The paper “Role of somatosensory cortex in visuospatial attention” by Balslev, Odoj and Karnath has just been accepted for publication at J Neuroscience.
The human somatosensory
cortex (S1) is not among the brain areas usually associated with visuospatial
attention. However, such a function can be presumed, given the recently
identified eye proprioceptive input to S1 and the established links between
gaze and attention. Here we investigated a rare patient with a focal lesion of the
right postcentral gyrus that interferes with the processing of eye proprioception
without affecting the ability to locate visual objects relative to her body or to
execute eye movements. As a behavioural measure of spatial attention we recorded
fixation time during visual search and reaction time for visual discrimination
in lateral displays. In contrast to a group of age-matched controls, the patient
showed a gradient in looking time and in visual sensitivity towards the
midline. Because an attention bias in opposite direction, towards the
ipsilesional space, occurs in patients with spatial neglect, in a second study
we asked whether the incidental co-injury of S1 together with the
neglect-typical perisylvian lesion leads to a milder neglect. A voxelwise
lesion behaviour mapping (VLBM) analysis of a group of right hemisphere stroke
patients supported this hypothesis. The effect of an isolated S1 lesion on visual
exploration and visual sensitivity as well as the modulatory role of S1 in
spatial neglect, suggest a role of this area in visuospatial attention. We hypothesize
that the proprioceptive gaze signal in S1, whereas playing only a minor role in
locating visual objects relative to the body, affects the allocation of
attention in the visual space.
Funded by the Danish Medical Research Councils (DB). With thanks to RW for helping us conducting this study.