Abstract #441, Date Monday, Jan 28 2002 1:00PM - 12:00PM Session K8 Auditory Cortex: Plasticity and Maturation
Characterization of Response Properties in Rat Posterior Auditory Cortex
Daniel L. Rathbun, Navzer D. Engineer, Raluca Moucha, Pritesh K. Pandya, Michael P. Kilgard
In the visual modality, spatial and temporal selectivity is more complex in higher cortical fields compared to primary visual cortex. In this study, we contrasted both spatial and temporal response properties of neurons in the rat posterior auditory cortical field (PAF) with those of the primary auditory field (A1). Frequency-intensity tuning curves were derived for each of ~50 cortical sites per animal (n=10). Response parameters derived from the tuning curves included best frequency (BF), threshold, bandwidth (BW) at 10,20,30&40 dB above threshold, and latency. Both minimum latency and bandwidth were significantly greater in PAF neurons (p< .01). The mean latency was 14.79 msec (SD=8.81) for A1 and 32.82 msec (SD=15.22) for PAF. The mean BW20 was 1.82 octaves (SD=0.77) for A1 and 2.93 octaves (SD=0.90) for PAF. The BF gradients in A1 and PAF form a mirror image with low frequency neurons at their border. Unlike A1, high frequency PAF neurons tend to have greater bandwidths and longer latencies than low frequency neurons. BF range and minimum threshold are similar in the two fields. These findings indicate that A1 and PAF may operate in conjunction to represent complex auditory stimuli. FM sweeps, tone burst trains, and noise burst trains were also presented to better characterize the response of PAF neurons. PAF and A1 neurons were equally selective for FM direction in response to fast sweeps, but PAF neurons were less selective for direction in response to slower sweeps. Preliminary analysis suggests that PAF has a slower maximum following rate for tone trains than A1. Further documentation of spatial and temporal response properties in non-primary cortical fields will be useful for future plasticity studies.