Figure 3. Receptive field maps of neurons isolated in PV/S2 region and their relationship to heat fMRI activation.

(A) Microelectrode penetration map (selected penetrations) shows the spatial relationship of neurons with different receptive fields and preferred stimulus. Green stars: low threshold mechanoreceptive (tactile) neurons with receptive fields on arm (penetration numbers of 1-3 and 11-14). Yellow stars: tactile neurons with receptive fields on hand/digits (penetration numbers of 4-10). Red stars: high threshold heat nociceptive neurons (penetration numbers of 15-20). Gray star (p21): low threshold tactile neuron on the shoulder. Dotted black line: estimated hand-face border in area 3b based on the receptive field map. (B) Composite, zoomed-in view of the PV/S2 region shows the spatial correspondences between (a) touch fMRI activation of digits (dark red patch) and cortical regions containing touch neurons (yellow dots within the red outline), and (b) heat fMRI activation (yellow-blue patch) and the cluster of nociceptive heat neurons (red stars within the red outline in the left side field of view). Surrounding inserts: body maps showing the properties (the color of the patches) and location of the receptive fields (the colored the patches: heat red, hand thermal; vibrotactile arm; olive, vibrotactile hand; gray, vibrotactile, shoulder). Numbers on each map represent the penetration number (i.e., # 12) and the depth of the electrode where the neuron was isolated and tested (i.e., 3000 μm: 3000 μm below the surface of the cortex). A total of 76 and 55 penetrations were placed into this PV/S2 region on the upper bank of the lateral sulcus and around the central sulcus, respectively, in this subject (SM-J). For presentation purposes, only selected penetrations (21 out of 76) are shown in A and B. a: anterior. p: posterior. m: middle. l: lateral. Monkey SM-J.