Differentiating Intended Sensory Outcome from Underlying Motor Actions in the Human Brain

Abstract

To achieve a certain sensory outcome, multiple actions can be executed. For example, unlocking a door might require clockwise or counterclockwise key turns depending on regional norms. Using fMRI in healthy human subjects, we examined the neural networks that dissociate intended sensory outcome from underlying motor actions. Subjects controlled a figure on a computer screen by performing pen traces on an MR-compatible digital tablet. Our design allowed us to dissociate intended sensory outcome (moving the figure in a certain direction) from the underlying motor action (horizontal/vertical pen traces). Using multivoxel pattern analysis and a whole-brain searchlight strategy, we found that activity patterns in left (contralateral) motor and parietal cortex and also right (ipsilateral) motor cortex significantly discriminated direction of pen traces regardless of intended direction of figure movement. Conversely, activity patterns in right superior parietal lobule and premotor cortex, and also left frontopolar cortex, significantly discriminated intended direction of figure movement regardless of underlying direction of hand movement. Together, these results highlight the role of ipsilateral motor cortex in coding movement directions and point to a network of brain regions involved in high order representation of intended sensory outcome that is dissociated from specific motor plans.

Multivariate fMRI Approaches to Flexible Sensorimotor Maps in Parietal Cortex

“…They found generalization in Vis and SPOC to the rotated visual direction and generalization in PMd, SMA, M1, and aCB to the movement direction. These results align closely with the proposed functional roles for these regions in visually guided movement (Andersen and Cui, 2009;Gallivan and Culham, 2015). mIPS was the only region to exhibit accurate within-condition classification without also generalizing from the baseline to rotated trials.…”

“…More stringent generalization (cross-classification) tests that probe whether local activity patterns elicited by one context generalize to other contexts can help distinguish which task features steer classification. This approach has been particularly fruitful in discovering the underlying components of movement from fMRI response patterns (Eisenberg et al, 2011;Ogawa and Inui, 2012;Barany et al, 2014;Krasovsky et al, 2014). The authors' generalization approach consisted of training a classifier to dissociate movement direction in baseline trials and using that classifier to predict direction on the rotated trials in two independent generalization tests.…”

“…Null classification in mIPS might also be related to the feedback control mechanisms and contextual modulation of sensory feedback used to improve motor performance (Diedrichsen et al, 2005). In this case, the feedback control necessary to drive movements in the rotation condition would be different than in the baseline condition, leading to chance generalization.…”

“…A key avenue for future research is to resolve the extent to which PPC encodes new visuomotor mappings relative to pre-existing maps after adaptation to altered feedback. Other multivariate approaches, such as representational similarity analysis and forward encoding models, can detect mixed representations within regions and may be useful to assess specific models of underlying neural representations within PPC (Eisenberg et al, 2011;Serences and Saproo, 2012). Future work using these techniques will help us gain a deeper understanding of how the human motor system adapts to an ever-changing environment.…”

How will it look like? Human posterior parietal and dorsal premotor cortex encode the visual properties of an upcoming action

“…While we cannot reliably test this hypothesis on the basis of the current dataset, it seems at least to be supported by findings of Krasovsky et al (2014) who also reported that representations of sensory action-outcomes are rather ipsi-, than contralaterally organized.…”