Neural interaction between cortical taste neurons in rats: a cross-correlation analysis

In the rat cortical taste area (CTA), we recorded 31 pairs of taste neurons and seven pairs of taste and non-taste neurons, with single or double electrodes. By using a cross-correlogram (CCG) in a stationary state, we examined the functional interaction between neurons of the pairs while activating them by taste stimulation. Though only 14.3% of the taste and non-taste neuron pairs were correlated, 54.8% of the taste neuron pairs showed correlated activities, 41.9% of them showing common inputs, including one with an additional excitatory connection. The remainder (12.9%) showed excitatory connections with a time lag of 1-3 ms. When pairs were recorded using single or double electrodes with an intertip distance of < 50 microns in a dorsoventral direction, a larger fraction had correlated activities than when the intertip distance was > 50 microns. Whereas pairs of neurons showed correlated activities in area DI whatever the vertical intertip distance was, most of the pairs having correlated activities in area GI were found within 50 microns of the vertical intertip distance. The taste profiles of common inputs to the pair were estimated on the basis of peak at time 0 in CCGs for various taste stimuli. The efficacy contribution of the source to target neurons tended to be larger when both had the same best stimulus. This tendency held true for pairs showing excitatory connections. Interlayer excitatory connections were also evident. It is concluded that a functional column with a diameter of 50 microns may present in the CTA in rats, and that information flow is larger between pairs of neurons with the same best stimulus.