THALAMUSTHALAMUS

Epithalamus: Habenular NucleiEpithalamus: Habenular Nuclei

Thought to be involved in emotional and Thought to be involved in emotional and visceral responses to odors.visceral responses to odors.

Projects to septal nuclei (in thalamus)Projects to septal nuclei (in thalamus)Via stria medullaris thalami.Via stria medullaris thalami.

Projects to interpeduncular nucleusProjects to interpeduncular nucleusVia habenulointerpeduncular tract.Via habenulointerpeduncular tract.

Epithalamus: Pineal BodyEpithalamus: Pineal Body

Secretes melatonin (hormone):Secretes melatonin (hormone):Regulates circadian rhythms.Regulates circadian rhythms.

Activity is modulated by light-dark cycle:Activity is modulated by light-dark cycle:Via sympathetic inputs activated by Via sympathetic inputs activated by

hypothalamic suprachiasmatic nucleus.hypothalamic suprachiasmatic nucleus.Calcification accrues with maturity.Calcification accrues with maturity.Lesions associated with precocious Lesions associated with precocious

puberty.puberty.

ThalamusThalamus

80 percent of diencephalon80 percent of diencephalonSeparated from hypothalamus via:Separated from hypothalamus via:

Hypothalamic sulcus (groove)Hypothalamic sulcus (groove)Other landmarks:Other landmarks:

Optic recessOptic recess

Infundibular recessInfundibular recess

Pineal recessPineal recess

Thalamus: CommissuresThalamus: Commissures

Habenular :Habenular :Above the pineal recessAbove the pineal recess

Posterior:Posterior:Below the pineal recessBelow the pineal recess

Thalamus: FunctionsThalamus: Functions

Relays all sensory information except Relays all sensory information except smell to the cerebral cortex.smell to the cerebral cortex.

Provides crude awareness.Provides crude awareness. Initial autonomic response of the body to Initial autonomic response of the body to

intense pain (physiologic shock).intense pain (physiologic shock). Interpretation center for crude pain, Interpretation center for crude pain,

temperature, light touch, pressure.temperature, light touch, pressure.

Thalamus: FunctionsThalamus: Functions

Plays a role in arousal and alerting.Plays a role in arousal and alerting.Plays a role in complex reflex movements.Plays a role in complex reflex movements.

Thalamic Sensory Relay NucleiThalamic Sensory Relay Nuclei

Medial geniculate body:Medial geniculate body:

AuditoryAuditory

Projects to primary auditory cortex in temporal Projects to primary auditory cortex in temporal lobelobe

Lateral geniculate body:Lateral geniculate body:

Visual Visual

Projects to primary visual cortex in occipital cortexProjects to primary visual cortex in occipital cortex

Ventral posterior nuclei:Ventral posterior nuclei:General sensations and tasteGeneral sensations and taste

Thalamic Motor Relay NucleiThalamic Motor Relay Nuclei

Ventral lateral:Ventral lateral:Voluntary motorVoluntary motor

Ventral anterior:Ventral anterior:Voluntary motor and arousalVoluntary motor and arousal

Subthalamic Subthalamic

Thalamus Reticular NucleusThalamus Reticular Nucleus

Modifies neuronal activity in the thalamus.Modifies neuronal activity in the thalamus.May be involved in regulating sleep-May be involved in regulating sleep-

wakefulness cycle and levels of wakefulness cycle and levels of awareness.awareness.

Thalamus Anterior NucleusThalamus Anterior Nucleus

Concerned with certain emotions and Concerned with certain emotions and memory.memory.

Receives input from hippocampus and Receives input from hippocampus and mamillary bodies (mamillothalamic tract).mamillary bodies (mamillothalamic tract).

Thalamus White MatterThalamus White Matter

Internal capsuleInternal capsuleStratum zonaleStratum zonaleExternal medullary laminaExternal medullary lamina Internal medullary laminaInternal medullary lamina