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D L McPherson

Publications and source records attributed to D L McPherson.

18 recordsLinked to original sources
PubMed1995

Auditory time-intensity cues in the binaural interaction component of the auditory evoked potentials.

Binaural interaction in the brainstem and middle latency auditory evoked potentials to intensity (dI) and timing differences (dT) between the two ears was studied in 10 normal hearing young adults. A component reflecting binaural interaction in the brainstem potentials occurred at approximately 7 ms and was of largest amplitude when dI and dT were 0. The latency of the binaural interaction component gradually shifted and its amplitude decreased as dI or dT increased and binaural interaction became undetectable when dI = 16 dB or when dT > or = 1.6 ms. In the middle latency potentials binaural interaction components peaking at 20, 32, and 45 ms were defined that were also largest when dI and dT = 0. The latency of the interaction did not shift with changes in dT and dI whereas the amplitude gradually decreased but binaural interaction components were still evident even at the largest values of dI (30 dB) and dT (3 ms). Psychophysical judgments of binaural perceptions showed binaural fusion of the stimuli to persist with dT values up to 1.6 ms and that lateralization of the intracranial image was complete when either dT = 1.6 ms or when dI = 16 dB. The results suggest that the presence of a binaural interaction component of auditory brainstem potentials correlates with the fusion of binaural click stimuli and the amplitude of the binaural interaction component correlates inversely with the degree of lateralization of the intracranial image. Binaural interaction components of middle latency potentials persist and continue to change even after the binaural stimuli cannot be fused.

Acoustic Stimulation↗
PubMed1993

Binaural interaction in auditory evoked potentials: brainstem, middle- and long-latency components.

Binaural interaction occurs in the auditory evoked potentials when the sum of the monaural auditory evoked potentials are not equivalent to the binaural evoked auditory potentials. Binaural interaction of the early- (0-10 ms), middle- (10-50 ms) and long-latency (50-200 ms) auditory evoked potentials was studied in 17 normal young adults. For the early components, binaural interaction was maximal at 7.35 ms accounting for a reduction of 21% of the amplitude of the binaural evoked potentials. For the middle latency auditory evoked potentials, binaural interaction was maximal at 39.6 ms accounting for a reduction of 48% of the binaural evoked potential. For the long-latency auditory evoked potentials, binaural interaction was maximal at 145 ms accounting for a reduction of 38% of the binaural evoked potential. In all of the auditory evoked potentials binaural interaction was long lasting around the maxima. The binaural interaction component extends for several milliseconds in the brainstem to tens of milliseconds in the middle- and long-latency components. Binaural interaction takes the form of a reduction of amplitude of the binaural evoked potential relative to the sum of the monaural responses, suggests that inhibitory processes are represented in binaural interaction using evoked potentials. Binaural processing in the auditory pathway is maximal in the time domain of the middle-latency components reflecting activity in the thalamo-cortical portions of the auditory pathways.

Acoustic Stimulation↗
PubMed1989

Auditory brainstem-evoked potentials in term infants born to mothers addicted to opiates.

A series of 20 normal newborn term infants and 12 infants born to mothers who had abused opiates during pregnancy were studied. Auditory brainstem-evoked potentials were used to describe neurophysiologic dysfunction in a group of drug-addicted term infants. Significant differences in the auditory brainstem-evoked potentials were found between the two groups. Specifically, a decrease in the central conduction times was noted for the I-III interpeak interval, suggesting neurophysiologic dysfunction in the area of the pons and cerebellum.

Evoked Potentials, Auditory↗
PubMed1987

Hydrocephalus: increased intracranial pressure and brain stem auditory evoked responses in the hydrocephalic rabbit.

The auditory evoked response (AER) was used to study the effect of increased intracranial pressure (ICP) on the auditory pathway in normal New Zealand rabbits and in those made hydrocephalic by intracisternal injections of kaolin. AERs were studied: (a) in the normal and then in the hydrocephalic animal; and (b) in the hydrocephalic animal during further ICP elevation by cerebrospinal fluid infusion. The AER was obtained from ongoing electroencephalographic activity after rarefaction auditory clicks presented at 90 dB sound pressure equivalent. In comparing base line normal AERs to those found in hydrocephalic conditions, a statistically significant increase in latency for AER components N2, P2, and P5 was noted in hydrocephalic rabbits. Increased ICP in the hydrocephalic model showed an increase in the latencies of AER components for P0 and P1 at 250 mm H2O, and a prolongation of P3-P5 central conduction time at 700 mm H2O above base line cerebrospinal fluid pressure. In addition, a decrease in the P4/N5 amplitude and an increase in P1-P3 central conduction times at 700 mm H2O was observed. The differences between normal and hydrocephalic rabbit AER base lines may be the result of the chronically increased ICP and presumed chronic anatomical changes within the auditory pathway due to kaolin itself. The differences in the AER from base line hydrocephalus to acute increased ICP may indicate that the hydrocephalic system is more sensitive to acute neuropraxic pressure effects on the brain stem auditory structures than is the normal brain.

Animals↗
PubMed1986

Cerebral cortical contributions to sensory evoked potentials: hydranencephaly.

The contribution of the cerebral cortex to the generation of sensory evoked potentials was studied in an infant with hydranencephaly. On CT scan no tissue above the thalamus was noted. Long-latency potentials to auditory stimuli were absent whereas the short-latency or brain-stem auditory evoked potentials and some of the components of the middle latency auditory evoked potentials (No and Po) were present. To visual stimulation only the electroretinogram was detected. To somatosensory stimulation only the spinal cord potentials could be detected. The absence of long-latency components in each of the sensory modalities supports the concept that these potentials require intact cerebral hemispheres in man.

Anencephaly↗
PubMed1985

Auditory brainstem response in infant hydrocephalus.

Fifteen infants with hydrocephalus ranging in age from 32 to 43 weeks from conception were studied. The auditory brainstem response (ABR) was measured 48 h prior to the placement of a CSF shunt and within 5 days following shunt insertion. Results of this study showed a general improvement in the ABR following placement of the shunt. No consistent patterns were observed that allowed a clear explanation of the cause and effect of the abnormal ABR. However, the changes seen in the ABR are caused by increased CSF pressure, which may compress the transmission fibers, and generators of the ABR producing a type of neuropraxis. Early shunting appears to have a better outcome on the ABR than later shunting.

Auditory Threshold↗
PubMedDate not supplied

Binaural interaction of the auditory brain-stem potentials and middle latency auditory evoked potentials in infants and adults.

Binaural interactions in brain-stem auditory evoked potentials and in middle latency auditory evoked potentials were studied in 18 normal hearing adults and 10 normal term infants. Binaural interactions at the times of ABR waves V and VI were comparable in term infants and adults. Binaural interaction during the time domain of the middle latency auditory evoked potentials was the greatest at N20 in term infants and at N40 in adults. Measurement of binaural interaction during maturation may be a useful tool in assessing neurologically affected infants.

Acoustic Stimulation↗
PubMedDate not supplied

Experimentally induced round window membrane lesions.

This investigation confirmed previous studies indicating that the middle and inner ear of the guinea pig have a pronounced tendency to healing. Middle ear hemorrhage of surgical origin appears to stop quickly in the guinea pig. A surgically created perforation of the round window with or without removal of perilymphatic fluid by suction resulted in a spontaneous healing of the round window membrane in 12/13 animals. Perilymphatic hemorrhage, associated with short post-surgical interval was found in a substantial number of cases. The origin of the perilymphatic hemorrhage is doubtful. Degeneration of the organ of Corti was found in four ears in three animals and appeared to be correlated to the perilymphatic hemorrhage. Electrophysiological measurements appeared to correlate well with the anatomical findings for one animal with very small changes and for three animals with pronounced middle and inner ear pathology. In three additional animals less agreement was observed. In general these animals showed a more pronounced decrease of function than would be expected by the anatomy.

Animals↗
PubMedDate not supplied

Auditory brain stem potentials recorded at different scalp locations in neonates and adults.

The auditory evoked brain stem potential was recorded in 14 normal full-term infants and nine normal-hearing adults. Silver-silver chloride electrodes were placed at nasion, forehead, vertex, each mastoid over the bony prominence, and the seventh cervical vertebra (noncephalic reference) in order to study the scalp distribution of the auditory brain stem response. Large differences in the scalp distribution between the newborn and adult populations were observed. At the ipsilateral mastoid, an x wave occurring at approximately 2 ms and a y wave occurring at approximately 3.3 ms were identified in the adult; this contrasts to a y wave at approximately 3.7 ms in the neonate. It appears that there are either separate generators for some of the components in the adult versus the neonate, and/or as the nervous system matures, myelinization occurs with a concomitant change in the scalp distribution of the auditory brain stem potentials.

Adult↗
PubMedDate not supplied

Preliminary observations of binaural hearing in an attention-deficit pediatric population.

Brainstem auditory evoked potentials and middle latency auditory evoked potentials were recorded from 21 normal hearing children between 8 and 13 years of age. An age-matched control group of 13 children was used to compare the results of 8 children diagnosed with ADHD. One sample of 2000 averages was collected for right monaural, left monaural, and binaural stimulus presentation conditions. The binaural interaction component was then determined using the formula: [(right monaural+left monaural)--binaural]. Absolute latencies and amplitudes for waves V, N20, P30, and N40 were then compared using descriptive statistics, analysis of variance, and matched t-tests. Percent binaural interaction was also computed for both groups. Significant differences were noted between control and ADHD groups on measures of N40 amplitudes for binaural stimulation, N40 amplitude for the sum of the right and left monaural waveforms, and percent binaural interaction at N40. These results suggest a dysfunction or immaturity in the auditory activity of the thalmo-cortical projections.

Adolescent↗