Chapter 2. Prehension

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AREA 7
(IPS)
THE PHASES OF PREHENSION
VISUAL ASSOCIATION AREAS
AREAS 8,9p, 6 A p
AREA4
(hand area)
Nuclei INPUTS
f
Figure 5.24 Hypothetical pathways of activity flow during
visually and proprioceptively guided movements of the hand.
Dashed line indicates inhibition of grasping or manipulative
movements of the hand by the supplementary motor area (SMA) on
primary motor cortex. IPS stand for intraparietal sulcus (from
Humphrey, 1979; adapted by permission)
Jeannerod (1986) provides evidence that the formation of finger
grip during prehension is a cortically mediated visuomotor pattern.
Lesions of the posterior parietal area seem to disconnect independent
finger movements from access to visual information. The posterior
parietal areas (especially Area 7, within the inferior parietal lobule)
have been implicated as key to the interactions and integration of visual
and somatosensory inputs at the cortical level. Eye position informa-
tion in Area 7 may combine with proprioceptive input about joint an-
gles, muscle lengths and muscle contractile states, contributing to ex-
trinsic-intrinsic transformations. This could give rise to population
output signals from Area 7 varying with intrinsic coordinates, even if
convergent inputs signal extrinsic information. Jeannerod (1986)