BACKGROUND:Proactive interference (PI) refers to the interference of previously learned materials with new learning and reflects the failure of inhibitory processes in memory. Retroactive interference (RI) refers to the unfavorable effect of new learning on the later recall of previously learned information. Although subthalamic nucleus deep brain stimulation (STN-DBS) does not affect global cognition in Parkinson's disease (PD), it has negative effects on specific aspects of cognition, including verbal fluency and executive inhibitory control of action.To this end, we set to test the acute effect of STN-DBS on PI and RI during verbal learning. METHODS:Twenty PD patients with STN-DBS were tested on the California Verbal Learning Test-II using an ON/OFF stimulation design. RESULTS:The results showed that stimulation increased PI ON stimulation (P = 0.012) but had no effect on RI (P = 0.816). CONCLUSIONS:Our results extend the role of STN to the inhibitory control that is required during memory encoding or recall for prevention of PI. © 2020 International Parkinson and Movement Disorder Society.

Parkinson's disease (PD) patients show signs of cognitive impairment, such as executive dysfunction, working memory problems and attentional disturbances, even in the early stages of the disease. Though motor symptoms of the disease are often successfully addressed by dopaminergic medication, it still remains unclear, how dopaminergic therapy affects cognitive function. The main objective of this study was to assess the effect of dopaminergic medication on visual and auditory attentional processing. 14 PD patients and 13 matched healthy controls performed a three-stimulus auditory and visual oddball task while their EEG was recorded. The patients performed the task twice, once on- and once off-medication. While the results showed no significant differences between PD patients and controls, they did reveal a significant increase in P3 amplitude on- vs. off-medication specific to processing of auditory distractors and no other stimuli. These results indicate significant effect of dopaminergic therapy on processing of distracting auditory stimuli. With a lack of between group differences the effect could reflect either 1) improved recruitment of attentional resources to auditory distractors; 2) reduced ability for cognitive inhibition of auditory distractors; 3) increased response to distractor stimuli resulting in impaired cognitive performance; or 4) hindered ability to discriminate between auditory distractors and targets. Further studies are needed to differentiate between these possibilities.

Diagnostic differentiation of neurodegenerative diseases presenting with parkinsonism and dementia can represent a major challenge in clinical practice. Although consensus criteria for dementia with Lewy bodies (DLB) have been defined, the diagnosis can be difficult, in particular the differentiation from Alzheimer's disease (AD) and Parkinson's disease with dementia (PDD). Previous studies have shown that DLB is associated with profound impairment in spatial and perceptual networks of visual information processing. Studies comparing all three syndromes for visuospatial impairment and brain perfusion patterns are lacking and the available results are sometimes controversial or overlapping. The aim of this study was to compare the visual-perceptual and visual-constructional performance in patients with early stage DLB, AD and PDD with results of brain perfusion single photon emission computed tomography (SPECT). We compared three groups of patients (presented in the table) with diagnoses of DLB, AD and PDD defined according to the international consensus criteria. Patients underwent clinical examination, neuropsychological assessment with the The Benton Judgement of Line Orientation (BJLO) test, Benton Facial Recognition (BFR) test and Rey-Osterrieth Complex Figure-Copy (Rey) test and [Tc-99m] ECD brain perfusion SPECT imaging. Three groups were matched in demographic variables and degree of global cognitive status (Mini Mental State Examination). Imaging analyis was performed using statistical parametric maping and multiple regression models. An ANOVA showed significant differences between DLB, PDD and AD groups on BJLO (F (2,40) = 3,48; p < .406) and Rey test (F (2,40) = 4,78; p < .0138) but no differences were found on BFR test. Post hoc Tukey HSD test analysis demonstrated that DLB patients performed significantly worse than AD patients on both BJLO and Rey test. There was a significant positive correlation between frontoparietal perfusion and cognitive perfomance in DLB (p < 0.05, cluster size > 100 voxel). No differences were found between DLB and PDD groups. Subjects with DLB have more severe visual-perception (BJLO) impairments as well as visual-construction (Rey) impairments than AD subjects. These results correlate with hypoperfusion in right parietal and both frontal areas. Otherwise perfusion correlations are not distinctive among diagnostic groups. Our findings confirm the considerable cognitive and perfusion overlap between studied groups as indicated in previous studies.

Through its capacity of plastic changes, the adult brain enables successful dealing with new demands of everyday life and recovery after an acquired brain damage either spontaneously or by the help of rehabilitation interventions. Studies which explored the effects of cognitive training in the normal population report on different types of changes in the performance of cognitive tasks as well as different types of changes in brain activation patterns.Following practice, brain activation can change in its extent, intensity or location, while cognitive processes can become more efficient or can be replaced by different processes.After acquired brain damage plastic changes are somewhat different. After the injury, the damaged brain area can either gradually regain its previous function, or different brain regions are recruited to perform that function.Studies of spontaneous and guided recovery of cognitive functions have revealed both types of plastic changes that follow each other, as well as significant correlations between these changes and improvement on the behavioural level.

BACKGROUND:The main clinical feature of dementia in Parkinson's disease is a dysexecutive syndrome. The neuropathology of PD dementia (PDD) is likely multifactorial and affects several neuronal populations. There is evidence that Parkinson's disease dementia is associated with a cholinergic deficit, supporting the therapeutic role of cholinesterase inhibitors, which are already first-line agents in the treatment of Alzheimer's disease. The paper includes short report on a pilot study with description of cognitive and imaging profiles in patients with mild to moderate stage of Parkinson disease dementia (PDD).SUBJECTS AND METHODS:A random sample of 16 patients with clinical diagnostic criteria for probable PDD was included in the study. Patients were characterized with mild to moderate cognitive decline slightly depressive mood and moderate motor performance. Brain perfusion [(99m)Tc]ECD / SPECT and structural MRI with emphasis on evaluation of the degree of cortical atrophy and the medial temporal atrophy index was performed. All patients had detailed neuropsychological evaluation using a "cognitive process approach". Neuropsychological data were correlated voxel-wise with normalized brain perfusion images, creating whole-brain correlation maps.CONCLUSIONS:Previously reported generalized cognitive impairment in PDD with predominant executive, visouspatial and attentional deficits was confirmed. Performance on specific cognitive measures was correlated with perfusion brain SPECT findings. It could be speculated that different pathological mechanisms underlie widespread significant brain perfusion decrements in temporal, parietal and frontal regions.