Dear Dr. Husain,
I guess the patients they may be able to detect still sth. in their neglected side? So I changed from "non-neglected side" to "neglected side".
Great article. I enjoyed reading it and cannot imagine how to improve it.
Maybe a figure depicting imaginal neglect (halved Piazza del Duomo or similar) might increase the impact with non-specialists?
If you wish, I can send you a powerpoint slide I always use in presentations. But this is not, of course, a crucial issue.
User 3: Left parietal lesions?
Hi Dr. Husain,
Great article. I really learned quite a bit from it. I have a question - why is neglect associated more with right parietal injury/lesions than left? Is this because there are fewer cases of left parietal lesions (though that seems unlikely)? Or is it that those with left parietal lesions do not suffer from neglect? If the biased competition theory of neglect is true, then lesions to either side should cause neglect on the contralesional side, but it seems that right parietal has a much greater correlation with the condition. Does right parietal do something special for attention that the left doesn't? I vaguely recall something from Rafal about right parietal being associated with the global direction of attention, but I don't fully understand it...
Navaneethan Santhanam (firstname.lastname@example.org)
Thanks for your interesting question. I'm afraid there is no established answer but below are some views on this issue:
1) To the best of my knowledge, strokes affecting the left parietal lobe are just as frequent as those affecting the right.
2) In general, the literature suggests rightward neglect from left hemisphere lesions are usually faster to resolve and therefore less frequent in the chronic stage. The left hemisphere syndrome is also often less profound, although there are always exceptions that most clinicians will have seen.
3) The biased competition model would indeed suggest that lesions to either hemisphere should cause attentional biases. And perhaps this is the explanation for the phenomenon of extinction being common after left and right hemisphere lesions, although some authors contend it is more frequent after right.
4) I tend to favour the view that the right parietal cortex does indeed do 'something special' and these functions are not necessarily spatial: for example, sustaining attention over time. When combined with attentional biases, deficits in such functions might be more likely to lead to neglect, rather than extinction alone. Other authors might stress the role of the right hemisphere for global processing of a scene, so when it is damaged there is a bias to local porcessing or shrinkage of the effective field of view. Again, when combined with attentional baises this might account for greater neglect after right hemisphere damage.