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W D Neff

Publications and source records attributed to W D Neff.

12 recordsLinked to original sources
PubMed1980

Sequential auditory and visual discriminations after temporal lobe ablation in monkeys.

Studies in the monkey have shown that cortex outside of the primary projection areas in the superior temporal gyrus and in the inferotemporal region in important for the execution of some auditory and visual descriminations. In this study, six monkeys were trained to perform four auditory and two visual discriminations. Retention tests were given prior to bilateral removal of the anterior part of the lateral surface of the superior temporal gyrus, the inferotemporal region, or both areas together. Superior temporal ablations elicited severe deficits on some auditory discriminations. Inferotemporal ablations caused little or no impairment on visual discriminations. This negative finding is attributed to the sequential rather than spatial mode of presentation of visual stimuli, and to overtraining. A single monkey trained on a spatial visual pattern problem without overtraining was impaired. Another monkey tranied to perform an auditory reverse intensity discrimination exhibited a deficit in ability to perform the problem after removal of auditory cortex within the lateral fissure.

Animals↗
PubMed1980

Apparent distance of sounds recorded in echoic and anechoic chambers.

With miniature microphones inserted into the external ear canals of a model and the sound source 90 degrees to left of midline, low-pass, and broadband noise bursts were picked up and recorded on magnetic tape. The bursts were generated in two highly contrasting acoustic environments: an anechoic and an echoic chamber. The taped sounds were played back monaurally and binaurally via headphones to 16 listeners seated in an acoustically neutral setting. They were instructed to estimate the distance of the stimuli. Apparent distances of bursts recorded in the echoic or reverberant chamber far exceeded those recorded in the anechoic chamber. It mattered not whether the sounds were presented monaurally or binaurally. What did influence distance estimates dramatically was the frequency composition of the stimuli. Low-pass sounds recorded in either acoustic environment were consistently judged to be further removed than high-pass sounds recorded in the same setting. They were also more likely to appear from behind the listener. In our moment-to-moment transaction with the acoustic environment, distant sounds generally have less acoustic energy in the higher audio frequency. We suggest that this lifetime of auditory experience influenced our listeners' scale of relative distance.

Auditory Perception↗
PubMed1977

Effects of unilateral ablation of auditory cortex on monaural cat's ability to localize sound.

1. Cats with one cochlea destroyed were trained to localize sound. After behavioral measures of the animal's accuracy of localization were made, cortical auditory areas were ablated unilaterally. 2. The results showed: a) like binaural localization, monaural localization of sound in space, as measured by the ability of an animal to move toward a sound source, depends on integrity of auditory cortex; b) it is only ablation of cortex contralateral to the functional ear that seriously affects localizing behavior; ablation of cortex ipsilateral to the intact cochlea has little or no effect on localizing behavior. 3. To explain the results, we suggest that auditory cortex is essential for an organized perception of space including the relation of the animal's position to other objects in space. We also suggest that auditory cortex contralateral to a given ear is necessary in order for the animal to recognize that a stimulus is presented to that ear of, when both ears are intact, to recognize that the stimulus to the given ear differs in some way (intensity, time of arrival, sequential arrangement of sounds) from the stimulus to the opposite ear.

Animals↗
PubMed1976

Efferent projections of the insular and temporal neocortex of the cat.

Anterograde degeneration resulting from small lesions placed in either the insular or temporal cortex were traced with the Fink-Heimer reduced silver procedure. In neocortical regions ipsilateral to the lesion axonal degeneration was present in auditory subdivisions AI, AII, Ep, I, T, in the second somatosensory area (SII), in the anterior and middle suprasylvian gyrus, in the posteromedial suprasylvian and posterior lateral gyri, in the posterior splenial gyrus, in the anterior two-thirds of the cingulate gyrus and in the orbitofrontal regions. With respect to interhemispheric connections, evidence was obtained for a dual pattern of projection. In addition to significant amounts of axonal and terminal degeneration in the corresponding insular or temporal fields, axonal degeneration was also present in posterior AII. In the thalamus degeneration was found in the medial dorsal, suprageniculate, and lateral posterior-pulvinar nuclei. In the posterior nuclear group (Po) and the principal division of the medial geniculate (GMp) evidence was obtained for a topographic pattern of projection; significantly more degeneration occurred in caudal Po following insular lesions whereas with temporal lesions more degeneration occurred in caudal GMp. Degeneration was also found in the dorsal cortex of the ipsilateral inferior colliculus, bilaterally in the deep layers of the superior colliculus and the periventricular central gray region, ipsilaterally in the ventromedial aspects of the head and body of the caudate nucleus, and in the lateral and central nuclei of the amygdala. These findings are discussed in terms of their significance for a possible role for the insular and temporal neocortex (I-T) in both multimodal sensory discrimination and sensory-visceral integrative functions.

Animals↗
PubMed1975

Auditory localization: role of auditory pathways in brain stem of the cat.

Cats were trained to localize sound in space. The animals' localization accuracy was determined before and after one of the following operations: 1) transection of the trapezoid body, 2) unilateral and 3) bilateral transection of the lateral lemniscus, 4) unilateral and 5) bilateral transection of the brachium of the inferior colliculus. The results after bilateral transections of the lateral lemniscus and the one deep bilateral transection of the brachium of the inferior colliculus indicate that some portion of the ascending auditory system must be intact above the medulla for an animal to be able to localize sound. A small loss in accuracy of localization was found after unilateral transection of the lateral lemniscus or brachium of the inferior colliculus. This loss, when compared with the much larger loss that monaural animals show, is an indication that binaural analysis, important for sound localization, occurs at the level of the medulla. Some transections of the trapezoid body resulted in a deficit in localization ability that appeared to be complete and permanent. The position of the lesions in the trapezoid body indicated that important encoding of the binaural cues to localization most likely occurs at the superior olivary complex, probably at the medial superior olive. But the trapezoid body or other commissures of the brain stem auditory system are probably also involved in transmission of information necessary for localization to higher centers.

Animals↗
PubMedDate not supplied

The brain and hearing: auditory discriminations affected by brain lesions.

After bilateral ablation of the auditory areas of the cerebral cortex, experimental animals have a severe deficit in ability to discriminate between temporal patterns of tonal stimuli and to localize sound in space. These two kinds of discrimination are basic for communication and for attack or avoidance of prey and predator. Recognition of which ear is stimulated may also depend upon excitation of auditory cortex contralateral to the given ear. Binaural discriminations are dependent upon interaction of nerve impulses from the two ears at a low level in the auditory nervous system. Similar hearing losses have been reported for human patients.

Animals↗
PubMedDate not supplied

Inner ear damage and hearing loss after exposure to tones of high intensity.

Experimental animals (cats) were exposed to tones of 125, 1000, 2000, and 4000 Hz at sound pressure levels in the range 120 to 157.5 dB, and for durations of one hour (1000, 2000, 4000 Hz) or four hours (125 Hz). Pure tone audiograms were obtained for each animal before and after exposure. Post-exposure tests were continued until complete recovery of hearing had occurred or until a stable permanent threshold shift had been measured. Cochleas of animals were examined by phase-contrast microscopy; condition of all hair cells was recorded. Extent of inner-ear damage and range of frequencies for which hearing loss occurred increased as exposure tone was decreased in frequency. For example, exposure to 4000 Hz produced damage in a restricted region of the cochlea and hearing loss for a relatively narrow range of frequencies; exposure to 125 Hz produced wide-spread inner ear damage and hearing loss throughout the frequency range 125 to 6000 Hz.

Acoustic Stimulation↗