Subcortical Structures
The forebrain contains subcortical regulatory systems and the cerebral cortex. The thalamus is the central sensory relay station, routing nearly all incoming sensory input to the correct cortical area. Pitfall: smell bypasses the thalamus entirely, projecting straight to limbic targets.
The hypothalamus is the master regulator of homeostasis, controlling hunger, thirst, temperature, and sexual behavior while directing the pituitary gland. The basal ganglia govern voluntary movement initiation and procedural learning; their dysfunction causes Parkinson's and Huntington's disease.
The Limbic System
The limbic system governs emotion, motivation, and memory through structures like the hippocampus and amygdala.
| Structure | Core role |
|---|---|
| Hippocampus | New declarative memory, spatial navigation |
| Amygdala | Fear and emotional memory |
Common pitfall: patient H.M. lost his hippocampi and could no longer form new long-term memories. But he kept old childhood memories, proving the hippocampus is required for creation, not permanent storage.