Telencephalon Flashcards
Number of Brodman areas
47
6 layers of cerebral cortex
Molecular
External granular
External pyramidal
Internal granular
Internal pyramidal
Multiform
Agranular cortex
Frontal lobe
Dominated by pyramidal rather than granular layers
Granular cortex
Parietal sensory cortex
Functions of non dominant hemisphere
Visual and spatial perception
Visual (non-language dependent) memory
Functions of dominant hemisphere
Language
Language dependent hemisphere
Wada test
Can be used to demonstrate hemispheric dominance.
Injection of sodium amytal into the ICA.
On the dominant side this will cause an arrest of speech for up to 30 seconds.
May be useful prior to temporal lobectomy when there is doubt over hemispheric dominance
Key gyri on the lateral surface of the frontal lobe
Superior frontal gyrus
Middle frontal gyrus
Inferior frontal gyrus (pars triangularis, pars orbitalis, pars opercularis)
Precentral gyrus
Key sulci on lateral surface of frontal lobe
Superior frontal sulcus
Inferior frontal sulcus
Pre-central sulcus
Key gyri on superior view of frontal cortex
Superior frontal gyrus
Middle frontal gyrus
Inferior frontal gyrus
Precentral gyrus
Key sulci on superior view of frontal lobe
Superior frontal sulcus
Inferior frontal sulcus
Precentral sulcus
Key gyri on medial view of frontal lobe
Superior frontal gyrus
Paracentral lobule
Cingulate gyrus
Key sulci on medial surface of frontal lobe
Cingulate sulcus
Key gyri on orbital view of frontal lobe
Gyrus rectus
Medial orbital gyrus
Anterior orbital gyrus
Posterior orbital gyrus
Lateral orbital gyrus
Key sulci on orbital surface of frontal lobe
Olfactory sulcus
Orbital sulcus
Function of precentral gyrus
Motor cortex.
Contralateral movement of face, arm, leg, trunk
Lesion to this area would result in?
This is the precentral gyrus
Monoplegia or hemiplegia depending on extent of damage
Function of Broca’s area (dominant hemisphere)
Expressive centre for speech
Lesions to this area would result in?
Dominant hemisphere:
Broca’s dysphasia (motor or expressive)
Function of SMA
Motor planning
Consequences of lesions affecting this area
SMA
Paralysis of head and eye movements to the opposite side.
Head turns and looks towards the diseased hemisphere and eyes look in the same direction
Hypokinetic mutism
What makes up the prefrontal areas?
Vast parts of the frontal lobes anterior to the motor cortex as well as orbital part of frontal lobes
Causes of prefrontal damage?
Often bilateral e.g. infarction, following haemorrhage from ACommA, neoplasm, trauma or frontal dementia resulting in a change of personality with antisocial behaviour/loss of inhibitions
What are the three prefrontal syndromes?
Orbitofrontal syndrome
Frontal convexity syndrome
Medial frontal syndrome
Feeatures of orbitofrontal syndrome
Disinhibition
Poor judgement
Emotional lability
Features of frontal convexity syndrome
Apathy
Poor abstract thought
Features of medial frontal syndrome
Akinetic
Incontinent
Sparse verbal output
Additional associations of prefrontal lesions
Primitive reflexes e.g. grasp, pout
Disturbance of gait
Resistance to passive movement of limbs- paratonia
Function of paracentral lobule
Cortical inhibition of bladder and bowel voiding
The consequence of a lesion to this area
Loss of cortical inhibition of
Incontinence of urine and faeces
Particularly likely with hydrocephalus and is an important symptom in NPH
If involving motor/sensory leg may also have monoparesis and sensory disturbance in the contralateral lower limb.
Key structures of parietal lobe
Post central gyrus
Superior parietal lobule
Inferior parietal lobule (angular gyrus and supramarginal gyrus)
Key sulci of parietal lobe
Post-central sulcus
Intraparietal suclus
Parieto-occpital sulcus
Function of post-central gyrus
Sensory cortex receives afferent pathways for appreciation of posture touch and passive movement
Function of supramarginal and angular gyri (dominant hemisphere)?
Constitue Wernicke’s language area
This is the receptive area where auditory and visual aspects of comprehension are integrated
Function of non-dominant parietal lobe
Important in concept of body image and awareness of external environment
The ability to construct shapes etc. results from such visual or proprioceptive skills
Optic radiation and parietal lobe
Fibres of lower visual field pass through the parietal lobe
Function of dominant parietal lobe
Implicated in the skills of handling numbers/caclulation
Consequence of lesions to postcentral gyrus
Will result in cortical disturbance of sensation:
Postural
Passive movement
Accurate localisation of light touch
Two-point discrimination
Astereogenesis
Perceptual rivalry (sensory inattention)
Astereognosis
Difficulty appreciating tactile size, shape, texture and weight of objects
Consequence of lesions to supramarginal and angular gyri
Wernicke’s dysphasia
Pathology in which lobes is commonly associated with seizures?
Frontal and temporal
Name structures on the left side of the image
What are the five segments of the internal capsule?
Anterior limb
Genu
Posterior limb
Sublenticular segment
Retrolenticular segment
Components of the anterior limb of the internal capsule
Frontopontine
Thalamocortical
Corticothalamic
Caudatoputamenal
Components of the genu of the internal capsule
Corticobulbar fibres
Corticoreticulobulbar fibres
Components of the posterior limb of the internal capsule
Corticospinal
Corticorubral
Corticothalamic
Thalamocortical
Components of the sublenticular segment of the internal capsule
Auditory radiations
Optic radiations
Corticopontine fibres
Components of the retrolenticular portion of the internal capsule
Optic radiations
Corticotectal fibres
Corticonigral fibres
Corticotegmental fibres
Consequence of dominant hemispheric parietal lesion?
Confusion of right and left limbs,
Difficulty in distinguishing fingers on hand (finger agnosia)
Disturbance of calculation (acalculia)
Disturbance of writing (agraphia)
Constitutes Gerstmann’s syndrome
Gerstmann’s syndrome
Finger agnosia
Agraphia
Acalculia
Left-right disorientation
Gerstmann’s syndrome, which part of the brain
Dominant parietal lobe
Consequence of damage to parietal optic radiation?
Inferior homonymous quadrantopia
Key gyri on the lateral view of temporal lobe?
Superior
Middle
Inferior temporal gyrus
Key gyri on inferior view of temporal lobe?
Inferior temporal gyrus
Fusiform (temporo-occipital gyrus)
Parahippocampal gyrus
Lingual
Uncus
The function of temporal lobe
Auditory cortex:
Dominant hemisphere- hearing of language
Non-dominant hemisphere- hearing of sounds/music
Middle and inferior temporal gyri are involved in learning and memory
Limbic lobe: inferior and medial portions of the temporal lobe including the hippocampus and parahippocampal gyrus
Visual pathways pass deep in the temporal lobe around the posterior horn of the lateral ventricle
Location of the auditory cortex
Lies on the upper surface of the superior temporal gyrus, buried in the lateral sulcus (Heschl’s gyrus)
Brodmann 41, 42
Where do the olfactory nerve fibres terminate?
Uncus
Impairment of temporal lobe function:
Auditory cortex
Cortical deafness- rare as requires bilateral lesions but the patient may develop complete deafness and be unaware
Lesions which involve the surrounding association areas may result in difficulty in hearing spoken words or appreciating rhythm or music (Amusia)
Auditory hallucinations may occur in temporal lobe disease
Impairment of temporal lobe function
Middle and inferior temporal gyrus
Disturbance of memory and learning
Complex partial seizures
Impairment of temporal lobe function:
Limbic lobe
Complex partial seizures
Aggressive or antisocial behaviours
Inability to establish new memories
Damage to temporal part of optic radiation
Upper homonymous quadranatopia
Dominant hemisphere temporal lobe lesion
Speech disturbance
Wernicke’s dysphasia
Location of the visual cortex?
Lies along the banks of the calcarine sulcus, this area is referred to as the striate cortex
Above and below this lies the parastriate cortex
Brodman area 17
Striate cortex=
Parastriate cortex function
Primary visual cortex
When stimulated relays information to the parastriate cortex which is the association visual cortex.
Consequence of cortical lesion affecting occipital lobe
Homonymous hemianopia with or without the involvement of the macula depending on the posterior extent of the lesion.
When only the occipital pole is affected, a central hemianopia field defect involving the macula occurs with a normal peripheral field of vision.
Cortical blindness
Extensive bilateral cortical lesions of the straite cortex will result in cortical blindness.
In this, the pupillary light reflex is normal despite the conscious perception of the presence of illumination
Anton’s syndrome
Cortical lesion affecting both striate and parastriate regions affects the interpretation of vision.
The patient is unaware of his visual loss and denies its presence. This denial in the presence of obvious blindness is Anton’s syndrome
Causes of cortical blindness
May occur in vascular disease (PCA infarct) but also follows hypoxia and hypertensive encephalopathy or after surviving tentorial herniation
Balint’s syndrome
Triad:
Simultagnosia- can see trees but not forest can test with Ishihara colour plates- will see colour but not the number
Optic ataxia- mislocalisation in space, hold a pen out they will miss but they can touch their own finger
Oculomotor apraxia- difficulty with visual pursuit, difficulty initiating
The inability to direct voluntary gaze associated with visual agnosia (loss of visual recognition) due to bilateral parieto-occipital lesions.
https://www.youtube.com/watch?v=A8BD5liH7ug
Posterior ramus of lateral sulcus
Post-central sulcus
Ascending ramus of lateral cerebral sulcus
Pars triangularis
Parieto-occipital sulcus
Cause of prosopagnosia
Patient unable to identify familiar face
Usually causd by bilateral lesions at occipito-temporal junction
Name structures 1-10
- Longitudinal fissure of cerebrum.
- Superior margin of cerebrum.
- Frontal pole.
- Superior frontal sulcus.
- Inferior frontal sulcus.
- Precentral sulcus.
- Central sulcus.
- Postcentral sulcus.
- Intraparietal sulcus.
- Parieto-occipital sulcus.
Name structures 11-20
- Transverse occipital sulcus.
- Occipital pole.
- Superior parietal lobule.
- Inferior parietal lobule.
- Postcentral gyrus.
- Paracentral lobule.
- Precentral gyrus.
- Inferior frontal gyrus.
- Middle frontal gyrus.
- Superior frontal gyrus
Name structures 1-10
- Central sulcus.
- Precentral gyrus.
- Precentral sulcus.
- Superior frontal gyrus.
- Superior frontal sulcus.
- Middle frontal gyrus.
- Middle frontal sulcus.
- Frontal pole.
- Orbital gyri.
- Olfactory bulb.
Name structures 11-20
- Olfactory tract.
12–14. Lateral sulcus.
- Anterior ramus.
- Ascending ramus.
- Posterior ramus.
- Frontal operculum.
- Frontoparietal operculum.
- Superior temporal gyrus.
- Middle temporal gyrus.
- Superior temporal sulcus.
- Inferior temporal sulcus.
Name structures 21-30
- Inferior temporal gyrus.
- Preoccipital notch.
- Occipital pole
- Transverse occipital sulcus.
- Inferior parietal lobule.
- Intraparietal sulcus.
- Superior parietal lobule.
- Postcentral sulcus.
- Postcentral gyrus.
- Supramarginal gyrus.
Name structures 31-36
- Angular gyrus.
- Pons.
- Pyramid (medulla oblongata).
- Olive.
- Flocculus.
- Cerebellar hemisphere.
Name structures 1-10
- Longitudinal fissure of cerebrum,
- Cingulate sulcus.
- Cingulate gyrus.
- Sulcus of corpus callosum.
- Corpus callosum.
- Lateral sulcus.
- Claustrum.
8–9. Corpus striatum.
- Caudate nucleus.
- Putamen.
9–10. Lentiform nucleus.
- Globus pallidus.
Name structures 11-19
- Thalamus.
- Subthalamic nucleus.
- Mamillary body.
- Amygdala.
- Optic tract.
- Third ventricle and choroid plexus.
- Body of fornix.
- Lateral ventricle and choroid plexus.
- Cortex of insula.
Name structures 1-10
- Frontal pole of frontal lobe.
- Medial frontal gyrus.
- Cingulate sulcus.
- Sulcus of corpus callosum.
- Cingulate gyrus.
- Paracentral lobule.
- Precuneus.
- Subparietal sulcus.
- Parieto-occipital sulcus.
- Cuneus.
Name structures 11-20
- Calcarine fissure.
- Occipital pole of occipital lobe.
13–16. Corpus callosum (cut surface).
- Rostrum.
- Genu.
- Body.
- Splenium.
- Lamina terminalis (cut surface).
- Anterior commissure (cut surface).
- Septum pellucidum.
- Fornix.
Name structures 21-30
- Tela choroidea of third ventricle.
- Choroid plexus of third ventricle (cut edge).
- Transverse cerebral fissure.
- Thalamus.
- Interthalamic adhesion (cut surface).
- Interventricular foramen of Monro.
- Hypothalamus.
- Suprapineal recess and pineal body (cut surface).
- Vermis of cerebellum (cut surface).
- Cerebellar hemisphere.
Name structures 31-40
- Choroid plexus of fourth ventricle.
- Medulla oblongata (cut surface).
- Fourth ventricle.
- Pons (cut surface).
- Tectal lamina (cut surface) and mesencephalic aqueduct of Sylvius.
- Mamillary body.
- Oculomotor nerve.
- Infundibular recess.
- Temporal lobe lateral occipitotemporal gyrus (fusiform gyrus)
- Rhinal fissure.
Name structures 41-44
- Hypophysis (cut surface) with adenohypophysis (anterior lobe) and neurohypophysis (posterior lobe) of the pituitary gland.
- Optic chiasm (cut surface).
- Optic nerve.
- Olfactory bulb and tract.
Name structures on the right side of the image
Age of cells in more superficial layers of cerebral cortex
Younger, they pass superficially and form connections with the cells they pass.
Neuronal cell morphology
Stellate, fusiform, pyramidal
Allocortex
Three layers, located in the olfactory cortex, hippocampus and dentate gyrus
External pyramidal layer projections
Commissural and ipsilateral cortico-cortical association fibres
Internal pyramidal layer projections
Main efferents to the brainstem and spinal cord
Broadman area
123
Location
Post-central gyrus
Broadman area
123
Functional area
1o somatosensory cortex
Broadman area
123
Function
Touch
Brodman area
4
Location
Precentral gyrus
Brodman area
4
Functional area
1o motor cortex
Brodman area
4
Function
Voluntary motor control
Brodman area
5
Location
Superior parietal lobule
Brodman area
5
Functional area
3o somatosensory cortex
Posterior parietal association
Brodman area
5
Function
Stereognosis
Brodman area
6
Location
Precentral gyrus and rostral adjacent cortex- SMA and premotor area.
Brodman area
6
Functional area
Supplementatry motor control
Supplemental eye field
Premotor adjacent cortex
Supplementary eye field adjacent cortex
Brodman area
6
Function
Limb and eye movement planning
Brodman area
7
Location
Superior parietal lobule
Brodman area
7
Functional area
Posterior parietal association
Brodman area
7
Function
Visuomotor control
Perception
Brodman area
8
Location
Superior, middle, frontal gyri
Medial frontal lobe
Brodman area
8
Functional area
FEF
Brodman area
8
Function
Saccadic eye movements
Brodman area
9, 10, 11, 12
Location
Superior, middle frontal gyri
Medial frontal lobe
Brodman area
9, 10, 11, 12
Functional area
Prefrontal association cortex
Frontal eye fields
Brodman area
9, 10, 11, 12
Function
Thought
Cognition
Movement planning
Brodman area
13, 14, 15, 16
Location
Insular cortex
Brodman area
17
Location
Banks of calcarine sulcus
Brodman area
17
Functional area
Primary visual cortex
Brodman area
17
Function
Vision
Brodman area
18
Location
Medial and lateral occipital gyri
Brodman area 18
Functional area
Secondary visual cortex
Brodman area 18
Function
Vision, depth
Brodman area 19
Location
Medial and lateral occipital gyri
Brodman area 19
Functional area
Tertiary visual cortex
Middle temporal visual area
Brodman area 19
Function
Vision, colour, motion, depth
Brodman area 20
Location
Inferior temporal gyrus
Brodman area 20
Functional area
Visual inferotemporal area
Brodman area 20
Function
Form vision
Brodman area 21
Location
Middle temporal gyrus
Brodman area 21
Functional area
Visual inferotemporal area
Brodman area 21
Function
Form vision
Brodman area 22
Location
Superior temporal gyrus
Brodman area 22
Functional area
Higher order auditory cortex
Brodman area 22
Function
Hearing speech
Brodman area
23, 24, 25, 26, 27
Location
Cingulate gyrus
Subcallosal area
Retrosplenial area
Parahippocampal gyrus
Brodman area
23, 24, 25, 26, 27
Functional area
Limbic association cortex
Brodman area
23, 24, 25, 26, 27
Function
Emotions
Brodman area
28
Location
Parahippocampal gyrus
Brodman area
28
Functional area
Primary olfactory cortex
Limbic association cortex
Brodman area 28
Function
Smell, emotion
Brodman area
29, 30, 31, 32, 33
Location
Cingulate gyrus and limbic association cortex
Brodman area
29, 30, 31, 32, 33
Functional area
Limbic association cortex
Brodman area
29, 30, 31, 32, 33
Function
Emotions
Brodman area
34, 35, 36
Location
Parahippocampal gyrus
Brodman area
34, 35, 36
Functional area
Primary olfactory cortex
Limbic association cortex
Brodman area
34, 35, 36
Function
Smell, emotion
Brodman area
37
Location
Middle and inferior temporal gyri at temporo-occipital junction
Brodman area 37
Functional area
Parietal-temporal-occipital association cortex
Middle temporal visual area
Brodman area 37
Function
Perception, vision, reading, speech
Brodman area
38
Location
Temporal pole
Brodman area
38
Functional area
Primary olfactory cortex, limbic association cortex
Brodman area
38
Function
Smell, emotions
Brodman area
39
Location
Inferior parietal lobule (angular gyrus)
Brodman area
39
Functional area
Parietal-temporal-occipital association cortex
Brodman area
39
Function
Perception, vision, reading, speech
Brodman area
40
Location
Inferior parietal lobule (supramarginal gyrus)
Brodman area 40
Functional area
Parietal-temporal-occipital association cortex
Brodman area
40
Function
Perception, vision, reading, speech
Brodman area
41
Location
Heschl’s gyri and superior temporal gyrus
Brodman area
41
Functional area
Primary auditory cortex
Brodman area
41
Function
Hearing
Brodman area 42
Location
Heschl’s gyrus and superior temporal gyrus
Brodman area 42
Functional area
Secondary auditory cortex
Brodman area 42
Function
Hearing
Brodman area 43
Location
Insular cortex
Frontoparietal operculum
Brodman area 43
Functional area
Gustatory cortex
Brodman area 43
Function
Taste
Brodman area 44
Location
Inferior frontal gyrus (frontal operculum)
Brodman area 44
Functional area
Broca’s area
Lateral premotor cortex
Brodman area 44
Function
Speech, movement planning
Brodman area 45
Location
Inferior frontal gyrus (frontal operculum)
Brodman area 45
Functional area
Prefrontal association cortex
Brodman area 45
Function
Thought, cognition, planing behaviour
Brodman area 46
Location
Middle frontal gyrus
Brodman area 46
Functional area
Prefrontal association cortex (dorsolateral prefrontal cortex)
Brodman area 46
Function
Thought, cognition, planning behaviour, eye movement
Brodman area 47
Location
Inferior frontal gyrus (frontal operculum)
Brodman area 47
Functional area
Prefrontal association cortex
Brodman area 47
Function
Thought, cognition, planning, behaviour
What are the main sensory cortices
Somatosensory (1, 2, 3)
Visual (17)
Auditory (41, 42)
Gustatory (43)
Olfactory (not distinctly localised) 34
How did Brodman map the brain?
Topographical analysis of cortical cytoarchitecture
Location of primary somatosensory area
Post-central gyrus (3, 1, 2)
Inputs to the primary somatosensory area
VPL and VPM thalamic nuclei (medial lemniscus, spinothalamic and trigeminothalamic tracts)
Input for 1: muscle spindles and skin
Input for 2: Deep (joint) receptors
Input for area 3a: Muscle spindles
Course of fibres to primary somatosensory area
ML/STT-> VPLc/VPM- > S1
Draw the sensory homunculus
What to note
Face and tongue have bilateral representation
Location of secondary somatosensory area
Located on the superior bank of the lateral sulcus
Input to secondary somatosensory area
Ipsilateral VPLc and VPM thalamic nuclei
Bilateral S1
Output secondary somatosensory area
Ipsilateral S1 and motor cortex
Difference between primary and secondary somatosensory areas
The secondary somatosensory area receives bilateral fibres from the entire body, most of its fibres come from the primary somatosensory area
Body is bilaterally represented in the 2o with the leg most posterior and the face anterior which is the reverse of the primary somatosensory cortex
Location of the somatosensory association area
Superior parietal lobule (5, 7)
Function of somatosensory association areas
Integrates sensory data
Lesion causes tactile agnosias or astereognosis
Location of 1o visual cortex
Located in the walls and floors of the calcarine sulcus, extends around the occipital pole (17)
1o visual cortex
Input and output
Input-LGN with geniculocalcarine passing in the outer wall of the lateral ventricle to the calcarine sulcus (external sagittal stratum)
Output- Internal sagittal stratum-> cortifcofugal fibres-> superior colliculus and LGB
Visual vertical meridian cortical region
Has commissural fibres for bilateral representation
Ganglion cell receptive field
A region of the retina that affects the firing of one retinal ganglion cell
It is either on centre and off surround or on surround and off centre
Band of Baillarger
In striate cortex- stripe of Gennari which are collaterals of the primary visual cortical axons in layer IVb
Input on 2o visual cortex
LGB and pulvinar
Lesion of 2o visual cortex
Causes visual agnosia
Location of the transverse gyri of Heschl
Superior temporal gyrus, buried in the temporal operculum of the Sylvian fissure
1o auditory cortex
Input-output
MGB fibres passing through the sublenticular internal capsule
Each cochlea projects bilaterally but more to the contralateral side.
The trapezoid body is the only auditory commissure needed for sound localisation