Thalamus

Diencephalon has 4 major parts

epithalamus, subthalamus, hypothalamus, thalamus

Epithalamus

contains habenula and pineal gland

Habenula (epithalamus)

pathway for limbic system to influence brainstem reticular formation;

emotions to influence autonomic functions

pineal gland (epithalamus)

endocrine organ that releases melatonin. Codes photoperiodism; inhibited by light

tumors associated w/ early puberty

Subthalamic nucleus (subthalamus)

major role in indirect pathway of basal h=ganglia cortex modulation;

inhibiting movements

zona incerta (subthalamus)

rostral continuation of the midbrain reticular formation;

regulate consciousness, arousal, and attention

Thalamus

-all sensory pathways relay in the thalamus except smell

-31 nuclei separated by internal medullary lamina

- divided into anterior, medial, lateral ( dorsal, ventral)

Blood supply of the thalamus

supplied by the tuberothalamic branch of posterior communicating artery and brs of the posterior cerebral artery; thalamogeniculate arteries

Thalamocortical relays

sending ahead to cortex

ex: spinothalamic

thalamic reticular nuclei

regulates if information leaves thalamus

like attention, consciousness

Anterior nucleus

-sensory from mammillothalamic tract

-motor info to cingulate gyrus

Dorsomedial nucleus DM

sensory: prefrontal cortex, olfactory, and limbic

Motor: prefrontal cortex

Laterodorsal nucleus LD

sensory: hippocampus

motor: cingulate gyrus

Lateral posterior LP/ pulvinar

Connected reciprocally w/ parieto-occipital-temporal association cortex; vision

Ventral anterior, ventral lateral (VA, VL)

motor control

VA: basal ganglia

VL: cerebellum

Ventral posterior lateral VPL

Sensory: medial lemniscus, spinothalamic (trunk and extremities)

Motor: somatosensory cortex

Ventral posterior medial VPM

Sensory: trigeminothalamic (head)

Motor: somatosensory cortex

Vascular damage in the thalamogeniculate arteries

cause major damage to VPL/VPM, thalamic pain

Thalamic syndrome

extensive damage can cause ataxia and tactile insensitivity+ thalamic pain

OCCURS CONTRALATERAL TO LESION

Medial geniculate nucleus

major auditory relay

Lateral geniculate nucleus

major visual relay

optic n-LGN-primary visual cortex

Intralaminar nuclei

Centromedian: motor to putamen and motor cortex

Parafascicular: motor to caudate and prefrontal cortex

external medullary lamina

this sheet covering surface of thalamus

tonic state of thalamic neurons

normal depolarization of thalamic neuron

burst state of thalamic neurons

thalamic neuron is hyperpolarized, sensory info blocked

TRN neurons control tonic and burst states

Attention: No TRN inhibition, high thalamocortical activity

Sleep: high TRN inhibition, low thalamocortical activity