THALAMUS Lecture 4

Epithalamus Habenular Nuclei: Thought to be involved in emotional and visceral responses to odors. Projects to septal nuclei (in thalamus): Via stria medullaris thalami. Projects to interpeduncular nucleus: Via habenulointerpeduncular tract.

Epithalamus Pineal Body Secretes melatonin (hormone): Regulates circadian rhythms. Activity is modulated by light-dark cycle: Via sympathetic inputs activated by hypothalamic suprachiasmatic nucleus. Calcification accrues with maturity. Lesions associated with precocious puberty.

Thalamus 80 percent of diencephalon Separated from hypothalamus via: Hypothalamic sulcus (groove) Other landmarks: Optic recess Infundibular recess Pineal recess

Thalamus Commissures: Habenular : Above the pineal recess. Posterior: Below the pineal recess.

Thalamus Functions: Relays all sensory information except smell to the cerebral cortex. Provides crude awareness. Initial autonomic response of the body to intense pain (physiologic shock). Interpretation center for crude pain, temperature, light touch, pressure. Plays a role in arousal and alerting. Plays a role in complex reflex movements.

Thalamic Sensory Relay Nuclei Medial geniculate body: Auditory. Projects to primary auditory cortex in temporal lobe. Lateral geniculate body: Visual. Projects to primary visual cortex in occipital cortex.

Thalamic Sensory Relay Nuclei Ventral posterior nuclei: General sensations and taste.

Thalamic Motor Relay Nuclei Ventral lateral: Voluntary motor Ventral anterior: Voluntary motor and arousal Subthalamic

Thalamus Reticular Nucleus Modifies neuronal activity in the thalamus. May be involved in: Regulating sleep-wakefulness cycle and levels of awareness.

Thalamus Anterior Nucleus Concerned with certain emotions and memory. Receives input from: Hippocampus Mamillary bodies (mamillothalamic tract).

Thalamus White Matter Internal capsule Stratum zonale External medullary lamina Internal medullary lamina