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.