Adaptation to leftward-shifting prisms reduces the global processing bias of healthy individuals.
When healthy individuals are presented with peripheral figures in which small letters are arranged to form a large letter, they are faster to identify the global- than the local-level information, and have difficulty ignoring global information when identifying the local level. The global reaction time (RT) advantage and global interference effect imply preferential processing of global-level information in the normal brain. This contrasts with the local processing bias demonstrated following lesions to the right temporo-parietal junction (TPJ), such as those that lead to hemispatial neglect (neglect). Recent research from our lab demonstrated that visuo-motor adaptation to rightward-shifting prisms, which ameliorates many leftward performance deficits of neglect patients, improved the local processing bias of patients with right TPJ lesions (Bultitude, Rafal, & List, 2009). Here we demonstrate that adaptation to leftward-shifting prisms, which can induce neglect-like performance in neurologically healthy individuals, also reduces the normal global processing bias. Forty-eight healthy participants were asked to identify the global or local forms of hierarchical figures before and after adaptation to leftward- or rightward-shifting prisms. Prior to prism adaptation, both groups had greater difficulty ignoring irrelevant global information when identifying the local level (global interference) compared to their ability to ignore irrelevant local-level information when identifying the global level (local interference). Participants who adapted to leftward-shifting prisms showed a significant reduction in global interference, but there was no change in the performance of the rightward-shifting Prism Group. These results show, for the first time, that in addition to previously demonstrated effects on lateralised attention, prism adaptation can influence non-lateralised spatial attention in healthy individuals.
Bultitude
Janet H
JH
Wolfson Centre for Clinical and Cognitive Neuroscience, School of Psychology, Bangor University, United Kingdom. j.bultitude@bangor.ac.uk
Woods
Jill M
JM
D000222:Adaptation, Physiological / Q000502:physiology*; D000328:Adult; D001288:Attention / Q000502:physiology*; D015982:Bias; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests; D010775:Photic Stimulation / Q000379:methods; D011601:Psychophysics; D013997:Time Factors; D014794:Visual Fields / Q000502:physiology*; D014796:Visual Perception; D055815:Young Adult