Cosyne 2008 Workshops
March 3-4, 2008
Snow Bird, Utah
Speaker Name
Tony Zador - Cold Spring Harbor Laboratory
Talk Title
Millisecond spike timing can guide behavior in auditory cortex
Talk Abstract
It is well established that animals can exploit the fine temporal structure of some stimuli; for example, interaural time differences of less than one millisecond are used for spatial localization of sound. It is also clear that cortical neurons can lock with millisecond precision to the fine temporal structure of some stimuli. However, it has been difficult to establish whether the fine temporal structure of cortical responses can be used in a behavioral context to guide decisions. Indeed, in the case of spatial localization of sound, the relevant interaural time differences cues are processed below the level of the cortex by means of specialized circuitry.
We have therefore adopted a direct approach to probe the precision with which cortical timing information can be used to guide behavior in the rat. To bypass subcortical auditory pathways, we stimulate primary auditory cortex directly, using transient biphasic current trains delivered via chronically implanted intracortical microelectrodes. The behavioral paradigm we use is a two-alternative choice task in which stimulus 1 consists of the simultaneous stimulation of two intracortical sites (A & B), and stimulus 2 consists of sequential stimulation of the two sites separated by a brief interval dt (A - dT - B). After the subjects are trained to perform to criterion (1-2 weeks) with the initial long interstimulus interval (dT > 50 msec) for stimulus 2, we probe the subjects' psychophysical threshold by reducing dT, until the subjects can no longer distinguish between the two stimuli.
Our experiments indicate that the cortex can make use of timing information as precise as 3 ms.
