Impaired neural processing of dynamic faces in left-onset Parkinson's disease

Parkinson's disease (PD) affects patients beyond the motor domain. According to previous evidence, one mechanism that may be impaired in the disease is face processing. However, few studies have investigated this process at the neural level in PD. Moreover, research using dynamic facial displays rather than static pictures is scarce, but highly warranted due to the higher ecological validity of dynamic stimuli. In the present study we aimed to investigate how PD patients process emotional and non-emotional dynamic face stimuli at the neural level using event-related potentials. Since the literature has revealed a predominantly right-lateralized network for dynamic face processing, we divided the group into patients with left (LPD) and right (RPD) motor symptom onset (right versus left cerebral hemisphere predominantly affected, respectively). Participants watched short video clips of happy, angry, and neutral expressions and engaged in a shallow gender decision task in order to avoid confounds of task difficulty in the data. In line with our expectations, the LPD group showed significant face processing deficits compared to controls. While there were no group differences in early, sensory-driven processing (fronto-central N1 and posterior P1), the vertex positive potential, which is considered the fronto-central counterpart of the face-specific posterior N170 component, had a reduced amplitude and delayed latency in the LPD group. This may indicate disturbances of structural face processing in LPD. Furthermore, the effect was independent of the emotional content of the videos. In contrast, static facial identity recognition performance in LPD was not significantly different from controls, and comprehensive testing of cognitive functions did not reveal any deficits in this group. We therefore conclude that PD, and more specifically the predominant right-hemispheric affection in left-onset PD, is associated with impaired processing of dynamic facial expressions, which could be one of the mechanisms behind the often reported problems of PD patients in their social lives

Selective loss of dopamine d2 receptors in temporal cortex in dementia with Lewy bodies, association with cognitive decline

Dementia with Lewy bodies (DLB) is a progressive dementia frequently accompanied by psychotic symptoms. Similar symptoms can occur in Alzheimer's disease (AD) to a lesser extent. The use of neuroleptic medication to treat psychosis in both diseases is of modest efficacy and can induce severe adverse reactions in DLB. Dopamine D2 receptors in the cerebral cortex are the putative target for the antipsychotic action of these drugs, but the status of these receptors in DLB is unknown. Autoradiography was used to examine the density D2 receptors in postmortem temporal cortex tissue from prospectively assessed patients with neuropathologically confirmed DLB and AD. D2 receptors were substantially (over 40%) and significantly (P < 0.001) reduced in temporal cortex in DLB, and in DLB with concomitant Alzheimer pathology, but was not significantly changed in AD. This reduction correlated with greater cognitive decline (P < 0.01), but was not significantly related to visual or auditory hallucinations or delusions. D2 receptor density was inversely correlated with cortical Lewy body pathology in the neocortex (P < 0.001). The specific loss of D2 receptors associated with Lewy body pathology, in conjunction with our previous finding of low D2 receptors in striatum in DLB, provides a possible explanation for neuroleptic intolerance. That the reduction of D2 receptors correlated with cognitive decline suggests that neuroleptics, as dopamine D2 receptor antagonists, may have a deleterious effect on cognition in DLB