Download Temporal Lobe

Brain Topography
Cerebrum
The largest division of the forebrain. It is divided into
two hemispheres, each of which is divided into four
lobes.
Cerebrum
Cerebrum
Cerebellum
 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.
Corpus callosum
Left hemisphere
Right hemisphere
Median Longitudinal fissure
 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.
Cortex
Basal
ganglia
W
M
Lateral
ventricle
Cerebral Cortex
The outermost layer of gray matter making up
the superficial aspect of the cerebrum.
Cerebral Cortex
Cerebral
Cortex
Cerebral Features
• Gyri – Elevated ridges “winding” around
the brain.
• Sulci – Small grooves dividing the gyri
– Central Sulcus – Divides the Frontal Lobe
from the Parietal Lobe
Highly convoluted arrangement. This arrangement maximize the
surface area of the cerebral cortex (about 70% is hidden within the
depths of sulci).
• 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 (ridge)
Sulci
(groove)
Fissure
(deep groove)
Specific Sulci/Fissures:
Central Sulcus
Longitudinal Fissure
Sylvian/Lateral
Fissure
Transverse Fissure
 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
visual processing
smell, hearing,
memory and
abstract thought
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
Premotor cortex: Located in the region
immediately anterior to the precentral
gyrus (Brodmann’s area 6).
Primary motor cortex: Located in
precentral gyrus (Brodmann area
4).
Prefrontal cortex:
Extensive region of the
frontal lobe anterior to
premotor area.
Broca’s (motor speech)
area: Located in the
inferior frontal gyrus of
the dominant hemisphere,
usually left (Brodmann’s
area 44 & 45).
Frontal eye field: Located in the middle frontal gyrus
immediately in front of motor cortex (Brodmann’s area 8).
Lateral Surface
Precentral Gyrus --- primary motor area:
Superior Frontal Gyrus
Middle Frontal Gyrus
Inferior Frontal Gyrus
Pars Opercularis
] Broca’s area (dominant hemisphere)
Pars Triangularis
Pars Orbitalis
Medial Surface
Medial Frontal Gyrus
Paracentral Lobule
Basal Surface
Rectus Gyrus
Orbital Gyrus
Inferior Frontal Gyrus
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
Somatosensory
Association Cortex
Primary
Gustatory 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
Primary somatosensory cortex:
located in postcentral gyrus
(Brodmann’s area 1, 2, 3).
Parietal association
cortex: located
posterior to primary
somatosensory cortex.
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 Lobe
Lateral Surface:
Lateral Occipital Gyrus
Superior Occipital Gyrus
Inferior Occipital Gyrus
Medial Surface
Cuneus
Lingual Gyrus
Basal Surface
Lingual Gyrus
Occipitotemporal 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
sts
its
insula
Temporal Lobe
• Primary Auditory Cortex – Responsible for hearing
located 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)
Auditory association
cortex: located immediately
around the primary
auditory cortex (also
includes Wernick’s area)
• Wernicke’s Area – Language comprehension. Located on the
Left Temporal Lobe.
Primary
Auditory Cortex
Wernike’s Area
Primary Olfactory
Cortex (Deep)
Conducted from Olfactory Bulb
Temporal Lobe
• 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
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 Surface
Superior Temporal Gyrus
Middle Temporal Gyrus
Inferior Temporal Gyrus
Basal Surface
Lingual Gyrus
Occipitotemporal Gyrus
Medial Occipitotemporal Gyrus
Lateral Occipitotemporal
Supplementary motor area
(programming of complex movement)
Primary motor cortex
(Voluntary movement)
Premotor cortex
Central
sulcus
(coordination of complex
movements)
Prefrontal association
cortex
Somatosensory cortex
(Somesthetic sensation and
proprioception)
Posterior parietal cortex
(integration of somatosensory and
visual input)
Parietal lobe
(planning for voluntary activity;
decision making;
personality traits)
Wernicke’s area
(speech
understanding)
Frontal lobe
Parietal-temporal-occipital
association cortex
Broca’s area
(speech formation)
(integraton of all sensory inputimp in language)
Primary auditory cortex
Occipital lobe
Limbic association cortex
(motivation, emotion, memory)
Temporal lobe
Primary visual cortex
Lobes and Structures of the Brain
A. Central Sulcus
B. Frontal Lobe
C. Sylvian/Lateral Fissure
D. Temporal Lobe
A. (groove)
G.
B.
F.
E. Transverse Fissure
F. Occipital Lobe
G. Parietal Lobe
C. (groove)
D.
E.
(groove)
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 Matter
Underlies 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
hemispheres
Projection 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
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
5
2
3
1
4
5. Cingulum: connects frontal &
parietal lobes to the parahippocampal gyrus and
adjacent temporal gyri
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)
Anterior
forceps
F
C
C
P
O
Posterior
forceps
Parts of Corpus Callosum
Body
Splenium
Genu
Rostrum
 Anterior
commissure:

connects the
inferior and
middle temporal
gyri & the
olfactory regions
of the two
hemispheres
Posterior
Commissure:
connects the left
and right midbrain.
Important in the
bilateral pupillary
reflex

Hippocampal
Commissure:
connects the two
hippocampi with
each other
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.
corona
radiata
Internal
capsule
crus
cerebri
pyramid
pyramidal
decussation
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): geniculotemporal fibers
C
1
2
T
L
3
4