Imaging executive functions in Parkinson's disease: An activation likelihood estimation meta-analysis

Introduction Executive dysfunction is a common and early cognitive symptom in Parkinson's disease (PD) with a detrimental effect on quality of life of patients and their care givers. Thus, a number of neuroimaging studies investigated the underlying neural correlates of such an impairment. Results of individual studies, however, are not univocal in terms of location and directionality of associated functional brain changes. Objective: To assess convergence of abnormal brain activation in patients with PD during the performance of tasks probing executive functions (EF). Methods: We screened the functional imaging literature on EF in PD using the PubMed database, extracted reported stereotactic data and tested for convergence of deviant neural activation in patients with PD when compared to healthy controls (HC) using a coordinate-based activation likelihood estimation approach. Results: We identified 22 eligible papers from which the main proportion was targeted at the investigation of working memory encompassing 354 patients and 306 HC. Surprisingly, no significant converging aberrant activation between HC and patients (ON, OFF or ON + OFF medication, respectively) could be observed when controlling for multiple comparisons using family-wise error correction on cluster-level. Conclusion: We conclude that there is currently not enough available evidence to pinpoint a specific neural correlate associated with executive dysfunction in PD. This might be due to the small number of studies performed and their methodical inconsistency. Therefore, it is important to conduct more research regarding functional brain changes associated with EF in these patients using more consistent frameworks and bigger samples.