With this study, the investigators want to investigate how deep brain stimulation (DBS) affects various cognitive and psychiatric symptoms of Parkinson's disease (PD). In particular, they will examine whether stimulation of the left hemisphere has a different effect than stimulation of the right hemisphere on cognitive and psychiatric symptoms.
Previous studies have shown that motor symptoms improve with DBS in PD. It is also know that DBS can have an effect on cognitive and psychiatric symptoms. However, in the studies completed so far, it has not yet been possible to conclusively assess the exact effect of the stimulation itself on various cognitive and psychiatric symptoms. In particular, there is currently no data on how the precise localization of stimulation at the target site-the subthalamic nucleus (STN)-affects cognitive and psychiatric symptoms. It is not yet clear whether electrical stimulation of the right subthalamic nucleus has different effects on cognition and mood than stimulation of the left subthalamic nucleus. The aim of this study is to investigate whether DBS of the left hemisphere affects cognition and mood differently than DBS of the right hemisphere.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
OTHER
Masking
DOUBLE
Enrollment
20
DBS is turned off for the left hemisphere during the experiment
DBS is turned off for the right hemisphere during the experiment
University Hospital Inselspital, Berne
Bern, Switzerland
RECRUITINGFluency
Change in composite verbal fluency score for left versus right hemispheric stimulation. To calculate the composite verbal fluency score, the standardized z-scores for phonemic and semantic verbal fluency task will be averaged. For the semantic fluency task, participants generate orally as many category names as possible during 2 minutes (German category 1: professions, category 2: hobbies; French category 1: furniture; category 2: fruit). During the phonemic fluency task, participants generate orally as many words as possible beginning with a certain letter while respecting the following rules: no repetition and no word with the same root, and no proper nouns (German: P-words, M-words; French: R-words, V-words). During each condition (right side stimulation OFF and left side stimulation OFF), one semantic fluency task and one phonemic fluency task will be performed (making sure the same letter and cateogry are only assessed once).
Time frame: Baseline visit
Impulsivity
Change for left versus right hemispheric stimulation in composite impulsivity score. The impulsivity score will be calculated by averaging the standardized z-values for a computerized Go/No-Go task (reaction time and mistakes) and a Stroop Task (inhibition time and mistakes). The Go/NoGo subtests measures selective attention and motor impulsivity. Subjects have to react as quickly as possible when they see a cross on the screen (x), but not when they see a plus sign (+). Both speed and number of mistakes are measured. The interference subtest of the Stroop test measures inhibitory control and selective attention. In the task, participants see color words (e.g., "RED," "BLUE," "GREEN") printed in a conflicting ink color. They are instructed to name the ink color rather than read the word. Time and number of mistakes are measured.
Time frame: Baseline visit
Neuropsychiatric
Change for left versus right hemispheric stimulation in Neuropsychiatric Fluctuation Scale (NFS). The Neuropsychiatric Fluctuations Scale for Parkinson's Disease is a self-report questionnaire. The NFS includes 10 items evaluating OFF neuropsychiatric symptoms and 10 items evaluating ON neuropsychiatric symptoms. Each item is rated from 0 to 3. The total score of the NFS ranges from 0-60, with higher scores indicating better mood. The NFS will be admistered once during each intervention (stimulation right side OFF and stimulation left side OFF).
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Time frame: Baseline visit