Thalamus

Question 1

What does the thalamus stand for?

Answer 1

inner chamber, room

Question 2

Where is the thalamus derived from?

Answer 2

derived from the embryonic diencephalon.

Question 3

Where si the thalamus located?

Answer 3

Comprising two halves, the thalamus is positioned
symmetrically on both sides of the third ventricle

Question 4

Whta do myelinated fibers within th ethalamus do?

Answer 4

form a system that separates clusters of neurons, defining thalamic
subparts.

Question 5

sensory system within th ebrain is connected where?

Answer 5

Every sensory system, excluding the olfactory
system, is connected to a thalamic nucleus,
responsible for receiving and transmitting sensory
signals to the corresponding primary cortical area

Question 6

major sensory relay station?

Answer 6

the thalamus

Question 7

which other inputs dies the thalamus convey?

Answer 7

1. motor inputs from the cerebellum and basal ganglia
2. limbic inputs
3. modulatory inputs involved in behavioral arousal and sleep–wake
   cycle

Question 8

What is the internal medullary lamina?

Answer 8

part of thalamus Divided into a medial , lateral, and anterior nuclear group by a Y-shaped white matter structure

Question 9

Nuclei within the internal medullary lamina itself are
called the:

Answer 9

intralaminar nuclei

Question 10

describe the midline thalamic nuclei

Answer 10

lie adjacent to the third
ventricle, several of which are continuous with and
functionally very similar to the intralaminar nuclei

Question 11

what is thalamic reticular nucleus?

Answer 11

forms a sheet
enveloping the lateral aspect of the thalamus

Question 12

WEach side of th ethalamus can be divided as? and by what is the thalamus covered?

Answer 12

a lateral nuclear group, a medial nuclear
group, and an anterior nuclear group by the internal medullary lamina. The thalamus is covered on its superior surface by a thin layer of white matter, called the stratum zonale, and on its lateral surface by another layer, the external medullary lamina

Question 13

where are smaller nuclear groups situated?

Answer 13

within the internal medullary lamina, and on the medial and lateral surfaces of the thalamus.

Question 14

explain the anterior neuroanatomical subdivision of the thalamus

Answer 14

The anterior part of the thalamus contains the
anterior thalamic nuclei.

They receive the mammillothalamic tract
from the mammillary nuclei. This is part of an important circuit called the Papez Circuit (functions primarily in the cortical control of emotion and memory storage and contains centers that regulate aversion and gratification).

These anterior thalamic nuclei also receive
reciprocal connections with the cingulate
gyrus and hypothalamus.

The function of the anterior thalamic nuclei is
closely associated with that of the limbic
system and is concerned with emotional
tone and the mechanisms of recent memory.

Question 15

explain the medial neuroanatomical division of the thalamus

Answer 15

• The medial part of the thalamus contains
  the large dorsomedial nucleus and smaller
  nuclei (centromedian and ventral
  posteromedial).
• The dorsomedial nucleus has afferent and
  efferent connections with the nuclei of the
  hypothalamus, as well as with the prefrontal
  cortex. The dorsomedial nucleus is the main relay center for information traveling to the frontal lobe’s prefrontal cortex.
• The medial part of the thalamus is
  interconnected with all other groups of
  thalamic nuclei.
• The medial part of the thalamus is
  responsible for the integration of a large
  variety of sensory information, and the
  relation of the information to one’s
  emotional feelings and subjective state.

Habenular nuclei-These lie on the medial surface of the dorsal medial nucleus of the thalamus. The lateral HN has been hypothesized to play a role during aversive learning.

Paraventricular thalamic nucleus- This is one of the midline thalamic nuclei and lies in the most medial aspect of the thalamus. It regulates arousal, as well as emotional and motivated behaviors

Question 16

the lateral subdivison is divided inti:

Answer 16

dorsal and ventral tier

Question 17

explain the contents of th edorsal tier of the latwral subdivision

Answer 17

• Lateral dorsal nucleus- processes somatosensory
  information
• Lateral posterior nucleus- determining visual saliency,
  visually guided behaviors
• Pulvinar nucleus- visual information processing,
  integrating visual and motor signals

These nuclei are known to have interconnections with
other thalamic nuclei and with the parietal lobe,
cingulate gyrus, and occipital and temporal lobes

Question 18

desfribe the intralaminar nuclei

Answer 18

located within the internal medullary lamina.
They receive input from the reticular formation, spinothalamic, and trigeminothalamic tracts, and send efferent output to other thalamic nuclei and the corpus striatum. These nuclei are involved in various
functions including awareness, consciousness, arousal, sleep, vigilance, cognition, sensation, and sexual processing.

Question 19

explain midline nuclei

Answer 19

located adjacent to the third ventricle and within
the interthalamic connection, include the paraventricular, paratenial, reuniens, and rhomboid nuclei. They receive input from the reticular formation and are termed “nonspecific” due to their
widespread projections to the cortex and limbic structures. These nuclei regulate arousal, cognitive function, basal ganglia circuits, nociceptive input to the cerebral cortex, activity levels in target structures, and awareness.

Question 20

explain reticular nucleus

Answer 20

is a thin layer of GABAergic neurons positioned
between the external medullary lamina and the posterior limb of the internal capsule. This nucleus receives input from various sources including other thalamic nuclei, the globus pallidus, reticular formation, and cerebral cortex. Additionally, it provides significant inhibition to thalamocortical neurons. It regulates thalamic activity, influencing sensory processing, arousal, cognition, movement initiation, alertness, and attention. Notably,
it lacks outgoing projections to the cerebral cortex.

Question 21

explain medial geniculate body

Answer 21

forms part of the auditory pathway and
is a swelling on the posterior surface of the thalamus beneath
the pulvinar. Its main afferent is the inferior colliculus. Its major
efferent projection is to the primary auditory cortex on the
superior temporal convolution. This region plays a critical role in the
complex auditory processing necessary for robust speech
perception

Question 22

explain geniculate body

Answer 22

forms part of the visual pathway,
appearing as a bulge beneath the pulvinar of the thalamus. It serves as the endpoint for most optic tract fibers. These fibers originate from the ganglion cell layer of the retina and convey visual
data. Each lateral geniculate body receives visual input from the contralateral visual field. Efferent fibers exit the lateral geniculate body to form the visual radiation, projecting to the visual cortex in
the occipital lobe. Thus, it provides a relay station for all the axons of the retinal ganglion cells subserving vision.

Question 23

The thalamus is an important relay station for two sensory motor axonal loops involving the cerebellum and the basal nuclei:

Answer 23

(i) the cerebellar-rubro-thalamic·corticalponto-cerebellar loop
(ii) the cortical-striatal-pallidal-thalamic-cortical loop- The cortico-striatal-thalamo-cortical (CSTC) pathway is a brain circuit that controls movement, habit formation, and reward. The CSTC includes the orbitofrontal cortex (OFC), the anterior cingulate cortex (ACC), the basal ganglia, and the thalamus.
both loops are necessary for normal voluntary movement

Question 24

explain the functional classification of specific thalamin nuclei

Answer 24

receive information (e.g. visual, acoustic, primary somatosensory, motor input) that is very specific and well-defined, and project this information to very specific, functionally discrete cortical areas. These nuclei include the ventral anterior (VA), ventral lateral (VL), ventral posterior (VP), medial geniculate and lateral geniculate nuclei.

Question 25

explain the functional classification of association thalamic nuclei

Answer 25

receive most of their information from the cerebral cortex itself, and then project back to the “association areas” in the cortex to regulate the integration and interpretation of the sensory information. These nuclei include the anterior nucleus, pulvinar, and dorsomedial nucleus. These nuclei provide much of the subcortical input to the association cortices: the pulvinar projects to the parietal association cortex, the lateral posterior nuclei to the temporal association cortex, and the medial dorsal nuclei to the frontal association cortex. Unlike the thalamic nuclei that receive peripheral sensory information and project to primary sensory cortices, the input to these three nuclei comes from other regions of the cortex. In consequence, the signals coming into the association cortices via the thalamus reflect sensory and motor information that has already been processed in the primary sensory and motor areas of the cerebral cortex, and is being fed back to the association regions.

Question 26

explain non specific nuclei from thalamus

Answer 26

show broad and diffuse projections through the cerebral cortex. Involved in general functions such as consciousness and attention. These nuclei include the reticular nucleus, and intralaminar and midline nuclei.

Question 27

Motor functions of specific nuclei

Answer 27

Cerebellum (Cb) and Basal ganglia (BG) have bilateral connection with:
thalamic ventral anterior (VA) and ventrolateral (VL) nuclei

Question 28

limbic functions of asociation nuclei

Answer 28

Thalamic anterior nucleus (AN)->
Cingulate ctx. ->
Subicular ctx. (of hippocampal formation) ->
Mamillary bodies (via mamillothalamic tract) ->
Thalamic dorsomedial nucleus (DM)->
Frontal ctx and hypothalamus
*Limbic functions associated with affective components of pain,
subjective feeling states, & personality!

Question 29

thalamic blood supply

Answer 29

*
Main artery supply: Posterior cerebral a. – from Basilar a.
*
Posterior choroidal a.- supplies anterior and posterior thalamus
*
Thalamic-subthalamic a.- supplies medial and posterior thalamus
*
Posterior communicating a.- supplies posterior thalamus
*
Thalamo geniculate a.- supplies posterior thalamus

Question 30

thalamic syndromes

Answer 30

1. Anterolateral thalamic syndromes
   Paresis (muscle weakness), motor incoordination
2. Posterolateral thalamic syndromes
   -Sensory disorders/speech
   -Dejerine-Roussy Syndrome- pain that can be allodynic in nature or triggered by seemingly unrelated stimuli (sounds, tastes). Symptoms are typically lateralized and may include vision loss or loss of balance (position sense).
   -VP nucleus- pain
3. Medial thalamic syndromes
   Disorders of consciousness
   Thalamic neglect (disorientation), thalamic amnesia

Question 31

What is the human connectome project

Answer 31

*
Two research consortia were established in 2009 by the National Institutes of Health to map the neural pathways that underlie human brain function:
➢
The WU/Minn Project- Washington University in St. Louis/University of Minnesota/Oxford University (the WU-Minn HCP consortium) – co-led by Dr. David Van Essen and Dr. Kamil Ugurbil - set out to comprehensively map human brain circuitry in 1200 healthy adults using cutting-edge methods of noninvasive neuroimaging.
➢
The Harvard/MGH-UCAL Project- Massachusetts General Hospital/Harvard University and the University of California Los Angeles (UCLA) – co-led by Dr. Bruce Rosen and Dr. Arthur Toga – set out to create a new magnetic resonance imager optimized for measuring connectome data.
➢
* Over 100 publications from initial 5 year studies.
➢
Many other consortia followed these initial projects to study brain connectomes throughout the ages (Lifespan Connectome Project) and neurological disorders (Disease Connectome).

Question 32

what are some non-invasive functional neuroimaging techniques

Answer 32

PET = Positron Emission Tomography
FDG = FluoroDeoxyGlucose
EEG = ElectroEncephaloGraphy
SPECT = Single Photon Emission Tomography
HMPAO = HexaMethylPropyleneAmine Oxime
MEG = Magnetoencephalography
NIRS = Near InfraRed Spectroscopy
fMRI = functional Magnetic Resonance Imaging