A Seven-Layer Signal-Processing Architecture for the Brain: A Candidate Functional Framework Derived from Lesion Specificity, Pharmacological Perturbation, and Disease Trajectory

Abstract

Existing organisational frameworks for the brain — anatomical, network-based, andcomputational — differ in the specificity of predictions they generate about lesion effects,pharmacological perturbation, and disease trajectory. We propose a candidate functionalframework, the Seven-Layer Signal-Processing Architecture (7L-SPA), that assigns engineeringanalogousfunctions to seven anatomically identified structures: L1 Brainstem (Gain), L2Claustrum/Insula (Signal Coordinator), L3 Basal Ganglia/TRN (Gate), L4 Thalamus (TunableFilter), L5 Posterior Hubs (Broadcast), L6 Hippocampus (Context Buffer), and L7mPFC/ACC/Insula (Self-Model). The framework is explicitly a candidate hypothesis: the presentlayer-function configuration is one of several viable interpretations, and the mapping should beevaluated through the falsification program it generates rather than through the preliminaryconsistency evidence reviewed here.We evaluate the 7L-SPA against three sources of converging evidence: lesion specificity(predictable functional deficits from focal damage at each layer), pharmacological perturbation(layer-specific drug effects consistent with assigned functions), and disease trajectory (progressionpatterns in major psychiatric and neurological conditions as layer-sequential failure). We thenderive fourteen falsifiable predictions that distinguish the 7L-SPA from three establishedcompeting frameworks — Global Workspace Theory, predictive processing, and thalamocorticalloop models — and identify the primary empirical test: whether focused ultrasound stimulation ofthe thalamic filter produces predicted changes in consciousness bandwidth in disorders ofconsciousness.