Striatal dopamine correlates to memory and attention in Parkinson's disease.

Parkinson's disease (PD) is clinically characterized by motor symptoms, however, specific cognitive impairments are common and poorly understood. This study was designed to assess whether cognitive performances are related to dopamine active transporter (DAT) availability in non-demented PD subjects. Fifty-four non-demented PD patients were enrolled. They underwent [99mTc] TRODAT-1 SPECT/CT and a comprehensive neuropsychological battery including attention/executive and memory tests. Multiple linear regression controlling the effect of age, disease duration and education was applied. The significance level was set at P values of < 0.02. After controlling the effect of age, disease duration and education, lower scores in Rey's Auditory-Verbal Learning Test (RAVLT)/immediate recall were significantly related with lower uptake values in the less affected striatum and more affected caudate. Lower scores in RAVLT/short-term recall were also significantly associated with lower uptake values in the more affected caudate and reduced performance in Trail Making Test part B was related with reduced DAT values in the less affected anterior putamen. Our findings suggest that reduced DAT availability in both caudate and putamen is related to reduced performances in some memory and attention/executive tasks. Nigrocaudate dysfunction is related to lower memory performance while dopamine depletion in the anterior putamen is related to poorer attention performance. If the dopaminergic defects can mostly explain all the cognitive symptoms or this phenomenon just co-occur with other anatomical and biochemical changes remains unknown. Further studies in larger patient samples are required to clarify this issue.

Is the dopaminergic loss associated with gait and postural impairments in subjects with Parkinson's disease at different motor stages?

Gait and postural control deficiencies in Parkinson's disease (PD) involve several specific motor aspects. The aim of this study was to identify and compare the main changes in gait kinematics and postural control with dopaminergic loss in the striatum region. This is a cross-sectional study that included 42 individuals with PD at different motor stages, according to the Hoehn & Yahr scale (H&Y). Motor subsection of the Movement Disorder Society-Unified Parkinson Disease Rating Scale-part III (MDS-UPDRS III) was used to evaluate general motor aspects. Gait kinematics was assessed using a three-dimensional motion capture system. Postural control was assessed by stabilometry using force platforms. Dopamine depletion was verified through 99mTc-TRODAT-1 (SPECT-CT) examination. We included 12, 15 and 15 individuals classified as H&Y I, II and III, respectively. We identified worse values of dopamine transporter uptake, MDS-UPDRS III, gait parameters (velocity, step length and stride length) and center of pressure displacement as the disease progressed. Our results indicate that higher dopaminergic loss and gait and postural control deficits occur between the H&Y levels II and III.