The Telencephalon

Xiaoming Zhang

The Telencephalon External features:

2 Cerebral hemispheres

(separated by longitudinal cerebral fissure) Transverse cerebral fissure intervenes between

the hemispheres and cerebellum. 3 poles, 3 surfaces

3 borders

The Telencephalon External features:

3 Main fissures on surface of each hemisphere: The Lateral sulcus The Central sulcus The Parietooccipital sulcus

Sulci and gyri of Superolateral surface

Postcentral sulcus Postcentral gyrus

Superior parietal lobule

Supramarginal gyrus

Intraparietal sulcus

Parietooccipital sulcus

5 Lobes: (divided by 3 sulci) The Frontal lobe The Parietal lobe The Occipital lobe The Temporal lobe The Insular lobe (insula)

Main gyri and sulci Dorsolateral surface: in frontal lobe: — precentral sulcus, superior and inferior frontal sulcus precentral gyrus

superior frontal gyrus

middle frontal gyrus

inferior frontal gyrus

in parietal lobe:

— postcentral sulcus supermarginal gyrus

— intraparietal sulcus angular gyrus

— postcentral gyrus — superior and inferior parietal lobule

in temporal lobe:

superior temporal sulcus

inferior temporal sulcus

superior

middle

inferior temporal gyrus

transverse temporal gyrus

Right superior figure:Lateral view of cerebral hemisphere

Transverse temporal gyri

Sulci and gyri of Superolateral surface

Precentral sulcus Precentral gyrus

Superior frontal sulcus

Inferior frontal sulcus

Superior,middleand inferioe frontal gyri

Postcentral sulcus Postcentral gyrus

Superior parietal lobule

Supramarginal gyrus

Angular gyrus

Superior temporal sulcus

Inferior temporal sulcus Superior temporal gyrus

Middle temporal gyrus

Inferior temporal gyrus

Sulci and gyri of medial surface

Corpus callosum Callosal sulcus

cingulate gyrus

Cingulate sulcus

Marginal ramus

Paracentral lobule

Calcarine sulcus

Cuneus

Parietooccipital sulcus

Lingual gyrus

Inferior surfaceOlfactory bulb

Olfactory tract

Olfactory trigone

Anterior perforated substance

Collateral sulcus

Occipitotemporal sulcus

Medial and lateraloccipitotemporal gyri

Parahippocampal gyrus

Uncus

Hippocampus

Dentate gyrus

Hippocampal formation

Limbic lobe and limbic system: Limbic lobe: composed of cingulate gyrus,

parahippocampal gyrus and uncus.

Limbic system: comprises of limbic lobe and relative cortex

and other structures of brain (hippocampal

formation, part of amygdaloid nucleus,

hypothalamus and anterior nucleus of

thalamus)

Internal structures: Gray matter

White matter

Lateral ventricle

Gray matter: Cortex: Functional localizations of cerebral cortex

— somatic motor area: in precentral gyrus and anterior part

of paracentral lobule; mainly control skeleton muscles on

the opposite side of body.

— somatic sensory area: in the postcentral gyrus and

posterior part of paracentral lobule; receive the sensory

signals from skin, proprioceptors and taste receptors on

the opposite side of body.

First somatic motor areaCharacters • Representation is inverted,

but head and face are upright

• A body part is represented by a cortical area proportional to its use rather than its size

• Receiving fibers from postcentral gyrus, VA, VL and VPL, sending out fibers to form pyramidal tract, controlling voluntary movements

First somatic sensory area

Characters • Sensory representation,

like motor area, is crossed and inverted

• Receiving and interpret sensation from opposite side of body

— visual area (striate area): surrounds the calcarine sulcus ;

receive the data from the temporal half of ipsilateral

retina and nasal half of the contralateral retina.

— auditory area (acoustic area): in the transverse temporal

gyri; efferent fibers of medial geniculate nucleus of

bilateral side end in this area.

— visceral moter area: in the limbic lobe.

— The language areas:

1. Writing area—posterior part of middle frontal gyrus.

2. Motor speech area— posterior part of inferior frontal gyrus.

3. Auditory language area posterior part superior temporal gyrus

4. Visual language area -angular gyrus

basal ganglion : Corpus striatum: Caudate nucleus: “C” – shaped head, body and tail of caudate nucleus

Lentiform nucleus: Claustrum: between the lentiform nucleus and insula. Amygdaloid body: holds the amygdaloid nucleus and lies at the end

of tail of caudate nucleus.

White matter: 3 kinds of fibers Association fibers:

— connect cortical areas in same hemisphere.

— Superior longitudinal fasciculus

— Inferior longitudinal fasciculus

— Cingulum

—Uncinate fasciculus

— Arcuate fibers

Commissural fibers: — Corpus callosum

* at the bottom of longitudinal cerebral fissure

* 4 parts : rostrum, genu, trunk and splenium

— anterior commissure

— commissure of fornix:

Projection fibers:

— connect the cortex and subcortical structures

— internal capsule:

* a plate of white matter

* position:

medially to the lentiform nucleus;

laterally to the caudate nucleus and

thalamus.

* “X” – shaped in the horizontal section

* 3 parts: anterior limb; posterior limb and genu.

* projection fibers passing through each part of the

internal capsule: anterior limb—frontopontine tract;

anterior thalamic radiation

genu—corticonuclear tract

posterior limb—corticospinal tract

thalamocortical tract

parieto-occipito-temporo-pontine tract

optic radiation

auditory radiation

Anterior thalamic radiation

Frontopontine tract

Lentiform nucleus

Corticorubral tract

Parieto-occipito-temporo-pontine tract

Acoustic radiation

Optic radiation

Head of caudate nucleus

Corticonuclear tract

Corticospinal tract

Dorsal thalamus

Central thalamic radiation

Medial geniculate body

Lateral geniculate body

Lateral ventricles: “C”- shaped cavity in each cerebral hemisphere. filled with cerebrospinal fluid 4 parts:

— anterior horn (in frontal lobe) — central part (in parietal lobe ) — posterior horn (in occipital lobe) — inferior horn (in temporal lobe) communicated with the third ventricle through the interventricular foramen.

The Coronary section of the brain

Superior view of lateral ventricle

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