Flashcards in Lecture 16: Thalamus Deck (20):
Dorsal thalamus (development)
Multiple nuclei that connect bidirectionally with cortex; ends up making up the majority of the thalamus
Ventral thalamus (development)
(Reticular nucleus) Connects bidirectionally with dorsal thalamus
What fiber divides the thalamus? What groups of nuclei? (3 + 1)
Internal medullary lamina (y shaped); anterior, medial, lateral (and intralaminar)
Back end of thalamus is...
Front end of thalamus is...
Describe ventral thalamus
Sheet of purely GABAergic inhibitory neurons; surrounds anterior, lateral, ventral surfaces of dorsal thalamus; sends axons ONLY to dorsal thalamus
What type of neuron is the GABA neuron w/in a dorsal thalamic nucleus.
Ascending thalamic input synapses where? Effect? Name?
On relay neuron AND GABA neuron (relay gets it first); delayed inhibition via GABA; Feedforward inhibition
Where does the relay neuron project? Then what?
Input to level IV of the cortex; return projection to the thalamus from level VI
Where else does the relay neuron project?
TRN to GABAergic neuron, which projects back to relay (feedback inhibition)
Where else do the return projections to the thalamus synapse?
TRN to GABAergic neuron, which projects back to relay (feedforward inhibition)
Describe thalamic/cortical EEG
Ensembles of thalamic and cortical neurons discharge synchronously at stereotyped frequencies associated with different conscious states (alert, drowsy, sleep)
Awake/alert = what mode and function?
Tonic firing (depolarized), allows information transfer to cortex
Drowsy/deep sleep = what mode and function? What wave?
Burst firing (hyperpolarized, so you get a "burst" of APs), blocks transfer to cortex; delta wave
How do we get from hyperpolarized to depolarized modes?
Turned on by ACh, 5HT, NA (project to dorsal thalamic nucleus), and histamine (note: histamine also projects TRN)
Lesions: Thalamic syndrome
Damage to posterior thalamus (usually vascular, including VPL/VPM); contralateral hemianesthesia with excruciating “central” pain
Lesions: Tremor states
Rhythmic bursts in VA/VLa in PD due to frequency abnormalities in pallidothalamic circuits
Lesions of the anterior and MD nuclei
Lesions: Absence seizures
Spike and wave patterns entrained by very long bursts in GABAergic neurons of the TRN