Cortical Fields in the PPC and Frontal Cortex

Cortical fields in the PPC and frontal cortex Abbreviations: in addition to Brodmann’s areas, which are indicated by numbers 1–7: AIP, anterior intraparietal area; CMAs, cingulate motor areas; CMAs FEF, frontal eye field; pSMA SS SMA A ip, intraparietal; 7m IT, inferotemporal cortex; M1 5d LIP, lateral intraparietal area; S1 PMdr M1, primary motor cortex; 5d PO M1 1 2 5c MIP, medial intraparietal area (also PMdc 3b IP VIP known as the parietal reach region 3a M SEF ip PRR); 5 LIP FEF MT/MST, middle temporal area and PF PMvc AIP 7a 7ab middle superior temporal area; 7b PF, prefrontal cortex; S2 V1 PMvr PM, premotor cortex; MT/MST PO, parieto-occipital area; pSMA, pre-supplementary motor area; S1, primary somatosensory areas; S2, secondary somatosensory areas; IT SEF, supplementary eye field; SMA, supplementary motor area; SSA, supplementary sensory area; V1, primary visual area (striate cortex); VIP, ventral intraparietal area

c, caudal; r, rostral; v, ventral; m, medial; d, dorsal CMAs

pSMA SS SMA A 7m M1 5d

PMdr S1 5d 5c PO M1 1 2 PMdc 3b MIP VIP 3a ip SEF 5 LIP FEF IP PF PMvc A 7a 7ab 7b PMvr S2 V1 MT/MST

5c PMdr PMdc M1 S1(3a/2) 5d 5ip MIP PO 7m Encoding of limb position in the dorsal spinocerebellar tract

D Sensitivity of neuronal discharge to limb position in M1 and PPC

A 25 spikes/s

B C

Irregular static No static No static signal signal Irregular 33% 33% 18% static 25% Planar static Planar static 42% 49%

M1 Area 5d Encoding of limb position in the primary somatosensory cortex

Discharge of a single cell

z= 10 cm

z= 0 cm

anterior Shoulder location

z= -10 cm right 30 cm left Non-uniform distribution of preferred displacements in somatosensory cortex dx Distribution of preferred J = displacements dθ ∆θ =∆Jx−1 Change in joint angles for 1 unit displacement in hand position

∆θe 0

-2

-4 -3 -2 -1 0 1 2 3 ∆s Encoding of limb position and visual information in 5ip These data suggest a gradual transition between a region, S1, that represents purely intrinsic, somatosensory information, and PPC, which also receives information from vision about the location of the hand (and other end effectors).

Thus, PPC has a special status: it receives extrinsic, spatial information from visual cortex and intrinsic, proprioceptive information from the somatosensory cortex Reaching in the dark: effect of lesion in areas 5, 7b and MIP

200 200

150 150

target (mm)

(mm) target

100 100 sition sition

50 50 vertical po vertical po 0 0 Consistent initial hand Varied initial hand location location -50 -50 -50 0 50 100 150 200 -50 0 50 100 150 200 horizontal position horizontal position Reaching in the light Reaching in the dark

400 400 200 200 0 0 -200 -200 ge in errors -400 ge in errors -400 an an -600 -600 ch ch -800 -800 control area 7b area 7a control area 7b area 7a MIP LIP MIP LIP area 5d area 5d Lesion of area 5, 7b, and MIP: monkey has trouble computing hand location from proprioception. Without vision, reach is inaccurate.

Lesion of 7a and LIP: monkey has trouble computing target position in when target is visible. These areas are important for computing target position.