Neural encoding of actual and imagined touch within human posterior parietal cortex

Abstract

In the human posterior parietal cortex (PPC), single units encode high-dimensional information with partially mixed representations that enable small populations of neurons to encode many variables relevant to movement planning, execution, cognition, and perception. Here, we test whether a PPC neuronal population previously demonstrated to encode visual and motor information is similarly engaged in the somatosensory domain. We recorded neurons within the PPC of a human clinical trial participant during actual touch presentation and during a tactile imagery task. Neurons encoded actual touch at short latency with bilateral receptive fields, organized by body part, and covered all tested regions. The tactile imagery task evoked body part-specific responses that shared a neural substrate with actual touch. Our results are the first neuron-level evidence of touch encoding in human PPC and its cognitive engagement during a tactile imagery task, which may reflect semantic processing, attention, sensory anticipation, or imagined touch.

Stability of motor representations after paralysis

“…Although previous studies have shown that the anterior intraparietal (AIP) area of PPC is involved in whole-hand grasping ( Schaffelhofer and Scherberger, 2016 ; Klaes et al, 2015 ; Murata et al, 2000 ), our work is the first to discover individual finger representations in PPC ( Figure 1—figure supplement 5 ). Likewise, many other BCI studies with tetraplegic participants have contributed to basic neuroscience, deepening our understanding of the human cortex ( Stavisky et al, 2019 ; Willett et al, 2020 ; Rutishauser et al, 2018 ; Zhang et al, 2017 ; Aflalo et al, 2020 ; Chivukula et al, 2021 ). A frequent ( Flesher et al, 2016 ; Armenta Salas et al, 2018 ; Stavisky et al, 2019 ; Willett et al, 2020 ; Fifer et al, 2022 ; Chivukula et al, 2021 ; Andersen and Aflalo, 2022 ) discussion question is: how well do these findings generalize to the brains of able-bodied individuals?…”

“…Likewise, many other BCI studies with tetraplegic participants have contributed to basic neuroscience, deepening our understanding of the human cortex ( Stavisky et al, 2019 ; Willett et al, 2020 ; Rutishauser et al, 2018 ; Zhang et al, 2017 ; Aflalo et al, 2020 ; Chivukula et al, 2021 ). A frequent ( Flesher et al, 2016 ; Armenta Salas et al, 2018 ; Stavisky et al, 2019 ; Willett et al, 2020 ; Fifer et al, 2022 ; Chivukula et al, 2021 ; Andersen and Aflalo, 2022 ) discussion question is: how well do these findings generalize to the brains of able-bodied individuals? Specifically, do the observed phenomena result from partial reorganization ( Kambi et al, 2014 ; Nardone et al, 2013 ) after spinal cord injury, or do they reflect intact motor circuits, preserved from before injury ( Makin and Bensmaia, 2017 )?…”

Preserved motor representations after paralysis

“…Gaussian receptive fields have been useful tools for understanding digit topographies within the sensorimotor cortex 30,53 . In another study with participant X, we found that the same recorded population encodes actual touch 54 with a Gaussian-like receptive fields. Based on these results, here the somatotopy model can be thought of as a sensory-consequence model.…”

Invisible doppelgänger and body image disorders in right superior parietal lobule stroke, a case series

“…Acute vascular lesions involving a parietal lobe were mostly associated with BIBS disorders, 14 while FOP is rarely presented with a circumscribed cerebral pathology due to acute vascular lesions. Other patients with larger and extensive even bilateral SPL and precuneus lesions have not reported these symptoms 15 . In our registry, there are no other cases with the same lesion and no such symptoms to compare the side and extent of the lesions.…”