This study with the so far largest number of prospectively recruited patients with PD-MCI indicates that non-amnestic PD-MCI is more frequent than amnestic PD-MCI; executive dysfunctions are the most typical cognitive symptom in PD-MCI; and age, gender and global cognition predict the PD-MCI subtype. Longitudinal data are needed to test the hypothesis that patients with PD-MCI with specific cognitive profiles have different risks to develop dementia.

ObjectivesParkinson’s disease (PD) is the second most common neurodegenerative disorder and is further associated with progressive cognitive decline. In respect to motor phenotype, there is some evidence that akinetic-rigid PD is associated with a faster rate of cognitive decline in general and a greater risk of developing dementia.The objective of this study was to examine cognitive profiles among patients with PD by motor phenotypes and its relation to cognitive function.MethodsDemographic, clinical and neuropsychological cross-sectional baseline data of the DEMPARK/LANDSCAPE study, a multicentre longitudinal cohort study of 538 patients with PD were analysed, stratified by motor phenotype and cognitive syndrome. Analyses were performed for all patients and for each diagnostic group separately, controlling for age, gender, education and disease duration.ResultsCompared with the tremor-dominant phenotype, akinetic-rigid patients performed worse in executive functions such as working memory (Wechsler Memory Scale-Revised backward; p=0.012), formal-lexical word fluency (p=0.043), card sorting (p=0.006), attention (Trail Making Test version A; p=0.024) and visuospatial abilities (Leistungsprüfungssystem test 9; p=0.006). Akinetic-rigid neuropsychological test scores for the executive and attentive domain correlated negatively with non-tremor motor scores. Covariate-adjusted binary logistic regression analyses showed significant odds for PD-mild cognitive impairment for not-determined as compared with tremor-dominant (OR=3.198) and akinetic-rigid PD (OR=2.059). The odds for PD-dementia were significant for akinetic-rigid as compared with tremor-dominant phenotype (OR=8.314).ConclusionThe three motor phenotypes of PD differ in cognitive performance, showing that cognitive deficits seem to be less severe in tremor-dominant PD. While these data are cross-sectional, longitudinal data are needed to shed more light on these differential findings.

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Only a few studies have explored cognitive changes with deep brain stimulation (DBS) in patients with essential tremor (ET). Furthermore, the cognitive effects after years of electrical stimulation are unknown. Assessing the impact of stereotactic electrode implantation and the actual electrical stimulation on cognition in patients with ET in the short and long term is of interest, because DBS is increasingly applied and can offer deeper insight into human brain functions. We examined nine ET patients before surgery (PRE-SURGERY), and 1 and 6 years thereafter with DBS switched on (DBS-ON) and off (DBS-OFF). Standardized neuropsychological tests and reaction time tests were applied. There were no differences in tasks of verbal fluency, memory, and executive and intellectual functions comparing PRE-SURGERY, DBS-ON, and DBS-OFF at 1 and 6 years post-surgery. Imaging data revealed that the dorsolateral prefrontal cortex and mamillo-thalamic tracts crucial for cognitive functioning were spared by electrode implantation. Additionally, with electrodes targeting the thalamus and adjacent subthalamic area, the actual electrical stimulation did not affect neuropsychological functioning. However, lesions caused by electrode implantation led to an increase in simple reaction time, while the actual electrical stimulation restored impaired reaction time. This is the second largest study of neuropsychological functioning in patients with ET treated with DBS, and the first covering a neuropsychological long-term follow-up over 6 years. Neither stereotactic surgery nor electrical stimulation affected higher cognitive processes. This study proposes that cerebello-thalamo-cortical pathways in humans are involved in tasks of simple reaction time.

Clinical, experimental, and functional imaging studies suggest overlapping neuronal networks and functional interactions of alertness and visuospatial attention within the right hemisphere of the brain. To examine the interaction of arousal and visuospatial attention in peripersonal and extrapersonal virtual space, we tested 20 healthy male adults during 24 hr of sleep deprivation at four points during the night (9 p.m., 1 a.m., 5 a.m., and 9 a.m.). The main finding concerning covert orienting in a virtual environment is a highly significant slowing of reorientation toward the left visual hemifield in extrapersonal space due to decreased arousal. The results provide additional evidence for the proposed anatomical and functional overlap of the two attentional systems and indicate a modulation of visuospatial attention by the level of arousal in extrapersonal space. (JINS, 2008, 14, 309-317.)

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Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is a treatment option for patients with Parkinson's disease (PD) in the advanced stage. Besides motor improvement, DBS of the STN may also modulate cognitive and attentional functions of the basal ganglia. In our study, 13 patients with PD and bilateral DBS of the STN were assessed with DBS switched on and off by the use of a wide range of neuropsychological tasks. This included reasoning, cognitive flexibility, phonemic and semantic word fluency, verbal and nonverbal short-term memory, learning, delayed verbal memory recall, and stimulus-response incompatibility. Special emphasis was put on basic attentional functions, in particular intrinsic and phasic alertness as well as visual search. DBS significantly improved intrinsic alertness, whereas phasic alertness and other neuropsychological domains were not affected. Additionally, the effects on intrinsic alertness were independent of motor improvements by DBS. The findings suggest that DBS modulates the fronto-parietal network of alertness.