Modified spike-triggered averaging to assess rat auditory cortex time-frequency receptive fields.

Receptive fields have been used as a tool to study the functional organization of the auditory system in several animals. In this study, they have been used to characterize the primary auditory cortex of rats, specifically to address the differences in auditory processing at different depths of the cortex. The depths chosen; 500, 800 and 1300 microm correspond to layers IV, V and VI of the cortex. This study aims at quantifying the differences in the receptive field in terms of changes in latency, differences in tuning curves, spectral bandwidth and the complexity of the receptive fields. The following preliminary trends were observed: the mean peak latency changes from 10 +/- 4 ms at a depth of 500 microm to 46 +/- 13.08 ms at a depth of 1300 microm. Mean spectral bandwidth changes from 6.4 +/- 0.95 kHz at 500 microm to 8.9 +/- 1.73 KHz at 800 microm to 8 +/- 2.53 KHz at 1300 microm. The mean temporal width changes with increasing depth from 13.6 +/- 1.15 ms at 500 microm to 9.4 +/- 1.88 ms at 1300 microm. Quantitative characterization of the receptive field can be used to generate mathematical models of the auditory neurons, which could aid the computation of stimulation levels for implantable cortical prosthetics. Preliminary data from our experiment on three animals has been presented here.