FOREBRAIN (TELENCEPHALON)
Joel Havemann (from A Life Shaken, 2002)
What seems astonishing is that a mere three-pound object, made of the same atoms that constitute
everything else under the sun, is capable of directing virtually everything that humans have done:
flying to the moon and hitting seventy home runs, writing Hamlet and building the Taj Mahal -- even
unlocking the secrets of the brain itself.
Ivan Petrovich Pavlov (1849-1936; in a lecture given in 1913 and published in Lectures on conditioned reflexes. Twenty-five
year of objective study of the higher nervous activity [behavior] of animals, London: Martin Lawrence, 1928, p. 222.)
If we could look through the skull into the brain of a consciously thinking person, and if the place of optimal excitability were
luminous, then we should see playing over the cerebral surface, a bright spot with fantastic, waving borders constantly
fluctuating in size and form, surrounded by a darkness more or less deep, covering the rest of the hemisphere.
Georgia Bishop PhD
OBJECTIVES
Describe the Anatomical Organization of the Cerebral Cortex
1. Identify the lobes of the cerebral cortex and their borders including the frontal lobe, parietal lobe,
temporal lobe, occipital lobe, cingulate lobe, and insula.
2. Describe the general function of each cortical lobe
3. Identify specific sulci in the cerebral cortex including the central sulcus, pre-central sulcus, post-central
sulcus, lateral sulcus, calcarine sulcus, cingulate sulcus, and parieto-occipital suclus.
4. Identify specific gyri in the cerebral cortex including the precentral gyrus, postcentral gyrus, parahippocampal
gyrus, superior temporal gyrus, inferior frontal gyrus and cingulate gyrus.
5. Recognize what is meant by Brodmann’s Areas.
6. Recognize the motor and sensory homunculi in the primary motor and sensory cortex
7. Differentiate between interhemispheric and intrahemispheric fiber tracts that link different regions of
the cerebral cortex.
8. Differentiate between neocortex, archicortex and paleocortex, give examples of each.
9. Locate and describe the axons contained within the internal capsule
10. List the names of the major arterial branches arising from the internal carotid and vertebral arteries and the
regions of the CNS that each vessel supplies
DIVISIONS of the FOREBRAIN
3 DIVISIONS:
1. CORTICAL – Thin Outer Mantle ~1.5 – 4.5 Mm Thick
2. SUBCORTICAL – Collection Of Nuclei In Deep White Matter Below Cortex. Primarily
These Consist Primarily Of Nuclei Called The Basal Ganglia (More Later).
3. LIMBIC – Hippocampus, Amygdala
ASSOCIATED FIBER TRACTS:
Internal Capsule
Corpus Callosum
Anterior Commissure
Superior Longitudinal Fasciculus
CORTEX
SUBCORTICAL NUCLEI
WM
WM
CORTEX
CEREBRAL CORTEX
The outer mantle, consisting of neurons that are distributed in 3-6 layers, is very thin measuring 1.5-4.5 mm.
There are 10-15 billion neurons, 50 billion glial cells, 100,000 km of axons, and 1014 synapses in the cerebral
cortex.
Highly infolded. If laid out flat it would be ~ 2 square feet. About 1/3 of cortex is visible and 2/3 is located in sulci
and fissures
DIVISIONS OF THE CORTEX
A. Isocortex (Homogeneous) Consisting Of:
Neocortex Which Represents 90 -95% Of The Cortex In Humans.
All Of The Cortex That Is Seen On Outside Of Brain.
Most Recently Evolved Cortex - Plays A critical role in abilities and activities that reach highest level of
development in humans
B. Allocortex (Gr. “Other”) – Consisting Of:
Archicortex (i.e., Hippocampus)
Paleocortex (Parahippocampal Gyrus of Temporal Lobe, Olfactory Cortex, Cingulate Cortex).
MAJOR SULCI OF LATERAL CORTEX
Pre-central
Sulcus
Central
Sulcus
Post
Central
Sulcus
ParietoOccipital
Sulcus
*
Lateral
Sulcus
LATERAL CEREBRAL CORTEX - LOBES
BORDERS:
PARIETAL LOBE
FRONTAL LOBE
FRONTAL LOBE
FRONTAL POLE OF BRAIN
CENTRAL SULCUS
LATERAL SULCUS
PARIETAL LOBE
CENTRAL SULCUS
LINE BETWEEN BASE OF CORTEX AND
PARIETO-OCCIPITAL SULCUS
OCCIPITAL LOBE
LINE BETWEEN BASE OF CORTEX
AND PARIETO-OCCIPITAL SULCUS
TEMPORAL
LOBE
OCCIPITAL
LOBE
TEMPORAL LOBE
LATERAL SULCUS
NO CLEAR DEMARCATION BETWEEN
PARIETAL LOBE AND OCCIPITAL LOBE
POSTERIORLY
GYRI
PRECENTRAL – PRIMARY
MOTOR CORTEX.
Gyri immediately anterior
are supplementary motor
areas
PRECENTRAL
POSTCENTRAL
INFERIOR FRONTAL
Including Broca’s area for
motor control of language
production (on left)
INFERIOR
FRONTAL
ORBITAL PART
Most anterior portion
ORBITAL
WERNICKE’S
AREA
BROCA’S
AREA
POSTCENTRAL- PRIMARY
SENSORY CORTEX
AUDITORY
AREA
SUPERIOR
TEMPORAL
More posterior gyri are
sensory association areas –
spatial orientation and
directing attention.
OCCIPITAL
SUPERIOR TEMPORAL –
Posterior part related to
interpretation of language –
Wernicke’s area
LATERAL OCCIPITAL GYRI
– Visual association areas
INSULAR CORTEX
BURIED DEEP IN THE LATERAL SULCUS. COVERED BY GYRI FROM THE TEMPORAL, PARIETAL AND FRONTAL LOBES.
CONTAINS GUSTATORY, AUTONOMIC, PAIN, VESTIBULAR AREAS.
MAJOR SULCI OF MEDIAL CORTEX
Cingulate
Sulcus
Parieto-Occipital
Sulcus
Calcarine
Sulcus
GYRI – MEDIAL CEREBRAL CORTEX
Cingulate (Limbic)
Lobe (Gyrus)
CINGULATE GYRUS –
Related to limbic
system
Cuneus
PARAHIPPOCAMPAL
GYRUS - Overlies
hippocampus. Is
continuous with
cingulate gyrus at
posterior end of corpus
callosum.
UNCUS – Anterior End
Parahippocampal
Gyrus; Overlies
Amygdala
Uncus
Lingual
CUNEUS, LINGUAL –
Visual association
cortex
Parahippocampal
NOTE: Primary visual
cortex is located on
walls calcarine sulcus
Histology
CORTEX IS MADE UP OF PYRAMIDAL (RED ARROWS) AND NON-PYRAMIDAL CELLS
(ORANGE ARROW)
PYRAMIDAL CELL IS PRIMARY OUTPUT NEURON OF THE CORTEX
LAMINATION IN NEOCORTEX AND ALLOCORTEX
III – Intracortical
Connections
IV – Thalamic Input
V – Cortical Output:
Corticospinal
Corticostriate
Corticopontine
Corticobulbar
VI– Corticothalamic
THERE ARE 6 LAYERS IN THE NEOCORTEX AND 3 LAYERS IN THE CORTEX RELATED TO THE
LIMBIC SYSTEM
THICKNESS OF CORTICAL LAYERS
ACROSS THE CORTEX, LAYERS ARE NOT EQUAL IN SIZE. THIS LEADS TO CYTOLOGICAL
DIFFERENCES.
Korbinian Brodmann
KORBINIAN BRODMANN 1868-1918
USED DIFFERENCES IN CYTOLOGICAL ORGANIZATION OF THE
CORTEX TO DEFINE AREAS – BRODMANN AREAS
BRODMANN’S CYTOARCHITECTURAL MAP
Study this
LOBE
BRODMANN
NUMBER
LOCATION
Frontal
4
Precentral gyrus (Primary Motor area)
Frontal
6
Premotor,Supplementary Motor
Frontal
44,45
Inferior frontal gyrus (Broca’s area for language)
Parietal
3,1,2
Postcentral gyrus (Primary somatosensory area)
Parietal
5,7
Somatosensory association area
Occipital
17
Banks of calcarine sulcus (Primary visual area)
Occipital
18,19
Surrounding 17 (Visual Association areas)
Temporal
41
Primary auditory area
Temporal
42
Auditory association area
Temporal
22
Superior temporal gyrus (Wernicke’s area for language on left)
SOMATOTOPIC MAP - HOMUNCULUS
SOMATOSENSORY CORTEX
MOTOR CORTEX
MOTOR HOMUNCULUS
FIBER TRACTS – CORTICO-CORTICAL
CORPUS CALLOSUM – INTERHEMISPHERIC
Links related areas of frontal, parietal , caudal temporal, and occipital lobes
ANTERIOR COMMISSURE – INTERHEMISPHERIC
Links related areas of inferior temporal lobe
Corpus Callosum
Fornix
Anterior
Commissure
INTRAHEMISPHERIC TRACT
Intrahemishperic tracts link cortical areas on the same side.
SUPERIOR LONGITUDINAL FASCICULUS –INTRAHEMISHERIC
Links Broca’s and Wernicke’s language areas
INTERNAL CAPSULE AND CORONA RADIATA
ALL AFFERENTS AND EFFERENTS RELATED TO THE CORTEX TRAVERSE THE INTERNAL CAPSULE .
INTERNAL CAPSULE:
BORDERS:
Lateral: Putamen, Globus Pallidus
Medial: Caudate Nucleus and Thalamus
A
INTERNAL CAPSULE:
DESCENDING FIBERS
INCLUDE:
Corticobulbar Axons
Corticopontine
Corticospinal
Corticostriatal
ASCENDING FIBERS INCLUDE:
Thalamocortical Axons
Tracts Terminating In Thalamus
G
P
R
Blood Supply to the Cortex
BLOOD SUPPLY TO THE CEREBRAL CORTEX
2 VESSELS SUPPLY MEDIAL ASPECT OF CORTEX:
ANTERIOR CEREBRAL (BRANCH OF INTERNAL CAROTID ARTERY)
POSTERIOR CEREBRAL (BRANCH OF BASILAR ARTERY)
PARIETAL
LOBE
CINGULATE
CORTEX
CC
FRONTAL
LOBE
OCCIPITAL
LOBE
POSTERIOR
CEREBRAL A.
ANTERIOR
CEREBRAL A.
BASILAR A.
INTERNAL
CAROTID A.
BLOOD SUPPLY TO THE CEREBRAL CORTEX
Major Blood Vessel To Lateral Cortex Is Middle Cerebral A. (Branch Of Internal Carotid A.
Also See Terminal Branches Of Anterior and Posterior Cerebral Arteries
ANTERIOR CEREBRAL A
POSTERIOR
CEREBRAL A
MIDDLE
CEREBRAL A
Thank you for completing this module
 If you have any questions, please contact me:
 Bishop.9@osu.edu
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