Neural processing of temporal information in auditory stimuli Free

Microelectrode recordings from single auditory nerve fibers in a variety of species have fully confirmed the basic assumption of the volley theory that stimulus periodicity is reflected in the rhythm of neural discharges. In response to low‐frequency pure tones, discharges occur preferentially during a restricted segment of the sinusoidal cycle. For such phase‐locked responses the time intervals between discharges are grouped around integral multiples of the period of the tone. Thus the array of active fibers conveys to the central nervous system (CNS) information in the form of a period time code. There is abundant physiological and psychophysical evidence that the CNS utilizes minute differences in the timing of the period codes from the two ears to localize a sound source in space and to improve the discrimination of a binaural signal in the presence of noise. While there are no direct physiological findings on the question of whether the CNS uses the period time code to extract information about stimulus frequency, psychophysical results have led several theorists to postulate an affirmative answer. [Supported by NINCDS grant NS12732.]