Understanding Effector Selectivity in Human Posterior Parietal Cortex by Combining Information Patterns and Activation Measures

Abstract

The posterior parietal cortex (PPC) has traditionally been viewed as containing separate regions for the planning of eye and limb movements, but recent neurophysiological and neuroimaging observations show that the degree of effector specificity is limited. This has led to the hypothesis that effector specificity in PPC is part of a more efficient than strictly modular organization, characterized by both distinct and common activations for different effectors. It is unclear, however, what differentiates the distinctions and commonalities in effector representations. Here, we used fMRI in humans to study the cortical representations involved in the planning of eye, hand, and foot movements. We used a novel combination of fMRI measures to assess the effector-related representational content of the PPC: a multivariate information measure, reflecting whether representations were distinct or common across effectors and a univariate activation measure, indicating which representations were actively involved in movement preparation. Active distinct representations were evident in areas previously reported to be effector specific: eye specificity in the posterior intraparietal sulcus (IPS), hand tuning in anterior IPS, and a foot bias in the anterior precuneus. Crucially, PPC regions responding to a particular effector also contained an active representation common across the other two effectors. We infer that rostral PPC areas do not code single effectors, but rather dichotomies of effectors. Such combinations of representations could be well suited for active effector selection, efficiently coding both a selected effector and its alternatives.

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

“…Functional neuroimaging research suggests that the homologue of PRR in the human brain may involve, as in the macaque monkey, the superior parietal lobule, including the adjacent cortex in the IPS and the parietooccipital fissure [18,19,[59][60][61] (for review, see [27]; also see electronic supplementary material, tables S2, S3). There is evidence that on the lateral surface of the posterior parietal cortex neural networks involved in planning and execution of saccades (putative area LIP homologue) and reaching and pointing hand movements (putative PRR homologue) overlap significantly; suggesting the absence of distinct effector-specific regions (see electronic supplementary material, table S2, and compare electronic supplementary material, tables S1, S3).…”

Action Observation as a Visual Process: Different Classes of Actions Engage Distinct Regions of Human PPC

“…In contrast, action observation might be more bilateral or display lateralization related to non-motor factors such as location within the visual field. Second, as discussed above, action observation may generalize over more effectors than does execution which might manifest a typical or dominant effector (Jastorff et al, 2010;Leone et al, 2014). Third, any representations related to action execution must maintain a fixed relationship to motor onset, while those related to action observation may be more flexible with regard to visual input onset, especially when the action is unpredictable (Rotman et al, 2006).…”

Functional versus effector-specific organization of the human posterior parietal cortex: revisited

“…From a motor perspective, there is abundant evidence that the PPC distinguishes the processing for eye and hand movements, especially in the monkey (Andersen and Cui 2009; Chang et al 2008; Premereur et al 2015), although this division appears gradual rather than absolute, especially in humans (Caminiti et al 2010; Filimon et al 2009; Gallivan et al 2011; Heed et al 2011; Hinkley et al 2009; Leoné et al 2014; Tosoni et al 2008). These observations have traditionally been interpreted in terms of an effector-specific organization of the PPC.…”