Neural Bases Ch 7: The Cerebrum: A Survey

list the four structures/systems that nourish and protect the brain

• Meninges (dura, arachnoid, pia) + CSF in the subarachnoid space • Blood-brain barrier • Cerebral arteries (carotid + vertebral → circle of Willis → anterior, middle, posterior cerebral arteries) • Venous system (4 sinuses in the meninges, then superficial and deep cerebral veins)

identify the important features of the cerebral hemispheres, including the lobes

• 2 hemispheres; layers superficial→deep: cortex (gray), white matter, deep gray (thalamus, basal ganglia), 4 ventricles • Cortex features: gyri, sulci, fissures (longitudinal, central, lateral) • 6 cortical layers • Lobes: frontal (reasoning, planning, motor), parietal (sensory perception/interpretation), occipital (vision), temporal (memory, receptive language)

describe hemispheric specialization, especially for language

• Left = the details/language: reading, writing, spoken language, auditory comprehension, reasoning • Right = the whole/creative: prosody, facial expression, body language, attention, visuospatial skills • Most people are left-hemisphere language dominant: 96% right-handers, 85% ambidextrous, 73% left-handers • Hemispheres linked by the corpus callosum; within-hemisphere links include the superior longitudinal and arcuate fasciculi

list and briefly describe causes of damage to the cerebral hemispheres

• Stroke/CVA: ischemic (blocked: thrombotic, embolic, TIA) or hemorrhagic (burst: intra-axial or extra-axial) • TBI: open vs closed (acceleration-deceleration coup/contrecoup or impact-based) • Cerebral palsy: nonprogressive, before/at/right after birth • Stuttering: possible brain differences (e.g., overactive right hemisphere)

describe brain plasticity and its principles

• Neuroplasticity = the adaptive capacity of the CNS; neurons alter structure and function in response to internal/external pressures, including behavioral training • Mechanism for normal learning AND for the damaged brain relearning in rehab • 10 principles: use it or lose it, use it and improve it, specificity, repetition, intensity, time, salience, age, transference, interference

Why does the brain need protection inside the skull?

Inside the skull is an inhospitable place for the delicate brain: it has lots of sharp, bony edges

Name the three meninges from outer to inner

• Dura mater (outer)
• Arachnoid mater (middle)
• Pia mater (inner)

Dura mater: position and what it does

• Outermost meningeal layer
• Protects; folds in on itself between the hemispheres

Arachnoid mater: position and what circulates there

• Middle meningeal layer
• CSF circulates through the subarachnoid space (between arachnoid and pia)

Pia mater: position and how it attaches

• Innermost meningeal layer
• Tightly adheres to the brain

Which meningeal spaces are potential spaces, and where is each?

• Epidural: between skull and dura mater
• Subdural: between dura mater and arachnoid
• Normally not real spaces; can occur due to injury

Which meningeal space is an actual space, and where is it?

Subarachnoid space: between arachnoid mater and pia mater

Blood-brain barrier: list its three functions

• Protects against foreign invaders
• Protects against hormones/neurotransmitters in the rest of the body
• Maintains a constant environment for the brain (glucose, oxygen, brain-required hormones)

Name the structures in the blood-brain barrier diagram

• Endothelial cells and tight junctions • Capillary (carries blood) • Pericyte • Astrocyte (protects the brain from things) • Interneuron

List what can violate the blood-brain barrier

• Hypertension (can cause aneurysm)
• Developmental problems with the BBB (e.g., arteriovenous malformation, likely to burst; Chiari malformation)
• Hyperosmolality
• Microwaves
• Radiation (vessels lose flexibility, become brittle)
• Infection
• Trauma, ischemia, inflammation, pressure (loss of blood supply to brain areas)

Blood flow order: artery → ? → ?

Big artery → little capillaries → veins

What percentage of the body's oxygen does the brain consume?

20%

Through which two sets of arteries does blood enter the brain, and where does the second go?

• Carotid arteries
• Vertebral arteries (go on to form the basilar artery)
• Both feed the circle of Willis

Why is the circle of Willis described as protective?

it can still get blood to one part of the brain if a vessel is blocked

Which artery joins the two anterior cerebral arteries in the circle of Willis?

Anterior communicating artery

Which common carotid do the internal and external carotids branch from in the aortic arch diagram?

Left common carotid artery (internal and external carotids come off it)

Circle of Willis: through which three arteries does it feed the brain oxygenated blood?

• Anterior cerebral artery
• Middle cerebral artery
• Posterior cerebral artery

Base-of-brain artery diagram: list the labeled vessels

• Anterior, middle, posterior cerebral arteries • Internal carotid • Anterior and posterior communicating arteries • Basilar (splits into the posterior cerebrals) • Vertebral • Anterior inferior and posterior inferior cerebellar arteries

Define perfuse

To provide blood to

Which territory does each cerebral artery perfuse?

• Anterior cerebral: medial and top of the brain
• Middle cerebral: lateral area
• Posterior cerebral: medial aspect of temporal lobe (and occipital lobe)

What does the venous system do?

Moves deoxygenated blood away from the brain

Name the four sinuses in the meninges that remove deoxygenated blood, in order

• Superior sagittal
• Transverse
• Occipital
• Sigmoid
• Then superficial and deep cerebral veins remove it

Where is the superior sagittal sinus?

Superficial; where the dura mater folds in on itself

Cerebrum: name the major layers from superficial to deep

• Surface gray matter (cerebral cortex; neuron somas)
• White matter (axons; forms fiber tracts)
• Deep gray matter, subcortical (e.g., thalamus, basal ganglia)
• Ventricles (4)

What does cortex mean?

Bark

Define gyri, sulci and fissures

• Gyri: hills
• Sulci: valleys
• Fissures: deep sulci

Name the three fissures of the cerebral cortex

• Longitudinal (sagittal; between hemispheres)
• Central (motor in front, sensory behind)
• Lateral

Lateral view: name the gyri

• Superior, middle, inferior frontal gyri • Precentral gyrus (motor strip) • Postcentral gyrus (sensory) • Supramarginal and angular gyri • Superior and inferior parietal lobules • Superior, middle, inferior temporal gyri • Lateral and inferior occipital gyri

Lateral view: name the sulci and fissures

• Superior and inferior frontal sulci • Precentral sulcus • Central fissure (separates frontal and parietal) • Postcentral sulcus • Lateral fissure • Superior and middle temporal sulci • Parieto-occipital and lateral occipital sulci

Medial view: name the gyri/lobules

• Paracentral lobule, precuneus, cuneus • Superior frontal gyrus • Cingulate gyrus (part of the limbic system + cognition) • Corpus callosum, fornix • Lingual gyrus • Parahippocampal gyrus (memory) • Fusiform gyrus, inferior temporal gyrus

Medial view: name the sulci

• Cingulate sulcus • Parieto-occipital sulcus • Calcarine sulcus • Collateral sulcus • Inferior temporal sulcus

Where is the angular gyrus?

Where the temporal lobe meets the parietal lobe

List the six cortical layers and their cells

• I (molecular): glia and neurons
• II (external granular): small pyramidal cells
• III (external pyramidal): large pyramidal cells
• IV (internal granular): nonpyramidal cells
• V (internal pyramidal): Betz cells
• VI (multiform): various cells
• All six = gray matter

Name the four fiber types in the cortex diagram

• Callosal • Projection • Thalamocortical • Association (corticocortical)

Frontal lobe: functions

• Reasoning, planning, motor movement (initiate and create the motor plan)
• Last part of the brain to myelinate

Parietal lobe: functions

• Sensory perception and interpretation
• Touch, taste, hearing, language comprehension, reading and writing

Occipital lobe: function

Vision

Temporal lobe: functions

• Memory
• Receptive language (auditory comprehension)

Left hemisphere: theme and functions

• The details = LANGUAGE (think lawyer/judge: reasoning)
• Reading, writing, spoken language, auditory comprehension, reasoning

Right hemisphere: theme and functions

• The whole = CREATIVE
• Prosody (the music of speech/language)
• Facial expression (producing, interpreting) and recognition
• Body language (producing, interpreting)
• Attention (maintaining)
• Visuospatial skills

What percentage of right-handers, ambidextrous people and left-handers are left-hemisphere language dominant?

• 96% of right-handers
• 85% of ambidextrous
• 73% of left-handers

What is the main interhemispheric connection, and what is it made of?

• Corpus callosum: a band of fibers connecting the right and left hemispheres
• White matter tracts (axons)

Interhemispheric

between hemispheres

Name the two example intrahemispheric connections and what each links

• Superior longitudinal fasciculus: front of the brain (forming thought) ↔ auditory processing
• Arcuate fasciculus: Broca's area (speech motor plans) ↔ auditory processing

Stroke facts: incidence and prevalence

• Incidence (new cases): 795,000
• Prevalence (people currently living with it): up from 2.7% to 2.9% of the population

BE FAST: what does each letter stand for?

• Balance: sudden loss
• Eyes: vision loss
• Face: uneven smile
• Arm: one arm weak
• Speech: slurred
• Time: call 911

Stroke prevention: five areas

• Disease management
• Active
• Nutrition
• Relax
• Sleep

Ischemic CVA: nickname and what happens

• Dry stroke
• Blood flow is blocked, restricting blood flow to the brain
• Focal lesion (smaller lesions)

Thrombotic stroke (cerebral thrombosis)

A clot that forms and doesn't move (e.g., high cholesterol)

Embolic stroke (cerebral embolism)

• A clot that moves until the capillaries get too small for it
• Clot formed elsewhere (atrial fibrillation, heart defect, blood clot disorder)

Transient ischemic attack (TIA)

• Mini-stroke lasting less than 24 hours
• Can be caused by a seizure

Thromboembolic stroke

A clot forms (unmoving), but a piece of fatty buildup breaks off and starts moving

Ischemic core

necrosis, dead tissue

Hemorrhagic CVA: nickname and what happens

• Wet stroke
• A blood vessel bursts
• Decentralized lesion

List causes of hemorrhagic stroke

• High blood pressure
• Congenitally weak blood vessels
• High cholesterol
• Tearing due to trauma (TBI)
• AVMs (pressure difference, no capillaries)

Intra-axial hemorrhage

• Intra-axial: inside brain tissue (intracerebral hemorrhage)

Stroke impact map: match Broca's area, Wernicke's area and the motor supplementary area to functions

• Broca's: control of muscles for speech production + comprehending grammatical structure • Wernicke's: comprehension of speech sounds and language (making meaning) • Motor supplementary area: orientation, head and eye movements, posture

closed head injury

skull remains relatively intact (more damage)

Two types of closed head injury

• Acceleration-deceleration (coup + contrecoup)
• Impact-based (something hits your head, or you hit your head on something)

Coup vs contrecoup

brain hits the front of the skull (first place it hits)

TBI facts: incidence and prevalence

• Incidence (new cases per year): 1.7 million
• Prevalence: 5.3 million

List the physical problems of TBI

• Coma, drowsiness, headache, seizures
• Hydrocephalus (water on the brain: too much CSF)
• Plegia/paresis
• Dyskinesias (difficulty with movement)
• Vision changes
• Multiple traumas (e.g., blunt chest trauma)

plegia

paralysis/no movement

List the cognitive-communicative problems of TBI, and which lobe handles most

• Attention, orientation, memory, new learning
• Thought organization, reasoning, problem solving, executive functions (all frontal lobe)

TBI speech-language issues: define each

• Dysarthria: difficulty with speech
• Aphasia: language impairment
• Apraxia of speech: difficulty programming the muscles of speech
• Hearing loss
• Dysphagia: difficulty swallowing

Cerebral palsy: progression and timing

• Nonprogressive brain disorder
• Occurs before, at, or right after birth

Cerebral palsy: list the causes

• Premature birth (spinal cord not done)
• Anoxia
• Infections
• Brain hemorrhages
• Jaundice
• Head injury

Cerebral palsy: symptoms

• Muscle tone issues
• Dyskinesias
• Gait problems (walking problems)
• Note: the 4 CP types are marked 'don't need to know'

CP diagram: pyramidal vs extrapyramidal damage

• Pyramidal (frontal) → spastic: hemiplegia, diplegia, quadriplegia • Extrapyramidal (cerebellum + subcortical) → dyskinetic (athetoid, dystonic) and ataxic

Stuttering: definition and term for the interruptions

• Interruptions in the normal smoothness of oral language
• Called disfluencies

Normal vs abnormal disfluency: examples

• Normal: 'um'
• Abnormal: 'b-b-ball'

Stuttering: brain differences, cause and genetics

• MAY be brain differences (e.g., overactive right hemispheres)
• No one cause
• Genetic markers present in some families with increased stuttering prevalence

nueroplasticity (textbk definition)

• The adaptive capacity of the central nervous system • Neurons can alter their structure and function in response to internal and external pressures, including behavioral training • The brain can recover a little at the cellular level

Neural plasticity is the mechanism for what two things?

• How the normal brain encodes experience and learns new behaviors
• How the damaged brain relearns lost behavior in response to rehabilitation

Plasticity principle: failure to drive certain functions can lead to loss

Use it or lose it

Plasticity principle: training certain brain functions can lead to improvement

Use it and improve it

Plasticity principle: the nature of the training experience dictates the nature of plasticity

Specificity

Plasticity principles: induction requires sufficient repetition / sufficient intensity

• Repetition matters
• Intensity matters

Plasticity principle: different forms of plasticity occur at different times of training

Time matters

Plasticity principle: the training experience must be important to induce plasticity

Salience matters (do you like it?)

Plasticity principle: training-induced plasticity occurs more readily in younger people

Age matters (older = reduced neuroplasticity)

Plasticity principle: one training experience enhances acquisition of similar behaviors

Transference (e.g., acoustic → electric guitar)

Plasticity principle: one experience interferes with acquisition of other behaviors

Interference (e.g., water ski → snow ski)

which structures protect, nourish and remove waste? (textbook summary)

• Protection: meninges and blood-brain barrier • Nourishment: cerebral arteries • Waste removal: venous system

what do the three fissures separate? (textbook summary)

• Longitudinal: right vs left hemispheres • Central: frontal vs parietal lobe • Lateral: frontal and parietal lobes vs temporal lobe

fissures vs sulci vs gyri (textbook summary)

• Fissures: deep grooves • Sulci: shallower grooves • Gyri: hills

main functions of each lobe (textbook summary)

• Frontal: reasoning, planning, voluntary motor movement • Parietal: sensory perception and interpretation • Temporal: perception and comprehension of speech; some memory • Occipital: visual processing

describe hemispheric specialization (textbook summary)

• The hemispheres aren't mirror images; each functions uniquely • Clearest example is language: 96% of right-handers have language lateralized to the left hemisphere

Textbook definitions: CVA, TBI, CP, stuttering (textbook summary)

• CVA (stroke): interrupted blood supply through blockage (ischemia) or bleeding (hemorrhage)
• TBI: traumatic blow impairing brain function; open (skull penetrated) or closed (not)
• CP: nonprogressive disorder acquired before, during or shortly after birth affecting movement, posture, balance
• Stuttering: in-word interruptions to the free flow of speech

brain plasticity (defintiion - textbook summary)

The adaptive capacity of the brain: always changing and rewiring itself in response to internal and external influences