Human Posterior Parietal Cortex Plans Where to Reach and What to Avoid

Abstract

In this time-resolved functional magnetic resonance imaging (fMRI) study, we aimed to trace the neuronal correlates of covert planning processes that precede visually guided motor behavior. Specifically, we asked whether human posterior parietal cortex has prospective planning activity that can be distinguished from activity related to retrospective visual memory and attention. Although various electrophysiological studies in monkeys have demonstrated such motor planning at the level of parietal neurons, comparatively little support is provided by recent human imaging experiments. Rather, a majority of experiments highlights a role of human posterior parietal cortex in visual working memory and attention. We thus sought to establish a clear separation of visual memory and attention from processes related to the planning of goal-directed motor behaviors. To this end, we compared delayed-response tasks with identical mnemonic and attentional demands but varying degrees of motor planning. Subjects memorized multiple target locations, and in a random subset of trials targets additionally instructed (1) desired goals or (2) undesired goals for upcoming finger reaches. Compared with the memory/attention-only conditions, both latter situations led to a specific increase of preparatory fMRI activity in posterior parietal and dorsal premotor cortex. Thus, posterior parietal cortex has prospective plans for upcoming behaviors while considering both types of targets relevant for action: those to be acquired and those to be avoided.

Decoding Effector-Dependent and Effector-Independent Movement Intentions from Human Parieto-Frontal Brain Activity

“…With respect to the activation topography of hand movements, eye movements, their overlap, and the spatial specificity of these effector-specific responses, the group findings reported here correspond remarkably well with the parieto-frontal network of areas engaged for planned and executed reaches and/or saccades (Sereno et al, 2001;Curtis et al, 2004;Medendorp et al, 2006;Schluppeck et al, 2006;Beurze et al, 2007Beurze et al, , 2009; Kastner et al, 2007;Kagan et al, 2010;Lindner et al, 2010), planned pointing and saccades (Connolly et al, 2000(Connolly et al, , 2003Astafiev et al, 2003;Hagler et al, 2007), and reaching and saccade execution (Levy et al, 2007;Filimon et al, 2009), as well as other work from our laboratory using actual reaching (Culham et al, 2003Culham and Valyear, 2006; see also Filimon, 2010 for review). These previous studies have also found overlapping and topographically mixed saccade and reach responses in the posterior and middle IPS and superior parietal cortex, as well as parts of PMd/ FEF, precentral gyrus, PMv, DMFC, and DLPFC.…”

Bilateral recruitment of prefrontal cortex in working memory is associated with task demand but not with age

“…In contrast, we here exclusively focused on lateralization during WM maintenance. To this end, we used comparatively long maintenance durations (∼15 s) allowing us to conduct a time-resolved analysis and to specifically estimate fMRI activity of the maintenance phase without any confounding influences of the encoding and retrieval phases (29,30). Current models of WM assume that DLPFC plays an executive role during such WM maintenance rather than being a mere content-specific buffer (29,31,32).…”

Different Representations of Potential and Selected Motor Plans by Distinct Parietal Areas

“…This distributed representation suggests that the same neurons involved in motor planning also compute the movement decisions (Cisek and Kalaska, 2010; Shadlen and Newsome, 2001). From an evolutionary point of view, forming multiple default motor plans and choosing between them in parallel may not only benefit decision making, but may also reduce reaction times and thus have a survival advantage (Andersen and Cui, 2009; Cisek and Kalaska, 2010; Lindner et al, 2010)…”