Intra-Imc inhibition in the horizontal plane.

<p>A) Image montage of the Imc in the horizontal plane. White dashed lines outline the Imc. The blue triangle (near the center of Imc) indicates the location of the recorded neuron. The grid of yellow dots represents locations of laser photostimulation across the Imc for assessing direct MNI-Cs. B) Example trace showing a single, direct MNI-C, recorded at −60 mV, evoked from the location indicated in the map in Fig. 2C. Arrow indicates time of photostimulation. C) Map of direct MNI-Cs for the neuron depicted in Fig. 2A. MNI-Cs were observed only at sites near the recorded neuron. White triangle represents location of the recorded neuron. D) Cumulative frequency plot of MNI-Cs (red, 7 maps from 7 neurons) and IPSCs (black, 13 maps from 9 neurons) recorded in the horizontal plane. Median distance of the distributions (followed by 25^th and 75^th percentiles) were: MNI-C: 97 µm (57–111 µm), IPSC: 362 µm (167–580 µm). E) Image montage of the Imc in the horizontal plane, showing two maps acquired on either side of the recorded neuron. Same conventions as in Fig. 2A. F) Example traces showing multiple, reliable photostimulation-evoked IPSCs from the two locations indicated in the map in Fig. 2G. Left traces are evoked by photostimulation at a site 1 mm away from recorded neuron; right spot by photostimulation at a site 880 µm away. Arrow indicates time of photostimulation. G) Map of evoked IPSCs for the neuron depicted in Fig. 2A and E. IPSCs were evoked from either side of the recorded neuron. H) IPSCs evoked by photostimulation were eliminated by 10 µM GABAzine. Arrow indicates time of photostimulation. I) Distances of the furthest MNI-C or furthest reliable IPSC for Imc neurons recorded in the horizontal plane. Mean distance (horizontal line) of MNI-C: 208 µm (n = 7), of IPSC: 680 µm (n = 9 neurons). J) Comparison of photostimulation-evoked IPSC magnitude to photostimulation site distance from recorded cell. Large amplitude IPSCs could be evoked from sites proximal to or distal to the recorded neuron. IPSCs from all recordings (13 maps from 9 neurons) are shown. K) Histogram of slopes from regressions comparing IPSC amplitude to photostimulation distance for individual maps. Only 4 of 13 regressions were significant (p<0.05; red bars), 2 with slope <0 and 2 with slope >0.