Deep Brain Structures Overview

Overview

This lecture reviews major deep cerebral structures, focusing on the basal nuclei and limbic system, and their roles in movement, emotion, and memory.

Basal Nuclei

• The basal nuclei are deep brain structures involved in motor control.
• The three main basal nuclei are the caudate nucleus, putamen, and globus pallidus.
• The caudate nucleus has a head and a curved tail that arches around the thalamus.
• The putamen and globus pallidus together form the lentiform nucleus, which is lens-shaped.
• The basal nuclei are located just outside the thalamus.
• White matter tracts, including the internal capsule, run between the basal nuclei and connect the cortex to lower brain structures.
• The function of the basal nuclei is subconscious adjustment of ongoing motor movements.
• Damage to basal nuclei leads to impaired control and coordination of muscle movements.
• The basal nuclei work closely with the substantia nigra from the midbrain to fine-tune motor movements.

Limbic System and Related Structures

• The amygdala, located at the tail of the caudate, assesses threats and modulates fear responses.
• The limbic system includes structures like the amygdala, cingulate gyrus, and parahippocampal gyrus.
• The parahippocampal gyrus contains the dentate gyrus and hippocampus.
• The hippocampus is essential for consolidating short-term memory into long-term memory (consolidation).
• Damage to the hippocampus (e.g., patient HM) prevents formation of new episodic and factual memories, but procedural memory remains intact.
• The hippocampus also plays a role in spatial navigation.
• The hippocampus is strongly linked to the hypothalamus via the fornix, especially mammillary bodies, which aid learning and memory.
• Emotional experiences enhance memory formation through increased hippocampal activity.
• The olfactory cortex is near the hippocampus, making smells powerful memory triggers.

Key Terms & Definitions

• Basal nuclei — deep brain structures regulating movement.
• Caudate nucleus — curved part of the basal nuclei with a head and tail.
• Putamen — one part of the lentiform nucleus.
• Globus pallidus — pale, rounded part of the lentiform nucleus.
• Internal capsule — white matter tract linking cortex and lower structures.
• Amygdala — limbic structure for threat and fear processing.
• Limbic system — interconnected structures managing emotion and memory.
• Cingulate gyrus — cortical belt involved in emotion.
• Parahippocampal gyrus — temporal lobe structure hosting the dentate gyrus and hippocampus.
• Hippocampus — structure vital for forming long-term memories and spatial navigation.
• Fornix — white matter tract connecting the limbic system and hypothalamus.
• Mammillary bodies — hypothalamic structures involved in memory consolidation.

Action Items / Next Steps

• Review diagrams of the basal nuclei and limbic system.
• Memorize the functions of major deep cerebral structures.
• Prepare for questions on clinical implications of damage to these regions.