Broad functional architecture of the brain

A broad whole-brain functional architecture. Feature detection is done by sensory systems, which likely operate by learning multiple hierarchical levels of features. These features together (multimodal) define a state, which is mapped to action by a policy. Ultimate state determination and high-level policy are likely represented by structures such as hippocampus, amygdala, limbic cortices, brainstem neuromodulatory systems (especially dopaminergic midbrain neurons), ventral striatum, basal forebrain, and hypothalamus. Finally selected actions must be mapped to motor function. This is likely done in a hierarchical fashion, with higher level representations feeding forward to lower level motor areas---ultimately with output at primary motor cortex. Most cortical areas will have corresponding corticostriatal loops, which are organized in a rostrocaudal direction. Note the division between ventral and dorsal striatum, which is often associated with the demarcation between model-based (aka goal-directed) and model-free (aka habitual) control. In a rostro-caudal direction, corticostriatal loops are near-parallel in their organization, potentially resulting in segregation of parallel cortical computations.