Chapters 11 12 Single

Diencephalon – midsaggital view ‘in-between brain’ „ Major divisions „

… Epithalamus … Thalamus … Subthalamus … Hypothalamus

Epithalamus „

Stria medullaris thalami …

„

Connects septal area (olfactory) with the habenular nuclei

Habenular nuclei …

Connect to each other by habenular commissure … Project to interpeduncular nucleus (midbrain) … Emotions and behavior

Epithalamus „

Pineal Gland … Endocrine … Single

structure [no left/right] … Circadian rhythm … Calcifies at 16yrs … Detection of midline shifts via xrays „

„ „

Subdural/epidural bleeding Hematoma tumor

Diencephalon – coronal view Thalamus „ Subthalamus „ Hypothalamus „ Third ventricle „ Lateral ventricles „ Internal capsule „

Thalamus ‘inner chamber’ „ Divisions „

… Anterior … Medial … Lateral … Intralaminar

reticular … Midline … Posterior

and

Thalamus „

Myelinated fibers … Internal

medullar

lamina „

Interconnects thalamic nuclei

… External

medullary

lamina „

Fibers entering/leaving the thalamus

Anterior thalamic nucleus „

Two nuclei … …

„

Principal anterior nucleus Anterodorsal nucleus

Reciprocal connections …

Mamillary bodies (hypothalamus) „

…

Cingulate gyrus (cerebral cortex) „

„ „

Internal capsule

Input from hippocampal formation via the fornix Limbic system … …

„

Mammillothalamic tract

Emotion/behavior Memory

Damage causes episodic long-term memory loss …

Spares short-term memory

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)

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

Lateral Thalamic Nuclei „

2 subdivisions … Dorsal „

Lateral dorsal …

Functionally part of anterior group (limbic system)

Lateral posterior „ Pulvinar „

Border with lateral posterior is vague … One complex …

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 intractable pain)

Lateral Thalamic Nuclei „

Ventral subdivision … Ventral

anterior … Ventral lateral … Ventral posterior „ „ „

Receive direct input from long ascending tracts Reprocal connections with cortex Retrograde degeneration on cortical lesions

Ventral Anterior „

Input … Globus

pallidus … Substantia nigra … Intralaminar nucleus (thalamus) … Premotor/prefrontal cortex „

Output (reciprocal connections) … Premotor

cortex … Prefrontal cortex „

FEF

… Intralaminar

nucleus

Ventral Anterior „

Roles: … Motor „

Regulate movement …

„

Eye, head, neck

Lateral part …

„

Control of voluntary movement

Medial part …

„

relay station

Body, limb

Lesion … Relieve

Parkinson’s symptoms

Ventral Lateral Nucleus „

Input … Deep

cerebellar nuclei … Globus pallidus … Primary motor cortex „

Output … Primary

motor cortex (reciprocal) … Parietal lobe „

Somatosensory areas

… Premotor/Supplementary

motor areas

Ventral Lateral Nucleus „

Role: … Motor „

relay station

Cerebellum/basal ganglia/cortex

… Lesions

for relief of Parkinson’s symptoms (tremor)

Ventral Posterior Nucleus „

2 divisions … …

„

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

Inputs …

Medial lemniscus „

…

Spinothalamic „

…

VPM

Primary somatosensory cortex „

„

VPL

Trigeminal lemniscus (taste) „

…

VPL

VPM & VPL

Output …

Primary somatosensory cortex (reciprocal) … Parietal operculum (taste)

Intralaminar Nuclei „

Inputs … Reticular

Formation … Cerebellum … Spinothalamic tract „

Pain

… Trigeminal

lemniscus „

Pain

… Globus

pallidus … Cerebral cortex

Intralaminar Nuclei „

Outputs: … Other „

thalamic nuclei

No direct cortical connections

… Striatum

„

Roles: … Cortical

arousal … Motor control … Pain sensation „ „

Poor localization Emotional quality

Posterior Thalamic Nuclei „

Inputs: … … … … …

„

Medial lemniscus Spinothalamic Auditory Visual (?) Note: no cortical feedback

Outputs: …

Parietal/temporal/occipital cortices

„ „

Multimodal Roles: …

Multimodal integration

Metathalamus „

Medial geniculate nucleus (MGN) … …

Auditory relay Inputs: „ „ „

…

Output: „

…

Lateral lemniscus Inferior colliculus Primary auditory cortex

„ „ „ „

Lateral geniculate nucleus (LGN) … …

Visual relay Inputs: „ „

…

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

Optic tract Primary visual cortex

Outputs: „

Primary auditory cortex

Roles: „

„

Primary visual cortex …

„ „

Optic radiations

Pulvinar Extrastriate cortex

Thalamic Functions „

Sensory integration …

„ „

Modality-specific sensory relay nuclei Nonspecific nuclei Multisensory (posterior nuclei)

Cortical lesions-> all sensory modalities lost „

„

„

…

aching/burning Not sharp/pricking

Part of reticular activating system

Affective behavior/Executive function …

„

Lesions relieve tremors Cerebellum/Basal ganglia/motor areas

Consciousness/Awareness …

Pain returns …

Motor Control … …

All senses but olfaction „

…

„

Prefrontal cortex

Memory/Emotions …

Hypothalamus/cingulate gyrus

Thalamic Circuitry „

Projection neurons …

„

Local circuit neurons …

„

Project to cortex 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)

Subthalamus „

3 main structures … Subthalamic „

nuclei

Inputs: Globus pallidus … Cerebral cortex … Thalamus … Reticular formation … Contralateral subthalamic nucleus ƒ supramamillary commisure …

Subthalamus „

3 main structures … Subthalamic „

nuclei

Outputs: Globus pallidus … Substantia nigra …

„

Hemiballismus Damage … Involuntary violent hyperkinesia of contralateral upper & lower extremities …

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

Subthalamus „

3 main structures … Zona „

incerta

Implicated in many functions …

Locomotion, oculomotor, arousal, attention, feeding, sociosexual, somatosensory

Clinical Correlates: Symptoms „ „ „ „ „ „ „ „

Sensory disturbances Thalamic pain Hemiparesis Dyskinesias Disturbances of consciousness Memory disturbances Affective disturbances Disoders of language

Posterolateral Thalamic Infarct Loss of sensation contralateral „ Paresthesia „

… Pins

„

and needles

Thalamic pain

Medial Thalamic Infarct „

Symptoms … Drowsiness

„

Akinetic mutism … Persistent

vegitative

state … Appear awake … Maintain sleep/wake cycle … Do not interact/communicate

Lateral Thalamic Infarct „

Symptoms … Contralateral

hemiparesis … Dysarthria „

Difficulty speaking

Posterior Thalamic Infarct „

Symptoms … Neuropsychological

effects Memory „ Aphasia „

Alien Hand Syndrome Unwilled, uncontrollable movements of an upper limb „ Failure to recognize it as your own except by vision „ Lesions of ventral posterior, ventral lateral and dorsomedial nuclei „