Figure 1.

The effect of BMI micro-iontophoresis on vFMCx and S1 L-6 neurons. (a) PSTHs show spontaneous MUA recorded from vFMCx during 80 500-ms epochs. Application of 10 mM BMI for 5 min caused an ∼threefold increase in MUA. MUA returned to baseline within 30 min of cessation of BMI application. (b) MUA was normalized to activity during control conditions for 21 BMI applications in four experiments. Error bars indicate mean ± s.e.m. ** P < 0.005, paired t test. (c) The spread of BMI’s effect was evaluated by recording MUA simultaneously from four electrodes placed ∼500 μm apart horizontally at a depth of 1,500 μm. One electrode delivered BMI (black solid line). BMI application for 10 min (gray area) increased MUA at the delivery site but minimally affected responses at other locations. (d) Histological localization of the recording sites. A small electrolytic lesion was made at each site (arrow and arrowheads). Numbers indicate the sites for data shown in c. Horizontal section (70 μm) was processed for cytochrome oxidase with thionin counterstain. Site 1 (full arrow) indicates the site of BMI application. Scale bar represents 500 μm. Inset, gray rectangle indicates the region shown in the photomicrograph and the dot represents the approximate location of bregma. (e) Effect of vFMCx activation on S1 L-6 neurons. ON response magnitudes for 29 topographically aligned and 12 nonaligned neurons were plotted for control and BMI conditions. Individual neurons showing a significant difference are indicated as closed circles (P < 0.05).