Body Scheme Gates Visual Processing

Abstract

. We used functional magnetic resonance imaging (fMRI) to explore how guidance of motor acts is influenced by the visually perceived body scheme. We found that when subjects view their hand as their opposite hand, i.e., the right hand is seen as the left hand and vice versa, activation in the visual cortex was lateralized opposite to the seen hand. This demonstrates for the first time that our body scheme to which vision relates our environment is already represented at the level of visual cortex.

Effect of a mirror-like illusion on activation in the precuneus assessed with functional near-infrared spectroscopy

“…[14][15][16] Apart from M1, Dohle and coworkers suggested an involvement of the precuneus (PC) of either hemisphere. 10,11 This area was also found to be activated in stroke patients under mirrored visual feedback only during bimanual movements. 17 One of the reasons for this heterogeneity of these results might be the heterogeneity in the chosen methodological approach to implement the mirror illusion.…”

“…15 In order to allow a systematic and randomized variation of the seen and moved hand without changing other cofactors, we implemented a mirror-like paradigm in accordance with the previous study of Dohle et al 10 by means of a video chain (Fig. 1).…”

“…7,8 In normal subjects, inversion of the visual feedback has already been shown to lead to an activation of the hemisphere ipsilateral to the moving hand. [9][10][11][12][13] However, in these studies, a change of activity in the ipsilateral primary motor cortex (M1) could not been established consistently. Similarly, studies using transcranial magnetic stimulation did not show consistent increase of cortico-muscular excitability due to the mirror illusion.…”

“…12 We, thus, decided to investigate this issue in a systematic fashion. In accordance with previous fMRI studies, 10,19 we made use of a video setup in order to establish a mirror-like illusion (MIR), allowing a systematic, randomized variation of the visual feedback. In order to allow subsequent studies for comparison of these effects with that of a real mirror, functional near-infrared spectroscopy (fNIRS) was selected for registration of brain activity.…”

Interactive visuo-motor therapy system for stroke rehabilitation

“…In mirror therapy, cortical representations of hand visual configuration and movements are lateralized contralateral to the limb performing the action [25]. If the visual input provided to a test subject is the mirror image of an upper limb action being performed, the activation switches to the ipsilateral side [8]. This phenomenon could possibly be exploited to stimulate a damaged region of motor cortex by using the non-paretic limb to control a visual representation of the paretic limb.…”