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Nov 1975

Volume 58, Issue S1, pp. S2-S132

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back to top Session GG. Physiological Acoustics III: Neurophysiology and Behavior
Contributed Papers
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Intracellular study of synaptic events related to phase‐locking responses of cat cochlear nucleus cells to low‐frequency tones (A)

R. Britt

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S64-S64 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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Intracellular recording techniques were used to record from 55 cochlear nucleus cells in 46 pentobarbital anesthetized cats. Computer‐generated peristimulus‐time histograms, stimulus phase‐locked histograms, and interspike interval histograms were used to study each unit. For units which show phase locking of discharges an excitatory postsynaptic potential (EPSP) is generated in response to each period of the sine wave. With lower‐frequency stimulation, the probability of a unit discharge occurring with each EPSP was high but never exceeded 0.8. As the frequency of the stimulus increased, the probability of firing to a given period dropped, even though the period of the stimulus was much longer than the refractory period of the neuron. Units showed variable degrees of phase locking. Primary‐like units of the same low characteristic frequency might or might not phase lock to the characteristic frequency. Units which showed phase locking at lower frequencies but not at higher frequencies often also changed response configuration from primary to onset, built‐up or pause. A decrease in stimulus intensity caused a decrease in the amplitude of the EPSD and a lowered probability of firing. Both the EPSP and the phase‐locked unit discharge can contribute to the frequency‐following response recorded with macroelectrodes in the cochlear nucleus. [Work supported by Bank of America—Gianinni postdoctoral fellowship.]
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Effects of intensity on responses of anteroventral cochlear nucleus (AVCN) neurons to clicks and noise (A)

J. W. Dickson, M. A. Ruggero, and R. E. Wickesberg

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S64-S64 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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Using clicks and noise at various intensities, we studied impulse responses of phase‐locking AVCN neurons in barbiturate‐anesthetized cats. AVCN click responses are similar to responses of the cochlear nerve: near threshold post‐stimulus time (PST) histograms show multiple peaks separated by the period of the unit's best frequency. With increasing click intensity, both earlier and later peaks appear. At high intensity, the initial peaks are much larger than the later peaks. The linear impulse response of the system may be calculated by cross‐correlating a Gaussian white‐noise input with the output. The cross correlations, determined by calculating the average stimulus waveform preceding a spike, appear as oscillatory transients with spindle‐shaped envelopes. At low noise intensity the maxima and minima correspond in time, and generally in shape, to the peaks of low‐intensity rarefraction and condensation click PST histograms. As the noise intensity increases, earlier oscillations appear, but the early peaks are not as exaggerated as in the PST histograms and additional late oscillations are not apparent. [Supported by NIH.]
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Response properties of single neurons in anteroventral (AVCN) of the newborn cat: Frequency selectivity and temporal ordering of discharges (A)

Eric Javel, John E. Brugge, and Leonard M. Kitzes

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S64-S64 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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In the cat, anatomic development of the peripheral auditory system, including the cochlear nuclei, proceeds for weeks after birth. We describe here some properties of functional maturation of responses to pure tones of AVCN neurons in kittens ranging in age from 4 to 30 days. In kittens less then one week old, AVCN units possessing best frequencies below 2000 Hz are somewhat more broadly tuned than are units found in the adult. Furthermore, thresholds at best frequency are greatly elevated (typically greater than 100 dB SPL), saturation discharge rates are relatively low, and the average latent periods to the first spike are relatively long. By the end of the third postnatal week these response properties are similar to those obtained in the adult AVCN. In kittens less than two weeks of age, the discharges of units resposive to low‐frequency tones are securely locked in phase for frequencies below 300 Hz; however, phase locking declines rapidly at higher frequencies and is generally absent above 1000 Hz, even though units may still be responding vigorously to the tone. The range of frequencies to which phase locking may be observed increases with the age of the animal, but, during the first 30 days postpartum, the degree of phase locking is, with few exceptions, poorer than that obtained in adult animals.
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Temporal sharpening within response areas of medullary neurons (A)

G. W. Crow, A. L. Rupert, and G. Moushegian

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S64-S64 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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It is well known that auditory medullary neurons preserve the temporal characteristics of low‐frequency sounds by discharging at integral multiples of the stimulus period. Monaural recordings from kangaroo rat cochlear nuclei and binaural superior olive neurons show that the variability in synchrony of neural discharges decreases as the frequency of the sound increases. Variability in synchrony is apparent from period histogram displays and may be expressed by vector strength and interquartile range. These results provide a possible neural basis for the finding that the difference limen for pitch and the minimum audible angle, in absolute time, decreases as the frequency of the sound increases. Evidence is also presented that relates the shortest intervals of neural discharge to the loss of synchrony as frequency of sound stimulation increases. [Supported by AFOSR and NINDS.]
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Effects of sectioning the dorsal stria on responses of cells in inferior colliculus to binaural clicks (A)

M. F. Bengry, M. S. Silverman, and B. M. Clopton

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S64-S65 (1975); (2 pages)

Online Publication Date: 11 Aug 2005

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In order to estimate the relative contribution of brain‐stem pathways to binaural interaction at the inferior colliculus, we severed the dorsal stria in anesthetized rats and examined binaural interaction at the inferior colliculus. Extracellular recording was contralateral to the lesion using monaural and binaural clicks of varying intensity as stimuli in order to access the suppression of firing usually caused by ipsilateral stimulation. Both averaging and categorization of cell responses indicated that they underwent a greater reduction of firing when stimulation of the ear ipsilateral to the recording site was added to contralateral stimulation than did unlesioned controls. Since cells from lesioned animals also had click thresholds that were higher than controls, and since this pathway has only minor, if any, projections to the region of binaural interaction in the superior olivary complex, our results suggest that binaural interaction seen at the inferior colliculus does not entirely mirror binaural integration performed at the superior olivary complex. The dorsal stria contributes to this interaction. [Work supported by NIH.]
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Effects of behavior performance on single‐unit firing patterns in the inferior colliculus of the Rhesus monkey: additional observations (A)

Allen Ryan

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S65-S65 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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In a previous report [J. Acoust. Soc. Am. 55, 468 (1974)], it was noted that performance in an auditory reaction‐time task tended to increase both the evoked firing rate and initial latency of single‐unit responses to acoustic stimuli in the inferior colliculus and medial geniculate nucleus of rhesus monkeys, while the spontaneous rates of these units were unaffected. Our sample of chronically recorded collicular units has been expanded and our earlier findings were in general confirmed. However, more specific effects of performance were noted. “Off” responses were consistently, and sometimes strikingly, suppressed in the performance condition when compared to responses to identical stimuli delivered while the animal sat passively. Moreover, in some units increases in evoked firing rate were confined to specific temporal portions of the response pattern, and might be offset by suppression of firing in other portions. Also, the timing of some neural events could be related to specific aspects of reaction time performance. [Work supported by NIH grant NS‐08181.]
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Representation of intensity and frequency information in auditory cortex of monkeys performing a simple auditory task (A)

Bryan E. Pfingst, Thomas A. O'Connor, and Josef M. Miller

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S65-S65 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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Intensity functions were measured for single neurons at the cell's best frequency and at surrounding frequencies within the receptive field. Subjects for these experiments were adult male rhesus monkeys. Single neurons were isolated using a vertical approach to the superior temporal plane. Subsequent electrophysiological and anatomical data indicated that cells were located in cortical areas A1, CM, L, and RL [Merzenich and Brugge Brain Res. 50, 275–296 (1973)]. Data were collected while monkeys were performing a simple auditory reaction‐time task. As shown in this and many previous studies, in the absence of such a uniform behavioral control much variation in responses of auditory cortex neurons is encountered. The reaction time task was also used to provide an ongoing measure of the subject's threshold and suprathreshold hearing during recording of neural responses. Data are reported for encoding of stimulus intensity and frequency and discussed relation to behaviorally measured hearing. [Supported by NIH Grants NS‐08181, PR‐00166, and GM‐00260.]
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Effects of behavior attention on unit responses in the auditory cortex (A)

Josef M. Miller, Bryan E. Pfingst, and Robert Hienz

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S65-S65 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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Evoked activity of single cells from the auditory cortex of monkeys was examined under two behavior conditions: when the monkey was “attending” to the auditory stimulus and when he was not. Monkeys were trained in a reaction‐time task, in which lights and tones of a fixed duration were randomly presented to the animal. Under one visual cue, the animal was to perform the reaction‐time response only to the tone. Under another visual cue he was to respond only to the light. Thus evoked unit activity to an auditory stimulus was recorded under two conditions: (1) when the animal was responding to that stimulus in a reaction‐time task (“attending”) and (2) when the animal was performing in a visual reaction‐time task with a free tone stimulus. For excitatory “on” responses, evoked discharges were consistently greater and occurred with a shorter initial latency in the condition under which the animal was behaviorally responding to the auditory stimulus than when he was not. Quantitative information on the changes in the characteristics of excitatory and suppressed responses under these two conditions of light‐tone discrimination as well as responses to the same stimuli seen in the simple auditory reaction‐time task and under the nonperformance condition are described. [Supported by NIH Grants NS‐08181 and RR‐00166.]
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Effects of attention on single‐unit activity in monkey auditory cortex (A)

D. A. Benson, M. H. Goldstein, Jr., R. Hienz, and S. Hocherman

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S65-S65 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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Single‐unit responses were recorded from the auditory cortex of rhesus monkeys while they responded to light or sound stimuli. The animals were rewarded with water for pressing a lever to the left for a noise burst or a left light and to the right for a tone burst or a right light. A light and sound stimulus was then presented simultaneously in four different combinations and in random order. Animals were conditioned to respond correctly (i.e., “attend”) to either the light or sound part of the combined stimulus. Responses of single units to sound stimuli were compared when the animal was not performing, attending the sound stimuli, and attending the light stimuli. Approximately 50% of the units showed behaviorally related increases or decreases in acoustically evoked activity. The number of units that showed a stronger response to acoustic stimuli when the light stimulus was attended equaled the number with stronger responses when the sound stimulus was attended. Regardless of the stimulus attended, most units responded more strongly when the light and sound stimuli both indicated the same direction of lever press. When contrasted to human performance in the same task, the monkeys' behavioral data suggest that the animals did not necessarily selectively attend one of the two stimulus modalities in performing the task. Preliminary results of this study were presented at the April 1974 meeting of the Acoustical Society [J. Acoust. Soc. Am. 55, S86(A) (1974)]. [Supported in part by NIH Grant No. NS‐05143.]
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Effect of auditory cortex ablation on sound localization in the monkey (A)

H. Heffner and B. Masterton

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S65-S66 (1975); (2 pages)

Online Publication Date: 11 Aug 2005

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Rhesus monkeys with and without primary auditory cortex were tested for their ability to localize the source of a single brief click by two different techniques. The first technique required the monkeys to indicate the direction of the source of a sound by pressing a lever on either its right or left side in response to a click emanating from loudspeakers on either its right or left side. The second technique required the monkey to locate the sound source by walking to one of two loudspeakers which had emitted a click. It was found that monkeys deprived of primary auditory cortex can indicate the direction of a sound source, but can not locate the source itself. This dissociation of abilitias implies that the profound sound localization deficits resulting from auditory cortex damage discovered in past are not the consequence of a sensory or perceptual loss, but instead are probably the consequence of an auditomotor or associative loss. [Supported by grants NDS‐7726, NDS‐7468, MH‐11218 to Florida State University, and grant HD 02528 to the Bureau of Child Research, University of Kansas.]
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Hemispheric asymmetry of auditory function in monkeys (A)

J. H. Dewson, III, A. Burlingame, K. Kizer, S. Dewson, P. Kenney, and K. H. Pribram

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S66-S66 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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On a test of recent auditory memory [J.H. Dewson and A. Burlingame, Science 187, 267–268 (1975)], some monkeys show a severe and enduring deficit following unilateral cortical ablation of the superior temporal gyrus (“auditory association cortex”). Six such operations have been performed, and the deficit exists in only those four instances in which the left cortical area has been removed. In two cases of unilateral ablation of the superior temporal gyrus of the right hemisphere, no performance decrements have been noted. Discrimination between very brief (2–3 msec) acoustic stimuli remains at normal (preoperative) levels for all animals regardless of the cerebral hemisphere damaged and, in general, at very short delays (less than 1 sec) on the auditory memory task, performance is maintained even by the deficient animals at their preoperative criterion levels. The deficit does not appear to depend upon the disruption specifically of either the crossed or the uncrossed ascending auditory pathway as determined by results obtained from unilaterally deafened monkeys. Preliminary investigations of the nature of the deficient recent auditory memory suggest that interference at the time of retrieval is a major element. [Work supported by NSF.]
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Effect of click repetition rate on the latency of human auditory brainstem responses (A)

M. Don, A. Allen, and A. Starr

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S66-S66 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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Auditory brainstem responses are the far‐field reflection of electrical activity originating in the auditory pathway in its course from the cochlea to cortex that can be recorded from scalp electrodes using computer averaging techniques. There are seven components in the initial 10 msec following a click signal which have been shown to have an orderly change in latency as a function of signal intensity. The results of this study show that click repetition rate can also significantly affect the response latency measure. Responses were measured in ten normal hearing subjects at click rates of 10 to 100/sec and at four intensity levels (30, 40, 50, 60 dB SL). The mean latency shift of component V was 0.5 msec when responses at 10 and 100/sec were compared. This is equivalent to a 20‐dB decrease of signal intensity at the 10/sec click rate. An analysis of the time of occurrence of this shift using brief click trains at 100/sec showed the shift to be complete by the fifth click. The latency shift was similar at the four signal levels tested. The results are interpreted as an objective measure of adaptation in the human auditory system with implication for the measurement in disorders of hearing.
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