Fig. 8

Selective control of cortico-nigral information transfer by SOM and PV cells. a, c Experimental set up: in vivo multi-channel extracellular recordings of SNr unit activity using 4-shank 32-site silicon probe in response to stimulation in CG2 (a) or S2 (c) cortex, while PV or SOM interneurons are opto-inhibited using an optic fiber implanted in the DMS (a) or DLS (c). b Top: A cortical stimulation is applied in the absence (left) or presence (right) of light (300 ms, 10 mW, stimulation 100 ms after light onset, cycle repeated at least 100 times, 2–6 s between trials). Bottom: Raster plot of a representative SNr unit recorded in the PV-DLS condition (unit in e bottom), showing the response to the cortical stimulation in interleaved Ctrl (black ticks) and LED ON (red ticks) trials. d, e Left: Activity of a representative SNr unit displaying a triphasic response upon cortical stimulation of CG2 (d) or S2 (e), in the absence of (Ctrl) or during the opto-inhibtion (LED ON) of SOM (top) or PV (bottom) interneurons in DMS (d) or DLS (e). The response is normalized to the baseline activity independently in each (Ctrl and LED ON) case. The measured areas of the trans-striatal phases (inhibition and late excitation) are illustrated in d, top, and the measured differences in area (LED ON – Ctrl) are indicated for each representative unit. Right: Change in response areas corresponding to the trans-striatal inhibition (left), and late excitation (right), in all units displaying the corresponding phase. The cortico-nigral inhibition phase is significantly reduced only by the opto-inhibition of SOM striatal interneurons in the DMS condition (d, top, p = 0.0481, n = 17 units, paired t-test), while the cortico-nigral late excitation phase is significantly reduced only by the opto-inhibition of PV interneurons in the DLS (e, bottom, p = 0.0237, n = 9 units, paired t-test); *p < 0.05. For the 3D images in a and c, brain and brain structures are captured from the Allen Institute for Brain Science’s Mouse Brain Atlas⁷⁴ (© 2004 Allen Institute for Brain Science, Allen Mouse Brain Atlas available from: mouse.brain-map.org/) using Brain Explorer®2⁷⁵