Event
Special Seminar: Hirokazu Takahashi, "Map plasticity, response variability in the auditory cortex"
Thursday, February 21, 2013
12:00 p.m.
1146 A.V. Williams Building
Jonathan Fritz
301 405 6557
ripple@umd.edu
Special Seminar
Map plasticity and response variability in the auditory cortex
Hirokazu Takahashi
Tokyo
PIZZA LUNCH WILL BE SERVED.
Abstract
The tonotopic map in the auditory cortex is subject to change during associative learning. However, the mechanism by which functional maps and map plasticity contribute to cortical computation remain controversial. Learning-induced map plasticity has been interpreted as evidence that cortical representations encode behaviorally relevant information, yet several pieces of evidence argue against the functional significance.
Here, we attempted to link a representational area in the tonotopic map to response variance within the given area. With microelectrode mapping, we first characterized plasticity in the rat auditory cortex, including primary, anterior and ventral/suprarhinal auditory fields (A1, AAF and VAF/SRAF), at the early and late stages of appetitive operant conditioning.
Our results first demonstrated that most plasticity at the early stage was tentative. Second, training-induced plasticity occurred both locally and globally with a specific temporal order. In parallel with the local plasticity previously reported, the tone responsive area globally shrank at the late stage independently of task-relevant frequency, and this shrinkage was also correlated with the behavioral improvements. Third, regardless of learning stage, the degree of response variance is closely correlated with the size of its representational area.
Further, we show that the response variance within a given population is altered through training. These results suggest that larger representational areas may help to accommodate heterogeneous populations of neurons. Thus, functional maps and map plasticity are likely to play essential roles in cortical computation, serving as an effective, but not absolutely necessary, structures to generate diverse response properties within a neural population.
