Temporal Nonlinearity During Recovery From Sequential Inhibition by Neurons in the Cat Primary Auditory Cortex

Abstract

Nakamoto, Kyle T., Jiping Zhang, and Leonard M. Kitzes. Temporal nonlinearity during recovery from sequential inhibition by neurons in the cat primary auditory cortex. J Neurophysiol 95: 1897-1907, 2006. First published December 7, 2005 doi:10.1152/jn.00625.2005. Auditory stimuli occur most often in sequences rather than in isolation. It is therefore necessary to understand how responses to sounds occurring in sequences differ from responses to isolated sounds. Cells in primary auditory cortex (AI) respond to a large set of binaural stimuli when presented in isolation. The set of responses to such stimuli presented at one frequency comprises a level response area. A preceding binaural stimulus can reduce the size and magnitude of level response areas of AI cells. The present study focuses on the effects of the time interval between a preceding stimulus and the stimuli of a level response area in pentobarbital-anesthetized cats. After the offset of a preceding stimulus, the ability of AI cells to respond to succeeding stimuli varies dynamically in time. At short interstimulus intervals (ISI), a preceding stimulus can completely inhibit responses to succeeding stimuli. With increasing ISIs, AI cells respond first to binaural stimuli that evoke the largest responses in the control condition, i.e., not preceded by a stimulus. Recovery rate is nonlinear across the level response area; responses to these most-effective stimuli recover to 70% of control on average 187 ms before responses to other stimuli recover to 70% of their control sizes. During the tens to hundreds of milliseconds that a level response area is reduced in size and magnitude, the selectivity of AI cells is increased for stimuli that evoke the largest responses. This increased selectivity results from a temporal nonlinearity in the recovery of the level response area which protects responses to the most effective binaural stimuli. Thus in a sequence of effective stimuli, a given cell will respond selectively to only those stimuli that evoke a strong response when presented alone.

Binaural interactions shape binaural response structures and frequency response functions in primary auditory cortex

“…Each panel is a ''binaural-level response area" (LRA), i.e., the response to the stimuli within the binaural matrix at a particular frequency. As found in earlier studies of LRAs in the inferior colliculus (Semple and Kitzes, 1987) and auditory cortex (Irvine et al, 1996;Nakamoto et al, 2004Nakamoto et al, , 2006Semple and Kitzes, 1993; 2005), these LRAs have a circumscribed focus of maximal responses to a subset of contiguous stimuli and a declining response to stimuli increasingly distant from the set of most effective stimuli. The set of LRAs is an estimate of the ''binaural response structure" (BRS) of the neuron.…”

“…The methods used to obtain data were essentially identical to those used previously Nakamoto et al, 2006); additional details regarding experimental methods can be found in those publications.…”

Neural Mechanisms of Fine-Grained Temporal Processing in Audition

“…This value is compatible with the neurophysiology data on un-anesthetized animals [1,[61][62][63][64][65] but rather shorter than the data (40-200 ms) on pentbarbiturateanesthetized animals [75][76][77].…”

Level Dependence of Contextual Modulation in Auditory Cortex

“…We conclude that forward suppression probably includes contributions from both response-gain control and level-gain control. In contrast, forward suppression of responses to different binaural level combinations appears to act by response-gain control and not level-gain control (Nakamoto et al 2006;Zhang et al 2005). Although our free-field stimulus reached both ears, we did not independently vary binaural levels and thus do not know whether the binaural response properties of our neurons showed response-gain control, level-gain control, or both.…”