Input normalization by global feedforward inhibition expands cortical dynamic range

3 years ago



Populations of pyramidal cells need to respond to inputs of various magnitudes without sacrificing sensitivity. In other words, they need to maintain a wide dynamic range. The authors measured currents in pyramidal cells of hippocampal and cortical slices in response to varying levels of input stimulation (electrical stimulation of Schaeffer collaterals of ChR2 stimulation of layer 2/3). The larger the stimulus, the larger the EPSC required to elicit a spike. This effect was mediated by fast, feedforward inhibition of basket cells, which were activated ~1 ms before the rest of the population and provided widespread, homogeneous inhibition. Such a mechanism is useful, as it allows populations to dynamically adjust their average threshold without the need to anticipate the strength of the incoming stimulus.