Early coding of reaching: frontal and parietal association connections of parieto‐occipital cortex

Abstract

The ipsilateral association connections of the cortex of the dorsal part of the rostral bank of the parieto-occipital sulcus and of the adjoining posterior part of the superior parietal lobule were studied by using different retrograde fluorescent tracers. Fluoro-Ruby, Fast blue and Diamidino yellow were injected into visual area V6A, and dorso-caudal (PMdc, F2) and dorso-rostral (PMdr, F7) premotor cortex, respectively. The parietal area of injection had been previously characterized physiologically in behaving monkeys, through a variety of oculomotor and visuomanual tasks. Area V6A is mainly linked by reciprocal projections to parietal areas 7m, MIP (medial intraparietal) and PEa, and, to a lesser extent, to frontal areas PMdr (rostral dorsal premotor cortex, F7) and PMdc (F2). All these areas project to that part of the dorsocaudal premotor cortex that has a direct access to primary motor cortex. V6A is also connected to area F5 and, to a lesser extent, to 7a, ventral (VIP) and lateral (LIP) intraparietal areas. This pattern of association connections may explain the presence of visually-related and eye-position signals in premotor cortex, as well as the influence of information concerning arm position and movement direction on V6A neural activity. Area V6A emerges as a potential 'early' node of the distributed network underlying visually-guided reaching. In this network, reciprocal association connections probably impose, through re-entrant signalling, a recursive property to the operations leading to the composition of eye and hand motor commands.

The Cortical Timeline for Deciding on Reach Motor Goals

“…LDs of several tens of milliseconds, as seen here and also in previous studies (Riehle, 1991;Kalaska and Crammond, 1992;Johnson et al, 1996;Pesaran et al, 2008), seem rather long to be attributable to transmission delays between the monosynaptically connected areas PMd and PRR (Pandya and Kuypers, 1969;Jones and Powell, 1970;Kurata, 1991;Johnson et al, 1996;Caminiti et al, 1999;Marconi et al, 2001;Tanné-Gariépy et al, 2002;BattagliaMayer et al, 2003). Instead, we prefer to attribute the observed large frontoparietal LDs to the dynamic reorganization of network activity, which is required in visuospatially organized areas like PRR in the case of spatial remapping.…”

Microstimulation reveals specialized subregions for different complex movements in posterior parietal cortex of prosimian galagos

“…These and other similarities raise the possibility of a number of homologous areas in PPC of prosimian and anthropoid primates. However, visual inputs to PPC in galagos seem to be largely limited to cortex caudal to the complex movement zones, whereas movement-related zones of VIP, LIP, and PRR of macaques all get inputs from subdivisions of visual cortex (8,10,13,14). Thus, the large posterior parietal region of macaques is also likely to differ in organization in some respects from the much smaller posterior parietal region of galagos.…”

“…Because VIP has interconnections with ventral premotor cortex (9)(10)(11)(12), possibly including cortex where the defensive zone of frontal cortex is located, the VIP region and part of premotor cortex may be critical nodes in a network mediating defensive behaviors (2). Furthermore, because PPC, including the intraparietal region, contains a number of proposed subdivisions with differing connection patterns with motor and premotor cortex (9)(10)(11)(12)(13)(14)(15), other parts of PPC might interact with parts of frontal cortex as nodes in systems for various biologically relevant complex behaviors.…”

Neural Substrates of Graphomotor Sequence Learning: A Combined fMRI and Kinematic Study

“…The early learning period was associated with activation of the dorsal and ventral visual streams and the dorsal premotor cortex (Burnod et al 1999;Caminiti and Johnson 1992;Caminiti et al 1996Caminiti et al , 1998Caminiti et al , 1999Lacquaniti et al 1995), and it may reflect the tuning of sensorimotor transformations that map, for example, visuospatial signals into motor commands. The important role of the superior parietal lobule in this graphomotor sequence task is consonant with earlier studies involving graphomotor learning (Seitz et al 1994(Seitz et al , 1997.…”