L46,47 - Higher Cortical Functions I&II Flashcards
Define the cerebral hemispheres (lobes)?
Frontal lobe
Parietal lobe
Temporal lobe
Occipital lobe
Gross structural organization of the cerebral cortex?
Laminar organization – 6 layers Composed of glial cells, neurons, each layer has diff. input and output
–I.MolecularorPlexiformlayer
–II.External(Outer)granularlayer
–III.Externalpyramidallayer
–IV.Internal(Inner)granularlayer
–V.Internalpyramidallayer
–VI.Multiform(Polymorphiclayer)
Gross functional organization of the cerebral cortex?
Columnar function organization:
“Column” of cells with similar response properties
» Overlapping / nearly identical receptive field
E.g. area 17: process Right eye and Left eye info.
Input of Layer I of cortex?
Brainstem modulatory systems Other cortical areas
Input and output of Layer II of cortex?
Brainstem modulatory systems Other cortical areas
Other cortical areas
Input and output of Layer III of cortex?
Brainstem modulatory systems
Other cortical areas Opposite hemisphere
Input of Layer IV of cortex?
Brainstem modulatory systems
Thalamus
Input and output of Layer V of cortex?
Brainstem modulatory systems Other cortical areas
Subcortical structures, e.g.: Striatum Superior colliculus
Input and output of Layer VI of cortex?
Brainstem modulatory systems
Thalamus
Thalamus input and output at which layer of the cortex?
Input at layer IV
Output at layer VI
Which layer of the cortex outputs to subcortical structures?
Layer V
Subcortical structures, e.g.: Striatum Superior colliculus
2 main types of neurons in the cortical layers?
1) Pyramidal neurons: Spiny excitatory (glutamatergic) neurons (majority)
2) Non-spiny inhibitory (GABAergic) interneurons
Compare the neurotransmitter, morphology and abundance of Pyramidal neurons vs interneurons in the cortical layers?
Pyramidal:
- Glutamate
- Homogeneousmorphology
- 70‐80%
Interneuron:
- GABA
- Heterogeneous
~20‐30%
Input and output of lateral geniculate nucleus?
Input = retinal ganglion cells
Output = Occipital lobe
Input and output of Dorsomedial nucleus of thalamus?
Input: Medulla, olfactory cortex
Output: Orbitofrontal cortex, amygdala
Input and output of VPL and VPM of thalamus?
Spinothalamic/ DCML input + trigeminothalamic (VPM only)
Postcentral gyrus/ primary somatosensory cortex output + Temporal lobe
Input and output of anterior nucleus of thalamus?
Hippocampus, Mammilary body input
Cingulate cortex output
Input and output of medial geniculate nucleus in thalamus?
Cochlear nucleus/ central auditory pathway input
Primary auditory cortex output
Output of Pulvinar (anterior, medial, lateral, inferior) of thalamus?
Occipital lobe
List the higher cortical areas in the frontal lobe.
Premotor, SMA
Primary motor
Speech motor - Broca
Prefrontal
List the higher cortical areas in the Parietal lobe.
Primarysomatosensorycortex,somatosensoryassociation area
List the higher cortical areas in the Occipital lobe.
Primary visual
Visual association
List the higher cortical areas in the temporal lobe.
Primary auditory
Wernicke’s area
Auditoryassociationcortex
Memory
Functions of the frontal lobe. (think about the higher centers there)
- Emotion,personality,socialcontrol,speaking
- Executivefunction:planning,decision‐making,makingjudgments,attention
- Controlofmovement
Functions of the Parietal lobe. (think about the higher centers there)
- somatosensoryfunction(e.g.senseoftouch)
- Interpretationofshapeandtextures
- Understandingspeechandformulatingwords
Functions of the Occipital lobe. (think about the higher centers there)
- Processesvisualinformation
* Correlationofvisualimageswithpreviousvisualexperience
Functions of the temporal lobe. (think about the higher centers there)
- Mostlyconcernedwithspeechandhearing
* Storageofauditoryexperience
Define the functional categories of cerebral cortex.
- Fourfunctionalcategories:
* Primary motor, primarysensory,unimodalassociationcortex (secondary),multimodalassociationcortex(tertiary)
Purpose of the Primary Sensory functional category of the cerebral cortex?
receives thalamocortical fibers from diencephalic relay nuclei related to their functional modality:
Somatosensory Visual Auditory
Function of the Unimodal association cortex?
Adjacent to primary cortex
Devoted to higher level of information processing:
primary sensory > motor and somatosensory association area > higher‐order somatosenory association area and premotor cortex
Function of Multimodal association areas?
receiveinformationfromseveral differentsensorymodalities:
(1)theproductionofaunifiedpercept (2)therepresentationoftheperceptinmemory
Which cognitive functions are executed at the multimodal association areas?
–Useoflanguage
–Futureplanning
–Imagineandcreate
–Appreciationofspace,etc.
List all the motor areas in the cerebral cortex?
- Primarymotorcortex(Area4)
- Premotorcortex(Area6)
- Frontaleyefield(Area8)
- Broca’sarea(Area44,45)
Location, function, organization of the Primary motor cortex?
- Locatedintheprecentral gyrus
- Allowsconsciouscontrolof precise,skilled,voluntary movements(ontheopposite sideofthebody) via direct connection with spinal cord
- representedinanorderly mannerinthecortex: Homunculi
Describe the mapping of the primary motor cortex?
Body is mapped upside down
Homunculi: body regions with the greatest number of motor innervations (e.g. hands, face, tongue) are represented by largest areas of motor cortex
disproportionate representation of the body on the primary motor cortex
Motor function planned in the primary motor area can be executed without additional sensory input. T or F?
False
Motor function Need continuous stream of tactile, visual, proprioceptive information for accuracy, proper sequence
List all 6 sensory areas in cerebral cortex?
- Primarysomatosensorycortex(Area1,2,3)
- Visualcortex(Area17)
- Auditorycortex(Area41,42)
- Vestibularcortex
- Gustatorycortex(Area43)
- Olfactorycortex
Location, Input, Mapping and function of primary somatosensory cortex?
- Locatedinthepostcentralgyrus
- Receivesinformationfromtheskinandskeletalmuscles
- Homunculi mapping
- Exhibitsspatialdiscrimination
Tract the visual pathway from retina to cortex?
Photoreceptor cells (rod, cone) > bipolar cells > ganglion cells
> optic nerve > optic chiasm > optic tract
> lateral geniculate nucleus/body (6 layers of neurons) of the thalamus
> optic radiation to visual cortex:
Right cortex process right temporal + left nasal field, vice versa
Which side of the thalamus relays visual information from which side of the visual field (nasal/ temporal)?
- Temporal hemiretina > ipsilateral lateral geniculate nucleus
- Nasal hemiretina > crosses over at optic chiasm > contralateral lateral geniculate nucleus
Tract the pathway for superior visual field quadrant processing? (from retina to cortex)
Superior VF > Inferior retinal field quadrant > Lateral half of LGN
> Temporal** optic radiation > Geniculocalcarine tract > Inferior Calcarine bank in visual cortex
Tract the pathway for inferior visual field quadrant processing? (from retina to cortex)
Inferior VF > Superior retinal field quadrant > Medial half of LGN
> Parietal** optic radiation
Geniculocalcarine tract
Superior calcarine bank in visual cortex
Organization of primary visual cortex?
Organized in Orientation columns and Ocular dominance columns + blobs (vertical) for color
After optic radiation relays visual signal to primary visual cortex, what are the next higher centers?
- Dorsal stream (magnocellular pathway) Projects to parietal association cortex
- Ventral stream (parvocellular pathway) Projects to temporal association cortex
Both Eventually converge onto frontal association cortex
Compare the function of the parvocellular and magnocellar pathways for visual processing?
- Dorsal stream (magnocellular pathway): Processes spatial information: position, motion, speed
- Ventral stream (parvocellular pathway): Processes information about form: color, shape, texture
Give the lesion site + one example of condition causing: Bitemporal hemianopia (lose lateral visual field)
Optic chiasma lesion
i.e. Pituitary adenoma
Give the lesion site + one example of condition causing: Monocular amaurosis (one eye lose all vision)
Optic nerve lesion
i.e. optic neuritis
Give the lesion site + one example of condition causing: Homonymous hemianopia (no ipsilateral temporal + no contralteral nasal field)
Optic tract lesion
i.e. Cranio- pharyngioma
Give the lesion site + one example of condition causing: Homonymous upper quadrantic hemianopia. (loss of upper quadrant field of the same side in both eyes)
Temporalopticradiationlesion
posttemporallobectomy
Give the lesion site + one example of condition causing: lowerquadrantic hemianopia (loss of lower quadrant field of same side in both eyes)
Parietalopticradiationlesion
e.g.parietal glioma
Give the lesion site + one example of condition causing: Dense hemianopia with macular sparing (Half of field loss on same side in both eyes, with normal macula spot)
Visualcorticallesion(e.g.occipitallobe infarct)
Central LGN still intact > Macular sparing > 1 of 2 bilateral projections to primary visual cortex still functional
Unilateral lesion in the auditory pathway can cause bilateral hearing loss. T or F?
False
Cochlear nucleus on each side projects fibers to ipsilateral (superior olivary complex) and contralateral tracts (lateral lemniscus)
Double decussation + bilateral processing means unilateral lesion unlikely to affect hearing
How is auditory info processed in the cerebral cortex? Brainstem centre processing?
All fibers from cochlear nucleus to primary auditory cortex maintain the tonotopic information pattern
Spatial mapping + Accurate localization of sound processed at cortex
Medial Geniculate body = upstream projection + downstream modulation
Inferior colliculus = Amplitude + frequency modulation, Reflex coordination (head movement + startle reflex), Downstream efferent modulation
Superior olivary complex = Gross localization of sound
Cochlear nucleus = frequency + temporal processing
Cochlear, basillar membrane = frequency + tonotropic map
Tract the gustatory pathway from taste buds to cortex?
Taste buds (CN VII, IX, X (epiglottis))
> > geniculate, petrosal, nodose ganglia
> > solitary tract + solitary nucleus***
> > central tegmental tract
> > VPM of thalamus
> > Gustatory cortex (area 43)
Brief outline of brain areas involved in forming vestibular cortex?
Balance needs many snesory integration:
Somatosensory cortex
Posterior insula
Premotor cortex (frontal eye field)
Parietal cortex
List some centers in the olfactory cortex?
- Piriform cortex
- Lateral entorhinal cortex
- Olfactory tubercule
- Anterior olfactory nucleus
- Anterior cortical amygdaloid nucleus
List the 4 association areas?
Parietal, temporal, Frontal, Limbic association cortices
Function of parietal and temporal association cortex?
- Parietalassociationcortex:sensoryguidanceofmotor behaviourandspatialawareness.
- Temporalassociationcortex:recognitionofsensory stimuli+storageofsemantic(factual)knowledge
Function of frontal and limbic association cortex?
•Frontal(prefrontal)associationcortex:organizing behaviour + workingmemory. •Limbicassociationcortex:(Locatedintheanteriorventralportionof thetemporallobe)emotion andepisodic(autobiographical)memory
List 4 functions of Prefrontal cortex?
- Highercognitivefunction,planning
- Personalityexpression
- Decisionmaking,workingmemory
- Socialbehavior
Input and output of prefrontal cortex? Can it evoke movement?
Input : Projectionzoneofthemediodorsal nucleusofthethalamus
electricalstimulationdoesnotevoke movements
Highlyinterconnectedwithother cortical,subcorticalareaandbrainstem
Consequence of prefrontal cortex dysfunction?
psychiatrydisorders,e.g.depression, schizophrenia
drasticand permanentpersonalitychanged
Lack of ability to plan ahead
Name of procedure done to limitinterhemisphericspreadof epilepticactivity?
cut Corpuscallosum
Compare the functions of Wernicke’s and Broca’s areas? Left or right brain?
Wernicke’s = comprehensionofwrittenandspokenlanguageand formationofcoherentspeech
Broca’s = motorprogramsofspeechandwriting»_space; primary motor cortex
Normallylocatedinthelefthemisphere (if right-handed)
Symptoms and area of brain affected in expressive aphasia?
Understandlanguageperfectlyand maybeabletowriteperfectly
Difficulty speaking spontaneously
> > Broca affected
Symptoms and area of brain affected in receptive aphasia?
unabletonameobjects
unabletounderstandthemeaningofwords
articulatespeechreadily,butusuallynonsensically
> > Wernicke affected
Symptoms and area of brain affected in global aphasia?
almosttotalreductionofallaspectsofspokenandwrittenlanguage
> > largerlesionsincentralregionaroundlateralsulcus;largeleft middlecerebralarteryinjuries
Symptoms and area of brain affected in Conductive aphasia?
comprehensionisnormalandexpressionisfluent
Difficulty translating what’s said into appropriate reply
> > interruptionoftheconnections (arcuatefasciculus)linkingtheBrocaandWernickeareas
Which association cortex is most highly lateralized in the brain?
Parietal association cortex
Brain area affected in Contralateral Neglect syndrome i.e. on the left side?
Damagetorightparietalassociation cortex(non‐dominant)
= defectinattention, spatialsurrounding, self‐imageontheleft side
List 4 cortical dysfunctions?
Aphasia
Apraxia
Agnosia
Ataxia
Define apraxia and brain areas affected?
Difficulty with the motor planning to perform tasks / movements »_space; Cannot internalize, duplicate the spatial relationships
Parietal association cortex;
Premotor cortex; or
Supplementary motor cortex
Define agnosia and list 3 subtypes?
higher level disorders of sensory perception even though afferent sensory pathways function normally
Tactile agnosia: cannot recognize objects through touch
Prosopagnosia: cannot recognize familiar faces / learn new faces
Visual agnosia: appreciative or associative
Clinical presentation of visual appreciative agnosia? (able to identify object? Normal object perception? Draw copy?)
- Cannot draw copy of image
- Can verbally identify object
- Cannot see object parts as a unified whole
- Cannot construct senosry representations of visual stimuli
Clinical presentation of visual associative agnosia? (able to identify object? Normal object perception? Draw copy?)
- Can copy image
- Cannot name objects/ interpret/ understand/ assign meaning
- Normal sensory representation but faulty association
> > Posterior multimodal association cortex lesion
Presentation and brain area affected in optic ataxia?
difficultywithvisuallyguidedgraspingandreaching
damagetothedorsomedialparietalcortex
Define dementia, area of brain affected and related impairments? How to assess dementia?
Clinical syndrome of impaired cognitive function in multiple domains but with preserved consciousness
global dysfunction in cerebral cortex
Deterioration of memory, intellect, concentration, comprehension, specific cortical functions
Mini‐Mental Sate Examination (MMSE)
Most common form of dementia? Related genetic factors?
Alzheimer’sDisease
Mutationofamyloidprecursor protein(APP),presenilins1(PSEN1)and presenilin2(PSEN2)
Pathogenesis of Alzheimer’s?
- Extracellulardepositionofamyloidplaques***, composedofbeta‐amyloid(Aβ)
- Intracellularneurofibrillarytangles(NFT),composed ofaggregatesofhighlyphosphorylatedmicrotubule bindingprotein,Tau
- Significantdecreaseinacetylcholinetransferase andlossofcholinergicneurons
> > Memoryloss,deficitsofcognitivefunction, mooddisorders
Sequence of brain areas affected in progression of Alzheimer’s
Medial temporal lobe
> Lateral temporal, parietal lobes
> Frontal lobe
> Occipital lobe
How does functional imaging of cognition work?
Cognition = change in energy metabolism of neurons, synaptic activity and strength
i.e. increase cerebral blood flow and volume, increase glucose uptake … etc
Principal of PET scans?
detectspairsofgamma raysemittedindirectlybyapositron emittingradionuclide(tracer e.g. oxygen-15)
measuredtheflow ofbloodtodifferentpartsofthebrain
Principal of fMRI?
detectingchangesassociatedwithbloodflow.
Usestheblood‐oxygen‐leveldependent(BOLD) contrast
(BetterresolutionthanPETscan)
Principal of EEG?
electricalpotentialdifference fromthesummationofpostsynapticpotentialsfrom pyramidalneuronsinthecortex
measured by many electrodes on the scalp
What in EEG used to dx?
epilepsy,comaandbraindeath
Monitor sleep
List the 4 EEG patterns and the cognitive states related?
Alpha = awake, relaxed state of wakefulness, eyes closed
Beta = awake, alert, with visual stimuli
Theta = Concentrating of emotional stress in adults, common in brain disorders, common in children
Delta = deep sleep, indicate brain damage in awake adults
Principal of Magnetoencephalography MEG?
Electromagneticfieldsaregeneratedby theneteffectof currentflowinneurons
•Theeffectofmultipleneuronsexcited togetherinaspecificareagenerates measureablemagneticfield
Define neuroplasticity and its function?
RemodelingoftheCNS/ Re‐organizationofsynapticnetworks to cause changeinbehavior/sensation
Function:
Learning and memory
Phantom limb sensation (i.e. after amputation)
Cortical remapping of referred sensation (i.e. after stroke)
