Joint-based organization of the forelimb region of the mouse motor cortex.

<p>Frequency distribution plots (A–E) show response topography. Axes show distances from bregma of the motor cortex area mapped. Medial-lateral (M–L) and anterior-posterior distances mapped were up to 1.9 and 2.1 mm respectively from bregma, which corresponds to most of the forelimb representation. Circle diameter for responses is directly proportional to response frequency across animals (10 responses maximum). (F) Representation maps were overlaid to determine any joint-bias within the cortical representation in the composite map. (G) The frequency plots were converted to an overall probability map based on the relative frequency of a dominant response at a specific site in relation to all responses at that site. Map shows the locations of dominant hind limb (H, grey), shoulder (S, green), elbow (E, red) and wrist (W, blue) responses. Shade intensity is directly proportional to the probability of provoking a response for a particular joint. (H) Representative EMG data from contralateral forelimb muscles in response to: threshold cortical stimulation for evoking an elbow response (21 µA, top traces); threshold cortical stimulation for evoking a wrist response (36 mA suprathreshold cortical stimulation for evoking both elbow and shoulder responses (41µA, bottom traces). Vertical and horizontal scales are 0.5 V and 20 ms respectively.