Sunday, June 5, 2016

Koziol: views of basl ganglia an cognitive control

1.  Basal ganglia are phylogenetically old and conserved for 560  millions of years. 
2.  There are  four cortical pathways that each contain a direct pathway D1 that releases behavior and an indirect pathway D2 that stops the behavior.  There is also a hyperdirect cortical path to the STN that generates global inhibition, and a fourth striosomal pathway from the paralimbic regions to the SN complex, that provides the basal ganglia with information about rewards of particular contexts.
3.  Basal ganglia subserve a variety of functions including category learning, motor learning, rule governed support of grammar systems, selection and gating of focused behaviors, cognitive control of working memory, and instrumental learning
4.  Through a series of excitatory and inhibitory processes, basal  ganglia gates behaviors based on reward based models.  How does it know what to gate?  D1  neurons stop GPi from inhibiting the thalamus.  However, it does so to release only a small specified behavior.  The behavior is amplified, the GO signal.  The decision is top down involving FPN and OF cortex, but once the behavior is represented in the premotor cortex, it can be gated outside cognitive conscious control.
5. Over time, a behavior shifts from cognitive loops to motor loops, and it also shifts from executive control to automatic control as it goes from limbic to DLPFC to OF to inf par to motor loops.  "Working memory" should be, but is not thought of as a dynamic, task dependent entity.  The "executive" can never be assessed except by task used to assess it. Hence EF tasks do not correlate with each other.  Towers tests, card sorting, and working memory tests do not predict each other.

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