Moise H. Goldstein

Responses to Acoustic Stimuli from Single Units in the Eighth Nerve of the Bullfrog

Single unit recordings from the eighth nerve of the bullfrog reveal two strikingly different kinds of auditory units. Both kinds of units exhibit sharply frequency dependent sensitivity (tuning curves). “Simple” units are maximally sensitive to tone bursts of frequency between 1000 and 1500 cps. Their frequency sensitivity and their capacity to “follow” pulse stimuli are well‐matched to the spectral composition and pitch period, respectively, of the bullfrogs croak. Simple units cannot be inhibited by acoustic stimuli. “Complex” units are inhibited by acoustic signals in the frequency range from 300 to 1000 cps. Some complex units are excited by acoustic stimuli, some are excited by both acoustic and vibratory stimuli, and some are excited by vibratory stimuli alone. Complex units that can be excited by sound are most sensitive to frequencies between 200 and 700 cps. Simple and complex units probably derive from separate sense organs (the basilar and amphibian papillae, respectively) within the otic caps...

Synchrony of Neural Activity in Electric Responses Evoked by Transient Acoustic Stimuli

Electric responses evoked by transient acoustic stimuli were recorded by gross electrodes from the periphery and cortex of the cat. The responses to clicks and to the rapid onset of bursts of noise or tones are characterized by a sharp N1 peak in the peripheral response and by a broader cortical response. When the rise time of the onset of bursts of noise (or tones) is lengthened, or when a burst of sudden onset is presented in a noise background, it is possible to obtain cortical responses under conditions for which the N1 component of the peripheral response is undetectable. These results and associated findings are interpreted by considering the degree of synchronization of the discharge and the wave forms of the activity of units that contribute to responses recorded by gross electrodes. A simple statistical interpretation is presented.

Cortical coding of repetitive acoustic pulses

Recordings were obtained from 179 cells, 53 of which were studied intracellularly; among these 26 cells were studied extracellularly before being studied intracellularly. A subgroup of units was characterized by spike durations of about one-third normal. These are referred to as ‘thin-spike units’. The population of cells was classified in 4 categories on the basis of responses to trains of repetitive chicks: Lockers had discharges precisely time-locked to the individual clicks. This category could be further subdivided into regular-spike lockers and thin-spike lockers. Intracellular recordings of response to single clicks from regular-spike lockers showed a short EPSP followed by a long IPSP. The limiting rate of locking for each unit was defined to be the highest rate of click repetition at which clear locking of spike activity to individual clicks in the trains could be observed. At repetition rates higher than their limiting rate regular-spike lockers usually exhibited one or two spikes at the train onset and suppression of spike activity throughout the remainder of the train. Thin-spike lockers had high rates of ongoing (spontaneous) activity and for clicks presented at low repitition rates responded with time-locked spikes and spontaneous spike activity between the locked spikes. When the limiting rate was exceeded the thin-spike lockers showed a sustained but unsynchronized discharge for the duration of the click train. Intracellular records exhibited a predominance of driven EPSPs with very little inhibitory impingement. Thirty-nine percent of the experimental population were lockers. The distribution of limiting rates was broad, from 10/sec to 1000/sec, with the median between 50/sec and 100/sec. Some lockers were studied with repetitive noise bursts. Evoked patterns of spike activity and limiting rates of these units were quite similar for clicks and brief noise pulses. The lockers exhibit a temporal coding of the repetition rate of acoustic stimuli which when presented to human listeners are judged to have periodicity pitch. Groupers had spike responses loosely synchronized to low rates of repetitive clicks. Intracellular records showed that single clicks evoked long lasting IPSPs. Spike activity was suppressed following the click sometimes returning with a rate higher than the ongoing rate. The latency of the return of activity after suppression is quite variable. For click train stimulation at low repetition rates the spike occurrences were grouped in part of the period between individual clicks. This loose synchrony was lmited to click repetition rates below 50/sec. Sixteen percent of the cells studied (but no thin-spike units) were in the grouper category. Special responders had patterns of spike activity related to the stimulus but their spikes were not synchronized with the individual clicks. The response patterns to the whole train could be described by the usual terms, on, off, through, etc. Seventeen percent of the cells studied were in this category. Twenty-eight percent of the experimental population did not respond to repetitive click stimulation. Possible neural coding mechanisms for periodicity pitch and the relationship of the present categories to those suggested on the basis of tuning curves are discussed.

Intracellular study of the cat's primary auditory cortex

Abstract Intracellular recordings were obtained from 139 neurons in unanesthetized muscle-relaxed cats primary auditory cortex. Patterns of nerve spike activity evoked by tone bursts, noise bursts, and clicks were similar to those observed extracellularly. Transmembrane recordings exhibited both excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs). For cells which had high or moderate rates of spontaneous spike activity, there was always a close relationship between synaptic input reflected in the average evoked membrane potential and the pattern of spike responses shown in the poststimulus time histogram. Active inhibition had an important role in the determination of patterns of spike activity. Acoustically evoked suppression of spike activity was always accompanied by evoked IPSPs. For cells which had low spontaneous spike activity, evoked IPSPs and subthreshold EPSPs were observed which did not apparently change the pattern of spikes from the cell. Thus evoked PSPs were obtained for a larger set of acoustic stimuli than evoked patterns of spikes. Quantitative data concerning patterns of response evoked by tone bursts, noise bursts, and clicks are given. Records were obtained from 28 ‘idle’ cells. These were presumably neuroglia. Resting potentials of these cells were not modified by acoustic stimuli.

Representation of Binaural Stimuli by Single Units in Primary Auditory Cortex of Unanesthetized Cats

The stimulus‐evoked activity of single units in the left primary auditory cortex (AI) of cats immobilized with gallamine triethiodide was observed as tone bursts, noise bursts, or clicks were presented at a moderate intensity to the right ear, to the left ear, and simultaneously to both ears. The right ear is represented more strongly in that more cells respond to monaural stimulation of the right ear than the left ear. An ear is said to be “represented” if a unit responds to stimulation of that ear, or if the response to stimulation of the other ear is modified by stimulation of that ear. There is extensive overlap of the populations of units representing the two ears; the population representing the left ear is almost completely contained within the larger population representing the right ear. The majority of units exhibited some form of binaural interaction. Binaural summation was the most common form of interaction; other units exhibited binaural inhibition or combinations of summation and inhibition.

Single‐Unit Activity in the Primary Auditory Cortex of Unanesthetized Cats

Activity of single cells in cats immobilized with gallamine triethiodide was recorded with metal microelectrodes and displayed by an on‐line dot display. Tone burst, noise burst, click, and other stimuli at moderate intensities were presented through condenser microphones at both ears. Spontaneous activity ranged from less than 1 spike/sec to greater than 40 spikes/sec. Almost all units were affected by acoustic stimuli, either by enhancement of activity, reduction of activity, or a combination. Units were affected at the onset and/or termination of a stimulus, throughout a stimulus, or a combination. Best frequency of units ranged from less than 1 kHz to greater than 50 kHz. Over half the units responding to tone bursts exhibited a response range greater than 12 oct. Some units had double response ranges. The pattern of response to tone bursts of some units changed as the frequency of the stimulus was changed. A minority of the units showed responses only to special stimuli such as swept tones or continu...

Voiced-speech representation by an analog silicon model of the auditory periphery

An analog CMOS integration of a model for the auditory periphery is presented. The model consists of middle ear, basilar membrane, and hair cell/synapse modules which are derived from neurophysiological studies. The circuit realization of each module is discussed, and experimental data of each modules response to sinusoidal excitation are given. The nonlinear speech processing capabilities of the system are demonstrated using the voiced syllable |ba|. The multichannel output of the silicon model corresponds to the time-varying instantaneous firing rates of auditory nerve fibers that have different characteristic frequencies. These outputs are similar to the physiologically obtained responses. The actual implementation uses subthreshold CMOS technology and analog continuous-time circuits, resulting in a real-time, micropower device with potential applications as a preprocessor of auditory stimuli.

Peripheral Inhibition in Auditory Fibers in the Frog

Two‐tone interactions in complex units in bullfrogs and leopard frogs were studied. The discharges of a complex unit in response to a tone at its best excitatory frequency (BEF) could be suppressed by addition of a second, higher‐frequency tone. The best inhibitory frequency (BIF) was that for which the least intense tone totally suppressed the response to a BEF tone. Between BEF and BIF, there was a frequency range in which tones had both excitatory and inhibitory effects. We call this range the “gray region.” During prolonged continuous presentation of a high‐level inhibiting tone, the inhibitory effect showed no adaptation. A rebound in firing rate occurred when a unit, which had been previously adapted and then inhibited, was released from the inhibition by terminating the inhibitory tone. The level of an inhibitory tone necessary for total inhibition depended on excitor level, even for levels at which the spike rate in response to the excitor alone had saturated. Results are discussed with regard to ...

Tactile aids for profoundly deaf children.

This paper treats acoustic-tactile communication aids for the deaf. Children who obtain negligible help from conventional hearing aids are of particular interest. For the prelingually deaf child tactile aids may facilitate the acquisition of lipreading, and improve vocal production. Although attempts to use tactile aids for the deaf go back many years, only recently have developments in technology led to greatly improved processing possibilities and the feasibility of aids that can be worn. Here, we report case studies in which prelingually, profoundly deaf young children used wearable tactile aids.

Speechreading sentences with single‐channel vibrotactile presentation of voice fundamental frequency

The main goal of this study was to investigate the efficacy of four vibrotactile speechreading supplements. Three supplements provided single-channel encodings of fundamental frequency (F0). Two encodings involved scaling and shifting glottal pulses to pulse rate ranges suited to tactual sensing capabilities; the third transformed F0 to differential amplitude of two fixed-frequency sinewaves. The fourth supplement added to one of the F0 encodings a second vibrator indicating high-frequency speech energy. A second goal was to develop improved methods for experimental control. Therefore, a sentence corpus was recorded on videodisc using two talkers whose speech was captured by video, microphone, and electroglottograph. Other experimental control issues included use of visual-alone control subjects, a multiple-baseline, single-subject design replicated for each of 15 normal-hearing subjects, sentence and syllable pre- and post-tests balanced for difficulty, and a speechreading screening test for subject selection. Across 17 h of treatment and 5 h of visual-alone baseline testing, each subject performed open-set sentence identification. Covariance analyses showed that the single-channel supplements provided a small but significant benefit, whereas the two-channel supplement was not effective. All subjects improved in visual-alone speechreading and maintained individual differences across the experiment. Vibrotactile benefit did not depend on speechreading ability.