Input normalization by global feedforward inhibition expands cortical dynamic range.
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.
Pouille
Frédéric
F
Howard Hughes Medical Institute and Neurobiology Section, Division of Biology, University of California San Diego, La Jolla, California, USA.
Marin-Burgin
Antonia
A
Adesnik
Hillel
H
Atallah
Bassam V
BV
Scanziani
Massimo
M
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D056547:CA1 Region, Hippocampal / Q000166:cytology / Q000502:physiology*; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D025461:Feedback, Physiological / Q000502:physiology; D007395:Interneurons / Q000502:physiology*; D008959:Models, Neurological; D009433:Neural Inhibition / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology; D017966:Pyramidal Cells / Q000502:physiology*; D012377:Rodentia; D013003:Somatosensory Cortex / Q000166:cytology / Q000502:physiology*; D013569:Synapses / Q000502:physiology