Population coding of stimulus location in rat somatosensory cortex

This study explores the nature of population coding in sensory cortex by ap plying information theoretic analyses to neuron pairs recorded simultaneous ly from rat barrel cortex. We quantified the roles of individual spikes and spike patterns in encoding whisker stimulus location. 82%-85% of the total information was contained in the timing of individual spikes: first spike time was particularly crucial. Spike patterns within neurons accounted for the remaining 15%-18%. Neuron pairs located in the same barrel column coded redundantly, whereas pairs in neighboring barrel columns coded independent ly. The barrel cortical population code for stimulus location appears to be the time of single neurons' first poststimulus spikes-a fast, robust codin g mechanism that does not rely on "synergy" in crossneuronal spike patterns .