Abstract 1377, Date 1:00 PM, Sunday February 22, 2004 (24 hours) Session D9:Auditory Midbrain and Cortex: Learning and Plasticity
Progressive Decay of Cortical Map Reorganization Induced by Basal Forebrain Activation in Rat A1
Rafael A. Carrasco, Amanda Puckett, Pritesh K. Pandya, Alyssa McMenamy, Joanna Gibbons, Raluca Moucha, Roshini Jain, Michael P. Kilgard
One of the ongoing goals of our research effort has been to determine the rules that govern remodeling of tonotopic maps in primary auditory cortex (A1) of young adult rats. It has previously been documented that massive and progressive reorganization of A1 can occur with daily episodic activation of neuromodulatory inputs paired with tonal stimuli (Kilgard & Merzenich, 1998). In previous studies, the magnitude of representational reorganization in A1 was determined twenty-four to forty-eight hours after the last conditioning session. An open question is how long these experimental manipulations on cortical representation endure. Therefore, the major goal of this study was to determine the duration and decay of cortical map reorganization after the cessation of one month of daily conditioning.       To determine the progressive decay of A1 map reorganization, a 19 kHz tone was repeatedly paired with electrical activation of the basal forebrain ~350 times a day for one month in sixteen animals. Cortical representation of tones was determined by conducting acute mapping experiments at 5, 10, or 20 days after the termination of the basal forebrain-tone pairing procedure. In addition to confirming robust map reorganization twenty-four hours after the last conditioning session, our preliminary results reveal a noticeable change in map structure over time. Specifically, it appears that cortical remodeling induced by our pairing protocol endures for at least ten days. At twenty days, we observe a restoration of the normal tonotopic map structure that more closely resembles nave control animals. Thus, we conclude that the magnitude of representational changes caused by our conditioning protocol decrements as a function of time.       Supported in part by R03-DC04534-02 (MPK), the McDonnell Foundation, and the Callier Excellence in Education Fund