Visual associative agnosia: aclinico-anatomic al study

SUMMARY A single casestudy ofapatient withvisual associative agnosia isdescribed. Thepatient hadwell preserved language, spatial, visual, andperceptual abilities butnevertheless was impaired inrecognising visually presented common objects. Itisargued thathisdeficit cannotbeaccounted forintermsofa disconnection syndrome. Behavioural andanatomical (MRIscan) evidence for focal unilateral dysfunction ispresented. Itisconcluded that theleft hemisphere plays acrucial role inrecognising themeaning ofcommon objects. Although impairment intherecognition ofvisually presented commonobjects withpreserved perceptual skills mayoccur occasionally inthecontext ofsevere aphasia ordementia, itisveryrarely observed asa selective deficit. Indeed convincing casesofvisual associative agnosia havebeensorare that its existence asaneurological syndrome hasbeendisputed.' Ina retrospective analysis ofover400cases ofunilateral cerebral lesion HecaenandAngelergues2 detected onlyonepatient inwhomthedeficit wasrelatively selective andthree further cases werenoted inwhom itoccurred inthecontext ofother severe cognitive impairments. DeRenzi etalhavereported asimilar lowincidence.3 Several cases ofvisual associative agnosia have beendescribed intheliterature; however, themajority havecomplicated additional disorders4-7 orextensive bilateral brain lesions.8"- Itispossible that there isonly onecase(although mild) ofaunilateral lesion giving rise tothis syndrome inits "pure" form. Hecaenetal2investigated quantitatively apatient whonotonlyhadsomedifficulty innaming common objects butwasalso impaired indescribing their function, indemonstrating their useandinallocating themtoacategory ofsimilar objects. Hewasalso profoundly dyslexic. Atthesametimehewasable to perform stringent perceptual tests (such asthePoppelreuter overlapping figures task) indicating that his visual processing capacity andperceptual analysis Address forreprint requests: DrRA McCarthy, DeptofExperimental Psychology, Downing St,Cambridge, UK.