If you read my post on visual neglect, (or if not you can read it here), you will know that damage to the right posterior parietal cortex can cause patients to be biased to information on the right side, and ignore stimuli on the left. This is because each hemisphere processes visual information from the opposite side of space. Therefore, patients will show symptoms such as not eating the food from the left side of their plate, or moving their limbs on their left side.
One clinical test which is used to show this rightward bias in attention is the line bisection task: participants are presented with a horizontal line, and have to put a mark at the midpoint. As you can see from the example below, neglect patients will put their mark towards the right side of the line.
However, you might not have noticed that healthy participants are biased for the left side, and will place their mark slightly towards the left of the midline. This has been termed pseudoneglect (Bowers & Heilman, 1980), as it has been suggested that healthy individuals show a weak form of neglect for the right side of space. This is the opposite deficit to that of neglect patients, who show a bias towards the right.
These findings therefore suggest a functional asymmetry between the hemispheres in controlling spatial attention (McCourt & Jewell, 1999). The right hemisphere is therefore thought to have a greater influence in directing spatial attention, as a bias is shown for the left side of space.
I hope you enjoyed this post, check back next week for a new update.