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.

FOREBRAIN (TELENCEPHALON)

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

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

CORTEX

CORTEX

WMWM

SUBCORTICAL NUCLEI

DIVISIONS of the FOREBRAIN

ASSOCIATED FIBER TRACTS: Internal Capsule Corpus Callosum Anterior Commissure Superior Longitudinal Fasciculus

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 10 14 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

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

DIVISIONS OF THE CORTEX

B. Allocortex (Gr. “Other”) – Consisting Of: Archicortex (i.e., Hippocampus) Paleocortex (Parahippocampal Gyrus of Temporal Lobe, Olfactory Cortex, Cingulate Cortex).

CEREBRAL CORTEX

Central Sulcus

LateralSulcus

Pre-central Sulcus

*

Parieto-OccipitalSulcus

PostCentralSulcus

MAJOR SULCI OF LATERAL CORTEX

FRONTAL LOBE

PARIETAL LOBE

OCCIPITALLOBETEMPORAL

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 LATERAL SULCUS NO CLEAR DEMARCATION BETWEEN PARIETAL LOBE AND OCCIPITAL LOBE POSTERIORLY

BORDERS:LATERAL CEREBRAL CORTEX - LOBES

POSTCENTRAL

PRECENTRAL – PRIMARY MOTOR CORTEX.Gyri immediately anterior are supplementary motor areas

INFERIOR FRONTAL Including Broca’s area for motor control of language production (on left)

PRECENTRAL

More posterior gyri are sensory association areas – spatial orientation and directing attention.

INFERIORFRONTAL

SUPERIORTEMPORAL

SUPERIOR TEMPORAL – Posterior part related to interpretation of language – Wernicke’s area

LATERAL OCCIPITAL GYRI – Visual association areas

ORBITAL PARTMost anterior portion

POSTCENTRAL- PRIMARY SENSORY CORTEXBROCA’S

AREA

ORBITAL

AUDITORYAREA

WERNICKE’SAREA

OCCIPITAL

GYRI

BURIED DEEP IN THE LATERAL SULCUS. COVERED BY GYRI FROM THE TEMPORAL, PARIETAL AND FRONTAL LOBES.

CONTAINS GUSTATORY, AUTONOMIC, PAIN, VESTIBULAR AREAS.

INSULAR CORTEX

Cingulate Sulcus

Parieto-Occipital Sulcus

CalcarineSulcus

MAJOR SULCI OF MEDIAL CORTEX

Cingulate (Limbic) Lobe (Gyrus)

CINGULATE GYRUS – Related to limbic system

Parahippocampal

CUNEUS, LINGUAL – Visual association cortex

NOTE: Primary visual cortex is located on walls calcarine sulcus

PARAHIPPOCAMPAL GYRUS - Overlies hippocampus. Is continuous with cingulate gyrus at posterior end of corpus callosum.

Uncus

UNCUS – Anterior End Parahippocampal Gyrus; Overlies Amygdala

Cuneus

Lingual

GYRI – MEDIAL CEREBRAL CORTEX

CORTEX IS MADE UP OF PYRAMIDAL (RED ARROWS) AND NON-PYRAMIDAL CELLS (ORANGE ARROW)

PYRAMIDAL CELL IS PRIMARY OUTPUT NEURON OF THE CORTEXHistology

LAMINATION IN NEOCORTEX AND ALLOCORTEX

THERE ARE 6 LAYERS IN THE NEOCORTEX AND 3 LAYERS IN THE CORTEX RELATED TO THE LIMBIC SYSTEM

IV – Thalamic Input

V – Cortical Output: Corticospinal Corticostriate Corticopontine Corticobulbar

III – Intracortical Connections

VI– Corticothalamic

THICKNESS OF CORTICAL LAYERS

ACROSS THE CORTEX, LAYERS ARE NOT EQUAL IN SIZE. THIS LEADS TO CYTOLOGICAL DIFFERENCES.

KORBINIAN BRODMANN 1868-1918

USED DIFFERENCES IN CYTOLOGICAL ORGANIZATION OF THE CORTEX TO DEFINE AREAS – BRODMANN AREAS

Korbinian Brodmann

BRODMANN’S CYTOARCHITECTURAL MAP

Study thisLOBE

BRODMANNNUMBER 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)

MOTOR CORTEXSOMATOSENSORY CORTEX

SOMATOTOPIC MAP - HOMUNCULUS

MOTOR HOMUNCULUS

Corpus Callosum

Fornix

CORPUS CALLOSUM – INTERHEMISPHERIC Links related areas of frontal, parietal , caudal temporal, and occipital lobes ANTERIOR COMMISSURE – INTERHEMISPHERIC Links related areas of inferior temporal lobe

Anterior Commissure

FIBER TRACTS – CORTICO-CORTICAL

Intrahemishperic tracts link cortical areas on the same side.

SUPERIOR LONGITUDINAL FASCICULUS –INTRAHEMISHERIC Links Broca’s and Wernicke’s language areas

INTRAHEMISPHERIC TRACT

ALL AFFERENTS AND EFFERENTS RELATED TO THE CORTEX TRAVERSE THE INTERNAL CAPSULE .

INTERNAL CAPSULE:

BORDERS:Lateral: Putamen, Globus PallidusMedial: Caudate Nucleus and Thalamus

INTERNAL CAPSULE:

DESCENDING FIBERS INCLUDE: Corticobulbar Axons CorticopontineCorticospinalCorticostriatal

ASCENDING FIBERS INCLUDE: Thalamocortical AxonsTracts Terminating In Thalamus

INTERNAL CAPSULE AND CORONA RADIATA

A

G

P

R

Blood Supply to the Cortex

INTERNAL CAROTID A.

ANTERIORCEREBRAL A.

POSTERIORCEREBRAL A.

FRONTALLOBE

PARIETALLOBE

OCCIPITALLOBE

CINGULATE CORTEX

BASILAR A.

CC

2 VESSELS SUPPLY MEDIAL ASPECT OF CORTEX: ANTERIOR CEREBRAL (BRANCH OF INTERNAL CAROTID ARTERY) POSTERIOR CEREBRAL (BRANCH OF BASILAR ARTERY)

BLOOD SUPPLY TO THE CEREBRAL CORTEX

ANTERIOR CEREBRAL A

MIDDLE CEREBRAL A

POSTERIOR CEREBRAL A

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

BLOOD SUPPLY TO THE CEREBRAL CORTEX

Organization of the Forebrain Quiz

Forebrain

Forebrain - Cross Section

Thank you for completing this module

If you have any questions, please contact me: Bishop.9@osu.edu

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