recognized at selected presentations, revealed that the amount but not the type of deprivation significantly altered word recognition. Moreover, the effect of motivation was significant already on the first slide presentation, while the effects of word characteristics (word category and generated value) occurred only after a number of presentations.

Drive↗
PubMedDate not supplied

Midlatency auditory evoked responses: differential abnormality of P1 in Alzheimer's disease.

The human 'P1' middle latency evoked potential is postulated to be generated in the thalamus by a cholinergic component of the ascending reticular activating system. To test the hypothesis that P1 and its generator substrate are abnormal in Alzheimer's disease (AD), a disorder of marked cholinergic deficiency, recordings of middle latency responses to click stimuli were carried out. Comparisons between the AD and age-matched control groups indicated normal auditory brain-stem and Pa responses but a significant decrease in P1 amplitude. This P1 abnormality suggests that the midbrain cholinergic cells in AD may be dysfunctional.

Adult↗