Inter and Intralaminar Excitation of Parvalbumin Interneurons in Mouse Barrel Cortex

Abstract

Parvalbumin (PV) interneurons are inhibitory fast-spiking cells with essential roles in directing the flow of information through cortical circuits. These neurons set the balance between excitation and inhibition, control rhythmic activity, and have been linked to disorders including autism spectrum and schizophrenia. PV interneurons differ between cortical layers in their morphology, circuitry, and function, but how their electrophysiological properties vary has received little attention. Here we investigate responses of PV interneurons in different layers of primary somatosensory barrel cortex (BC) to different excitatory inputs. With the genetically-encoded hybrid voltage sensor, hVOS, we recorded voltage changes simultaneously in many L2/3 and L4 PV interneurons to stimulation in either L2/3 or L4. Decay-times were consistent across L2/3 and L4. Amplitude, half-width, and rise-time were greater for PV interneurons residing in L2/3 compared to L4. Stimulation in L2/3 elicited responses in both L2/3 and L4 with longer latency compared to stimulation in L4. These differences in latency between layers could influence their windows for temporal integration. Thus PV interneurons in different cortical layers of BC show differences in response properties with potential roles in cortical computations. Key points summaryO_LIExcitatory synaptic responses were imaged in parvalbumin (PV) interneurons in slices of mouse barrel cortex using a targeted genetically-encoded voltage sensor. This approach revealed simultaneous voltage changes in approximately 20 neurons pre slice in response to stimulation. C_LIO_LIPV interneurons residing in layer 2/3 had larger amplitudes, longer half-widths, and longer rise-times than PV interneurons residing in layer 4. C_LIO_LIResponses of PV interneurons residing in either layer 2/3 or layer 4 had shorter latencies to stimulation of layer 4 compared to stimulation of layer 2/3. C_LIO_LIExcitatory synaptic transmission to PV interneurons varies with layer of residence and source of excitation. C_LI