Affiliations: Department of Cognitive Neuroscience, Faculty of
Psychology and Neuroscience, University of Maastricht, Maastricht, The
Netherlands | Maastricht Brain Imaging Center, Maastricht, The
Netherlands
Note: [] Corresponding author: Alexander Sack, Department of Cognitive
Neuroscience, Faculty of Psychology and Neuroscience, Maastricht University,
P.O. Box 616, 6200 MD, Maastricht, The Netherlands. E-mail:
a.sack@maastrichtuniversity.nl
Abstract: Visuospatial processing refers to the spatial perception,
recognition and analysis of visual input. Human functional brain imaging
studies have consistently revealed the involvement of fronto-parietal brain
areas during the execution of visuospatial tasks. Just as the execution of
these tasks activates fronto-parietal regions in the healthy brain, lesions to
those structures, e.g. after stroke or brain injury, cause specific spatial
deficits. The most prominent of these is known as spatial neglect. There are
several competing theories on the neural mechanisms underlying spatial neglect.
Although each of these theories postulates different underlying physiological
mechanisms, they all account in their own way for the fact that the prevalence
of neglect is much higher following right hemisphere lesions. This makes it
difficult to distinguish between the different models at a behavioural level.
Until today, it was impossible to empirically address these matters and to
provide direct and conclusive empirical evidence in favour of one of the
competing theories of spatial neglect. This review article describes the neural
correlates of intact visuospatial processing as revealed by non-invasive
functional brain imaging studies. It subsequently focuses on the approach of
using the non-invasive brain inference technique of transcranial magnetic brain
stimulation (TMS) to transiently and reversibly disrupt neural activity in
these visuospatial processing-related brain regions. Using this approach, we
can now imitate specific spatial deficits and neglect-like symptoms in healthy
volunteers. Mimicking and manipulating the spatial deficits following
unilateral brain lesions, under controlled experimental conditions, may allow
for the development of new therapeutic interventions for parietal stroke
patients suffering from real spatial neglect. The perspective is to use
non-invasive brain interference to guide and promote functional recovery on a
brain-system level in stroke and neglect patients, based on knowledge directly
derived from fundamental brain research in healthy volunteers.
