A multivariate classification study of attentional orienting in patients with right hemisphere lesions.

Objective: To characterize patterns of orienting dysfunction that were typical to patients with lesions in the right hemisphere (RH).

Background: Brain lesions in the right hemisphere are commonly associated with dysfunction of visual orienting (e.g., visual neglect and extinction). In a clinical study of these symptoms, the multicomponent nature of attentional orienting calls upon a multivariate statistical design with careful selection of neurocognitive variables.

Methods: Thirty-eight patients with verified brain lesions and four patients with peripheral motor dysfunction after poliomyelitis were included in the study. Cognitive function was evaluated in all patients. Three reaction-time (RT) measures derived from the cue-target paradigm were selected as features in a data-driven multivariate classification scheme to generate natural subgroups of patients.

Results: Four subgroups were generated, with only RH patients allocated to two of them. All patients within one of the RH subgroups were characterized by a pattern of impairment earlier described as a "disengage failure" by Posner et al. ( 5, 6), signs of visual neglect on Behavioral Inattention Test, and a severely impaired cognitive function. Results for the other RH subgroup were heterogeneous on both experimental and clinical variables. Age and cognitive function were found to strongly influence two of the features, but could not predict the clusters generated from the RT measures.

Conclusions: The present findings show that the cue-target paradigm together with multivariate clustering of selected feature variables can serve as a useful tool to explore and characterize patients with right hemisphere lesions. Although the concept of "disengage failure" was suited to describe the typical RT pattern in patients with neglect, other neurocognitive models and concepts can be applied to the results in the current study.