Abstract #5708, Date Sunday, Feb 20 2000 1:00PM - 12:00PM , Session ,

Frequency tuning plasticity in rat primary auditory cortex

Pritesh K Pandya , Jessica Vazquez , Daniel Rathbun , Navzer D Engineer , Raluca Moucha , Michael P Kilgard

It is well documented that powerful plasticity mechanisms can substantially alter the receptive fields (RF) of auditory cortex neurons. Episodic electrical stimulation of the cholinergic nucleus basalis (NB) paired with tonal stimuli can be used to mimic naturally occurring experience-dependent plasticity. This plasticity paradigm is sufficient to generate dramatic changes in the representation of both spectral (Kilgard & Merzenich, Science, 1998) and temporal (Kilgard & Merzenich, Nature Neuroscience, 1998) information in the primary auditory cortex (A1) of adult rats. RF size (spectral selectivity) can be narrowed, broadened, or left unchanged depending on the specific parameters of the stimulus paired with NB activation. Previous work using NB stimulation suggests that frequency bandwidth varies systematically as a function of spectral variability and modulation rate. A primary goal of our ongoing research is to precisely characterize how differential acoustic experience shapes cortical response properties. The present study represents a further step in our effort to determine the rules of plasticity for frequency selectivity. Adult rats were chronically implanted with NB stimulating electrodes and received electrical stimulation of NB paired with a single tone with a high degree of spectral variability (1 of 10 randomly interleaved tone frequencies) 200-300 times per day for approximately 20 days. Frequency-intensity tuning properties were derived using multi-unit data from 50-70 microelectrode penetrations for each animal during an acute mapping experiment using barbiturate anesthesia. Our present model of A1 plasticity predicts that pairing NB stimulation with different tone frequencies will trigger maximal sharpening of A1 frequency tuning. Preliminary results are encouraging and the final results of this study will be discussed in the context of previous work on the differential RF plasticity in A1 dependent upon the degree of spectral variability and modulation rate of the paired stimuli.

Supported by the Callier Excellence in Education Fund