Lec 15 Thalamus Flashcards Preview

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Flashcards in Lec 15 Thalamus Deck (43):
1

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

- 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]

2

What does dorsal thalamus do?

- 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]

3

What structure is epithalamus most directly connected to?

hypothalamus

4

What is corticothalamic input?

- info the thalamus receives from cortical areas
- feedback inhibition from TRN
- feedfoward inhibition from descending cortical fibers

5

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

- both excitatory
- use glutamate
- strictly ipsilateral

6

What is the TRN?

- ventral hypothalamus
- composed entirely of GABAergic inhibitory interneurons
- send axons ONLY to dorsal hypothalamus [not to cerebral cortex]

7

What two types of neurons exist in dorsal thalamus nuclei?

- excitatory relay neurons --> project via internal capsule to middle layers [4] of cortex

- local GABAergic inhibitory interneurons --> axons remain local

8

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

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

9

What is function of nuclei within internal medullary lamina?

- receive ongoing info from all cortical areas
- project to striatum and layer 1 of cortex
- integrate info across modalities

10

What 3 input/output tracks via VPL? function?

function = sensory

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

spinothalamic Ad, C, 3, 4 --> S1/S2

vestibular nuclei --> posterior parietal cortex

11

What 3 input/output tracks via VPM? function?

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

12

What 2 input/output tracks via VM? function?

function = sensory

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

spinothalamic --> insula

13

What 1 input/output track via LGN? function?

function = sensory

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

LGN = Light

14

What 1 input/output track via MGN? function?

function = sensory

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

MGN = Music

15

What 2 input/output tracks via VA? function?

function = motor

input --> output
substantia nigra --> frontal cortex

globus pallidus --> frontal cortex

16

What 1 input/output track via VLa? function?

function = motor

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

17

What 1 input/output track via VLp? function?

function = motor

input --> output
cerebellum --> M1

18

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

function = limbic/cognitive

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

19

What 2 input/output tracks via MD? function?

function = limbic/cognitive

input --> output
amygdala --> prefrontal cortex

hippocampus via subiculum --> prefrontal cortex

20

What 1 input/output track via LD? function?

function = limbic/cognitive

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

21

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

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

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

function = sensory

superior colliculus --> temporal cortex and parietal cortex

23

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

both relay neurons and local GABA interneurons

24

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

- 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