Setting A Behavioral Task For Assessing Decision Making In Urodele Amphibian
Résumé
Decision making takes a crucial role in daily life and can be seriously impaired in neurodegenerative diseases. It implies cortical-basal ganglia loops, but the respective roles of each structure are still debated. Urodeles offer a remarkable opportunity to address this question.
First, whereas the organization of the basal ganglia in these animals is similar to the one of mammals, it has orders of magnitudes fewer neurons1 and is therefore at a level of complexity that is more tractable in terms of comprehension and modelling. Second, the extensive regenerative capacities of their midbrain networks allow the use of local lesions to investigate their connectivity and functionality. This also makes the urodele a unique experimental model for investigating the mechanisms of decision-making network plasticity after a midbrain injury.
Therefore, we decided to set up a behavioral test of decision making in this animal model. Our task was based on the ability of urodele to discriminate polarized light. The animals were trained2,3 to associate the location of a shade shelter (urodeles do not like exposure to direct light) with a specific orientation of the polarization axis. We then performed a test to assess if the animals learned this association. This paradigm gave us access to a motor decision making mode. In a second step, we will perform selective lesions of the pallium (i.e. the cortex in lower vertebrates), the thalamus and the basal ganglia to determine the respective role of each structure. We will then study implication of dopamine4 in this behavioral task. To our knowledge, urodele is the earliest group of limbed vertebrates in which decision-making process has been successfully addressed yet.
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