Visuospatial neglect, most commonly associated with injury to the right cerebral hemisphere, is primarily a disorder of attention. Whilst at its core there undisputedly lies a spatially-lateralised bias, there is now wide acceptance that it also comprises non-spatial components, including deficits of selective and sustained attention. Furthermore, following reports of reward-related improvement in neglect, there is increasing evidence that motivational factors may be involved, which may be amenable to dopaminergic modulation. The experiments described here aim to examine the interaction between reward and the non-spatial components of the neglect syndrome, and to determine what influences dopamine has on the disorder and on the reward-attention interaction in neglect.
The effect of anticipated monetary reward on the attentional blink (AB), an index of temporal selective visual attention, was assessed using a rapid serial visual presentation task. Whilst reward abolished the AB effect in healthy controls, it improved overall performance of stroke patients, which was more evident in patients whose neglect had recovered. Reward modulation of sustained attention, probed using a continuous performance task, was also apparent. The effects were much clearer in the control group compared to stroke patients, and the majority of stroke patients did not exhibit a reward-attention response.
Finally, I investigated how dopaminergic stimulation affects reward and attention in neglect. Compared to placebo, a single dose of levodopa improved cancellation and working memory, and reward was again shown to modulate neglect. Levodopa appeared to induce a reward-attention interaction in those patients where this was previously absent, but conferred no advantage in those with a pre-existing motivational response.
These results confirm that attentional deficits in the neglect syndrome are amenable to motivational and dopaminergic modulation. Furthermore, they shed light on the dynamics between reward-attention interactions and dopamine, increasing the understanding of how these might be harnessed for effective neglect rehabilitation.Open Acces
