Amplifying and Linearizing Apical Synaptic Inputs to Cortical Pyramidal Cells.

Intradendritic electrophysiological recordings reveal a bewildering repertoire of complex electrical spikes and plateaus that are dif-ficult to reconcile with conventional notions of neuronal function. In this paper we argue that such dendritic events are just an exu-berant expression of a more important mechanism- a proportional current amplifier whose primary task is to offset electrotonic losses. Using the example of functionally important synaptic inputs to the superficial layers of an anatomically and electrophysiologically re-constructed layer 5 pyramidal neuron, we derive and simulate the properties of conductances that linearize and amplify distal synap-tic input current in a graded manner. The amplification depends on a potassium conductance in the apical tuft and calcium conduc-tances in the apical trunk. ·To whom all correspondence should be addressed