RIGHT-LEFT CONFUSION IN GERSTMANNS SYNDROME - A MODEL OF BODY-CENTERED SPATIAL ORIENTATION

Gerstmann's syndrome encompasses the tetrad of finger agnosia, agraphi a, acalculia and right-left confusion and is associated with lesions o f the dominant angular gyrus. The localizing value of this syndrome ha s been questioned because multiple mechanisms can account for each of the components of the syndrome. We present the case of a man who devel oped Gerstmann's syndrome following a focal infarct of the left angula r gyrus. The patient's right-left confusion could not be accounted for by either an aphasia or a degraded body schema. A series of experimen ts that investigated the patient's spatial mapping system by progressi vely restricting the degrees of freedom for spatial rotation revealed an isolated defect in deriving the relative position of an object alon g the horizontal axis. Defective horizontal mapping can account for th e other components of Gerstmann's syndrome because they all share a co mmon dependency on relative horizontal positioning.