Diencephalon

Diencephalon

Thalamus dorsal thalamus Hypothalamus pituitary gland Epithalamus habenular nucleus and commissure pineal gland Subthalamus ventral thalamus subthalamic nucleus (STN) field of Forel

Diencephalon

dorsal surface

Diencephalon

ventral surface

Diencephalon Medial Surface

THALAMUS

Classification of Thalamic Nuclei

I. Lateral Nuclear Group II. Medial Nuclear Group III. Anterior Nuclear Group IV. Posterior Nuclear Group V. Metathalamic Nuclear Group VI. Intralaminar Nuclear Group VII. Thalamic Reticular Nucleus

Classification of Thalamic Nuclei

LATERAL NUCLEAR GROUP

Ventral Nuclear Group Ventral Posterior Nucleus (VP)

ventral posterolateral nucleus ventral posteromedial nucleus (VPM) ventral posteroinferior nucleus (VPI)

LATERAL NUCLEAR GROUP

Ventral Lateral Nucleus (VL) Ventral Anterior Nucleus (VA, L.po.)

LATERAL NUCLEAR GROUP

Ventral Nuclear Group

TTTML, STTCbllGPi

SNr

Prefrontal SMA MI, PM SI

LATERAL NUCLEAR GROUP

Dorsal or Lateral Nuclear Group Lateral Dorsal Nucleus (LD, D.sf.)

Lateral Posterior Nucleus (LP, D.im. & Z.im.) Pulvinar (P, Pu.)

LATERAL NUCLEAR GROUP

SC, PretectalHF

Visual Association

area

Somesthetic Association

Area

cingulate gyrus, precuneus

MEDIAL NUCLEAR GROUP

Dorsomedial Nucleus (MD) - pars magnocellularis - pars parvocellularis Midline Nuclear Group

ANTERIOR NUCLEAR GROUP anteroventral nucleus (AV, A.pr.) anterodorsal nucleus (AD, A.d.) anteromedial nucleus (AM, A.m.)

POSTERIOR NUCLEAR GROUP suprageniculate nucleus (SG, Li.) nucleus limitans (Lim, Li.) posterior nucleus (PO, Li.por.)

MEDIAL & ANTERIOR NUCLEAR GROUP

MB, HFPrefrontal

CortexFrontal

Eye Field Medial Frontal Gyrus

cingulate gyrus Basal

forebrain SNr, SC, RF

METATHALAMIC NUCLEAR GROUP

Medial Geniculate Nucleus (MG) ventral nucleus dorsal nucleus medial nucleus

Lateral Geniculate Nucleus (LG) dorsal nucleus ventral nucleus

INTRALAMINAR NUCLEAR GROUP

Rostral Intralaminar Nuclei central lateral nucleus, central medial nucleus, paracentral nucleus,

Caudal Intralaminar Nuclei (CM-PF nuclear complex)

centre median nucleus, parafascicular nucleus,

THALAMIC RETICULAR NUCLEUS

Cerebral Cortex

Subcortical Structure

Thalamic Reticular Nucleus

Thalamocortical Neuron

Summary of Thalamic Connectivity

I. Sensory Input general sensation special sensation taste, equilibrium, hearing, vision II. Motor Input cerebellum, basal ganglia III. Reticular Formation IV. Limbic System mammillary nucleus hippocampal formation

Sensory Input

(1) General Sensation 1. Medial lemniscus

VPLc ----------- S I, S II 2. Spinothalamic tract

VPLc ----------- S I, S II POm ----------- retroinsular cortex Sm ------------- frontal lobe(?) CL ------------- diffuse cortical areas 3. Trigeminothalamic tract VPM ------------- S I, S II

Sensory Input

(2) Taste sensation VPM pc ------- gustatory area (Brodmann area 43) (3) Sense of equilibrium VPLo ---------- S I (4) Auditory sensation MGv ----------- A I (Brodmann area 41, 42) MGd ----------- A II (5) Vision LGd ---------- V I (Brodmann area 17) Pi, Pl ---------- V I, V II (Brodmann area 17, 18, 19)

Motor Input

(1) Cerebellum VLc, VPLo, - M I (Brodmann area 4), Premotor area (2) Basal ganglia 1. GPi (internal segment of globus pallidus) -------- SMA (supplementary motor area) ------- frontal cortex 2. SNr (pars reticularis of substantia nigra) - fronal cortex --------- medial frontal cortex ---------- frontal eye field (Brodmann area 8)

Reticular Formation & Limbic System

Reticular formation rostral intralaminar nuclei (CL, Cem, PC), Rh ----- diffuse cortical areas thalamic reticular nucleus (R), LGv ----- adjacent thalamic nucleus Limbic System Mammillary Body AV, AD, AM ----- cingulate gyrus Hippocampal Formation AV, AD, AM ----- cingulate gyrus LD ------------------ cingulate gyrus, precuneus Re ------------------- medial cortex, entorhinal cortex

Clinical Syndromes of the Thalamus

Posterolateral thalamic syndromes sensory disorders Thalamic (Dejerine-Roussy) syndrome ----- VP nucleus - pain Medial thalamic syndromes disorders of consciousness thalamic neglect, thalamic amnesia, akinetic mutism

Anterolateral thalamic syndromes motor disorders paresis, ataxia, motor incoordination, dysphagia

Thalamic (Dejerine-Roussy) Syndrome

Joseph Jules Dejerine (1849-1917)

Gustave Roussy (1874-1948)

Modality: Vision Receptor: Photoreceptor Cell of Retina Cranial Nerve: II (Optic nerve)

1st Neuron: Bipolar Cell 2nd Neuron: Ganglion Cell optic nerve optic chiasm optic tract 3rd Neuron: Lateral Geniculate Nucleus optic radiation Termination: Visual Areas (V I, V II) Brodmann area 17 (V I), 18, 19 (V II)

Visual (Optic) Pathway

1. Pigment Epithelium - retinal detachment 2. Neuronal Layer (1) Photosensitive Cell Layer Rod Cell, Cone Cell (2) Bipolar Cell Layer Bipolar Cell Horizontal Cell Amacrine Cell (3) Ganglion Cell Layer Ganglion Cell Optic Nerve (II)

RETINA - Pars Nervosa

Visual Pathway

1. Optic nerve 2. Optic chiasm 3. Optic tract 4. Lateral geniculate body 5. Optic radiation 6. Visual cortex

Visual (Optic) Pathway

Visual Pathway Lateral Geniculate Nucleus (LGd)

Dorsal Nucleus (LGd) Magnocellular Part

1, 2 Parvocellular Part 3, 4, 5, 6 contralateral afferents

1, 4, 6 ipsilateral afferents 2, 3, 5

Ventral Nucleus (LGv) part of thalamic reticular nucleus

dorsolateral

ventromedial

Optic Radiation (Geniculocalcarine Tract)

Meyers loop

Clinical Features of Visual Pathway Lesion

1. optic nerve 2. optic chiasm 3. optic tract 4. 5. optic radiation A. unilateral blindness

B. bitemporal hemianopsia C. left homonymous hemianopsia D. left inferior homony-

mous quadranopsia E. left superior homony-

mous quadranopsia

Signs of Visual Pathway Lesion

Optic nerve - ipsilateral blindness Optic chiasm - bitemporal hemianopsia Optic tract - contralateral homonymous hemianopsia Optic radiation - contralateral homonymous quadranopsia - intact light reflex Visual Cortex - contralateral homonymous quadranopsia - macular sparing

Visual Field Defect

left inferior optic radiation lesion right superior quadranopsia

Hypothalamus Limbic System

Epithalamus Limbic System

Habenular Nucleus

Medial Habenular Nucleus

Lateral Habenular Nucleus

Habenular Commissure

Pineal Gland

Subthalamus Basal Ganglia

Subthalamic nucleus

zona incerta

Field of Forel H ansa lenticularis

H1 thalamic fasciculus H2 lenticular fasciculus