Connecting the lines after a stroke

Abstract

In mice, stimulating cortical areas in the undamaged hemisphere of a brain affected by stroke impairs recovery.

Keywords: brain; functional connectivity; mouse; neuroscience; optogenetics; plasticity; stroke.

Figure 1.. Stimulating cortex areas contralateral to the site of a stroke impairs recovery and reconnection.

(A) Dorsal view of the human brain. Cortical areas in the human brain are functionally connected with regions in both the same (ipsilateral) and opposite (contralateral) hemisphere. These connections (represented by arrows) are present when brain areas are co-active in time and are associated with a behavioral output, such as moving or sensing the hand. (B) Dorsal view of the mouse brain. Stimulation of the mouse forepaw activates a specific region of the primary somatosensory cortex that the paw is mapped on to, which is the area studied by Bice et al. (C) Inducing a stroke in the forepaw area (red circle) stops the activation of this region and the surrounding cortex following forepaw stimulation for at least seven days. At later time points (one month), stimulation of the forepaw is once again able to activate the brain, this time in a forepaw representation that is shifted to a new site due to cortical plasticity. At later time points, the forepaw cortical area is re-integrated into a network in which it is connected to ipsilateral sensory, motor and cortical associated areas, and contralateral sensory and motor areas. (D) Chronic, daily stimulation of the somatosensory cortex that is contralateral to the stroke site (lightning bolt) impairs the local remapping of the forepaw area and interferes with the integration of the recovered cortex into functional brain networks. Under these conditions, callosal connections, when activated, actually inhibit large areas of the cortex in the opposite hemisphere.