Biomedical subjects

Fadila Hadj-Bouziane

Publications and source records attributed to Fadila Hadj-Bouziane.

3 recordsLinked to original sources

PubMed2006

Conditional visuo-motor learning and dimension reduction.

Conditional visuo-motor learning consists in learning by trial and error to associate visual cues with correct motor responses, that have no direct link. Converging evidence supports the role of a large brain network in this type of learning, including the prefrontal and the premotor cortex, the basal ganglia BG and the hippocampus. In this paper we focus on the role of a major structure of the BG, the striatum. We first present behavioral results and electrophysiological data recorded from this structure in monkeys engaged in learning new visuo-motor associations. Visual stimuli were presented on a video screen and the animals had to learn, by trial and error, to select the correct movement of a joystick, in order to receive a liquid reward. Behavioral results revealed that the monkeys used a sequential strategy, whereby they learned the associations one by one although they were presented randomly. Human subjects, tested on the same task, also used a sequential strategy. Neuronal recordings in monkeys revealed learning-related modulations of neural activity in the striatum. We then present a mathematical model inspired by viability theory developed to implement the use of strategies during learning. This model complements existing models of the BG based on reinforcement learning RL, which do not take into account the use of strategies to reduce the dimension of the learning space.

Basal Ganglia↗

PubMed2003

Neuronal activity in the monkey striatum during conditional visuomotor learning.

The frontostriatal system has been implicated in linking sensory information and action through arbitrary rules. The aim of the present study was to investigate the role of the striatum, a key, integrative structure in such behavior. We recorded single neuronal activity from the anterior striatum of two macaque monkeys as they learned to associate new visual cues with motor responses. Monkeys held a joystick which they could move in one of four constrained directions. During the recording sessions, they were presented with a set of well-learned associations (familiar condition), and with sets of new cues which they were required to map, by trial and error, with joystick movements (novel condition). A sample of 50 striatum neurons were studied during execution of familiar and novel conditions. Activity of most of them was strongly modulated during learning. These modulations were either transient or long lasting changes of neuronal firing rate. The findings suggest that the striatum is involved in early stages of conditional visuomotor learning, and are interpreted in relation with previous data on frontal cortex.

Action Potentials↗

PubMedDate not supplied

Conditional visuo-motor learning in primates: a key role for the basal ganglia.

Sensory guidance of behavior often involves standard visuo-motor mapping of body movements onto objects and spatial locations. For example, looking at and reaching to grasp a glass of wine requires the mapping of the eyes and hand to the location of the glass in space, as well as the formation of a hand configuration appropriate to the shape of the glass. But our brain is far more than just a standard sensorimotor mapping machine. Through evolution, the brain of advanced mammals, in particular human and non-human primates, has acquired a formidable capacity to construct non-standard, arbitrary mapping using associations between external events and behavioral responses that bear no direct relationship. For example, we have all learned to stop at a red traffic light and to go at a green one, or to wait for a specific tone before dialing a phone number and to hang up when hearing a busy signal. These arbitrary associations are acquired through experience, thereby providing primates with a rich and flexible sensorimotor repertoire. Understanding how they are learned, and how they are recalled and used when the context requires them, has been one of the challenging issues for cognitive neuroscience. Valuable insights have been gained over the last two decades through the convergence of multiple complementary approaches. Human neuropsychology and experimental lesions in monkeys have identified a network of brain structures important for conditional sensorimotor associations, whereas imaging studies in healthy human subjects and electrophysiological recordings in awake monkeys have sought to identify the different functional processes underlying the overall function. The present review focuses on the contribution of a network linking the prefrontal cortex, basal ganglia, and dorsal premotor cortex, with special emphasis on results from recording experiments in monkeys. We will first review data pointing to a specific contribution of each component of the network to the performance of well-learned arbitrary visuo-motor associations, as well as data suggesting how novel associations are formed. Then we will propose a model positing that each component of the fronto-striatal network makes a specific contribution to the formation and/or execution of sensorimotor associations. In this model, the basal ganglia are thought to play a key role in linking the sensory, motor, and reward information necessary for arbitrary mapping.

Animals↗