Visually evoked calcium action potentials in cat striate cortex

EARLY intracellular studies of cerebral cortical neurons indicated that synaptic input evokes dendritic action potentials that convey information towards the soma¹.Subsequent work in vitro established that neocortical neurons produce dendritic Ca² action potentials^2–5. To determine whether natural stimuli elicit Ca²⁺ spikes, we combined the techniques of whole-cell recording^6,7, pharmacology⁸ and quantitative receptive field mapping9. Our findings show that visual stimulation routinely evoked Ca²⁺ spikes in distinct functional¹⁰ and anatomical¹¹ classes of cells in different layers of the cat striate cortex12. Hence regenerative Ca²⁺ potentials appear to play a role in both the initial and later stages of cortical sensory processing.