12. Cerebral cortex Flashcards
temporal:
define
relating to time;
has more to do with temporal region of the skull;
where the hair start to turn gray, denoting the passage of time
neocortex:
definition, % of cortex
“new, young”; newest evoluntionarily
90% of cortex
paleocortex:
define, location, function
“ancient, primitive”;
location: ventral surface
function: olfactory cortex
archicortex:
define, function
“primary, early, chief”; oldest evolutionarily;
function: hippocampal portions of limbic system
as mammals get more complex, which subdivision of the cortex has more “real estate” devoted to it?
what other effect does this have?
isocortex (neocortex);
sacrfices some of the olfactory capability of “lower mammals”
what are the 6 layers of the cerebral cortex?
the cortex itself is very thin (only about 2.5 mm thick)
- molecular layer (most superficial)
- mostly cell processes (dendrites)
- few granule (Stellate cells)
- pyramidal and granular levels
- multiform layer is deepest
- projects to thalamus
direction of most information traveling in the cerebral cortex?
most traveling vertically;
granule (stellate) cells help information move horiztonally
describe layers 2-5 of cerebral cortex
- alternating pyramidal and granular layers
characteristics of pyramidal layers (external - III and internal -V)
-
pyramidal: chief cortical afferent cell;
- apical dendrites from surface &
- basal dendrites: horizontal;
- w/ axons leaving the cortex for other cortical areas or subcortical nuclei
characteristics of granular layers (II-external) and (internal-IV)
granular: cortical interneurons;
- especially numerous in sensory regions;
- short dendrites and axons (extending in all directions)
- input from the thalamus
intracortical fibers:
location, characteristics
- located superficially (layer I of cerebral cortex); just deep to the arachnoid and pia mater
- ipsilateral: travels shorts distances w/in the same hemisphere
cortical columns:
define
vertically oriented functional units of the cerebral cortex;
each is a few mm in diameter and contains
thousands of neurons that are interconnected in the vertical direction
association fibers:
define, characteristics
- layers II & III
- ipsilateral
- connects adjacent gyri or lobes
arcuate loop:
define
association fibers connecting adjacent gyri
arcuate fasciculus:
define
association fibers connecting frontal and temporal lobes
commisural fibers:
characteristics
- cross midline
- connect Right and Left homologous areas
- 2 major commissural fibers bundles:
- anterior commissure
- corpus callosum
corpus callosum:
define and components
- thick and tough “like a callus” body; fiber body, connects cerebral hemispheres; just deep to cingulate gyrus (involved in Papaz circuit - memory formation in limbic system)
- components
- Rostrum: “beak”
- Genu: “knee”
- Trunk:
- Splenium: “bandage”
anterior commissure:
function
connects right and left TEMPORAL lobes
trunk of corpus callosum connects…
connects R & L frontal and parietal lobes
in what view would you find both the genu and splenium of the corpus callosum connecting the two?
in a horizontal view;
how connections between homologous areas L and R thru the corpus callosum
cortex has been removed from this image:
what structure is transmitting fibers from side to side?
corpus callosum
projection fibers:
characteristics
- cortex <–> subcortical nuclei
- two directions
- corticofugal
- corticopetal
corticoFUGAL vs corticoPETAL
- corticoFUGAL: efferent to nuclei
- corticoPETAL: afferent from thalamus
pathway of projection fibers?
pass thru subcortical areas (such as internal capsule)
located b/w thalamus and corpus striatum
w/in the internal capsule, what are the different limbs?
- ANTERIOR limb
- Genu
- POSTERIOR limb
- Retrolenticular limb
- optic radiation fibers
- Sublenticular limb
- auditory radiation fibers
where are the optic radiation fibers found in the internal capsule?
in the retrolenticular limb
think: RETRO glasses for optic radiation?
where are the auditory radiation fibers found in the internal capsule?
in the sublenticular limb:
think SUBwoofer speakers = SUBlenticular = AUDITORY radiation
components of ANTERIOR limb
-
corticofugal: motor tracts; darker matter
- to corpus striatum
- to pontine nuclei
-
corticopetal:
- thalamic nuclei –> cortex
components of genu
(of internal capsule)
- corticofugal: corticobulbar tract
-
corticopetal: motor thalamus; (VA/VL) - cortex
- hitting the PEDAL = motor accelerates
posterior limb: components
- somatotopic organization
-
corticofugal:
- these are the axons of the upper motor neuron
-
corticopetal:
- thalamic radiations
difference between anatomical lobes vs functional?
- anatomic lobes: subdivided by gyri and sulci
- functional lobes: subdivided by numbered Brodmann areas
primary motor (M1)
of frontal lobe
(location, fxn)
- located: posterior portion of precentral gyrus
- motor control fro contralateral body
- somatotopically organized (homunculus)
premotor area
of frontal lobe
(location, fxn)
- location: sl anterior to M1 (primary motor) area
- contralateral control (motor control)
- receives input from the basal ganglia
supplementary motor area
of frontal lobe
(location, fxn)
- location: medial frontal lobe, anterior to LE (lower extremity) portion of M1
- bilateral projections
- motor planning of complex movements
FUNCTIONAL areas of the frontal lobe
- primary motor (m1)
- premotor
- supplementary motor
- frontal eye fields
- prefrontal
- broca speech
which functional area is used for motor planning of complex movements?
supplementary motor
frontal eye field:
function
- origin of voluntary saccadic movements
- projects to vertical & horizontal-gaze centers & to superior colliculus
prefrontal cortex of frontal lobe:
function
orbitofrontal region: frontal part; overlies the orbit (eyesocket)
dorsolateral region: anterior to broca’s area; for judgement, concentration, planning, and problem-solving
region of the brain for judgement, concentration, planning, and problem-solving
dorsolateral region of the prefrontal cortex
(found in frontal lobe)
orbitofrontal region:
location and fxn
found in prefrontal cortex
location: ventral; overlying orbits + medial surface anterior to the corpus callosum
fxn: limbic connections for social behavior
cc: damage to dorsolateral region of prefrontal area?
causes lack of cognitive abilities (judgement, concentration, planning, problem solving)
Phineas Gage: consequences of his prefrontal cortex injury
- his demeanor completely changed;
- “surly, aggressive drunkard”
- loss of social inhibition, inappropriate behaviors
broca speech:
definition
- location: inferior frontal gyrus (brodmann: 44, 45)
- contains motor program for formation of words
- projects to lateral M1 (primary motor) areas for oral, glossal, pharyngeal, laryngeal muscles used in articulation
parietal lobe:
functional areas
- primary somatosensory (S1): somatotopically organized
- parietal association area
- secondary somatosensory (S2)
- inferior parietal lobule
primary somatosensory (S1):
location, fxn, characteristics
- located: post central gyrus
- somatotopically organized (M1)
- receives contralateral sensory input from:
- proprioceptive
- skin sensation (pain, temperature, touch)
secondary somatosensory:
location
found in operculum (meaning lid); thought to be on top of insular region
parietal association cortex:
location, fxn
- location: superior parietal lobe (posterior to S1)
- fxn:
- stereognosis (detecting object on clues alone)
- somatognosos: can differentiate own body from things not your own body
- receives input from:
- S1,
- motor areas,
- audio- and
- visual- areas
stereognosis vs somatognosis
stereognosis (detecting object on clues alone)
somatognosos (soma=”body”): can differentiate own body from things not your own body
CC: lesions in parietal association cortex can cause
- phantom limb: see in up to 70% of pts w/ hx of amputation; sxs of “foot itching” or “foot pain” due to parietal assoc. cortex damage
- unilateral neglect: usually on R side; so the pt can only recognize things on the Right side, etc. If putting his left hand in front of him, he may not even recognize it as his own hand
inferior parietal lobule:
fxn, location
- fxn: cognition, speech, and language processing
- part of parietal lobule; adjacent to Wernicke’s area
occipital lobe:
functional areas
- Primary visual cortex (V1)
- parastriate cortex
- peristriate cortex
primary visual cortex:
location & fxn
- located: in occipital lobe; posterior portion of occipital lobe; wrapping into medial surface of cortex
- gyri superior and inferior to calcarine sulcus
- superior: cuneus
- inferior: lingual gyrus
parastriate vs. peristriate cortex
(locations)
- PARAstriate = areas alongside, immediately anterior to V1 location
- PERIstriate = “peri = around”; border between parastriate and parietal temporal lobes
function of parastriate and peristriate cortices?
involved in complex visual perceptions: color, shape, direction, and location
temporal lobes:
functional areas
- primary auditory cortex (A1)
- secondary auditory cortex (A2)
- auditory association cortex
primary auditory cortex (A1):
location & function
- fxn: bilateral hearing
- part of temporal lobe; located deep in lateral fissure
- bilateral projections to A1
which aspect of primary auditory cortex corresponds to the apex of the cochlea?
lower frequency;
more ANTERIOR aspect of A1 (primary auditory cortex)
the base of the cochlea corresponds w/ posterior aspect of A1
secondary auditory cortex (A2)
location & fxn
- adjacent and inferior to A1
- fxn: bilateral hearing
auditory association cortex:
location
superior temporal gyrus;
wernicke’s areas posteriorly
Broca vs. Wernicke’s areas
- Broca (brodmann 44)
- MOUTH - motor, expressive speech
- Wernicke’s (brodmann 22)
- SENSORY/RECEPTIVE speech
Broca’s area:
fxn and correlation
- motor (expressive speech)
- word production
- projects to M1
Wernicke’s area:
fxn and correlation
- sensory (Receptive) speech; brodmann 22
- language comprehension
- connects w/ broca’s area via arcuate fasciculus
- (located posterior to broca’s area)
when would you use a sagittal section view?
- ?pyramidal tumor
- *corpus callosotomy: split-brain surgery performed in cases of severe epilepsy –> less severe caes of epilepsy
cc: hydrocephalus
(define, and causes)
- expansion/enlargement of the ventricles
- due to either accumulation of excess CSF, or diminished reabsorption of CSF, OR blockage of CSF circulation
what does the following radiograph show?
hydrocephalus in the image on the right
what is the most common cause of hydrocephalus?
what can result if untreated?
blockage of CSF circulation;
sequelae can result frmo brain damage due to compression of CNS structures
what is the infant’s “relief valve” from hydrocephalus?
treatment?
the fontanel can allow the cranium to expand because the skull is not completely ossified;
tx is to catheterize the enlarged ventricle
cc: intracranial hematoma
ruptured blood vessls (arterial or venous)
- bleeding into a fixed space
- can increase intracranial pressure
- can initially compensate
- midline shift of structures
- herniating of structures
- life-threatening
difference between epidural and subdural?
- epidural: typically arterial; dura is peeled off skull
- subdural: typically venous; dura is still attached to skull
what are the mechanisms for initial compensation for intracranial hematoma?
- ventricles
- dural venous sinuses
what type of fx may rupture the middle meningeal artery?
(causing an epidural hematoma)
skull fx thru the pterion; –> relatively thin –> so easy to rupture the middle meningeal artery
located outside the dura mater
what is in the picture?
epidural hematoma causing a midline shift
what causes the banana sign?
what about the lemon sign?
banana sign – SUBDURAL hematoma
lemon sign – EPIADURAL hematoma
intracranial herniation
can cause undue pressure on the respiratory centers;
often incompatible w/ life
cc: aneurysm
a brain (cerebral) aneurysm is a bulging, weak area in the wall of an artery that supplies blood to the brain
cc: cerebrovascular accident (CVA)
ischemic: BV gets blocked; *87% of strokes
hemorrhagic: BV ruptures; 13% of strokes
types of ischemic CVAs?
- thrombotic: clot forms locally
- embolic: clot travels from elsewhere
- –> causes structures downstream from the blockage infarct (die) and lack of oxygen and nutrients
what happens during a hemorrhagic CVA?
- bleeds into region of rupture –>
- the escaping blood takes up space –>
- pressure builds up w/in confined space –>
- brain damage caused by swelling and lack of oxygen
