Cerebral Cortex Lecture Flashcards
Cerebral Cortex: 2 categories of layers
1) Supragranular layer
- layers 1-4
- last to develop
- associational fibers-neurons talking to neurons on same side of brain
2) Infragranular Layer
- Layers 5 & 6
- commissural fibbers (neurons that communicate to other side of brain)
Golgi Stain
- Silver strain
- neurons, axons, and dendrites
Nissl stain
1) all cells in brain
- Nissl Bodies (ReR)
Weigert Stain
Myelin Stain
-myelinated axons
Layers of Cerebral cortex
1) Molecular Layer
2) External Granular Layer
3) External Pyramidal Layer
4) Internal Granular Layer
5) Ganglionic Layer (internal pyramidal layer)
6) Multiform layer (layer of polymorphic cells)
- many different types of neurons and microfilm
- many astrocytes and oligoendroglia (satellite cells)
- Blood supply from pail surface
Hippocampal Cortex
Has only 3 layers
1) Molecular
2) Pyramidal
3) Polymorphic
Blood Brain Barrier
1) Capillaries are tight, do not leak
2) Blood is toxic to CNS tissue
3) Endothelial cells bound tightly to capillaries via tight junctions to create BBB
- water, gases, and lipid soluble small molecules can diffuse across endothelial cells
- other substances=transport systems-highly selective
4) Brain bleed=toxins pouring into head-» kills brain cells
* *Protects neurons from direct exposure to tissue fluids
Excitotoxicity
Increase in excitatory Neurotransmitters=Kills neurons
Glutamate
1) Excitatory Neurotransmitter
- causes neuron action potentials
2) Plasma is loaded with glutamate
- brain bleed= excitotoxity
- causing the neurons to overexcite and kill them
3) BBB KEEPS FROM CNS
Glial vs neurons
10: 1 glial to neurons
- most brain tissue is made of glial cells not neurons
Cortical Cell types
1) Pyramidal Cells
2) Betz Cells
3) non-pyramidal cells (aka interneurons/internuncial neurons)
Pyramidal Cells of cerebral cortex
1) Excitatory
- ex: Glutamate
2) Found in all layers EXCEPT layer 1
- mostly found in layers 3 & 5
- cells in layer 2/3 give rise to associational fibers
- cells in layer 4, project to thalamus
- layer 5-project to anterior (Ventral) horn of the spinal cord, brain stem, thalamus, basal nuclei, other regions of cortex.
- AXONS from these cells going to spinal cord form=CORTICOSPINAL TRACTS
- layer 6- project to thalamus and cortex
Betz Cells of cerebral cortex
1) Very large Pyramidal Cells
2) Found only in layers 5 of precentral gyrus
- projects to the lumbar spinal cord
- control leg movement
Non-pyramidal Cells of cerebral cortex
Aka interneurons or internuncial neurons
-function as local circuits (talk to neurons in area=short axons)
4 types of cells-receive excitatory input from the thalamus
1) Spiny stellate cells
- excitatory
- layer 4
- projects to other columns
2) Aspiny stellate cells
- inhibitory
- layer 4
- projects to other columns
3) Basket cells
- inhibitory
- all layers
- projects to other columns
4) Chandelier Cells
- inhibitory
- layer 3
- projects to Pyramidal cells within a column
- may be involved in schizophrenia, by not doing its job
Inhibitory Neurons
1) use GABA (game-aminobutyric acid) to systems=become overactive
Afferent projections to the cortex from lower centers
-think thalamus
1) Ventral lateral nucleus of thalamus
- motor cortex
- layer 3 and 4
2) Specific afferent projections- moving toward cortex
- layers 3 and 4
- lateral geniculate projects toward visual cortex
- medial geniculate projects toward auditory
- ventral posterior nucleus of thalamus projects to pain and temps
3) Nonspecific afferent projections
- Lateral dorsal nucleus
- Pulvinar nucleus
- Reticular Nucleus
- mostly layers 1 and 2
Projection
1) axons carrying impulses from the cortex to lower centers or from lower centers to the cortex
Association efferent
Interconnecting different regions of the cortex of the SAME SIDE OF THE BRAIN
Commissural Efferents
Interconnecting similar regions of the cortex on the OPPOSITE SIDES OF THE BRAIN
-ex: Corpus Callosum, ANt commissure
MAturation of major neural tracts and cortical areas for reflexes/behavior
Pattern of myelination-when your fully developed tract
1) spinal reflex
- fetal months to 2 months old
2) Motor control
- ending of fetal months-> 2-4 y.o.
3) Sensory
- fetal months-> 2/3 y.o. (Motor a little longer)
4) Behavior
- birth-> early 20’s
5) Judgement and reason
- 3 y.o.-> rests of life
Myelination of fibers
Myelin allows for faster signal down axon
-myelination is a gradual process
Prefrontal Cortex
-Brodmanns areas
Areas 9,10, 11, 12
- judgement
- reasoning
- personality
- working memory (temporary)
- motivation
Male vs female cerebral cortex
Females cerebral cortex= 19 billion neurons
Male cerebral cortex= 23 billion neurons
Developmental Neuro
1) at 100 days basic parts are there
2) a 7months start developing gyri
3) at 9 months=fully developed
- no new neurons are added after birth
- 73,000 miles of myelinated tracts
- lose 30% of myelinated tracts as you get older
as you get older-> same number of neurons but different levels of complexity w/age
- more enrichment=more complexity of dendrites
- Dr. B less complex dendrites with less spines (coming off of dendrites)
Muscle Spindles
Intramural fibers
-sensory fibers that tell CNS what skeletal muscles are doing
Cerebral localization-Penfield Homunculus
1) Postcentral Gyrus=SENSORY CORTEX
- middle cerebral artery supplies Upper Extremity and Face (lips, tongue, teeth, pharynx)
- ANterior Cerebral artery supplies Lower Extremity and Head/neck
2) Precentral Gyrus= MOTOR CORTEX
- Middle cerebral artery supplies Hand and Face (lips, tongue, swallowing)
- Anterior Cerebral artery supplies Upper and Lower extremity (minus Face and Hands)
Apraxia
1) Inability to perform a a purposeful movement w/out paralysis
2) disorder of motor control
- may occur after damage in parietal association cortex, premotor cortex, or supplementary motor cortex
3) May affect the muscles of speech
- seperate disorder from aphasia
Brodman’s Area for Post Central Gyrus
Primary Sensory Cortex (S1)
Post central gyrus
3a-Propioception (aware of body parts in space) from muscle spindles
3b+1->-cutaneous afferent
2- Golgi tendon organ and joint afferent
S1
Primary Somatosensory cortex
- post central gyrus
- Brodmanns area 1,2,3
- 3a=propioception from muscle spindles
- 2-golgi tendon organs and joint afferents
- 1+ 3b= cutaneous afferents
M1
Primary Motor Cortex (M1)
- Brodmans Area 4
- Precentral Gyrus (right Half)
Broca’s area
Brodmanns ares 44 and 45 of Left Brain
- inferior frontal gyrus
- speaking and writing language
Broca’s Aphasia
Lesions of Frontal inferior gyrus Broca’s area 44 and 45 of Left brain
AKA expressive aphasia or nonfluent aphasia
1) Able to comprehend language but can’t speak fluently (can’t express themselves)
- Not paralysis of vocal aparatus
- difficulty writing (agraphia) but they can understand written language (read)
2) most common causes:
- tumors/occlusion of- frontal M4 branches of middle cerebral artery
3) other Symptoms-contralateral motor signs and symptoms such as
- weakness (paresis) of the lower part of face
- weakness of the arm
- motor weaknesses + aphasia=occlusion of branches from the proximal parts of the middle cerebral artery (M1) including lenticulostriate arteries
4) Full-blown brocas aphasia
- doesn’t affect just brocas area-> includes insular cortex and white matter
5) Severe Brocas aphasia
- unable to speak=mutism
- still understand speech, can swallow and breathe normally
6) Less severe case
- limited speech is possible
- short habitual phrases such as “Hi, fine, thank you, and yes or no are the first to come back
7) Mild Broca aphasia
- damage only affects cortical area
Brodmanns area 5
To the Right of postcentral sulcus/gyrus
Sensory association
Wernickes area
Brodmanns areas:
- 39=written
- 40=connecting
- 22=spoken (sometimes)
Language center
- left side of brain
- comprehend spoken or written language
Visual Cortex
-Brodmanns areas
17, 18, 19
- more complex moving towards 19 (inner) from occipital pole
- 17=light patterns
Brodmanns area 21
Higher order visual audio memories
- middle temporal gyrus
- memories and language
Heschls gyrus
Brodmann areas-41 and 41
- Primary Auditory Cortex
- process what is heard
Brodman’s Area 43
Primary Gustatory Center
- Located below central sulcus above Sylvian fissure
- dysgeusia (gustatory illusions)
Brodmanns areas 7
Parietal Eye field
-eye movement
Brodmanns Area 6
1) Premotor cortex
2) Supplemental motor cortex (M2)
Achromatopsia
Damage up area 19 of visual cortex
- has to be bilateral
- no color seen or able to imagine
Akinotopria
- lesion along inferior temporal sulcus
- cannot perceive motion
Brodmanns area M3
Cingulate Sulcus
-medial view
Brodmanns area S2
Medial view
- deep within central sulcus
- receives input from S1
- has strong connection with amygdala and Hippocampus
Brodmanns area 34 and 36
Medial view
- recognizing faces
- parahippocampal gyrus
- read emotions on someone’s face
Brodmanns area 20
Inferior Temporal Gyrus
-higher order visual memories
Brodmanns 37
Inferior Temporal Gyrus
-higher order visual processing
Premotor Cortex
- function
- lesion
Premotor Cortex
- voluntary motor function that is dependent on sensory input
- ex: reaching for object in space
- involved in planning and executing movements
- approx 30% of pyramidal fibers are from here
- has strong projections to primary motor cortex (area 4)
- receives input from the supplementary motor cortex
Lesion:
- causes apraxia=cannot perform purposeful movement in the absence of paralysis
- pt has difficulty walking and performing other complex motor tasks
Supplementary Motor area
Aka (M2)
- approximately 5% of pyramidal fibers
- involved in planning movement (rather than executing movements)
- activated when pt asked to flex multiple fingers in a SPECIFIC sequence (along with m1)
- Mental reps (not actually doing reps)
Area 5 and 7-non dominant hemisphere
- function
- lesion
Personal Geography
- knowledge of where you are in enviroment
- knowledge that your body parts are yours (angular gyrus involved-area 39)
Lesion:
- cannot learn a new enviroment
- may deny a body part is yours or neglect it
Hemineglect
1)aka contralateral neglect
2) damage to the right parietal association cortex (nondominant)
-pts will be unaware of objects and events in the left half of his/her surrounds
3) Milder forms:
-tendency to ignore things on the left side of the patients surroundings
4) Extreme cases
-don’t even recognize the left side of his or her won body (ASOMATOGNOSIA)
-ex: ignore left side when dressing
5) other symptoms:
-losing the ability to function successfully within spatial surroundings
-ex:unable to describe his/her route on the way home from work
-unable to manipulate objects in space (contraction always apraxia)
Ex: legos
Area 39 and 40-non dominant hemisphere
- function
- lesion
1) Rhythm and feeling into speech
- the way one says words
- interpreting the emotional tone of the speech of another person
2) Lesion
- cannot sing
Area 22-Nondominant hemisphere
-function
Comprehending voice inflections (pitch/tone)
Right vs Left brain:
Right:
- creative (mostly)
- can-simple quantitative functions (summing small integers)
- can understand simple language
Left:
- Language
- Verbal
- Analytical
- quantitative
- Linear (mostly)
Anosognosia
1) Inability to acknowledge disease in oneself
2) ONLY RIGHT brain stroke-insular cortex and S1 and S2 + motor cortex= L side paralysis
- pts tend to have anosognosia
- Right side S1, S2 and insular cortex=centers for integration of body awareness
3) Left brain stroke-same area=no anosognosia
- have issues with social interaction and personal decisions
Right side S1, S2 and insular cortex
Centers for integration of body awareness
Corpus Callosum
Larger in females than males
ACC
AGENESIS OF CORPUS CALLOSUM
- doesn’t develop at all
- doesn’t hinder person much
Hypoplastic Corpus Callosum
-underdeveloped corpus callosum
Lissencephaly
- Smooth brain
- no gyri or sulci developed
- vary degrees of severity
- live 1-2 years at most
- caused by: genetic or viral infection during pregnancy
Visual Fields to Visual Cortex
1) Each eye talks to both visual cortices
2) Visual fields are lateralized, not eyes
Sodium Amytal test
Aka Wade Test
1) Inject a barbiturate (drug-shuts down activity) into R or L internal carotid Artery
- determines which hemisphere is dominant for speech function
- avoids neurosurgical procedures that might destroy language ability
2) Pt asked to count backwards will being injected
- Hemisphere dominant for speech is affected= pt stops speaking and does not respond to a command to a command to continue
3) Test revealed that:
- 96% of Right handed people are L brain dominant for speech
- 70% of L handed people are L brain dominant for speech
- 15% of L handed people control of speech in both hemispheres (injection didn’t supress speech fxn)
- suppressing L hemisphere produces brief depression feeling
- suppressing R hemisphere produces brief feeling of euphoria (buzz)
- Functions related to MOOD may be lateralized in brain
- Smage w/ R hemisphere-pathological indifference to their disability
Split Brain Experiments
1) Epileptics
- provided hemisphere function
- prevent seizures from spreading from one side of the brain to other=cut the corpus callosum and anterior commisure
- each hemisphere can function independently
- R-generally mute and cannot communicate about its experience verbally ; can do many things of L
- Sensory analysis, memory, learning, and calculation performed by each hemisphere (R limited)
2) Split Brain patients
- function normally
- both hemispheres receive information from the world bc of the crossing pattern of visual input
Split Brain patient- Right side removed; apple experiment
1) Shown apple in right visual field
- projects only to left hemisphere visual cortex
- sees object
2) Shown apple in L visual field
- pt denies seeing anything
- if brain doesn’t know why you did something, it will manufacture a reason yo will believe is true
Memories
- reconstruction of fragmented parts
- assembling wrong=false memory (feels right)
- ego edits memories to make us remember them how we want to remember them
Microglia
1) like macrophages-phagocytic
- predominant cells involved in CNS inflammation
2) secrete IL-1B, TNF-a, prostaglandins, and neurotoxic molecules (glutamate, oxygen radicals)
- secondary cause of neuronal damage following trauma or stroke
HIV
targets microglial in the CNS
-leads to neuronal damage and dementia
Wernickes Aphasia
1) AKA receptive or fluent aphasia
2) defect of the comprehension rather than expression of language
3) Cause:
- occlusion of temporal and parietal M4 branches of the middle cerebral artery
- hemorrhage/tumors into thalamus extending laterally and caudally to invade the subcortical white matter
5) Severe wernickes aphasia
- unable to understand what is said to them
- unable to read (Alexia)
- unable to write (agraphia)
- fluent paraphasic speech (can talk normally)
- unintelligible bc of frequent errors of word choice or made-up words
7) less severe cases
- paraphasias occur:
- literal paraphasia (incorrect but similar sounding word),
- verbal paraphasia (word seems appropriate to the patient but is incorrect)
8) Much less aware of the extent of their disability vs patients with Broca’s
9) Damage to basal nuclei-> associated with language disorders similar to wernickes
Damage to basal Nuclei
Associated with language disorders similar to wernickes
Agnosia
1) Disorder of sensory perception
- not a loss of primary sensation (touch, vision, hearing)
- Loss of the ability to interpret the sensation
2) only one sensory modality
3) difficulty in recognizing complex sensory stimuli
4) Forebrain lesion may cause variety
Visual Agnosia
Inability to recognize a familiar object by sight
Somatosensory agnosia
inability to recognize a common objects such as a coin, pencil, or key using sense of touch alone (tactile agnosia, asterognosis)
Olfactory Agnosia
deficits to sense of smell
Gustatory agnosia
Deficit to sense of taste
Color Agnosia
Inability to recognize colors
Hippocampus
- Involved in memory (declarative)
- bilateral-in temporal lobes
- strong connection with S2 (along with amygdala)
Amygdala
- responsible for base emotion (rage, anger, sexual)
- limbic system
- emotion valence driven by Amygdala
- temporal lobe
- strong connection with S2 (along with hippocampus)
Written/spoken/and hearing language
1) NOt wired for written language
- only hearing and speaking language