Effects of right-hemisphere cortical infarction and muscarinic acetylcholine receptor blockade on spatial visual attention performance in rats

The syndrome of hemispatial neglect is defined as an inability to report, respond or orient to stimuli contralateral to a cerebral lesion despite intact elementary sensory or motor function. This syndrome is typically observed after lesions of the right cerebral cortex, and has been associated with impairment of attention. We studied whether visual attention performance is impaired after right-hemisphere infarction in rats. Using a behavioural paradigm measuring spatial visual attention, we tested the effects of photothrombotic infarction to either the frontal cortex or the parietal cortex on attention performance. Since the cholinergic system is known to modulate attention performance, we additionally evaluated the role of cholinergic receptor blockade with scopolamine in our task paradigm. Our results show a transient response bias immediately after cortical infarction, with a decrease in contralesional responses and an increase in contralesional omissions after frontal infarction. Parietal infarction and systemic administration of scopolamine also resulted in a decrease in correct responses and an increase in omissions, but without a difference in side responding. In conclusion, right frontal infarction induces a transient impairment in contralesional spatial visual attention that we explain as left-sided neglect. Right parietal infarction and cholinergic blockade shows non-lateralized deficits in spatial visual attention, suggestive of global attentional impairment. We postulate that both effects of cortical infarction on attention performance may be related to cholinergic dysfunction. Our study confirms the role of frontal and parietal cortices in attention performance in rats, and corroborates the theory that attention performance is impaired in hemispatial neglect in human stroke patients.