The Brain, Explained: A Comprehensive Theory of Brain Function

Abstract

Understanding brain function is one of the most important problems in human history. At present, there is no concrete theory for how the brain works. Here, a theory is presented that provides a detailed mechanistic biological account of the brain's capacities, including motor control, functional states, language, and thinking. Brain function is managed by a well-defined r e sponse ( R ) p r ocess t h at i s generally similar to the process underlying the immune system. The R process is strongly reflected in the brain's anatomy, physiology, and external i n teractions. Different R process stages are supported by distinct excitatory networks located in different cortical layers, hippocampal fields, and bagal ganglia paths, by distinct coordination networks comprised of GABAergic interneurons, and by distinct molecular agents. The roles of norepinephrine, serotonin, dopamine and acetylcholine is to promote the alert, planning, goal-setting and execution R process modes, respectively. Opioids and oxytocin promote termination by success, failure, fight o r r un, w hile g lucocorticoids and cannabinoids suppress acute responses to protect cells. The R process has two instances occurring at different time scales. The millisecondscale Quax process implements the execution of hierarchical sequences of movements and thoughts, in which the selection of the next action is determined via interaction between top-down predictions and sensory inputs. The slower Need process controls the satisfaction of internal and external needs. The theory differs from the existing standard accounts in many of the major topics (e.g., the basal ganglia, dopamine, language), and shows how cognition results from biological processes.

Basal Ganglia Paths Support Acute vs. Learned Execution, Not Movement vs. Stopping

“…The direct and indirect paths are the most important architectural feature of the BG, but there are other features that are significant to BG function. The distinction between striosomes (patches) and matrix, the role of serotonin, the participation of the BG in imagery, and BG plasticity are independent of the paths and should be included in a complete theory of BG function (see [Rappoport, 2018]). Histamine is an important agent that acts in the STR, generally serving to signal urgency of response execution.…”

“…It is selectively expressed by direct path MSNs and retrogradedly suppresses them to halt acute responses. In general, the role of DYN is to promote innate disengage (freeze, withdraw) responses, so it opposes D1Rs, which promote engage actions [Rappoport, 2018].…”

“…The focus here is on DA action in the BG. A complete account of DA in the brain, which includes the brain process stage that it promotes, its association with specific cortical networks, its goal setting role, and its relationship with acetylcholine, serotonin, and opioids, is given in [Rappoport, 2018], which presents a comprehensive theory of brain function.…”

“…Substance P (SP). SP is released in situations requiring sustained need-driven action, such as pain inputs and sexual approach [Rappoport, 2018]. It is expressed by direct path MSNs, but excites the indirect path via the neurokinin 1 (NK1) receptor.…”

A Complete Biological Theory of Sleep

“…The theory of sleep presented here is based on a theory I developed that explains brain function [Rappoport, 2018b, Rappoport, 2018a. To make reading the paper easier, it is completely selfcontained.…”