Development of routine and supervisory processes in sequential action control

The sequential actions that children and adults perform regularly if not daily (e.g., preparing for and going to school/work, preparing meals, and so on) are often un-der routine control in that they appear not to require overt attention. The study of routine action control in adults has benefited from influential theories, such as the Norman and Shallice’s (1986) dual-systems theory, supported by comprehensive computational models. Drawing on the latter theory, and comparing it with other existing accounts of sequential action selection, this thesis aims at improving our understanding of the development of routine action control throughout the school-age years. It investigates how children control complex action sequences, at several levels, and with the involvement of various supervisory functions (including inhibitory control and monitoring functions). It furthermore explores the interaction between the two hypothesised action control systems in children under the lens of the dual-systems theory, but also under the lens of the so-called model-free and model-based types of reinforcement learning. This is done by designing child-friendly tasks, developing a computational model, and proposing novel analysis methods for kinematics data. The findings in this thesis support the view that children use two modes of control which may follow different developmental trajectories, with a supervisory system following a more protracted development. The results furthermore suggest that the development of inhibitory control throughout the school-age years might reduce children’s propensity to interferences from environmental distractors, and might improve their abilities to select the appropriate action in an ambiguous context (e.g., when an action needs to be related more strongly to the overarching goal than to the preceding’s action) or under increased cognitive load. In conclusion, this thesis shows that by 5 or 6 years old, children readily use conjointly two modes of action control and are able to control action sequences in a routinised fashion, yet the supervisory mode of control seems to substantially improve throughout mid-childhood. It furthermore brings evidence for the fact that changes in executive functions underlie improvements in sequential action control with age

Temporary Nerve Block at Selected Digits Revealed Hand Motor Deficits in Grasping Tasks

Peripheral sensory feedback plays a crucial role in ensuring correct motor execution throughout hand grasp control. Previous studies utilized local anesthesia to deprive somatosensory feedback in the digits or hand, observations included sensorimotor deficits at both corticospinal and peripheral levels. However, the questions of how the disturbed and intact sensory input integrate and interact with each other to assist the motor program execution, and whether the motor coordination based on motor output variability between affected and non-affected elements (e.g., digits) becomes interfered by the local sensory deficiency, have not been answered. The current study aims to investigate the effect of peripheral deafferentation through digital nerve blocks at selective digits on motor performance and motor coordination in grasp control. Our results suggested that the absence of somatosensory information induced motor deficits in hand grasp control, as evidenced by reduced maximal force production ability in both local and non-local digits, impairment of force and moment control during object lift and hold, and attenuated motor synergies in stabilizing task performance variables, namely the tangential force and moment of force. These findings implied that individual sensory input is shared across all the digits and the disturbed signal from local sensory channel(s) has a more comprehensive impact on the process of the motor output execution in the sensorimotor integration process. Additionally, a feedback control mechanism with a sensation-based component resides in the formation process for the motor covariation structure