Inactivation of Parietal Reach Region Affects Reaching But Not Saccade Choices in Internally Guided Decisions

Abstract

The posterior parietal cortex (PPC) has traditionally been considered important for awareness, spatial perception, and attention. However, recent findings provide evidence that the PPC also encodes information important for making decisions. These findings have initiated a running argument of whether the PPC is critically involved in decision making. To examine this issue, we reversibly inactivated the parietal reach region (PRR), the area of the PPC that is specialized for reaching movements, while two monkeys performed a memory-guided reaching or saccade task. The task included choices between two equally rewarded targets presented simultaneously in opposite visual fields. Free-choice trials were interleaved with instructed trials, in which a single cue presented in the peripheral visual field defined the reach and saccade target unequivocally. We found that PRR inactivation led to a strong reduction of contralesional choices, but only for reaches. On the other hand, saccade choices were not affected by PRR inactivation. Importantly, reaching and saccade movements to single instructed targets remained largely intact. These results cannot be explained as an effector-nonspecific deficit in spatial attention or awareness, since the temporary "lesion" had an impact only on reach choices. Hence, the PPR is a part of a network for reach decisions and not just reach planning.

What if you are not certain? A common computation underlying action selection, reaction time and confidence judgment

“…Desirability provides a more general measurement to evaluate an alternative, since it includes information not only about the goal itself, but also the action required to achieve that goal. Our theory is inline with a series of neurophysiological and pharmacological intervention studies in animals reporting that areas in the posterior parietal cortex integrate value information to estimate the relative desirability of available options [30–34]. On the contrary, although neurons in specific PPC regions exhibit activity patterns that directly resemble the evidence accumulation process posited in race models [35, 36], recent studies reported that silencing these neurons does not influence the decision process [37, 38].…”

Partially Mixed Selectivity in Human Posterior Parietal Association Cortex

“…Reversible inactivation of PRR produces reach specific deficits and LIP a bias toward saccade deficits (Christopoulos et al, 2015; Kubanek and Snyder, 2015; Yttri et al, 2014). A grasp specific deficit has been reported for AIP (Gallese et al, 1994).…”

The neural basis of hand choice: An fMRI investigation of the Posterior Parietal Interhemispheric Competition model

“…Areas within monkey superior parietal (Caminiti et al, 1996;Scherberger et al, 2005) and dorsal premotor Hoshi and Tanji, 2004) cortices are necessary for the transformation of visual information to motor commands for reaching, and critically, the neural responses within these areas also reflect reach choices (Cisek and Kalaska, 2005;Scherberger and Andersen, 2007;Pesaran et al, 2008;Pastor-Bernier and Cisek, 2011;Thura and Cisek, 2014). Temporary inactivation of the "parietal reach region"area PRR, located within the medial bank of the intraparietal sulcusimpairs reach (but not saccade) selection (Christopoulos et al, 2015b). These data provide powerful evidence for the causal involvement of the PPC in reach choices.…”

“…Further, although these studies tend to investigate reach choices involving the same effector, recent data suggest that similar "action-based" competitive models can explain effector-selection (Christopoulos et al, 2015a). Temporary inactivation of reach- (Christopoulos et al, 2015b) versus saccade-selective (Christopoulos et al, 2018) areas in monkey posterior parietal cortex (areas PRR, mentioned above, and the lateral intraparietal area, LIP, respectively) selectively impairs reach versus saccade choices, respectively, and these data can be explained by a computational model that specifies competitive interactions between these brain areas (Christopoulos et al, 2015a). Conceptually, our PPIC model is consistent with this framework.…”