L05 - Thalamus and Cortex Flashcards by Max Kam

Shape and location of the Thalamus in relation to the brainstem?

Shape = Large ovoid mass of gray matter. Anterior end is narrow and rounded and posterior end is expended to form the pulvinar

Location: Major part of diencephalon, both sides of 3rd ventricle joined by Interthalamic adhesion

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Topographic location of the thalamus - Anterior and Posterior?

Anterior: interventricular foramen

Posterior: pulvinar (+ Pineal gland)

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Topographic location of the thalamus - Superior and inferior?

Superior: stratum zonale (White mater) & strita terminalis

Inferior: tegmentum of midbrain

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Topographic location of the thalamus - Medial and lateral?

Medial: lateral wall of 3rd ventricle

Lateral: nerve fibers of internal capsules

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What internal structures are destroyed in a lateral dissection of the thalamus?

Caudate nucleus and putamen

Lentiform nucleus = Putamen + Globus pallidus. Inside basal ganglia

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4 parts of the diencephalon?

Epithalamus
Thalamus
Subthalamus
Hypothalamus

(Hypothalamic sulus divides thalamus from hypothalamus)

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List some structures that lie inferior to the hypothalamus?

Oculomotor nerve
Mammillary body
Infundibulum
Optic nerve and chiasm

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Function of epithalamus?

pineal gland secretes melatonin

Control circadian rhythm

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Function of thalamus?

1) Relays all sensory input to the cortex (esp. frontal motor region)
2) Controls the perception of touch, pressure, temperature
3) Involved in movement control

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Function of Subthalamus?

 Connects subthalamic nuclei and basal ganglia

 Controls body movement, emotion

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Function of Hypothalamus?

 Controls body temperature

 Regulates feeding behavior

 Regulates emotion, circadian rhythms, pattern of wake/sleep

 Releases hormones to regulate pituitary gland (vs. reticular formation = nerve control)

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Function of the Anterior group of thalamic nuclei?

part of limbic system: memory, emotion:

Hippocampus, Mammilary body input
Cingulate cortex output

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Function of the Ventral (antero-lateral) group of thalamic nuclei?

 Signals from cerebellum, basal nuclei, globus pallidus to motor areas of cortex

 Somesthetic output to postcentral gyrus

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Function of the Lateral group of thalamic nuclei?

 Somesthetic output to cortical association areas

 Contributes to emotional function of limbic system

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Function of the Posterior group of thalamic nuclei?

 Visual signals to occipital lobe / primary visual cortex (via lateral geniculate nucleus)

 Auditory signals to temporal lobe / primary auditory cortex (from inner ear > inferior olivary nucleus > medial geniculate nucleus)

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What separates the thalamic nuclei into groups?

Lamina

i.e. internal medullary lamina separates lateral and medial thalamus

External medullary lamina enclose Lateral thalamus

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Describe the division of the ventral thalamic nuclei

From antero- lateral to postero- lateral:

Ventral anterior (VA)
Ventral lateral (VL)
Ventral posterior (VP)

VP subdivided into:
V. Intermedial (VI),
V. posteromedial (VPM),
V. posterolateral (VPL)

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Input and output flow of:

Ventral lateral thalamus?

Input: Globus pallidus + Cerebellum

Output: Motor cortex

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Input and output flow of: 
Ventral posterior (VPL and VPM included) thalamus?

Input: Medial, spinal and trigeminal lemnisci (sensory from lower and upper extremities + head and neck)

Output: Somatosensory cortex

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Input and output flow of:

Ventral anterior thalamus?

Input: Globus pallidus/ basal ganglia

Output: Premotor cortex

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Input and output flow of:

Lateral geniculate body?

Input: Optic tract

Output: Primary visual cortex

Input and output flow of:

Medial geniculate body?

Input: Inferior branchium (inner ear)

Output: Primary auditory cortex

Input and output flow of:

medial thalamus?

Input: substantia nigra, Amygdala, Olfactory cortex

Output: Prefrontal cortex

(Emotional signals, Awareness of emotions)

Difference in the input of VPL and VPM?

VPL = sensory from lower and upper extremities

VPM = sensory from Head and neck

Pain at dorsum of the foot: trace the neural pathway to the CNS?

``` Nociceptor in skin > dorsal horn spinal cord > spinothalamic tract > medulla oblongata > VPL > Somatosensory cortex ```

Descending motor pathway passes through thalamus for processing. True or False?

False | Motor never passes through thalamus, only bypasses to brainstem/ spinal cord/ Diencephalon/ Cerebellum

List the components of the Basal Ganglion circuit?

- Striatum - Globus pallidus (internal and external segments) - Subthalamic nucleus - Substantia nigra (pas compacta + pars reticulata)

Go through the direct pathway in Basal ganglion circuit to increase motor output?

Cortex release Glutamate >> Stimulate striatum to increase more GABA/ Substance P >> Inhibit globus pallidus Internal** + Substantia nigra pars reticulata, less GABA released >> Thalamus less inhibited by GABA, release more Glu. >> Increase stimulation of Supplementary motor area, increase motor output

Go through the indirect pathway in Basal ganglion circuit to decrease motor output?

Cortex releases Glutamate >> Striatum stimulated, Increase GABA/ Enkephalin release to Globus Pallidus External** >> G.P. external more inhibited, released less GABA to Subthalamic nucleus >> Subthalamic nucleus less inhibited, releases more Glutamate to G.P. Internal** >> G.P. Internal releases more GABA to Thalamus >> Thalamus more inhibited, releases less Glutamate to supplementary motor area >> Decrease motor output

What is the role of substantia nigra in the basal ganglion circuit?

Cortex releases glutamate >> Striatum releases GABA to Substantia nigra pars compacta >> Inhibit S.N, less dopamine released back to Striatum >> Fine tune motor control

List the lobes in the cerebral cortex.

Frontal, Parietal, Occipital, Temporal

How to locate frontal and parietal lobes?

Central sulcus Anterior to Parietal lobe (i.e. primary somatosensory cortex) Posterior to frontal lobe (i.e. primary motor cortex)

List the areas of the frontal lobe of cortex?

``` Primary motor cortex Motor association area Broca area Prefrontal cortex Olfactory association cortex ```

List the areas of the Parietal lobe of cortex?

Primary somatosensory cortex | Somatosensory association cortex

List the areas of the temporal lobe of cortex?

Wenicke area Primary auditory cortex Auditory association area

List the areas of the occipital lobe of cortex?

Primary visual cortex | Visual association cortex

Which cortex areas are involved in language?

Broca's area in frontal lobe = Generate and use of language Wenicke's area in temporal lobe = Comprehension of language Connected by Arcuate fasciculus

3 types of fibers in the cortex and their functions?

1) Association fibers: interconnect cortical areas within the same hemisphere 2) Arcuate fibers: interconnect gyri within a lobe 3) Longitudinal fasciculi (e.g. superior longitudinal fasciculus): interconnect frontal lobe with other cerebral lobes

Failure of the Broca's/ Wernicke's area produces what symptoms?

Broca's = speaks vocabulary but not sentence, expressive aphasia Wernicke's = speaks sentence but no comprehension, receptive aphasia

List the layers of the cortex from superior to inferior.

Molecular layer External granular layer External pyramidal layer Internal granular layer Internal pyramidal layer Multiform layer

List the sequence of brain areas involved in the Limbic system, starting with Parahippocampal gyrus.

Parahippocampal gyrus >> Hippocampus >> Fimbria >> Fornix >> Mamillary body >> Anterior Thalamus >> Posterior cingulate gyrus >> Cortex/ back to Parahippocampal gyrus

List the sequence of brain areas involved in the Papez circuit, starting with the Hippocampus.

Hippocampus >> fornix >> mammillary body + mammillothalamic tract >> anterior nucleus of thalamus >> anterior cingulate gyrus / area and prefrontal association area of cortex (layer 5) >> cingulum >> entorhinal cortex of parahippocampus gyrus >> hippocampus

What is the function of the Hippocampal formation?

Learning, recent memory, perception of time, navigation and emotion

Function of the Amygdaloid complex?

Amygdala complex connected to Stria terminalis above thalamus:  Involved in defense and attack, fear, rage  Influences endocrine functions of hypothalamus

Function of Entorhinal cortex?

Inside parahippocampus at medial temporal lobe Interface between hippocampus and neocortex: memory, navigation and the perception of time

List the components of the Hippocampal formation?

Parahippocampus Dentate gyrus Hippocampus Fimbria

If a SPECT scan reveals isolated frontal lobe shrinkage, is it Alzheimer's disease or Frontotemperol lobe dementia?

Not alzheimer's >> temoral lobe degeneration mostly + diffuse involvement

Histological change seen in CJD?

Creutzfeldt-Jakob Disease (CJD) = prion disease Spongiform cortex: formation of vacuoles (empty space), tau Rapidly affects mental acuity, memory

Parts of brain involved in explicit memory?

Includes episodic and semantic memory: Hippocampus, Nucleus Basalis, Medial temporal lobe

Divide Implicit memory into subcategories and their related brain areas.

1) Skill and habit >> Striatum, Motor areas of cortex, cerebellum 2) Emotional association >> Amygdala, Insula 3) Conditioned reflexes >> Cerebellum

Part of brain involved in Working memory?

Prefrontal cortex >> Ventrolateral prefrontal cortex for non-spatial memory e.g. color & shape >> Dorsolateral prefrontal cortex for Spatial memory