Goal-directed behaviour (GDB) refers to the ability to formulate a goal, to develop an action plan and to select and carry out actions in order to achieve a particular outcome. Fatigue tends to be associated with decline in GDB. Fatigue and reduction of GDB have a high prevalence in several acute and chronic diseases and in healthy individuals and are known to impact quality of life. This thesis work concerns the study of their multidimensional components.
Effects of age-related have been described in terms of changes in motivational preference for different rewards, of reduced cognitive performance across a variety of domains, of reduced affective and neural responses during anticipation of losses and of difficulties to consider long-term outcomes. In this context, I have investigated the impact of normal aging on GDB and the effect of age-related monetary reward during the anticipation phase between expected reward and action. This is a relevant phase which informs about the processing underlying decision-making. Results demonstrated a difference in age-related patterns for cognitive and emotional components leading to less adapted decision-making over the long term for older people.
Fatigue is a common symptom after COVID-19 infection. In this context, I studied fatigue and the profile of cognitive impairment after a severe form of COVID-19, without brain injury, in the acute (at 2-10 days after discharge from intensive care unit) and chronic phase (at 12 months), providing a fine-grained evaluation of sub- dimensions of fatigue and of multidomain complaints through standardized neuropsychological tests/scales/questionnaires and visual analogue scales. In acute phase, 2/3 of patients presented mild to severe cognitive disorders, mainly in memory, executive, attentional and visuospatial functions, and cognitive disorders were correlated with mental fatigue. At 12 months, mental fatigue was omnipresent and multidomain complaints - including cognitive complaints and functional limitations - were reported, without however systematic cognitive disorders. Other sequelae have also been noted for some patients, including physical and neurobehavioural/psychiatric symptoms and poorer health-related quality of life.
Finally, I investigated, using a functional magnetic resonance imaging paradigm, neural and behavioural mechanisms involved in chronic fatigue, at 9 months after severe COVID-19, when patients performed an effortful cognitive task. Results demonstrated that patients presented different patterns of mental fatigue complaints (all patients), behavioural performance (most patients) and/or activation networks (half of them) from those of healthy subjects