Article

Left unilateral spatial neglect resulting from right brain damage is
characterized by loss of awareness for stimuli in the contralesional side of
space, despite intact visual pathways. We examined using fMRI whether patients
with neglect are more likely to consciously detect in the neglected hemifield,
emotionally negative complex scenes rather than visually similar neutral pictures
and if so, what neural mechanisms mediate this effect. Photographs of emotional
and neutral scenes taken from the IAPS were presented in a divided visual field
paradigm. As expected, the detection rate for emotional stimuli presented in the
neglected field was higher than for neutral ones. Successful detection of
emotional scenes as opposed to neutral stimuli in the left visual field (LVF)
produced activations in the parahippocampal and anterior cingulate areas in the
right hemisphere. Detection of emotional stimuli presented in the intact right
visual field (RVF) activated a distributed network of structures in the left
hemisphere, including anterior and posterior cingulate cortex, insula, as well as
visual striate and extrastriate areas. LVF-RVF contrasts for emotional stimuli
revealed activations in right and left attention related prefrontal areas whereas
RVF-LVF comparison showed activations in the posterior cingulate and extrastriate
visual cortex in the left hemisphere. An additional analysis contrasting detected
vs. undetected emotional LVF stimuli showed involvement of left anterior
cingulate, right frontal and extrastriate areas. We hypothesize that beneficial
role of emotion in overcoming neglect is achieved by activation of frontal and
limbic lobe networks, which provide a privileged access of emotional stimuli to
attention by top-down modulation of processing in the higher-order extrastriate
visual areas. Our results point to the importance of top-down regulatory role of
the frontal attentional systems, which might enhance visual activations and lead
to greater salience of emotional stimuli for perceptual awareness.
CI - Copyright (c) 2011 Elsevier Ltd. All rights reserved.

Langue : ANGLAIS