Neuroanatomy: Cerebral Cortices
Neocortex
- - layers correlate with different functions and connections - layering is mechanism for sorting its inputs and outputs - Afferent from other cortical areas from thalamus adn from nuclei in the brainstem and elsewhere
Afferent input to the lobes
- Afferent from other cortical areas is the contra lateral hemisphere - Many of these fibers project from sites in the frontal, parietal, or occipital cortex on one side to the mirror-image sites on the other side
Efferent Connections- Cerebral cortex
- Efferent are axons of pyramidal cells (excitatory) - Projected fibers from the primary sensory and motor cortex form the largest input to the basal ganglia
Broca's area
- Frontal lobe of dominating hem - Responsible for motor aspects of the production of speech
Fluent Aphasia
- Inability to speak- in this case lesion in left temporal - Sentences make zero sense. - Wernicks area
What are association areas?
- Involved in same function as "primary areas" that receive projections - Usually adjacent to each of the primary cortical area - Less precise somatotopic, tonotopic, retinotopic
"Where" Pathway
- Lateral part of area 19- detects movement - Visual cortex sends projections to posterior parietal cortex - then sends those to premotor cortex and FEF
Broca's Aphasia
- Lesion in frontal lobe affecting motor - Can not generate the words he is wanting to say -Becomes frustrated because he knows what he wants to say
Brodmann's areas
- Map of cortical areas based on appearance of cortical tissue under miscroscope. - Korbinian Brodmann split them up in 52 areas
Temporal lobe function
- Primary auditory cortex (Brodmanns 41/42) - wernicke's area for speech comprehension
"What" Pathway
- Recognition of individual objects and faces -Area 20/38
Orbital Gyri
- Rest on the orbital plate of the frontal bone - Not related to eye function
Wernick's Area
- Temporal lobe - area 22 - Responsible for speech comprehension
Interconnections within each cerebral hemisphere
- The second source of Cortico-cortical Afferent is the other area in the same hemisphere Arcuate Fasciculus: interconnect two prominent language areas - Association bundles: fibers travel in these. Intermingled with other bundles
Cerebral cortex structure
- Varies in thickness - more than half hidden - Have layered or laminar appearance - Some parts of the cortex, like the olfactory cortex and the hippocampal formation and dentate gyrus are made up three cellular lamina. - 90% of cerebral cortex has 6 laminae
Six layers of Neocortex
- one molecular - two outer granular and pyramidal - two inner granular and pyramidal - one fusiform - some parts of cortex only have 3
Main Gyri (occipital lobe)
- parietal-occipital fissure -calcarine fissure: divides medial surface into cuneus and lingual gyrus
Main Gyri (Temporal lobe)
- superior middle, and inferior temporal gyri -Uncus- Medial side, adjacent to pathways to vision -fusiform -parahippocampal gyrus
Corticonuclear
- to contralateral motor and somatic sensory cranial nerve nuclei in the pons and medulla
When two hemispheres cannot communicate
-Ex. Lesion on left occipital lobe affects Splenium of the corpus Callosum - Info form the right cannot flow to angular gyrus(transfers visual info to wernicks) - results in alexia without agraphia (unable to read, but can write)
Components of the cerebrum
-cerebral cortex -gyri -sulci -longitudinal fissure -cerebral hemispheres -diencephelon
frontal lobe function
-motor cortex -working memory -decision making -creativity -social interaction: inhibition of socially inappropriate behavior *** Bilateral prefrontal damage may cause little change in basic intelligence but have all other aspects affected
Main sulci (frontal lobe)
-precentral gyrus : motor cortex -superior middle and inferior frontal gyri -orbital gyri - straight gyrus (Gyrus Rectus) -cingulate gyrus (Considered part of limbic lobe)
Main sulci (parietal lobe)
-supra-marginal gyrus -angular gyrus -precuneus
Brodmanns area most relevant to clinical optometry
8, 17, 18, 19, 22, 44
Visual allesthesia
A disorder which the retinotopic VF is rotated, flipped, or even inverted
4. Inner granular later
Afferent from the thalamus
V5
Area 19 has movement detection and functions in the "where" visual pathway.
Brodmann's areas of the frontal lobe
Area 4, area 6, area 8, area 44&45.
Remember HAL
Area of cortex devoted to a particular body part is proportional to the degree of precision with which movement and can be excited or the amount of sensory innervation
Brodmann's areas of occipital lobe
Areas 17, 18, & 19
The ventral or what pathway
Begins V1, goes to angular gyrus (visual- verbal pathway), inferior temporal lobe (visual- visual pathway) and limbic structures (visual- Limbic pathway)
V1
Bormann area 17
V2 and V3
Brodmann area 18/19
V4
Brodmanns area 19 Color vision center and a component of the "what" visual pathway
The dorsal or where pathways
Concerned with visuospatial analysis,. Moves forward to premotor cortex and FEF to convey
1. Molecular layer
Contains dentrites of pyramidal cells and axons
2. Outer granular layer
Contains small pyramidal and Stellate cells
Are the areas of the somatotopic map related to the ipsilateral or contralateral body part?
Contralateral
5 & 7 areas
Correspond to association areas
3-1-2 area
Correspond to the post central gyrus
Afferent and efferent corona radiata
Cortical afferent and efferent fibers that go from the cerebral cortex to other structures such as corpus striatum, thalamus, brainstem and spinal cord
Ocularmotor apraxia
Difficulty in fixating the eyes
Hemispatial Field neglect
Far more common with damage to the right hemisphere, plays a whole in spatial attention
What area of the somatotopic map is more medial, the feet or the tongue?
Feet
5. Inner pyramidal layer
Fibers projecting to extracortical areas such as stratum, brainstem and spinal cord
Area 8
Frontal Eye Field (FEF) which controls voluntary conjugate deviation of the eyes
Prosopagnosia
In ablility to recognize the faces of familiar people, typically as a result of brain damage
Agnosia
Inability to interpret sensations and hence to recognize things, typically as a result of brain damage - In Visual Agnosia patients are unable to recognize previous known objects
Optic ataxia
Inability to move the hand to a specific object by using vision
Simultagnosia
Inability to perceive the visual field as a whole
Brodmann's areas of the parietal lobe
Low numbers, 3-1-2 areas, 5&7 areas
Precuneus
Medial aspect, adjacent to occipital lobe
3. Outer layer pyramidal
Medium size pyramidal and stellate cells
6. Fusiform layer
Modified pyramidal cells association and projection to the thalamus
Video of diseases
Parkinson's disease- basal ganglia Brain - Cerebral palsy, hemiplegia due to stroke Cerebrellar dysfunction: intoxication adn metabolic and toxic disorders Spinal cord: Devices disease or neuromyelits optics NMO, amytrophic lateral sclerosis
Right vs left hemispheres
Right: Spatial and musical patterns, solving problems in intuitive fashion left: Language, math ability, planning skilled movements, logical sequential analysis
parietal lobe function
Somatic sensory processing (Postcentral gyrus)
What areas are relevant to the somatotopic and association areas?
Somatotopic: Precentral and postcentral gyri in frontal and parietal lobe Association: Surround "primary" function areas
Corticospinal
Spinal cord
Environmental rotation
The field of the environment rather than the field is rotated
Where is the lesion if there is visual field loss with macular sparing?
The occipital lobe
Corticopontine
To the ipsilateral pontine nuclei
Angular Gyrus
Transferring visual information to *Wernickes area, in order to make meaning out of visual perceived words
Area 44, 45
broca's area (motor speech)
Afferent and efferent internal capsule
dense sheet of white matter deep in the hemisphere. Carries information past the basal ganglia.
Lobes of the brain
frontal, parietal, occipital, temporal
Area 4
precentral gyrus (primary motor cortex)
Area 6
premotor cortex or supplemental motor area
Occipital lobe function
primary visual cortex
Area 17
principal visual cortex
Areas 18 &19
visual association areas two sets on each side of the Calcarine fissure