brain topography
DESCRIPTION
Brain Topography. Cerebrum. Cerebrum. Cerebellum. Cerebrum. The largest division of the forebrain . It is divided into two hemispheres, each of which is divided into four lobes. Corpus callosum. - PowerPoint PPT PresentationTRANSCRIPT
Brain Topography
The largest division of the forebrain. It is divided into two hemispheres, each of which is divided into four lobes.
Cerebrum Cerebrum
Cerebellum
Cerebrum
Right hemisphere Left hemisphere
Corpus callosum
Median Longitudinal fissure
Divided into two halves, the cerebral hemispheres, which are separated by a deep Median longitudinal fissure which lodges a dural fold called falx cerebri.
In the depth of the fissure, the hemispheres are connected by a bundle of fibers called the corpus callosum.
The structure of cerebral hemispheres includes:Superficial layer of grey
matter, the cerebral cortex.Deeper to the cortex, axons
running to and from the cells of the cortex form an extensive mass of white matter (WM).
Burried within the white matter lie a number of nuclear masses (caudate, putamen, globus pallidus) collectively known as the basal ganglia.
The cavity of hemisphere is called the lateral ventricle.
CortexBasal
ganglia
WM
Lateral ventricle
Cerebral Cortex
Cerebral Cortex
The outermost layer of gray matter making up the superficial aspect of the cerebrum.
Cerebral Cortex
Cerebral Features
• Sulci – Small grooves dividing the gyri– Central Sulcus – Divides the Frontal Lobe
from the Parietal Lobe
• Fissures – Deep grooves, generally dividing large regions/lobes of the brain – Longitudinal Fissure – Divides the two
Cerebral Hemispheres– Transverse Fissure – Separates the
Cerebrum from the Cerebellum– Sylvian/Lateral Fissure – Divides the
Temporal Lobe from the Frontal and Parietal Lobes
• Gyri – Elevated ridges “winding” around the brain.
Highly convoluted arrangement. This arrangement maximize the surface area of the cerebral cortex (about 70% is hidden within the depths of sulci).
Gyri (ridge)
Fissure
(deep groove)
Sulci (groove)
Longitudinal Fissure
Transverse Fissure
Sylvian/Lateral Fissure
Central Sulcus
Specific Sulci/Fissures:
Three sulci, consistent in their position (central, lateral & parieto-occipital) are used to divide each hemisphere into lobes. Each hemisphere is divided into FOUR lobes (named after overlying bones).
motor function, motivation, aggression, smell and mood
reception and evaluation of sensory information
smell, hearing, memory and abstract thought
visual processing
Lobes of the Brain (4)
• Frontal• Parietal• Occipital• Temporal
* Note: Occasionally, the Insula is considered the fifth lobe. It is located deep to the Temporal Lobe.
Lobes of the Brain - Frontal
• The Frontal Lobe of the brain is located deep to the Frontal Bone of the skull.
• It plays an integral role in the following functions/actions:
- Memory Formation
- Emotions
- Decision Making/Reasoning
- Personality
- In addition to its major role in motor functions
Frontal lobe• Precentral gyrus.• Superior & inferior
frontal sulci divide the lobe into superior, middle & inferior frontal gyri.
Frontal Lobe
Primary motor cortex: Located in precentral gyrus (Brodmann area 4).
Premotor cortex: Located in the region immediately anterior to the precentral gyrus (Brodmann’s area 6).
Frontal eye field: Located in the middle frontal gyrus immediately in front of motor cortex (Brodmann’s area 8).
Broca’s (motor speech) area: Located in the inferior frontal gyrus of the dominant hemisphere, usually left (Brodmann’s area 44 & 45).
Prefrontal cortex: Extensive region of the frontal lobe anterior to premotor area.
Lateral SurfacePrecentral Gyrus --- primary motor area:
Superior Frontal Gyrus Middle Frontal GyrusInferior Frontal Gyrus
Pars Opercularis Pars Triangularis
Pars Orbitalis Medial SurfaceMedial Frontal Gyrus Paracentral Lobule
Basal SurfaceRectus Gyrus
Orbital GyrusInferior Frontal Gyrus
Gyri of the Frontal Lobe
]Broca’s area (dominant hemisphere)
Gyri of the Cerebral Cortex (Lateral Surface)
Gyri of the Cerebral Cortex (basal surface)
Basal Surface
Rectus Gyrus Orbital Gyrus
Inferior Frontal Gyrus
Gyri of the Cerebral Cortex (Medial Surface)
Medial Surface
Medial Frontal Gyrus Paracentral Lobule
Lobes of the Brain - Parietal Lobe• The Parietal Lobe of the brain is located deep to the
Parietal Bone of the skull.
• It plays a major role in the following functions/actions:
- Senses and integrates sensation(s)
- Spatial awareness and perception(Proprioception - Awareness of body/ body parts in space and in relation to each other)
Parietal Lobe
Parietal lobe: Postcentral gyrus.Intraparietal
sulcus dividing the lobe into superior & inferior parietal lobules.
Primary Somatosensory Cortex/ Postcentral Gyrus
Primary Gustatory Cortex
Somatosensory Association Cortex
Parietal Lobe
• Primary Somatosensory Cortex (Postcentral Gyrus) – Site involved with processing of tactile and proprioceptive information.
• Somatosensory Association Cortex - Assists with the integration and interpretation of sensations relative to body position and orientation in space. May assist with visuo-motor coordination.
• Primary Gustatory Cortex – Primary site involved with the interpretation of the sensation of Taste.
Parietal lobe
Parietal association cortex: located posterior to primary somatosensory cortex.
Primary somatosensory cortex: located in postcentral gyrus (Brodmann’s area 1, 2, 3).
Gyri of the Parietal Lobe• Lateral Surface • Postcentral Gyrus
----• Superior Parietal
Lobule • Inferior Parietal
Lobule ---- Wernicke’s area ??
Supramarginal Gyrus Angular Gyrus
• Medial Surface• Paracentral Lobule• Precuneus
Lobes of the Brain – Occipital Lobe
• The Occipital Lobe of the Brain is located deep to the Occipital Bone of the Skull.
• Its primary function is the processing, integration, interpretation, etc. of VISION and visual stimuli.
Occipital Lobe • Primary Visual Cortex – This is
the primary area of the brain responsible for sight -recognition of size, color, light, motion, dimensions, etc.
• located on the medial surface of the hemisphere, in the gyri surrounding the calcarine sulcus (Brodmann’s area 17).
• Visual Association Area – Interprets information acquired through the primary visual cortex. located around the primary visual cortex.
Primary Visual Cortex
Visual Association Area
Gyri of the Occipital LobeLateral Surface:Lateral Occipital Gyrus Superior Occipital Gyrus Inferior Occipital Gyrus Medial Surface
CuneusLingual Gyrus
Basal SurfaceLingual GyrusOccipitotemporal Gyrus
Lobes of the Brain – Temporal Lobe
• The Temporal Lobes are located on the sides of the brain, deep to the Temporal Bones of the skull.
• They play an integral role in the following functions:
- Hearing- Organization/Comprehension
of language
- Information Retrieval (Memory and Memory Formation)
Temporal lobe: Superior & inferior
temporal sulci giving rise to superior, middle & inferior temporal gyri.
Insula: the gyri in the depth of lateral fissure, covered by parts of frontal, parietal & temporal lobes called the opercula (removed in lower picture.).
Superior, middle & inferior temporal gyri
insula
stsits
Temporal Lobe • Primary Auditory Cortex – Responsible for hearinglocated in the superior surface of the superior temporal gyrus (Brodmann’s area 41, 42)• Primary Olfactory Cortex – Interprets the sense of smell once it reaches the cortex via the olfactory bulbs. (Not visible on the superficial cortex)
• Wernicke’s Area – Language comprehension. Located on the Left Temporal Lobe.
Auditory association cortex: located immediately around the primary auditory cortex (also includes Wernick’s area)
Primary Auditory Cortex
Wernike’s Area
Primary Olfactory Cortex (Deep)Conducted from Olfactory Bulb
• Parahippocampal gyrus:
• located in the inferomedial part of temporal lobe.
• Deep to this gyrus lies the hippocampus and the amygdala, which are parts of limbic system
Temporal Lobe
Language Area Organized around the lateral
fissure. Broca’s area: concerned with
expressive aspects of language. Wernick’s area: responsible for
comprehension of the spoken words.
Nearby regions of temporal lobe and parietal lobe (angular gyrus & supramarginal gyrus of the inferior parietal lobule) are important in naming, reading, writing, and calculation.
• Arcuate Fasciculus - A white matter tract that connects Broca’s Area and Wernicke’s Area through the Temporal, Parietal and Frontal Lobes. Allows for coordinated, comprehensible speech. Damage may result in:- Conduction Aphasia - Where auditory comprehension and speech articulation are preserved, but people find it difficult to repeat heard speech.
Gyri of the Temporal Lobe
Lateral SurfaceSuperior Temporal GyrusMiddle Temporal Gyrus Inferior Temporal Gyrus Basal Surface
Lingual Gyrus Occipitotemporal Gyrus
Medial Occipitotemporal GyrusLateral Occipitotemporal
Supplementary motor area(programming of complex movement) Primary motor cortex
(Voluntary movement)
Centralsulcus
Somatosensory cortex(Somesthetic sensation and
proprioception)
Posterior parietal cortex(integration of somatosensory and
visual input)
Wernicke’s area(speech
understanding)
Parietal lobe
Parietal-temporal-occipitalassociation cortex
(integraton of all sensory input-imp in language)
Occipital lobe
Primary visual cortex
Temporal lobeLimbic association cortex(motivation, emotion, memory)
Primary auditory cortex
Broca’s area(speech formation)
Frontal lobe
Premotor cortex(coordination of complex
movements)
Prefrontal association cortex
(planning for voluntary activity; decision making;personality traits)
Lobes and Structures of the Brain
B. A. (groove)
C. (groove)
D. E.
F.
G.
B. Frontal Lobe
G. Parietal Lobe
F. Occipital Lobe
D. Temporal Lobe
A. Central Sulcus
(groove)
E. Transverse Fissure
C. Sylvian/Lateral Fissure
Hemispheric Dominance The localization of speech
centers & mathematical ability is the criterion for defining the dominant cerebral hemisphere.
In 96% of normal right-handed individuals and 70% of normal left-handed individuals, the left hemisphere contains the language centers. These are left hemisphere dominant.
Cerebral dominance becomes established during the first few years after birth.
Verbal Memory
Shape Memory
Hemispheres communicate via the corpus callosum
White MatterUnderlies the cortex and contains:
Nerve fibers, Neuroglia cells & Blood vessels. The nerve fibers run in different directions and originate,
terminate or sometimes both, within the cortex.
Depending on their origin & termination, the nerve fibers in the cerebral white matter are classified into three types: Association, Commissural & Projection
Association fibers: Unite different parts of the same hemisphere
Commissural fibers: Connect the corresponding regions of the two hemispheresProjection fibers: Consisting of Afferent fibers conveying impulses to the cerebral cortex. Efferent fibers conveying impulses away from the cortex.
Association Fibers Unite different parts
of the same hemisphere.
Are of two kinds: Those connecting
adjacent gyri, short association fibers
Those connecting more distant parts, long association fibers.
Short association fibers
Long association fibers
1. Uncinate fasciculus: connects frontal to temporal lobe
2. Superior longitudinal fasciculus: connects the frontal, occipital, parietal, and temporal lobes
3. Arcuate fasciculus: connect gyri in frontal to temporal lobes
4. Inferior longitudinal fasciculus: connects occipital to temporal pole
13
2
4
5
5 .Cingulum: connects frontal & parietal lobes to the para-hippocampal gyrus and adjacent temporal gyri
Long Association Fibers
Commissural Fibers
Connect the corresponding regions of the two hemispheres.
Include: Corpus callosum. Anterior
commissure. Hippocampal
commissure (commissure of fornix).
Posterior commissure.
Corpus Callosum Connects the corresponding
regions of the two hemispheres except the temporal lobes, that are connected by anterior commissure
It is shorter craniocaudally than is the hemisphere
The callosal fibers linking the frontal poles curve forward forming anterior forceps (forceps minor)
The callosal fibers linking the occipital poles curve backward forming posterior forceps (forceps major)
O
F
P
CC
Anterior forceps
Posterior forceps
Parts of Corpus Callosum
Rostrum
Genu
Body
Splenium
Anterior commissure: connects the inferior and middle temporal gyri & the olfactory regions of the two hemispheres
Hippocampal Commissure: connects the two hippocampi with each other
Posterior Commissure: connects the left and right midbrain. Important in the bilateral pupillary reflex
Projection Fibers Consist of:
Afferent fibers conveying impulses to the cerebral cortex.
Efferent fibers conveying impulses away from the cortex.
Deeper to the cortex, these fibers are arranged radially as the corona radiata.
Then the fibers converge downward, form internal capsule, between thalamus and basal ganglia.
Continue in the crus cerebri of the midbrain, basilar part of pons, & pyramid of medulla oblongata.
crus cerebri
Internal capsule
corona radiata
pyramidal decussation
pyramid
Corticospinal tract
Internal Capsule
• Bundle of projection fibers, passes through the interval between the Thalamus (T) and the basal ganglia: Caudate (C) & Lentiform nucleus (L)
Has 5 parts: 1-Anterior limb: Thalamocortical &
Frontopontine fibers 2-Genu: corticobulbar fibers 3-Posterior limb: Corticospinal,
Corticobulbar & Thalamocortical fibers 4-Retrolenticular part: Geniculocalcarine
fibers 5-Sublenticular part (not shown): geniculo-
temporal fibers
C
T
L
12
3
4