Visual object recognition in multiple sclerosis

Deficits in tasks measuring visual processing have been earlier reported in studies of MS. Yet. the nature and severity of visual-processing deficits in MS remains unclear. We used a new method in order to measure the differe nt stages of visual processing in object recognition: shape recognition, fa miliarity recognition, semantic categorization, and identification with nam ing. Six two-choice reaction-time tasks were presented to 30 MS patients an d 15 healthy controls. The patients were divided into cognitively preserved and cognitively deteriorated study groups according to Their cognitive sta tus. The purpose was to find out whether deficits at specific stages of vis ual processing can be found in cognitively deteriorated MS patients Cogniti vely deteriorated MS patients did not perform as well as cognitively preser ved MS patients or healthy controls. They were slower already at the early stage of visual processing where discrimination of whole objects from scram bled ones was required. They also had higher error rates in tasks requiring object familiarity detection and object identification with naming. Thus, cognitively deteriorated MS patients had difficulties in visual shape recog nition and semantic-lexical processing. However, variation of performances was large within both of the patient groups indicating that even patients w ithout a generalized cognitive decline may have deficits in some stages of the visual processing. We suggest that because of the heterogeneity of the patients, every single case needs to be examined separately in order to ide ntify the possible deficits in visual processing. (C) 2001 Elsevier Science B.V, All rights reserved.