Biomedical subjects

C Tsuchitani

Publications and source records attributed to C Tsuchitani.

6 recordsLinked to original sources

PubMed1992

Excitatory/inhibitory interaction in the LSO revealed by point process modeling.

We studied lateral superior olivary (LSO) unit responses to binaural tone-bursts using a general point process approach. We show that inhibition of the ipsilaterally elicited response by contralateral stimulation cannot be modeled simply as a reduction of the ipsilateral input. Statistical analyses reveal that inhibition operates by scaling the intensity of the point process describing the ipsilateral response. In some cases the scaling process has secondary effects: Binaurally elicited discharges produce bimodal interspike interval histograms from units that produce unimodal interval histograms under monaural stimulation. We present a specific point process model that describes the scaling process and successfully replicates the observed responses to monaural and binaural stimulation of the three types of LSO units: slow choppers, fast choppers, and bimodal units. We interpret scaling as a shunting inhibitory process in these LSO neurons. By relating scaling magnitude to interaural level difference, we demonstrate the spatial sensitivity of LSO units.

Acoustic Stimulation↗

PubMed1990

Function-based modeling of binaural processing: interaural level.

The function-based modeling approach applies optimal estimation theory to sensory phenomena for determining how relevant sensory parameters are extracted from stimuli and how the characteristics of the resulting optimal processing system compare with those of the sensory system. This approach is applied to the neural system involved in the binaural localization of sustained high-frequency sound sources: the lateral superior olive (LSO) of the cat. The sufficient statistic produced by the optimal processor is shown to be related to the interaural level difference. This level difference is processed optimally when the inputs are excitatory from one ear and inhibitory from the opposite ear. Response characteristics of LSO single units are remarkably similar, thereby strongly supporting the notion that LSO units are intimately involved in high-frequency binaural hearing. Optimal processor theory is also used to assess lateralization performance when the hearing thresholds of the two ears differ.

Algorithms↗

PubMed1988

The inhibition of cat lateral superior olive unit excitatory responses to binaural tone bursts. I. The transient chopper response.

1. The temporal properties of lateral superior olivary (LSO) unit discharges to binaural tone bursts were studied to determine the general time course and statistical properties of these discharges and to provide a basis for extending a point process model of LSO unit monaural discharges to describe their binaural discharges. Single-unit activity was recorded extracellularly from the LSO of the anesthetized cat. The initial transient and the gross temporal features of LSO unit discharges to binaural simultaneous tone bursts are examined in this paper. 2. The poststimulus time (PST) histograms generated by LSO unit discharges to monaural and binaural tone bursts illustrated that the ipsilaterally elicited tone-burst discharges were most strongly inhibited during the initial segment of the binaural response and that the degree of inhibition decreased (i.e., discharge rate increased) as the poststimulus onset time increased. Hence, the contralateral inhibitory effect "adapts" in a manner similar to the ipsilaterally elicited discharges. 3. When the interaural level difference was decreased, the degree of discharge inhibition increased: the period of maximal inhibition spread to shorter and longer poststimulus onset times as the contralateral latency decreased and as the contralateral response magnitude increased. The latency of the inhibitory effect could decrease sufficiently to result in the suppression of the first spike of the ipsilateral discharge. Also, when the binaural stimulus was of sufficient intensity, an increase in spike output, the OFF discharge, was often observed during the last 1-10 ms of the response. 4. It was concluded that the initial and general time course of the binaural response could serve as cues of binaural stimulus level, interaural level differences, and interaural time-of-arrival differences of high-frequency stimuli. The binaural response could be discriminated from a monaural response of similar discharge rate as the former either occurred with shorter latency or, when the first spike was suppressed, with much longer and/or more variable latency than the latter. The gross temporal differences between the monaural and binaural responses could be accounted for in terms of differences in certain gross temporal features (e.g., latency and adaptation) of the ipsilateral and contralateral responses. 5. The effect of stimulating the contralateral ear was not limited to the inhibition of discharges. The timing of a discharge to an ipsilateral stimulus could be perturbed (lengthened) by a contralateral stimulus at levels below that which suppressed the discharge.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗

PubMed1988

The inhibition of cat lateral superior olive unit excitatory responses to binaural tone bursts. II. The sustained discharges.

1. Preliminary to extending a point process model of lateral superior olive (LSO) unit activity to describe the units' binaural responses, the statistical properties of their discharges to binaural tone bursts were studied. The hypothesis that stimulation of the contralateral ear results in the simple reduction of the ipsilateral input was also examined. Single-unit activity was recorded extracellularly from the LSO of the anesthetized cat. The sustained discharges to characteristic frequency (CF) tone bursts presented simultaneously to the two ears were examined to determine whether the fine temporal (statistical) properties of these discharges differed from those of the discharges elicited by stimulating the ipsilateral ear alone. 2. The major effect of simultaneously stimulating the contralateral ear was the inhibition (i.e., the reduction in the mean discharge rate) of the sustained discharges to the ipsilateral control stimulus. The temporal pattern of discharges to the ipsilateral stimulus was also affected by stimulation of the contralateral ear. The discharges to binaural stimulation were more irregular in pattern: they often produced bimodal or multimodal interval histograms where unimodal interval histograms had been produced by the discharges to the ipsilateral control stimulus alone. The hazard function, an estimate of the unit recovery function, also often differed in form for the binaural and monaural discharges. 3. The binaural discharges could be distinguished from an ipsilaterally elicited discharge of comparable mean rate: there was a greater incidence of "short" interspike intervals in the binaural discharge. These short interspike intervals occurred most frequently in the discharges to the ipsilateral control stimulus alone and infrequently in the discharges to an ipsilateral stimulus that produced a mean rate similar to that of the binaural discharge. Thus the dead time estimates derived from the binaural discharges were more similar to the estimates derived from the ipsilateral control discharges than to those derived from the comparable-rate ipsilaterally elicited discharges. 4. Although the measures of the recovery properties of LSO unit discharges differed under monaural and binaural stimulus conditions, the serial dependence observed between successive interspike intervals in the binaurally elicited discharges was similar to that in the ipsilaterally elicited discharges. The conditional mean function, an estimate of the serial dependence or unit shifting function, did not differ greatly in form for the monaural and binaural discharges.(ABSTRACT TRUNCATED AT 400 WORDS)

Acoustic Stimulation↗

PubMed1985

The effects of ipsilateral tone burst stimulus level on the discharge patterns of cat lateral superior olivary units.

Discharges were recorded extracellularly from single units localized in the lateral superior olive (LSO) of barbiturate anesthetized cats. The statistical properties of the unit discharges to monaurally presented tone bursts were determined. Increasing the stimulus level of an ipsilaterally presented tone burst produced an increase in the discharge rate and the emergence and growth of a time-locked discharge pattern in the initial portion of the response. The initial time-locked response was transient and was followed by a nontime-locked sustained response. In the sustained portion, increasing stimulus level produced increases in rate and changes in the interspike interval statistics. Average rate and interval statistics were found to be systematically related. LSO units were differentiated on the basis of rate and pattern of their initial discharges into two main types: the fast and slow chopping units. An analysis of the results indicated that some aspects of response type differences may be related to input characteristics rather than to neuron response mechanisms.

Acoustic Stimulation↗

PubMed1977

Functional organization of lateral cell groups of cat superior olivary complex.

1. Single-unit discharges to auditory stimuli were recorded extracellularly from superior olivary complex (SOC) units located lateral to the medial superior olive. Stimuli consisted of monaurally or binaurally presented tone bursts. The response measures obtained were effective ear, nature of effect, stimulus-frequency representation, maximum output, latency of response, and temporal pattern of tone burst-elicited discharges. Electrolytic marks were made at the unit studied or at the end of the electrode tract and in the medial superior olive. Following each experiment the locations of the units studied were determined histologically. An atlas of the laterally located SOC cell groups was developed to permit classification of units on the basis of localization within cell groups. Units were also classified according to the effects of stimulating the two ears. 2. All SOC units located lateral to the medial superior olive were excited by stimulation of the ipsilateral ear. Stimulation of the contralateral ear either excited, inhibited, had no effect, or had a potentiating effect on the discharges elicited by stimulating the ipsilateral ear. 3. Most lateral superior olivary (LSO) units were inhibited by contralateral stimulation, were narrowly tuned, produced low to high levels of maximum output, had short latencies, and produced regular discharge patterns characterized by chopper PST histograms with narrow initial peaks. 4. Most units within the caudal margins of the LSO (pLSO) were not affected or were inhibited by a contralateral stimulus; many were broadly tuned and exhibited intensity functions with large dynamic range and low slope. These units also had long latencies and produced chopper PST histograms with wide initial peaks. 5. Most units located dorsal to the LSO (DPO and DLPO) were not affected by the contralateral stimulus, were narrowly tuned, produced moderate levels of maximum discharge, had long latencies, and produced chopper PST histograms with wide initial peaks. 6. Units located ventral to the LSO appeared to have response characteristics related to unit location. Most units below the ventral hilum of the LSO (VLPO) were inhibited by the contralateral stimulus and many were broadly tuned VLPO units produced wide or poorly defined narrow-chopper discharge patterns and intensity functions with high maximum output. Most units located ventral to the lateral loop of the LSO (LNTB) were not affected by the contralateral stimulus and had response characteristics that may be related to the rostrocaudal location of the unit. 7. The cell groups located dorsal and ventral to the LSO were tonotopically organized with low-frequency-sensitive units located laterally and high-frequency-sensitive units located medially. The units located along the caudal margins of the LSO had a tonotopic organization similar to that of the LSO.

Acoustic Stimulation↗