BRAIN RESPONSES TO DETECTION OF RIGHT OR LEFT SOMATIC TARGETS ARE SYMMETRICAL IN UNILATERAL PARKINSONS-DISEASE - A CASE AGAINST THE CONCEPTOF PARKINSONIAN NEGLECT

Signs of attentional dysfunction mimicking spatial neglect have been d escribed both in humans with lateralised Parkinson's Disease (PD) and in animals with MPTP-related hemiparkinsonism. Such deficits have been attributed to dopamine loss in basal ganglia and cortical targets. Ho wever, in previous studies the existence of neglect was assumed from b ehavioural tests which needed a motor output, thus entailing interpret ation ambiguities due to effects of directional hypokinesia. We record ed brain event-related potentials (ERPs) evoked by the presentation of target somatic stimuli to the affected and non-affected sides in 44 p atients with unilateral or asymmetrical PD. The N2 and P3 ERP componen ts were specifically analysed, since (a) they are triggered selectivel y by I-ask-relevant, attended sensory stimuli; (b) their latency refle cts stimulus evaluation time, independently from the execution of a mo tor response, and (c) they have proved to be abnormal in hemineglect s yndromes due to focal brain lesions. Irrespective of the side (left or right) of motor symptom predominance there were no significant ERP di fferences to stimulation of the affected and non-affected limbs, nor w as there any correlation between ERP latencies and the degree of dopam ine related motor impairment. The P3 latency was abnormally delayed in 23% of the patients, but there was no trend for abnormalities to conc entrate on the affected side. This study does not confirm the existenc e of a significant attentional impairment toward the affected limb in lateralised PD, and suggests that previous clinical evidence of 'negle ct' behaviour in PD might be linked to directional hypokinesia, thus r eflecting intentional, rather than attentional lateralised deficits.