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Brain and Behavior Exam 2 > Lec 15 Thalamus > Flashcards

Lec 15 Thalamus Flashcards

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1
Q

What is the order of diencephalon structures from dorsal to ventral?

A
  • epithalamus [including pineal, pretectal nuclei, habenula]
  • dorsal thalamus [nuclei that communicated wiht cerebral cortex mostly]
  • ventral thalamus [mostly TRN]
  • hypothalalmus [underneath and adjacent to ventricle 3]
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2
Q

What does dorsal thalamus do?

A
  • processes ascending sensory, motor, and limbic/cognitive info
  • sharpens and refines receptive fields and other aspects of coding
  • relays info to cortical areas [somatosensory, visual, auditory, motor, etc]
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3
Q

What structure is epithalamus most directly connected to?

A

hypothalamus

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4
Q

What is corticothalamic input?

A
  • info the thalamus receives from cortical areas
  • feedback inhibition from TRN
  • feedfoward inhibition from descending cortical fibers
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5
Q

What type of transmitters do thalamocortical and corticothalamic projections use? contralateral or ipsilateral?

A
  • both excitatory
  • use glutamate
  • strictly ipsilateral
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6
Q

What is the TRN?

A
  • ventral hypothalamus
  • composed entirely of GABAergic inhibitory interneurons
  • send axons ONLY to dorsal hypothalamus [not to cerebral cortex]
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7
Q

What two types of neurons exist in dorsal thalamus nuclei?

A
  • excitatory relay neurons –> project via internal capsule to middle layers [4] of cortex
  • local GABAergic inhibitory interneurons –> axons remain local
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8
Q

What are the 3 nuclear groups of the dorsal thalamus? What divides them?

A
  • medial [MD]
  • lateral [VA, VL, LD, LP, VPL, pulvinar, LGN, MGN]
  • anterior [anterior nuclei]
  • divided by internal medullary lamina
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9
Q

What is function of nuclei within internal medullary lamina?

A
  • receive ongoing info from all cortical areas
  • project to striatum and layer 1 of cortex
  • integrate info across modalities
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10
Q

What 3 input/output tracks via VPL? function?

A

function = sensory

input –> output
DC-ML AB, group 1, 2 –> S1/S2

spinothalamic Ad, C, 3, 4 –> S1/S2

vestibular nuclei –> posterior parietal cortex

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11
Q

What 3 input/output tracks via VPM? function?

A

function = sensory

input –> output
principal CN V nucleus = AB, 1, 2 –> S1, S2

spinal nucleus of V –> S1, S2

spinothalamic Ad, C, 3, 4 –> S1, S2

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12
Q

What 2 input/output tracks via VM? function?

A

function = sensory

input –> output
solitary nucleus [taste] –> gustatory cortex

spinothalamic –> insula

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13
Q

What 1 input/output track via LGN? function?

A

function = sensory

input –> output
optic nerve/tract –> V1 [primary visual cortex in occipital]

LGN = Light

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14
Q

What 1 input/output track via MGN? function?

A

function = sensory

input –> output
inferior colliculus –> A1 [primary auditory cortex in lateral fissure/heschl’s]

MGN = Music

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15
Q

What 2 input/output tracks via VA? function?

A

function = motor

input –> output
substantia nigra –> frontal cortex

globus pallidus –> frontal cortex

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16
Q

What 1 input/output track via VLa? function?

A

function = motor

input –> output
globus pallidus –> premotor cortex [PM], primary motor cortex [M1], supplementary motor cortex [SMC]

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17
Q

What 1 input/output track via VLp? function?

A

function = motor

input –> output
cerebellum –> M1

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18
Q

What 1 input/output track via anterior nuclei? function?

A

function = limbic/cognitive

input –> output
hypothalamus [mamillothalamic tract] –> cingulate cortex[gyrus]

19
Q

What 2 input/output tracks via MD? function?

A

function = limbic/cognitive

input –> output
amygdala –> prefrontal cortex

hippocampus via subiculum –> prefrontal cortex

20
Q

What 1 input/output track via LD? function?

A

function = limbic/cognitive

input –> output
hippocampus [via subiculum] –> prefrontal cortex, retrosplenial cortex, parahippocampal gyrus

21
Q

What input/output to intra-laminar nuclei? function?

A

function = widespread activation of cortex/striatum, arousal integraiton

input: globus pallidus, spinothalamic, cerebellum, substantia nigra, multiple cortical areas
output: striatum [caudate and putamen], multiple cortical areas [layer 1]

22
Q

What 1 input/output track via LP/pulvinar? function?

A

function = sensory

superior colliculus –> temporal cortex and parietal cortex

23
Q

What type of neurons in the relay nuclei do ascending input neurons synapse onto?

A

both relay neurons and local GABA interneurons

24
Q

What kind of collateral do thalamocotical axons give off en route from thalamus to layer 4 of cortex?

A
  • give off collateral to TRN GABA cells that in turn project back into dorsal thalamus = feedback inhibition
25
Q

What neurons are responsible for feedforward inhibition of dorsal thalamus relay neurons?

A
  • collateral branches of corticothalamic axons [axons from cortex to thalamus] give off collateral to TRN which synapse onto GABAergic that target dorsal thalamus
26
Q

When do you get tonic firing of thalamus? what is it?

A
  • see it in awake/alert states
  • high frequency, desynchronized activity
  • thalamus fires single, high-freq APs –> favorable for information transfer through to cortex
  • resting membrane potential relatively depolarized relatively depolarized
27
Q

When do you get burst firing? what it it?

A
  • see it when drowsy or in deep sleep
  • slow, rhythmic oscillations, delta and spindle waves with bursts of APs
  • not favorable for information flow
  • resting membrane potential hyperpolarized, blocking flow of info to cortex
  • maintained by functional loop between TRN and dorsal thalamus
28
Q

What are the steps by which TRN-dorsal thalamus functional loop maintains burst firing?

A
  • TRN AP causes release of GABA –> generates ISPs [hyperpolarization] in dorsal thalamus relay nuclei
  • ISPSs trigger hyperpolarization sensitive channels –> increase conductance of Na –> triggers AP in neurons –> triggers AP in TRN via feedback

–> cycle repeats

29
Q

How do you transition burst to tonic?

A

When you sleep, 5HT [serotonin] hyperpolarized membrane

causes burst firing mode and prevents info going to cortex

30
Q

How do you transition tonic to burst?

A

ACh, histamine, and NE depolarize membrane of dorsal thalamic nuclei

–> kick relay neurons into tonic firing mode

31
Q

What is the name for the set of systems of cells/nuclei that produce modulatory NTs?

A

reticular activating system

32
Q

What kind of waves when you are awake?

A

low voltage, high frequency > 30 Hz, random, fast

33
Q

What kind of waves when you are drowsy?

A

alpha waves

8-12 cps

34
Q

What kind of waves when you are in REM sleep?

A

low voltage, random fast

sawtooth waves

35
Q

What kind of waves when you are in stage 1 sleep?

A

3-7 cps

theta waves

36
Q

What kind of waves when you are in stage 2 sleep?

A

12-14 cps
sleep spindles and k complexes
synchronized oscillations
6-15 Hz

37
Q

What kind of waves when you are in delta sleep?

A
  • 1/2 - 2 cps
    delta waves [0.5-4 Hz]
    deep sleep
    synchronized oscillations
38
Q

What is thalamic syndrome?

A

damage to posterior thalamus [eg VPL/VPM]
- causes contralateral hemianesthesia with excruciating “central” pain

  • usually due to some vascular damage [thrombosis of one of arteries off of posterior cerebral artery]
39
Q

What happens in tremor states due to thalamic lesion?

A
  • rhythmic bursts in VA/VLa due to frequency abnormalities in GP-thalamus circuits
  • ex parkinsons
40
Q

What are 4 types of lesions that can happen from thalamus?

A
  • thalamic syndrome
  • tremor state
  • amnesia
  • absence seizres
41
Q

What happens in amnesia due to thalamic lesion?

A
  • vascular lesion of anterior or medial [MD] group nuclei

- disrupts amygdala/hippocampus circuitry

42
Q

What happens in absence seizure due to thalamic lesion?

A
  • form of epilepsy
  • characterized by sudden arrest of movement, blank stare, fluttering eyelid, loss of ability to interact
  • related to abnormal spindle wave generation caused by sustained periods of TRN GABA-ergic neuron activity
43
Q

What are corticothalamic vs thalamocortical neurons?

A

corticothalamic: from cortex to thalamus
thalamocortical: from thalamus to cortex

Brain and Behavior Exam 2 (21 decks)

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