Modulation of connectivity in visual pathways by attention: cortical interactions evaluated with structural equation modelling and fMRI |
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Authors: | Buchel C; Friston KJ |
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Institution: | The Wellcome Department of Cognitive Neurology, Institute of Neurology, London, UK. cbuechel@fil.ion.ucl.ac.uk |
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Abstract: | Electrophysiological and neuroimaging studies have shown that attention to
visual motion can increase the responsiveness of the motion- selective
cortical area V5 and the posterior parietal cortex (PP). Increased or
decreased activation in a cortical area is often attributed to attentional
modulation of the cortical projections to that area. This leads to the
notion that attention is associated with changes in connectivity. We have
addressed attentional modulation of effective connectivity using functional
magnetic resonance imaging (fMRI). Three subjects were scanned under
identical stimulus conditions (visual motion) while varying only the
attentional component of the task. Haemodynamic responses defined an
occipito-parieto-frontal network, including the, primary visual cortex
(V1), V5 and PR A structural equation model of the interactions among these
dorsal visual pathway areas revealed increased connectivity between V5 and
PP related to attention. On the basis of our analysis and the
neuroanatomical pattern of projections from the prefrontal cortex to PP we
attributed the source of modulatory influences, on the posterior visual
pathway, to the prefrontal cortex (PFC). To test this hypothesis we
included the PFC in our model as a 'modulator' of the pathway between V5
and PP, using interaction terms in the structural equation model. This
analysis revealed a significant modulatory effect of prefrontal regions on
V5 afferents to posterior parietal cortex.
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