Chapters 11 12 Single

8/14/2019 Chapters 11 12 Single

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Diencephalon midsaggital view

in-between brain Major divisions

Epithalamus

Thalamus

Subthalamus

Hypothalamus


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Epithalamus Stria medullaris

thalami Connects septal

area (olfactory) withthe habenular nuclei

Habenular nuclei Connect to each

other by habenularcommissure

Project tointerpeduncularnucleus (midbrain)

Emotions and

behavior


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Epithalamus Pineal Gland

Endocrine Single structure

[no left/right]

Circadian rhythm Calcifies at 16yrs

Detection of mid-

line shifts via x-rays Subdural/epidural

bleeding

Hematoma tumor


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Diencephalon coronal view

Thalamus Subthalamus

Hypothalamus Third ventricle

Lateral ventricles Internal capsule


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Thalamus

inner chamber Divisions

Anterior

Medial

Lateral

Intralaminar andreticular

Midline

Posterior


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Thalamus

Myelinated fibers Internal medullar

lamina

Interconnectsthalamic nuclei

External medullarylamina

Fibersentering/leaving thethalamus


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Anterior thalamic nucleus Two nuclei

Principal anterior nucleus Anterodorsal nucleus

Reciprocal connections Mamillary bodies (hypothalamus)

Mammillothalamic tract Cingulate gyrus (cerebral cortex)

Internal capsule

Input from hippocampal formation viathe fornix

Limbic system Emotion/behavior Memory

Damage causes episodic long-term

memory loss Spares short-term memory


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Medial Thalamic Nuclei Dorsomedial nucleus

Reciprocal connections Prefrontal cortex

FEF

Via anterior thalamic peduncle Input from

Temporal lobe

Inferior thalamic peduncle

Amygdaloid nucleus

Substantia nigra

Lateral/intralaminar thalamic

nuclei (adjacent)


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Medial Thalamic Nuclei Roles:

Affective behavior Decision making/judgement Memory

Damage:

Loss of physical self-activation Apathy Indifference Poor motivation

Prefrontal leukotomy Lesion prefrontal-dorsomedial

nucleus pathway Relieves severe anxiety/psychiatric

disorders No longer in use due to

pharmaceuticals


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Lateral Thalamic Nuclei 2 subdivisions

Dorsal Lateral dorsal

Functionally part of

anterior group (limbicsystem)

Lateral posterior

Pulvinar Border with lateral

posterior is vague

One complex


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Lateral Thalamic Nuclei Pulvinar

Reciprocal connections

Lateral geniculate nucleus Parietal lobe

Temporal lobe

Occipital lobe

Inputs Pretectal area

Superior colliculus

Tecto-fugal pathway in blindsight

Roles: Visual relay center

Selective attention

Speech

Pain (lesion to treat intractablepain)


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Lateral Thalamic Nuclei

Ventral subdivision Ventral anterior

Ventral lateral

Ventral posterior

Receive direct input fromlong ascending tracts

Reprocal connections withcortex

Retrograde degeneration on

cortical lesions


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Ventral Anterior

Input Globus pallidus

Substantia nigra

Intralaminar nucleus (thalamus) Premotor/prefrontal cortex

Output (reciprocal connections)

Premotor cortex

Prefrontal cortex

FEF

Intralaminar nucleus


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Ventral Anterior

Roles:Motor relay station

Regulate movement

Control of voluntary movement

Medial part

Eye, head, neck

Lateral part Body, limb

Lesion

Relieve Parkinsons symptoms


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Ventral Lateral Nucleus

InputDeep cerebellar nuclei

Globus pallidus

Primary motor cortex

OutputPrimary motor cortex

(reciprocal)

Parietal lobe Somatosensory areas

Premotor/Supplementarymotor areas


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Ventral Lateral Nucleus

Role:

Motor relay station

Cerebellum/basalganglia/cortex

Lesions for relief ofParkinsons symptoms(tremor)


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Ventral Posterior Nucleus 2 divisions

Ventral posterior medial (VPM) Ventral posterior lateral (VPL)

Inputs Medial lemniscus

VPL

Spinothalamic VPL

Trigeminal lemniscus (taste) VPM

Primary somatosensory cortex VPM & VPL

Output

Primary somatosensory cortex(reciprocal) Parietal operculum (taste)


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Intralaminar Nuclei

InputsReticular FormationCerebellum

Spinothalamic tract Pain

Trigeminal

lemniscus Pain

Globus pallidus

Cerebral cortex


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Intralaminar Nuclei

Outputs:

Other thalamic nuclei

No direct corticalconnections

Striatum

Roles:

Cortical arousal Motor control

Pain sensation

Poor localization Emotional quality


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Posterior Thalamic Nuclei Inputs:

Medial lemniscus

Spinothalamic

Auditory

Visual (?) Note: no cortical feedback

Outputs:

Parietal/temporal/occipitalcortices

Multimodal

Roles:

Multimodal integration


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Metathalamus Medial geniculate nucleus

(MGN) Auditory relay Inputs:

Lateral lemniscus

Inferior colliculus Primary auditory cortex

Output: Primary auditory cortex

Roles: Spectral analysis Sound pattern recognition Auditory memory Localization of sound Multimodal integration

Lateral geniculate nucleus

(LGN) Visual relay Inputs:

Optic tract

Primary visual cortex Outputs:

Primary visual cortex Optic radiations

Pulvinar Extrastriate cortex


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Thalamic Functions Sensory integration

All senses but olfaction Modality-specific sensory

relay nuclei Nonspecific nuclei

Multisensory (posteriornuclei)

Cortical lesions-> allsensory modalities lost Pain returns

aching/burning Not sharp/pricking

Motor Control Lesions relieve tremors Cerebellum/Basal

ganglia/motor areas

Consciousness/Awareness Part of reticular activating

system

Affective behavior/Executivefunction Prefrontal cortex

Memory/Emotions Hypothalamus/cingulate gyrus


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Thalamic Circuitry Projection neurons

Project to cortex

Local circuit neurons Inhibit projection cells

Inputs are excitatory Except basal ganglia (inhibitory)

Direct excitatory pathway

Indirect inhibitory pathway

Reticular nucleus Acts like local circuit neurons,

but is a separate thalamic

nucleus (modulatory)


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Subthalamus

3 main structuresSubthalamic nuclei

Inputs:

Globus pallidus Cerebral cortex

Thalamus

Reticular formation Contralateral

subthalamic nucleus

supramamillary

commisure


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Subthalamus

3 main structuresSubthalamic nuclei

Outputs:

Globus pallidus Substantia nigra

Hemiballismus

Damage Involuntary violent

hyperkinesia ofcontralateral upper &

lower extremities


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Subthalamus 3 main structures

Fields of Forel Globus pallidus &

cerebellum fibers

H field of Forel

Prerubral

H1 field of Forel Thalamic fasciculus

H2 field of Forel Lenticular fasciculus


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Subthalamus

3 main structuresZona incerta

Implicated in many

functions Locomotion,

oculomotor, arousal,attention, feeding,

sociosexual,somatosensory


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Clinical Correlates: Symptoms Sensory disturbances

Thalamic pain

Hemiparesis

Dyskinesias Disturbances of consciousness

Memory disturbances

Affective disturbances

Disoders of language


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Posterolateral Thalamic Infarct

Loss of sensationcontralateral

Paresthesia

Pins and needles

Thalamic pain


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Medial Thalamic Infarct Symptoms

Drowsiness

Akinetic mutism

Persistent vegitativestate

Appear awake

Maintain sleep/wakecycle

Do not

interact/communicate


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Lateral Thalamic Infarct

SymptomsContralateral

hemiparesis

Dysarthria Difficulty speaking


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Posterior Thalamic Infarct

SymptomsNeuropsychological

effects

Memory Aphasia


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Alien Hand Syndrome

Unwilled, uncontrollable movements of anupper limb

Failure to recognize it as your own except

by vision

Lesions of ventral posterior, ventral lateral

and dorsomedial nuclei

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