The Telencephalon

SHANDONG UNIVERSITY

Liu Zhiyu

General Appearance of Cerebrum

The telencephalon consists of right and left cerebral hemisphere, partially separated by cerebral longitudinal fissure

In the depths of the fissure, the corpus callosum connects the hemispheres across the midline

The cerebral transverse fissure intervenes between the hemispheres and the cerebellum

Each hemisphere has three surfaces: superolateral, medial and inferior

Main SulciThree principal sulci Central sulcus Lateral sulcus Parietooccipital sulcus

Central sulcus

Lateral sulcus

Parietooccipital sulcus

Lobes of Cerebral Hemisphere

Five lobes Frontal lobe Parietal lobe Temporal lobe Occipital lobe Insular lobe

Frontal lobe Parietal lobe

Occipital lobe

Temporal lobe

Insular lobe

Sulci and gyri of frontal lobe

Precentral sulcus Precentral gyrus Superior frontal sulcus Inferior frontal sulcus Superior frontal gyrus Middle frontal gyrus Inferior frontal gyrus

Sulci and gyri of frontal lobe

Precentral sulcus

Precentral gyrus

Superior frontal sulcus

Inferior frontal sulcus

Superior, middleand inferioe frontal gyri

Sulci and Gyri of Parietal Lobe

Postcentral sulcus Postcentral gyrus Intraparietal sulcus Superior parietal lobule Inferior parietal lobule Supramarginal gyrus Angular gyrus

Sulci and Gyri of Parietal Lobe

Postcentral sulcus

Postcentral gyrus

Superior parietal lobule

Supramarginal gyrus

Angular gyrus

Intraparietal sulcus

Sulci and Gyri of Temporal Lobe

Superior temporal sulcus Inferior temporal sulcus Superior temporal gyrus Middle temporal gyrus Inferior temporal gyrus Transverse temporal gyri

Sulci and Gyri of Temporal Lobe

Superior temporal sulcus

Inferior temporal sulcus Superior temporal gyrus

Middle temporal gyrus

Inferior temporal gyrus

Transverse temporal gyri

Sulci and Gyri of Temporal Lobe

Sulci and gyri of Superolateral surface

Precentral sulcus

Precentral gyrus

Superior frontal sulcus

Inferior frontal sulcus

Superior,middleand inferior 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

Intraparietal sulcus

Sulci and Gyri of Medial Surface

Corpus callosum Callosal sulcus Cingulate gyrus Cingulate sulcus Marginal ramus Paracentral lobule Calcarine sulcus Cuneus Lingual 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

Sulci and Gyri of Inferior Surface

Olfactory bulb Olfactory tract Olfactory trigone Anterior perforated substance Collateral sulcus Occipitotemporal sulcus Medial occipitotemporal gyrus Lateral occipitotemporal gyrus Hippocampal sulcus Parahippocampal gyrus Uncus Hippocampus Dentate gyrus

Sulci and Gyri of Inferior Surface

Olfactory bulb

Olfactory tract

Olfactory trigone

Ant. Perforated substance

Collateral sulcus

Occipitotemporal sulcus

Medial occipitotemporal gyrus

Parahippocampalgyrus

Uncus

Lateral occipitotemporal gyrus

Hippocampus

Dentate gyrus

Hippocampal formation

Sulci and Gyri of Inferior Surface

Histology of Cerebral Cortex Archicortex (hippocampal formation) Paleocortex (rhinencephalon) Neocortex (most of cerebral cortex)

3 cell layers

6 cell layers

Functional Location of Cerebral Cortex

First Somatic Motor Area

Position: Located in precentral gyrus an

d anterior portion of paracentral lobule

First Somatic Motor Area

Characters Representation is inverted, but he

ad and face are upright A body part is represented by a c

ortical area proportional to its use rather than its size

Receiving fibers from postcentral gyrus, ventral anterior, ventral lateral and ventral posterior nuclei

Sending out fibers to form pyramidal tract, controlling voluntary movements

First Somatic Motor Area

First Somatic Motor Area

First Somatic Sensory Area

Position: Lies in postcentral gyrus and p

osterior portion of paracentral lobule

First Somatic Sensory Area

Characters Sensory representation, like m

otor area, is crossed and inverted

Receiving fibers from ventral posterior nucleus

Interpret sensation from opposite side of body

First Somatic Sensory Area

Visual Area

Lie on either side of calcarine sulcus in medial surface of occipital lobe

Visual cortex of one hemisphere receives impression from temporal part of retina of same side and nasal part of opposite side

Lesions of visual cortex produce contralateral homonymous visual field defections

Auditory Area

Located in transverse temporal gyri

Receive auditory information from both ears

Vestibular area: located in front of superior temporal gyrus

Olfactory area: located near the uncus

Taste area: located at frontal operculum

Language Area

Motor speech area Located in posterior portion of inferior fr

ontal gyrus Damage: motor aphasia

Writing area Located in posterior portion of middle fr

ontal gyrus Damage: agraphia

Auditory speech area Located in posterior portion of superior t

emporal gyrus Lesion: sensory aphasia

Visual speech area Located in angular gyrus Lesion: alexia

It is dominant in left hemisphere in right-handed person

Position: located in cerebral hemispheres

Four parts Central part: lies in parietal lobe Anterior horn: extends into

frontal lobe Posterior horn: extend into

occipital lobe Inferior horn: extend into

temporal lobe

Lateral Ventricle

Lateral Ventricle

Transverse MRI scan, at the level of the anterior horn of the lateral ventricle.

Lateral Ventricle

Communication

lateral ventricle → interventricular foramen → third ventricle

Basal Nuclei

Corpus striatum Lentiform nucleus Caudate nucleus

Claustrum

Amygdaloid body

PutamenNeostriatum

－ paleostriatumGlobus pallidus

Basal Nuclei

Caudate nucleus

Putamen

Globus pallidus

Claustrum

White Matter

Association fibers Run between gyri within the same he

misphere Cerebral arcuate fibers Superior longitudinal fasciculi Inferior longitudinal fasciculi Uncinate fasciculus Cingulum

White Matter

Commissural fibers Corpus callosum

Rostrum Genu Trunk Splenium

Anterior commissure Fornix and commissure of fornix

White Matter

Projection fibers connect cortex with lower part of brain and spinal cord and they include both ascending and descending fibers

★Internal capsule Position: a thick lamina of white

matter lying between caudate nucleus, thalamus and lentiform nucleus

Internal Capsule

Lentiform nucleus

Caudate nucleus

Dorsal thalamus

Internal CapsuleThree parts Anterior limb of internal capsule

Lies between caudate nucleus and lentiform nucleus

Containing frontopontine tract and anterior thalamic radiation

Genu of internal capsule Is angle at which anterior and posterior limbs

meet Containing corticonuclear tract

Posterior limb of internal capsule Lies between thalamus and lentiform nucleus Contain corticospinal tract, corticorubral tract,

central thalamic radiation, parieto-occipito-temporo-pontine tract, acoustic radiation and optic 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

Limbic System

Composition Limbic lobe: includes septal area,

cingulated gyrus, parahippocampal gyrus, hippocampus, dentate gyrus, temporal pole, anterior part of insular lobe and so on

Associated subcortical nuclei: amygdaloid body, septal nuclei, hypothalamus, epithalamus, anterior nucleus group of thalamus, tegmentum of midbrain

Function: concerned with visceral activities, olfaction, emotion and memory, so this system is called ‘visceral brain’