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.

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Figure 1: The stronger the stimulus, the larger the excitation necessary to recruit a pyramidal cell.
Figure 2: Feedforward inhibition expands the dynamic range of the pyramidal cell population.
Figure 3: Pyramidal cells spike after the onset of feedforward inhibition.
Figure 4: Homogeneous inhibition and heterogeneous excitation control the recruitment of pyramidal cells.
Figure 5: Fast-spiking interneurons enforce dynamic EPSGT.
Figure 6: Model of activation curve with dynamic EPSGT.
Figure 7: The stronger the photostimulation of L2/3 pyramidal cells, the larger the excitation necessary to recruit L5 pyramidal cells.


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We thank P. Abelkop for anatomical reconstructions of biocytin filled neurons, F. Fröhlich for developing the initial versions of model, M. Carandini and J. Isaacson for comments and suggestions during the entire course of the project, C. Poo and F. Bertaso for inputs on the manuscript, and all of the members of the Scanziani laboratory for their input on the project and the manuscript. M.S. thanks C. Staub for the original discussions leading to the project. This work was funded in part by the US National Institutes of Health (MH71401 to M.S. and NS061521 to B.V.A.). H.A. is a fellow of the Helen Hay Whithney Foundation. M.S. is an investigator of the Howard Hughes Medical Institute.

Author information




F.P. and A.M.-B. conducted the experiments in the hippocampus; H.A. conducted the experiments in the somatosensory cortex; B.V.A. made the model; and M.S. supervised the project and wrote the manuscript.

Corresponding author

Correspondence to Massimo Scanziani.

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Pouille, F., Marin-Burgin, A., Adesnik, H. et al. Input normalization by global feedforward inhibition expands cortical dynamic range. Nat Neurosci 12, 1577–1585 (2009).

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