Executive and memory functioning in Parkinson’s disease: an integrative approach

Abstract

Cognitive impairment is one of the most disabling non-motor symptoms in Parkinson’s disease (PD). Despite its relevance, much remains unknown about its exact pattern of executive and memory impairment. The main purpose of the present thesis was to provide an overview of executive and memory dysfunctions characterizing PD. To this end, we investigated them through a multidimensional approach that includes objective and subjective measures and takes into account emotional components of executive functions (EF). We further explored the interplay between these different sources of information. In Study 1 (Siquier & Andrés, 2021a), we portrayed a comprehensive picture of executive impairment in PD, with particular attention on inhibition and cognitive flexibility. In this vein, we unraveled the interaction between executive deficits and patients’ everyday functioning. In study 2 (Siquier & Andrés, 2022a) we examined facial expression recognition (FER) abilities and their possible affectation in PD. In addition, relationships between cognitive and emotional alterations with FER deficits were evaluated. Studies 3 and 4 (Siquier & Andrés, 2021b, 2022b) intended to characterize episodic memory (EM) functioning in PD. Different statistical procedures were carried out to compare memory performance of PD patients and healthy controls (HC) on encoding, consolidation, and retrieval processes. Finally, the interplay between subjective memory complaints and objective cognitive performance was explored. Fifteen patients with PD and 15 healthy volunteers underwent a comprehensive cognitive and clinical evaluation. In addition, hetero-applicated measures were collected to gain multiple perspectives on the participant's cognitive and behavioral functioning. The most relevant findings emerging from this thesis were: first, cognitive and behavioral executive/inhibition difficulties were observed in patients with PD. Second, FER and especially recognition of anger, independently of the level of intensity, was significantly impaired in these patients as well, and FER deficits were influenced by the magnitude of cognitive inhibition deficits rather than by mood disturbances. Third, the mnesic pattern of our PD sample was characterized by retrieval but also, encoding failures. Fourth, associative memory deficits in patients with PD correlated specifically with self-reported memory complaints. In summary, this thesis contributes to expand the understanding of executive and memory functioning in PD. Our empirical findings demonstrate that memory impairment in PD extend to an encoding problem in addition to retrieval failures. Also, we highlight the role of inhibition dysfunction as a relevant contributor of FER abilities in PD. Altogether, the integrative approach adopted helps to pinpoint the nature of everyday problems faced by patients with PD and endorse the use of reliable instruments to better understand the complexity of cognitive impairment in PD at different levels.