Thesis defence: Joel Sjöbom
Title: The role of cortico-basal ganglia systems in the construction of movement: Action selection and sequencing
Opponent: Dr. Hagai Bergman, Hebrew University
Abstract: The cortico-basal ganglia system is instrumental in t he construction of movement , through its involvement in aspects such as act ion select ion , initiation/termination and sequencing, though the precise role of the different structures and how t hey collaborate on a network level to allow us to fluidly change from one behavior to another has long proven to be elusive.
We have here recorded neuronal acitivity thoughout the cort ico-basal ganglia circuit in rats, in a series of pro jects in order to underst and more about how some of t hese functions are cont rolled.
We first set out to study the sequencing of actions through the rat grooming behavior, whose phase s were shown to be concatenated in a stepw ise mann er where the selection of an up coming phase depended primarily on the curr ent one. Onr data also suggested an involvement of both cortex and st riat um in the initi at ion and term inat ion of t he behavior as a whole, while mainly primary motor corte x was modulated during the transitions between phases. In the primar y moto r cortex act ivity we also found correlat ion to t he transition probability in the moment of t ra nsit ion, as well as the momentaneous probability of transitioning away from the current phase throughout its execution.
Next, we showed that ont of the neuronal changes in activ ity that occur aft er administration of Dl or D2 typ e receptor antagonists, the only one that reliabl y precede the onset of cat al epsy in any of the structrures thoughout the loop is a balanc ed change in firing rate.
Finally, we show that tactile input to the cortico-basa l ganglia system in rats changes ag an effect of acquiring a novel reaching skill, indi cat ing that reshap ing t he represent ation of t a ct ile input to motor circuits could be an important part of t he learning process in skill acquisition in reaching and grasping.