Input normalization by global feedforward inhibition expands cortical dynamic range.

FREDERIC POIULLE ; ANTONIA MARIN BURGIN; HILLEL ADESNIK; BASSAM ATALLAH; MASSIMO SCANZIANI

NATURE NEUROSCIENCE.

NATURE PUBLISHING GROUP

Año: 2009 vol. 12 p. 1577 - 1585

1097-6256

The cortex is sensitive to weak stimuli, but responds to stronger inputs without saturating. The mechanisms that enable this wide range of operation are not fully understood. We found that the amplitude of excitatory synaptic currents necessary to fire rodent pyramidal cells, the threshold excitatory current, increased with stimulus strength. Consequently, the relative contribution of individual afferents in firing a neuron was inversely proportional to the total number of active afferents. Feedforward inhibition, acting homogeneously across pyramidal cells, ensured that threshold excitatory currents increased with stimulus strength. In contrast, heterogeneities in the distribution of excitatory currents in the neuronal population determined the specific set of pyramidal cells recruited. Together, these mechanisms expand the range of afferent input strengths that neuronal populations can represent.