Spike train analysis reveals cooperation between Area 17 neuron pairs that enhances fine discrimination of orientation

We recorded from 22 pairs of neurons neurons in cats anesthetized with Propofol and N2O and paralyzed with Pavulon following established guidelines. We used type analysis (Johnson et al., 2001) to calculate the Resistor Average Kullback-Leibler distance between ensemble responses to fine ( 10deg, >0.1c/deg) variations of OR and SF from the optimal parameter (see panel below). This “distance” provides an estimate of the reduction in classification error between responses (i.e., reduction in error = 2-distance). Discharge history was incorporated into types by testing for a stable Markov order (i.e., where discharge history ceases to contribute) using conditional types on previous bins for distance calculations. PURPOSE Bursting in Area 17 is tuned more sharply than spike rate for orientation (OR) and spatial frequency (SF) (Cattaneo et al., 1981a,b). Burst length is reduced at non-optimal orientations (DeBusk et al., 1997) and leads to less efficient synaptic coupling (Snider et al., 1998). We describe how these interspike interval (ISI) properties could contribute to discriminations between spike trains for fine and gross differences in OR and SF. We also describe changes in neural dependency as a function of OR, SF, contrast, and time to demonstrate how cooperative information (synergy) arises and is transmitted.