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Lesions of the subthalamic nucleus (STN) alleviate the cardinal signs of idiopathic as well as MPTP-induced Parkinson's disease in primates. For this reason, the STN is a target for clinical treatment of Parkinson's disease using deep brain stimulation. Despite its small size, the STN plays a vital role in the cortico-basal ganglia-thalamic network. However, the functional features of the STN have yet to be fully uncovered. The research presented in this thesis examines the functions of the STN by measuring behavioural changes resulting from STN lesions in rats performing executive abilities. In the first experiment, a ‘signal change' reaction time task was developed and the performance of humans and rats was compared. The main findings were that although humans and rats used different strategies in the task, the task did challenge the ability to inhibit unwanted responses. In the second and third experiments, the effects of bilateral lesions of the STN on performance of two variants of the ‘signal change' task were examined. Rats with the STN lesions were able to inhibit responses when under stimulus control, but were less able to inhibit responses that were not under stimulus control. In the final experiment, the effects of lesions of the STN on inhibitory control in a nonmotor, cognitive domain were examined. Rats with STN lesions were not impaired on reversal learning, suggesting intact inhibition of previously rewarded responses. The rats with STN lesions did show impairments in selective attention which resulted in an inability to form an attentional set. Together, these findings challenge the conventional view that the STN simply plays a global inhibitory role. Rather, the contribution of the STN to inhibitory control is more complex and neither the motor nor the cognitive effects of the lesions are easily explained simply as a failure of inhibition.

Stockholm Neonatal Project is a longitudinal population-based study of children born prematurely in 1988-93, with a very low birth weight (&lt;1500 g), who have been followed prospectively from birth through adolescence. A matched control group was recruited at age 5 ½ years. The overall aim was to investigate long-term developmental outcome, paying particular attention to executive functions (EF) in relation to degree of prematurity, birth weight and medical risks. Study I showed a disadvantage in visuo-motor development at 5 ½ years, especially among the preterm boys. Visuo-motor skills were highly related to IQ, and also to EF. In Study II, neuropsychological profiles typical of preterm children and term born children, respectively, were identified through cluster analysis. The general level of performance corresponded well with IQ, motor functions and parental education in both groups, but preterm children had overall lower results and exhibited greater variability across domains. Study III showed that extremely preterm birth (w. 23-27) per se poses a risk for cognitive outcome at age 18, particularly for EF, and that perinatal medical complications add to the risk. By contrast, adolescents born very preterm (w. 28-31) performed just as well as term-born controls in all cognitive domains. However, adolescents born moderately preterm (w. 32-36) and small for gestational age showed general cognitive deficits. Study IV found that cognitive development was stable over time, with parental education and EF at 5 ½ years as significant predictors for cognitive outcome at age 18. Among preterm children, perinatal medical risks and being small for gestational age had a continued negative impact on cognitive development from 5 ½ to 18 years. Study V demonstrated that neuropsychological scoring of Bender drawings, developed in study I, predicted cognitive outcome in adolescence, indicating that the method  may be useful in developmental screening around school entry. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript. Paper 5: Submitted.</p>

Pourquoi agissons-nous dans certaines circonstances de manière irrépressible ? Nos actes doivent-ils pour autant être considérés comme inconscients ? Peut-on apprendre inconsciemment ? La conscience et le contrôle peuvent-ils être dissociés? Ces questions ont été abordées dans le cadre de ma thèse de doctorat.

Individuals who have experienced a traumatic event and develop Post-Traumatic Stress Disorder (PTSD) frequently show deficits in both primarily “cool” and “hot” cognitive executive functions (e.g., traditional & emotional Stroop tasks, respectively) that can be impacted by high affective salience. Given the dimensional nature of psychopathology, questions remain about individuals within the general population who have experienced trauma but do not meet full criteria for PTSD and yet may manifest problems in these areas, especially areas of hot and cool executive functioning (EF). Thus, the current project was designed to assess hot and cool EF in a relatively large sample of individuals from the general population who have experienced trauma and currently demonstrate sub-clinical levels of post-traumatic symptoms. The Stroop task, Emotional Stroop task, and a novel modified Implicit Association Test were utilized to assess EF across a spectrum of individuals with varying traumatic histories and level of post-traumatic symptoms. Results suggest that a greater frequency of trauma experiences was moderately associated with worse performance on both hot and cool executive functioning measures. Specifically, females within the sample evidenced a close relationship between traumatic experiences, post-trauma symptoms, and executive functioning. Clinical and theoretical implications are discussed.

This thesis assesses the link between action and cognition early in development. Thus the notion of an embodied cognition is investigated by tying together two levels of action control in the context of reaching in infancy: prospective motor control and executive functions. The ability to plan our actions is the inevitable foundation of reaching our goals. Thus actions can be stratified on different levels of control. There is the relatively low level of prospective motor control and the comparatively high level of cognitive control. Prospective motor control is concerned with goal-directed actions on the level of single movements and movement combinations of our body and ensures purposeful, coordinated movements, such as reaching for a cup of coffee. Cognitive control, in the context of this thesis more precisely referred to as executive functions, deals with goal-directed actions on the level of whole actions and action combinations and facilitates directedness towards mid- and long-term goals, such as finishing a doctoral thesis. Whereas prospective motor control and executive functions are well studied in adulthood, the early development of both is not sufficiently understood. This thesis comprises three empirical motion-tracking studies that shed light on prospective motor control and executive functions in infancy. Study I investigated the prospective motor control of current actions by having 14-month-olds lift objects of varying weights. In doing so, multi-cue integration was addressed by comparing the use of visual and non-visual information to non-visual information only. Study II examined the prospective motor control of future actions in action sequences by investigating reach-to-place actions in 14-month-olds. Thus the extent to which Fitts’ law can explain movement duration in infancy was addressed. Study III lifted prospective motor control to a higher that is cognitive level, by investigating it relative to executive functions in 18-months-olds. Main results were that 14-month-olds are able to prospectively control their manual actions based on object weight. In this action planning process, infants use different sources of information. Beyond this ability to prospectively control their current action, 14-month-olds also take future actions into account and plan their actions based on the difficulty of the subsequent action in action sequences. In 18-month-olds, prospective motor control in manual actions, such as reaching, is related to early executive functions, as demonstrated for behavioral prohibition and working memory. These findings are consistent with the idea that executive functions derive from prospective motor control. I suggest that executive functions could be grounded in the development of motor control. In other words, early executive functions should be seen as embodied.

Walking outdoors requires one to deal with a wide range of visual and cognitive perturbations, i.e., multiple object tracking and making timely decisions while ignoring irrelevant information, etc. Using dual-task gait paradigm, the purpose of this thesis was to evaluate the age effects of different types of visuospatial cognitive tasks, i.e. designed cognitive game tasks and commercial computer games on gait and cognitive performances in older adults as compared to the younger adults. A standardized dual-task assessment approach, i.e. objectively evaluating both gait and cognitive performances simultaneously, has potential to be the screening tool to detect gait and cognitive impairments in early stages. Further, evaluating the training value of commercial computer games by comparing them with the designed cognitive games with objective outcome measures will help in developing multimodal dual-task intervention platform to treat and prevent age-related physical and cognitive impairments. / October 2016

Les fonctions exécutives (FE) sont définies comme des processus de contrôle permettant d'adapter les comportements dans des situations nouvelles. La littérature sur l'homme fait état de fortes variabilités interindividuelles dans l'exécution de ces FE, notamment liées à l'âge des individus. Dans une approche comparative, nous avons cherché à savoir si le primate non humain exprimait de telles variabilités interindividuelles, dans quelle mesure, et pour quelle(s) fonctions(s). Nous avons proposé une série de tâches à un groupe de babouins Papio papio où des individus mâles et femelles d'âges différents, et de statuts sociaux différents cohabitent. Ces expériences ont bénéficié de l'environnement exceptionnel de la plateforme de Comportement et Cognition du Primate située sur la station de Primatologie CNRS de Rousset, où un groupe de babouins a accès ad libitum à dix systèmes de conditionnement opérant automatisés. Les tâches proposées impliquaient chacune une FE particulière, notamment les fonctions d'inhibition et de flexibilité cognitive. Les procédures utilisées, qui reposent sur un principe de conditionnement opérant, consistaient à présenter les tâches sur des écrans tactiles sur lesquels les babouins devaient donner leur réponse. Les expériences impliquant principalement l'inhibition ont montré que le babouin est capable de mettre en place un contrôle inhibiteur efficace. Cependant, les individus les plus âgés montrent des déficits dans leurs performances. Au contraire, lorsque la tâche d'inhibition a une forte composante motrice, les jeunes ont plus de difficultés à adapter leur mouvement. / Executive functions (EF), which are defined as control processes, serve the adaptation of the behaviour in new situations. The human literature reveals important inter-individual variabilities in the efficiency of EF, in particular when age is considered. In a comparative perspective, we investigated if similar individual differences also exist in nonhuman primates, and for which function(s). Several tasks were thus proposed to a group of baboons Papio papio, comprising individuals of both sexes and different ages and social status. These experiments were run in a unique research facility, the Primate Behaviour and Cognition platform (Primatology center, Rousset-sur-Arc), where the baboons had an ad libitum free access to ten automated operant conditioning test systems equipped with touch screens. Each task targeted a particular EF, including the functions of inhibition and cognitive flexibility. The baboons demonstrated an efficient inhibitory control in our tasks. Overall, older individuals showed deficits in inhibitory control when compared to the younger subjects. However, this pattern of results is inverted when motor rather than cognitive inhibition was required. The second set of experiments studied cognitive flexibility. That EF appears deficient in adults, in comparison to the younger individuals. Thus, as in humans, monkeys show significant individual differences in executive control. It is concluded that their analysis requires to distinguish motor from cognitive inhibition, and to pay special attention to the factor of age.