Abstract
In the visual cortex, inhibitory neurons alter the computations performed by target cells via combination of two fundamental operations, division and subtraction. The origins of these operations have been variously ascribed to differences in neuron classes, synapse location or receptor conductances. Here, by utilizing specific visual stimuli and single optogenetic probe pulses, we show that the function of parvalbumin-expressing and somatostatin-expressing neurons in mice in vivo is governed by the overlap of response timing between these neurons and their targets. In particular, somatostatin-expressing neurons respond at longer latencies to small visual stimuli compared with their target neurons and provide subtractive inhibition. With large visual stimuli, however, they respond at short latencies coincident with their target cells and switch to provide divisive inhibition. These results indicate that inhibition mediated by these neurons is a dynamic property of cortical circuits rather than an immutable property of neuronal classes.
Highlights
In the visual cortex, inhibitory neurons alter the computations performed by target cells via combination of two fundamental operations, division and subtraction
Differences regarding the role of PV þ and SOM þ neurons could be imputed to differences in optogenetic stimulation protocols[27], suggesting that the functions performed by different inhibitory neurons is not a fixed property of cortical networks but is a consequence of more complex dynamics[28]
By recording from identified target neurons in mouse primary visual cortex (V1), we show that the response timing and profile of inhibitory neurons, and in particular SOM þ neurons, shapes the operations they perform
Summary
Inhibitory neurons alter the computations performed by target cells via combination of two fundamental operations, division and subtraction. They respond at short latencies coincident with their target cells and switch to provide divisive inhibition These results indicate that inhibition mediated by these neurons is a dynamic property of cortical circuits rather than an immutable property of neuronal classes. It has been suggested that different cortical inhibitory cell classes provide distinct combinations of divisive or subtractive inhibition during stimulus-mediated synaptic drive in vivo[16,17,18,19]. A computational model shows that such response modes arise from simple rules of network connectivity and synaptic summation, yet enable dynamic switching of function between subtraction and division These findings help to explain many of the diverse results described previously for inhibitory neuron function
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