Pitch-Synchronous Response of Cat Cochlear Nerve Fibers to Speech Sounds

Abstract

Responses of individual fibers of the cat cochlear nerve to Japanese monosyllabic speech sounds were described. Responses were analyzed by making post-stimulus time histograms and "pitch-synchronous" period histograms. Almost all neurons responsive to speech sounds showed repetitive discharges synchronous with the pitch period irrespective of their characteristic frequencies (CF). The frequency relation between the tuning characteristics of single neurons and the spectral distribution of the stimulus was systematically investigated to find out stimulus parameters to produce the "pitch-synchronous" impulse discharges. It was found that the neurons responded to vowels if the latter contained formants with frequencies near the neurons' CFs.The aim of the authors is to investigate the response characteristics of single neurons at lower levels of the auditory pathway of various animals to human speech sounds and to disclose the neural mechanism of feature extraction preceding the recognition of the acoustic patterns from the comparative physiological point of view. The present report describes responses of individual fibers of the cat cochlear nerve. The temporal characteristics of the response to speech sounds were systematically investigated and the distribution of responsive neurons in the cochlear nerve was analyzed. The primary process of the feature extraction was discussed on the basis of the experimental result. A plausible system of "pitchsynchronous" analysis at the higher stations of the auditory pathway was also suggested. The outline of the present research was preliminarily reported (HASHI-MOTO et al., 1973).

Speech recognition by an artificial neural network using findings on the afferent auditory system

“…Thus, if the pitch synchronous mechanism triggers the firing of a cell, some intermediate features are detected and the OFF and ON-OFF responses take place. In addition, by the same mechanism, it is possible for the response types to change each other according to speech sounds, as was observed in the auditory system [3]. Figure 4 shows responses of FDL1 and FDL2 to a consonant-vowel combination /pa/.…”

“…Further, a CN cell shows two-tone inhibition which indicates lateral inhibition [2]. Not only CN cells but the cells on the afferent auditory pathway generate impulses synchronously with the pitch of voiced sounds [3].…”

“…(1) (2) (3) where the dot denotes d/dt, "c a and % are time constants, and r(t) indicates the amplitude of speech sound. The function q~(.)…”

“…the mechanism that emphasizes the major energy peaks, contributes to generating linearly independent features, which is important for correct feature detection as was explained before. [3]. The IC has the cells showing selectivity to simple spatiotemporal features, such as FM (frequency-modulated) tone [12].…”

“…The IC has the cells showing selectivity to simple spatiotemporal features, such as FM (frequency-modulated) tone [12]. The GM has the cells showing selectivity to consonant or consonant-vowel combination [3]. The cerebral cortex has many ON, OFF and ON-OFF type cells, where feedback inhibition is considered to play an important role [4].…”