A natural history of skills

Abstract

The dorsal pallium (a.k.a. cortex in mammals) makes a loop circuit with the basal ganglia and the thalamus known to control and adapt behavior but the who's who of the functional roles of these structures is still debated. Influenced by the Triune brain theory that was proposed in the early sixties, many current theories propose a hierarchical organization on the top of which stands the cortex to which the subcortical structures are subordinated. In particular, habits formation has been proposed to reflect a switch from conscious on-line control of behavior by the cortex, to a fully automated subcortical control. In this review, we propose to revalue the function of the network in light of the current experimental evidence concerning the anatomy and physiology of the basal ganglia-cortical circuits in vertebrates. We briefly review the current theories and show that they could be encompassed in a broader framework of skill learning and performance. Then, after reminding the state of the art concerning the anatomical architecture of the network and the underlying dynamic processes, we summarize the evolution of the anatomical and physiological substrate of skill learning and performance among vertebrates. We then review experimental evidence supporting for the hypothesis that the development of automatized skills relies on the BG teaching cortical circuits and is actually a late feature linked with the development of a specialized cortex or pallium that evolved in parallel in different taxa. We finally propose a minimal computational framework where this hypothesis can be explicitly implemented and tested.

Mutations in CalDAG-GEFI Lead to Striatal Signaling Deficits and Psychomotor Symptoms in Multiple Species Including Human

“…Our evidence for the presence of CDGI in the striatum is confirmed by mRNA and protein analyses in the mouse and human (Crittenden et al, 2010), and traits compatible with striatal dysfunction (Boraud et al, 2018;Graybiel, 2008) were present upon neurologic examination of the human subjects: hyperkinetic movement disorders including mild chorea, tremor and dystonia, behavioral manifestations including anxiety, insomnia and drug use, and a mild dysexecutive syndrome. Platelet aggregation responses were clearly better in heterozygous than in biallelic mutant individuals, but the neurologic symptoms were more variable among the genotypes.…”

Primate hippocampus size and organization are predicted by sociality but not diet

“…This is likely due to a reallocation of functions such as memory, spatial cognition, and inhibition from the hippocampus to the neocortex. With neocorticalization, parallel systems are thought to have emerged, leading to an increased neocortex ratio [79] and allocation of functions to the neocortex [80]. Whereas in smaller brained species the hippocampus is of utmost importance in many cognitive abilities, as the neocortex expands there may be a greater proportion of these functions allocated to it, or the neocortex might be taking up on an array of new social functions that do not exist in smaller brained species.…”

The Nigro-Thalamic Projection contributes to the Control of Action Initiation Timing

“…This gain function combined with an adjustable threshold values, could serve as a timer for action release, as well as a system for selection based on activity level. Indeed it is possible that other actions compete (Boraud et al, 2018;Leblois et al, 2006) for the highest motivation value, and that a winner take all mechanism is implemented. Such a possibility is also compatible with our proposed mechanism (Figure 7), in which the first action to reach the threshold would be released.…”