Coding of intention in the posterior parietal cortex

Abstract

To look at or reach for what we see, spatial information from the visual system must be transformed into a motor plan. The posterior parietal cortex (PPC) is well placed to perform this function, because it lies between visual areas, which encode spatial information, and motor cortical areas. The PPC contains several subdivisions, which are generally conceived as high-order sensory areas. Neurons in area 7a and the lateral intraparietal area fire before and during visually guided saccades. Other neurons in areas 7a and 5 are active before and during visually guided arm movements. These areas are also active during memory tasks in which the animal remembers the location of a target for hundreds of milliseconds before making an eye or arm movement. Such activity could reflect either visual attention or the intention to make movements. This question is difficult to resolve, because even if the animal maintains fixation while directing attention to a peripheral location, the observed neuronal activity could reflect movements that are planned but not executed. To address this, we recorded from the PPC while monkeys planned either reaches or saccades to a single remembered location. We now report that, for most neurons, activity before the movement depended on the type of movement being planned. We conclude that PPC contains signals related to what the animal intends to do.

Morphological patterns of the intraparietal sulcus and the anterior intermediate parietal sulcus of Jensen in the human brain

“…The anterior intraparietal area (AIP) is located in the anterior part of the IPS and its neuronal activity has been linked to grasping with the hand [3][4][5]. By contrast, neurons in the lateral intraparietal area (LIP), which is located on the lateral bank of the IPS posterior to area AIP, have saccade-related activity, including ongoing and anticipated saccades, and their activity is modulated by visual attention [6][7][8]10,[13][14]. The posterior reach region (PRR) is located posteromedial to area LIP in the medial bank of the IPS and it is involved in reaching arm movements [10][11].…”

“…By contrast, neurons in the lateral intraparietal area (LIP), which is located on the lateral bank of the IPS posterior to area AIP, have saccade-related activity, including ongoing and anticipated saccades, and their activity is modulated by visual attention [6][7][8]10,[13][14]. The posterior reach region (PRR) is located posteromedial to area LIP in the medial bank of the IPS and it is involved in reaching arm movements [10][11]. The limited available evidence suggests that the border between the AIP and LIP regions in the macaque monkey may be placed at the same anteroposterior level as the border between areas PF/PFG and PG (or area 7b, corresponding to PF/PFG, and area 7a, corresponding to area PG, in an older terminology used in macaque monkey studies) on the free surface of the inferior parietal lobule [50][51][52][53].…”

“…By contrast, in the monkey, it is a relatively simple furrow and its functional organization has been clarified by elegant single-neuron recording studies. The anterior intraparietal sulcal cortex (area AIP) has been shown to be involved in complex sensorimotor integration [2][3][4][5], whereas its more central and caudal parts (lateral, medial and caudal intraparietal areas) play critical roles in visuospatial and attentional processing [6][7][8][9][10][11][12][13][14][15]. More recently, there have been several attempts to explore the functional organization of the intraparietal sulcal cortex in the human brain using functional neuroimaging methods [16 -24] (for reviews, see [25][26][27]).…”

Mirroring of attention by neurons in macaque parietal cortex

“…Mirror neurons are motor neurons that discharge not only during enactment, but also during observation of a particular behavior (15,16). LIP, although not classically a motor area, is active in gaze-related sensorimotor transformations (47)(48)(49)(50), and its activity contributes to both overt (51) and covert shifts of attention (32,41), and to maintenance of attention at fixation (52,53). We here report that neurons in LIP respond not only when monkeys orient attention toward their RFs, but also when other monkeys are observed orienting in the same direction.…”

An ecological approach to cognitive (im)penetrability

“…Although this is easy to identify at the level of sensory transducers and of muscles, it is a lot fuzzier closer to the sensorimotor transformation. Evidence from the dorsal stream suggests that even quite early parietal areas already code the intention to make movements (Snyder et al 1997). [See also Jeannerod: "The Representing Brain" BBS 17(2) 1994.]…”