The Posterior Parietal Cortex Encodes in Parallel Both Goals for Double-Reach Sequences

Abstract

The parietal reach region (PRR) is known to be involved in the preparation of visually guided arm movements to single targets. We explored whether PRR encodes only the target of the next movement or, alternatively, also a subsequent goal in a double-reach sequence. Two monkeys were trained to memorize the locations of two peripheral cues and to prepare for a memory-guided delayed double-reach sequence. On a GO-signal they had to reach in a predefined order to both remembered target locations without breaking eye fixation. The movement goals were arranged such that either the first or the second target was inside the response field of an isolated neuron. We analyzed the neural activity of single cells in PRR during the late memory period between cue offset and the GO-signal. During this memory period, most PRR cells encoded the first as well as the second goal of the planned reaching sequence. The results indicate that the posterior parietal cortex is involved in the spatial planning of more complex action patterns and represents immediate and subsequent movement goals.

Online Control of Hand Trajectory and Evolution of Motor Intention in the Parietofrontal System

“…Therefore, the results of this study suggest that the parietofrontal system can update a not-yet-accomplished motor plan during movement execution. This is reminiscent of other studies showing that cell activity in the premotor cortex can be related to two potential targets during the delay period (Cisek and Kalaska, 2002), and in parietal cortex can encode in a parallel fashion two motor goals, related to two sequential intended reaches (Baldauf et al, 2008). A study performed in humans came to the same conclusion (Mochizuki et al, 2005).…”

Eye-Hand Coordination During Target Selection in a Pop-Out Visual Search

“…In addition to an immediate movement goal, the PRR also encodes subsequent movement goals, suggesting its role in more complex sequential target selection (Baldauf et al 2008). Neural activity in PPC also reflects the choice of specific effector (eye or hand): neurons in the lateral intraparietal area (LIP) are selective for saccades, whereas those in the PRR are selective for reaches.…”

Toward More Versatile and Intuitive Cortical Brain–Machine Interfaces

“…Whereas sensory areas represent the contralateral space, and motor cortex the contralateral limb, PPC represents both limbs and both spatial hemifields, and thus a single implant in one cerebral hemisphere can be used for decoding bimanual operations across space. 3) Sequences of movements are represented in PPC [11]. Most motor behaviors require a sequence of individual movements which can be read out at once in PPC.…”