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Elizabeth Torres, Kyuwan Choi; A neural correlate of intentionality persists in the parietal cortex of a patient without proprioception. Journal of Vision 2014;14(10):1102. doi: https://doi.org/10.1167/14.10.1102.
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The posterior parietal cortex (PPC) has been identified as a critical node to encode the intention to move (Andersen and Buneo, 2002). Recently it has been asked whether or not this region encodes an abstract intentional signal, a signal independent of afferent inputs from active movements (kinesthetic re-afference) (Desmurget and Sirigu 2009, 2012). In this work we investigate this question in patient Ian Waterman (IW) who lost his sense of movement (proprioception) at 19 years of age due to large fiber neuropathy. IW replaced his sense of proprioception with vision and regained control of his movements. Yet he always has to predict ahead the sensory consequences of his actions, a forward-computation that is also thought to occur in the posterior parietal region (Mulliken et al., 2008). We compared the electroencephalographic (EEG) patterns of IW to those of 15 neurotypical participants as they mastered a Brain Computer Interface (BCI) and gained volitional-mental control of the direction of motion of an external cursor. We examined patterns of activation across different frequency bands and used synchronization metrics of phase locking value and phase lagging index to assess coupling patterns that self emerged during the learning progression. The participants were trained using visual feedback. A subset (including IW) was tested using auditory feedback as well, even though they never trained under this form of sensory guidance. We found coupling along the fronto-parietal networks that differed between controls and patient-IW. Specifically, as neurotypical participants improved the intentional mind-control of the cursor, they engaged the prefrontal cortex (PFC) with the highest levels of activation. In contrast, patient IW engaged the PPC with the highest levels of activation all throughout. These results strongly suggest that (1) the intentional signal in the PPC stands independent of re-afference and (2) The PFC typically encodes an externally-prompted intentional signal.
Meeting abstract presented at VSS 2014
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