=== CCNBook Executive-PBWM in a Nutshell ===
This article tries to summarize the PBWM (Prefrontal cortex Basal ganglia Working Memory) model in [[https://grey.colorado.edu/CompCogNeuro/index.php/CCNBook/Executive|the Executive chapter]] of [[https://grey.colorado.edu/CompCogNeuro/index.php/CCNBook/Main|the CCNBook]].  The PBWM model is further explained in O’Reilly & Frank’s paper: [[http://psych.colorado.edu/~oreilly/papers/OReillyFrank06_pbwm.pdf|Making Working Memory Work: A Computational Model of Learning in the Prefrontal Cortex and Basal Ganglia]], Neural Comput., 18(2) (2006). 
Here are points:
  * The executive function requires controlling (i.e., keeping & releasing) states.
  * The states are held in PFC.
  * The control is carried out with the reinforcement learning mechanism described in [[https://grey.colorado.edu/CompCogNeuro/index.php/CCNBook/Motor|the Motor chapter]] (cf. [[ccnbook-motor_summary|the nutshell]]).
Figure 1 is from Figure 5 in O’Reilly & Frank’s paper slightly modified explaining the model conformable to the last figure in [[ccnbook-motor_summary|the Motor nutshell]].
|  {{ccnexecutivenutshell1.png}}  |
|  **Figure 1**  |
Here, BG is controlling gates for states in PFC, while it was for controlling in general in the Motor chapter.  Besides the gating, BG also controls output (Figure 10.11).
|  {{https://grey.colorado.edu/mediawiki/sites/CompCogNeuro/images/c/cd/fig_pbwm_architecture_mnt_out.png}}  |
|  **Figure 10.11** (from [[https://grey.colorado.edu/CompCogNeuro/index.php/File:fig_pbwm_architecture_mnt_out.png|CCNBook]])  |
For a most abstract level of understanding, these figures will suffice.
The chapter notes that there is a hierarchy of control in the frontal cortex (Figure 10.16).
|  {{https://grey.colorado.edu/mediawiki/sites/CompCogNeuro/images/thumb/b/b7/bgpfc_hier_Probs.png/320px-bgpfc_hier_Probs.png}}  |
|  **Figure 10.16** (from [[https://grey.colorado.edu/CompCogNeuro/index.php/File:bgpfc_hier_Probs.png|CCNBook]])  |