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Brain and Behavior Exam 2 > Lec 15 Thalamus > Flashcards

Lec 15 Thalamus Flashcards

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
What neurons are responsible for feedforward inhibition of dorsal thalamus relay neurons?
- collateral branches of corticothalamic axons [axons from cortex to thalamus] give off collateral to TRN which synapse onto GABAergic that target dorsal thalamus
26
When do you get tonic firing of thalamus? what is it?
- 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
When do you get burst firing? what it it?
- 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
What are the steps by which TRN-dorsal thalamus functional loop maintains burst firing?
- 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
How do you transition burst to tonic?
When you sleep, 5HT [serotonin] hyperpolarized membrane causes burst firing mode and prevents info going to cortex
30
How do you transition tonic to burst?
ACh, histamine, and NE depolarize membrane of dorsal thalamic nuclei --> kick relay neurons into tonic firing mode
31
What is the name for the set of systems of cells/nuclei that produce modulatory NTs?
reticular activating system
32
What kind of waves when you are awake?
low voltage, high frequency > 30 Hz, random, fast
33
What kind of waves when you are drowsy?
alpha waves | 8-12 cps
34
What kind of waves when you are in REM sleep?
low voltage, random fast | sawtooth waves
35
What kind of waves when you are in stage 1 sleep?
3-7 cps | theta waves
36
What kind of waves when you are in stage 2 sleep?
12-14 cps sleep spindles and k complexes synchronized oscillations 6-15 Hz
37
What kind of waves when you are in delta sleep?
- 1/2 - 2 cps delta waves [0.5-4 Hz] deep sleep synchronized oscillations
38
What is thalamic syndrome?
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
What happens in tremor states due to thalamic lesion?
- rhythmic bursts in VA/VLa due to frequency abnormalities in GP-thalamus circuits - ex parkinsons
40
What are 4 types of lesions that can happen from thalamus?
- thalamic syndrome - tremor state - amnesia - absence seizres
41
What happens in amnesia due to thalamic lesion?
- vascular lesion of anterior or medial [MD] group nuclei | - disrupts amygdala/hippocampus circuitry
42
What happens in absence seizure due to thalamic lesion?
- 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
What are corticothalamic vs thalamocortical neurons?
corticothalamic: from cortex to thalamus thalamocortical: from thalamus to cortex

Brain and Behavior Exam 2 (21 decks)

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