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Systems Neuroscience > Diencephalon-Thalamus (2/2) > Flashcards

Diencephalon-Thalamus (2/2) Flashcards

1
Q 
Thalamus
-size
-location 
-location among animals
-receives 
-sends to
-relationship to the cortex 
**
-
A
  • The largest part of the mammalian diencephalon
  • It is positioned in the same place in every animal. If you have a brain you have a thalamus
  • Receives all sensory information, with the exception of olfaction, first
  • The major relay to the neocortex
  • “Gateway” to cortex
  • Each major area of the neocortex depends on a defined thalamic group
  • Details differ for each species, but general relationships apply to all mammals
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2
Q

how big is the thalamus in humans?

-dont need to know

A

the size of a walnut

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3
Q

What is the only sensory information to bypass the thalamus?

A

the olfaction

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4
Q

Ways to divide up the thalamus

A

*By Projections/Circuitry:
Relay, Association, and Non-specific nuclei

*Dorsal vs Ventral

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5
Q

Thalamic Circuitry

A

4 features that characterize circuitry:
Projection to cerebral cortex
4 ways to classify

Classifying Thalamic Nuclei by Projections

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6
Q

Classifying Thalamic Nuclei by Projections

A

*Can classify based on axon terminations (4)

  • Projecting to single cortical area
  • Projecting densely to one area, but diffusely to another
  • Projecting diffusely to several cortical areas, but with a concentration in a single field
  • Projecting diffusely over widespread areas
  • Can also classify based on cortical laminar termination of thalamic efferents
  • Classify nuclear groups according to whether or not it has a projection to the striatum and/or amygdala in addition to the cortex
  • Divide into specific and non-specific nuclei
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7
Q

Sight information projections

A
  • eye ball –> LGN or Superior Colliculus

- eye ball –> LGN–> Visual Cortex

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8
Q

Projecting to single cortical area

-example

**

A

*Dorsal Lateral Geniculate Nucleus

Classifying Thalamic Nuclei by Projections

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9
Q

Projecting densely to one area, but diffusely to another

  • example
  • dont think need to know
A

Lateralis Dorsalis (Dorsolateral Nucleus)

(Classifying Thalamic Nuclei by Projections

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10
Q

Lateralis Dorsalis (Dorsolateral Nucleus)

-what is this an example of and what does it do?

dont need to know

A

Projecting densely to one area, but diffusely to another

To the: Parietal Cortex (Precuneate) and Splenium of Corpus Callosum

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11
Q

Projecting diffusely to several cortical areas, but with a concentration in a single field

-example

dont need to know

A 
Nucleus Ventomedialis (Ventromedial Nucleus)
Convergence of several motor pathways (Chevalier and Deniau, 1982; Herkenham, 1979; MacLeod and James, 1984)
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12
Q

Projecting diffusely over widespread areas
-example

dont need to know

A

Suprageniculate Nucleus
Link between limbic and sensory information/structures (Hicks et al, 1986)
Also projects to striatum… at least in cats (Hu and Jayaraman, 1986)

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13
Q

Classifying Thalamic Nuclei by Projections
-Can classify based on axon terminations (4)

A

*Can classify based on axon terminations (4)

  • Projecting to single cortical area
  • Projecting densely to one area, but diffusely to another
  • Projecting diffusely to several cortical areas, but with a concentration in a single field
  • Projecting diffusely over widespread areas
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14
Q

Problem with classifying the Thalamic nuclei by projections
based on cortical laminar termination of thalamic efferents

dont need to know

A

Just because it projects to one layer does not mean it cannot project to another layer
(she does not think that this is a good way to classify (divide up the thalamus): because most is super specific)

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15
Q

Divide into specific and non-specific nuclei
*specific vs non-specific

A

Specific: relay nuclei that terminate in discrete cortical areas
Nonspecific: project diffusely to cortex and other groups

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16
Q

Specific Nuclei (Relay)

A

*Relay nuclei receive very well-defined inputs and project this signal to functionally distinct areas of the cerebral cortex.
Mostly the lateral nuclear group and geniculate group
Relay nuclei are specific nuclei
Most specific nuclei are relay nuclei

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17
Q

Types of Relays

A

First Order

Higher Order

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18
Q

First Order Relays

A

Send messages to cortex about what is going on subcortically

{Receive information from outside the thalamus and sending it to the cortex }

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19
Q

Higher Order Relays

-important for?

A

{From the cortex and to the cortex}

  • Receive their driving input from the cortex itself
  • Provide a transthalamic relay from one part of the cortex to another
  • Indirect corticocortical connections
  • Approximately ½ of the thalamic nuclei in primates are higher order nuclei

{-This is how humans can do complicated things : powerful way of incorporating information, decide how to respond to it (should we attend to it?), helps to decide if should move
-These circuits are super important for everyday functioning}

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20
Q

Relay vs Association vs Non‐specific ***

A
  • Relay nuclei receive very well-defined inputs and project this signal to functionally distinct areas of the cerebral cortex.
  • Nonspecific: project diffusely to cortex and other groups
  • association: Receive most of their input from the cerebral cortex and project back to the cerebral cortex in the association areas where they appear to regulate activity
21
Q

Association Nuclei **

A

Receive most of their input from the cerebral cortex and project back to the cerebral cortex in the association areas where they appear to regulate activity

Dorsomedial (Mediodorsal) Nucleus
Pulvinar
Anterior Group

22
Q

Relay vs Specific ***

A

Relay nuclei are specific nuclei

Most specific nuclei are relay nuclei

23
Q

First‐order vs Higher order ***

A

First‐order: Send messages to cortex about what is going on subcortically

Higher order : Receive their driving input from the cortex itself {From the cortex and to the cortex}

  • Provide a transthalamic relay from one part of the cortex to another
  • Indirect corticocortical connections
24
Q

Specific Example of a first‐order relay nucleus ***

A

The LGN is considered a first-order thalamic nucleus on the basis of its close relationship with the retina.
-I think it communicates with the LG in the occipital lobe

Relays visual inputs from retina to
Primary visual cortex

25
Q

[This is where find some of the biggest difference between primate brain and non-primate brain]

-dont need to know

A

[-in primates: we have a huge amount of our thalamus dedicated to ….. Judgment, attention, makes us more complex (our ability to send the important information to the cortex and bounce it to another part of the cortex and get more areas more aware)

-example: something come running at you- smells like tiger= olfactory cortex, see it running at you – going to visual cortex; the thalamus helps to make the association

]

26
Q

Nonspecific Nuclei **

A

*Many of the intralaminar nuclei and midline nuclei have diffuse projections to the cortex and have been termed “nonspecific”.
*Project broadly to the cortex
*Also project to more ‘nonspecific’ regions of the cortex
[in comparison there are “specific” regions of the cortex]
*These nuclei are probably mostly involved in arousal and alertness.
[The purpose : being at the ready or not]

27
Q

Specific Example of an association nucleus ***

A
  • pulvinar (you have to know it anyway)
  • Dorsomedial (Mediodorsal) Nucleus
  • note: I think dorsomedial nucleus is also a higher order nucleus
  • communicates with prefrontal cortex
  • important for learning and decision-making.
28
Q

No known communication between thalamic nuclei directly, except the ___

A

No known communication between thalamic nuclei directly, except the reticular nucleus

29
Q

External medullary lamina

***

A
  • a layer of axons (white matter) that covers the dorsal thalamus on the lateral sides
  • Includes fibers coming to and from the cortex
  • The cells of the reticular nucleus reside here
30
Q

The cells of the reticular nucleus reside at the

A

External medullary lamina

31
Q 
Dorsomedial Nucleus (Mediodorsal Nucleus)
(as your example of association nucleus but I really wouldnt bother to learn this, you should learn the pulvinar as your example)
A

An association nucleus that has a medial and lateral subdivision.
The lateral part receives projections from the superior colliculus, olfactory cortex and the ventral pallidum.
Efferent projections to the frontal eye fields and to the anterior cingulate cortex of the frontal lobes.
Involved in controlling eye movements and attending to visual stimuli but it also plays a role in emotional “tone”.
The medial part receives inputs from several brain areas including the solitary nucleus, substantia nigra reticulata, amygdala and ventral pallidum.
Projects to limbic areas of the cortex, including insular cortex, orbital frontal cortex and subcallosal region.
These cortical areas are involved in autonomic regulation and emotions.
Damage to this area can also impair memory as may happen with the amnestic syndrome due to alcoholism.

32
Q

Reticular Nucleus of the Thalamus ***

A

*Sheet of neurons that surrounds all but the medial and dorsal surface of the thalamus
[important part of the ventricle thalamus]
*Pierced by fibers of thalamic radiations
[The position is important. It is surrounding the thalamus ]

*Homogenous neurotransmitter phenotype- GABA
*Receives excitatory branches from corticothalamic/thalamocortical axons and send inhibitory axons to other parts of the thalamus
*Each circuit sends to and from through the same part of reticular nucleus
*Role in adjusting messages based on attentive state of the whole animals (wake/sleep) and salience (threat/no threat)
*Keeping everything in check. Not misrepresenting something. Match the attentive shape: example if sleeping make sure that you do not awake by small things
*Strategically placed over the axons being sent between thalamus and cortex
[Around and hugging the thalamus (best place!)]

[ i think: knows everything - It reads every message to make sure does not get out of hang ]

33
Q

metaphor for Reticular Nucleus of the Thalamus

A

a student driver

34
Q

Subdivisions of the Thalamus

A

dorsal vs

35
Q

Medullary Lamina divides the

A

“While the thalamus is mostly gray matter (cell bodies of neurons), there are some areas of white matter (axons). The external and internal medullary laminae are white matter structures of the thalamus. The external medullary laminae cover the lateral surface of the thalamus, and the internal medullary laminae divide the thalamic nuclei into anterior, medial, and lateral groups.[1]”

36
Q

Internal medullary lamina **

A
  • Internal medullary lamina- white matter fibers that subdivide the (dorsal?) thalamus into:
  • anterior
  • medial
  • lateral
  • midline
  • intralaminar nuclear groups

Thin layer of nerve fibers that are made up of afferent and efferent projections of some thalamic nuclei
Roughly Y-shaped when viewed from above

37
Q

T/F the Internal medullary lamina defines the thalamus geographically

A

true i think

38
Q

Pulvinar Nucleus ***

  • type of nucleus
  • location
  • receives
  • projects
  • result
A

-in the Lateral Nuclear Group (of the dorsal thalamus) it is posterior

*Largest of these association nuclei
*Occupies the posterior part of the dorsal tier of the thalamus
*Receives afferent projections from the superior colliculus as well as from the association cortex.
*Projects to secondary visual areas and to association areas in the parietotemporal region.
This contributes to visual perception and eye movements, probably relating to attention to these stimuli.

(low key alex thinks that pulvinar can also be considered higher order)

39
Q

Lateral Geniculate Nucleus ***

A
  • Receives retinotopic input via the optic tract from the contralateral visual world.
  • Projects in a topographic manner to the primary visual cortex via the optic radiations.
  • Optic radiations from the upper visual world loop through the temporal lobe white matter on the way to the visual cortex (Meyer’s loop), while optic radiations from the lower visual world pass just deep to the parietal lobe.

*first‐order relay nucleus

40
Q

Medial Geniculate Nucleus **

A

Receives tonotopically organized auditory afferents from the inferior colliculus via the brachium of the inferior colliculus.
Projects to the primary auditory cortex on the superior temporal gyrus (transverse gyrus of Heschel).

-pretty sure it is a type of relay nucleus

[For hearing; want to keep certain frequency separate
-tonotopic map]

[-alex thinks that the ventral portion of the medial geniculate nucleus is first order ]

41
Q

Epithalamus (pineal gland) ***

A
  • Pineal gland: contains modified photoreceptor cells (pinealocytes)
  • Release melatonin in a circadian rhythm
  • Do not respond directly to light in humans
  • Respond to circadian differences in sympathetic nervous system activity
  • Sleep-wake cycle
  • Sexual maturation?
42
Q

pineal gland

A

-found in the Epithalamus

Pineal gland: contains modified photoreceptor cells (pinealocytes)
Release melatonin in a circadian rhythm
*Do NOT respond directly to light in humans
Respond to circadian differences in sympathetic nervous system activity
Sleep-wake cycle
Sexual maturation?

[In some animals it IS directly related to light: example – if an animal only breads in a certain season, the pineal gland helps this process ]

43
Q

where is the pineal gland found

A

the epithalamus

44
Q

which nuclei provide a transthalamic relay from one part of the cortex to another

A

higher order relay nucleus

45
Q

*These nuclei are probably mostly involved in arousal and alertness.

A

nonspecific nuclei

46
Q

The ____ is the only thalamic nucleus that does not project to the cerebral cortex. Instead it primarily modulates the activity of other thalamic nuclei.

A

The reticular nucleus is the only thalamic nucleus that does not project to the cerebral cortex. Instead it primarily modulates the activity of other thalamic nuclei.

47
Q

External medullary lamina is a layer of axons (white matter) that covers the _____ thalamus on the lateral sides

A

External medullary lamina is a layer of axons (white matter) that covers the dorsal thalamus on the lateral sides

48
Q

The primary function of the thalamus

A

The primary function of the thalamus is to relay motor and sensory signals to the cerebral cortex. It also regulates sleep, alertness, and wakefulness.

49
Q

the hypothalamus integrates _____ information to regulate ______ responses

A

the hypothalamus integrates sensory, cognitive, and emotional information to regulate endocrine, autonomic, and behavioral responses

Systems Neuroscience (24 decks)

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