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