Cerebral Cortex 2 and Language Flashcards
what are the structural methods for imaging a live brain?
- CT
- MRI
- DTI
functional methods for imaging a live brain
- PET
- fMRI
Computerized tomography (CT)
a narrow beam of x-rays is aimed at a patient and quickly rotated around the body, producing signals that are processed by the machines computer to generate cross sectional images or slices
- These images can be reconstructed to form a 3D view of the body
- CT scanner is like a donut, not a tube like an MRI
- Can be easier for claustrophobic patients to tolerate it
clinical situations when you use a CT (5)
- Stroke
- Headache
- Abdominal pain
- Unexplained bleeding
- Guiding neurosurgery
how are CT’s used in research situations?
- Can do CT on a variety of animals as well as humans
- Allows for tracking changes in an animal over time
what identifying things are in a CT? (3)
- The very bright region is the skull
- Acute blood would be bright
- Chronic blood would be dark
Subdural hematoma features (3)
- Midline shift
- Sulci in right hemisphere are thin or difficult to see ⇒ due to swelling
- Isointensity indicates subacute blood
what dye can be used to examine blood supply to the brain
iodine based
Advantages of CT (4)
- Non invasive
- Can use tracers to distinguish particular tissues of interest
- Very little distortion
- Quick
Disadvantages of CT (2)
- Difficult to see fine features ⇒ low resolution
- Like X-rays you need to worry about repeated exposure to radiation
Magnetic resonance imaging (MRI)
uses powerful magnets that produce a strong magnetic field to force protons in the body to align with the field
how does MRI work?
- When radiofrequency current is pulsed through the patient, the protons are stimulated and strain against the pull of the magnetic field
- When the radiofrequency is turned off, the MRI sensors detect the energy that is given off as the protons realign
- The amount of energy released varies with various environments
what can be difficult for patients with an MRI?
Can be difficult for claustrophobic patients
when can you use MRI clinically (3)
- Stroke ⇒ not acute
- Dementia
- Tumor
when can you use MRI for research?
Whenever you want a detailed image of the brain
MRI settings (4)
- PD
- TD
- T1
- MRA => MR angiography
PD MRI
good for viewing subtle changes in anatomy
TD MRI
fluid appears light and good for viewing edema, MS lesions, demyelination
T1 MRI
good for viewing general anatomy and with contrast (gadolinium) good for detecting breakdown in blood brain barrier
MRA MRI
good for viewing blood vessels
what happens in frontotemporal dementia
Reduced volume of gyri because the brain has shrunk
what do multiple sclerosis lesions look like?
white dots on the MRI
advantages of MRI (4)
- Non invasive
- Beautiful, very detailed images of the brian
- Aligned with functional MRI
- No significant radiation exposure
disadvantages of MRI (3)
- Take longer to obtain and can be uncomfortable
- Expensive
- Not possible for people who have metal in their bodies
Diffusion tensor imaging (DTI)
specific sequences are used that take advantage of diffusion of water molecules along white matter in the brain ⇒ used to look at white matter
- Technically a particular type of MRI
Positron emission tomography (PET)
radioactive tracer is given before the scan and will build up in areas of higher chemical activity
- may bind to particular receptors, transporters, etc.
- can be combined with Ct to look for cancer
where does Fluorodeoxyglucose build up
in areas where brain cells are more active ⇒ consuming more glucose
Functional magnetic resonance imaging (fMRI)
takes advantage of the fact that changes in blood flow are associated with neural activity
- Measures the BOLD (blood oxygenation level dependent) signal
- Does not measure neural activity, but BOLD correlates highly with neural activity
how fast do BOLD measurements change?
over seconds
how is fMRI used in clinical settings? (3)
- Plan surgical approach
- Plan radiation treatment
- Use for biofeedback
does fMRI or PET have better temporal resolution
fMRI offers a much faster temporal resolution than PET
what is an advantage of PET?
PET can give molecular specificity with the use of particular radiotracers
what sensorimotor cortices are functions of the cerebral cortex?
- primary visual
- primary auditory
what association cortices are functions of the cerebral cortex?
- Parietal association cortex
- Temporal association cortex
- Frontal association cortex
association areas
parts of the cortex that don’t receive direct sensory information through the major sensory pathways or motor thalamic nuclei
unimodal
information type located adjacent to or near the primary sensorimotor cortical areas
- processes one type of sensorimotor information
multimodal
process many types of information in complex ways
what is special about association cortexes?
- have extensive connections with sensory, other, and other association regions
- Integrate information and perform higher mental function
- Occupy a much larger fraction of the total brain in humans vs other animals
modularity
particular brain areas are highly specialized for specific functions
- Obviously true of primary sensorimotor cortical areas
- Probably true for higher cognitive functions in association areas as well
which parietal cortex(s) does the right visual field send stimulation to?
both the left and the right
which parietal cortex(s) does the left visual field send stimulation to?
only the right parietal cortex
what happens if there is damage to the right parietal cortex?
damage is very impactful because there will be no extra representation of the left visual field
Partial neglect
patients with damage to the right parietal cortex have trouble attending to the left visual field ⇒ in this case patients are not aware the visual field is there
- Different from occipital damage because they know the left visual field is still there and will move their head to see it
Temporal association cortex
processes high level features of objects, faces, and places
- lesion will cause agnosia
agnosias
difficulty recognizing and or naming things
what is the face area that is one of the strongest examples of modularity in the association cortex
fusiform face area
- part of the brain that is more active when someone views faces than when they view almost anything else
what is the result of frontal lobe damage?
a problem with the patients character
- Diverse functions found in different areas of the frontal lobe, including planning, decision making, abstract thought, representation of self, etc.
- Phineas gage is a classic example
language
method of communication that is not specific to a given context ⇒ includes content that hasn’t been previously described or conceived
- Can be used for a variety of functions
brain regions involved in language (3)
- Broca’s
- Wernicke’s
- Transcortical motor area
vocal language
uses sounds for communication
sign language
uses gestures and facial expressions for communication
written language
uses written symbols for communication
what do bees do when they find nectar?
dance to show direction and distance to nectar source
- the angle of the figure 8 is the angle from the hive relative to the sun to the nectar source and the length is proportional to the distance away
- The energy the bee performed the dance is proportional to how good the source is
what do velvet monkeys do to communicate?
have specific cries for specific predators ⇒ eagle, leopards, and snakes
- Nearby monkeys respond appropriately
what did Washoe the monkey do?
Washoe the monkey could use 160 words with sign language and could teach sign language to her child
why is animal communication not language?
language includes discussion for more than just survival purposes and can come up with concepts not thought of before
Sounds (phonemes)
are combined into words in spoken languages ⇒ combinations of gestures and facial expression can be combined into words in signed language
syntax
specifies word order when combining words into sentences to express more complex thoughts
Aptitude in language
humans appear to be naturally equipped for language and it seems to be unique to humans
- Communication by vocalization, gestures, or symbols may not be completely unique to humans, but humans have dramatically expanded its usefulness
what is universally observed about language acquisition in cultures?
same sequence across cultures is universally observed
- There are no genetic predisposition for specific languages ⇒ we learn what is spoken to us
when does ability to learn new language easily end?
12-16 => puberty
Sequence of acquisition of language comprehension (7)
- 1-11 months: newborns will notice differences between different vowel sounds, including sounds that ultimately wont be used in their native language
- 5 months: newborns start to recognize vowel sounds that are used in the language they are spoken to
- 11 months: newborn responses start to decline to sounds not used in the language in which they are spoken to
- 12 months: newborns understand 60-90 words in native language
- 15 months: understand basic word combinations ⇒ sleep now
- 18 months: understand basic word order ⇒ come with mommy
- 28 months: understand more complex word order ⇒ stop sweetie, you’re spilling milk
prosody
intonation and emphasis in language ⇒ Meaning can be changed by emphasis and tone as well as by the words
- Can communicate emotional state of speaker
how does prosody change across languages?
There are characteristic prosodic patterns to different languages so there are different rhythms to speech in different languages
what are fetuses exposed to in utero?
prosody but not language because prosody employs lower frequency sound than speech itself
- They prefer hearing their mothers voice
- They prefer hearing the language the mother spoke when the child was in utero
people with lesions on the left cerebral hemisphere have difficulties with what?
speaking
ischemic stroke
vessel clots
- when in the vessel supplying the left hemisphere it frequently impairs speech
difficulties in language after a left hemisphere stroke? (3)
- people will have difficulty speaking or following spoken instructions
- difficulty writing, or following written instructions
- ASL will have difficulty comprehending or using ASL
brocas area
cannot produce speech well but can comprehend it ⇒ expressive aphasia
- Closer to homunculus area at the level where the head and mouth are represented
- Telegraphic speech leaving out articles and connecting words
Wernicke’s area
you can produce words well but they carry no meaning ⇒ fluent aphasia
- Next to the primary auditory cortex in the head homunculus area as well
global aphasia
complete loss of language ⇒ creation and comprehension of speech, signing, writing
- Results from lesions (strokes) encompassing both Broca’s area and Wernicke’s area
what is the Wernicke-Geschwind model of language?
- wernicke’s area decodes meaning from words ⇒ comprehension of language spoken, written, and signed
- Broca’s area creates language ⇒ sounds, signs, symbols with meaning
Arcuate fasciculus
connects Wernicke’s area with Broca’s area
what happens in the anterior and posterior structures of the right hemisphere that are mirror images of Broca’s and Wernicke’s?
- Anterior is production of prosody ⇒ like Broca’s
- Posterior is comprehension of prosody ⇒ like Wernicke’s
Note: more recent studies implicate parts of the left hemisphere in prosody as well
what happens with damage to the right hemisphere prosody areas?
persons speech can lack prosody and sound flatter/less emotional that we are used to hearing
what will T1 MRI show?
regions in which blood flow is absent
- Signs of stroke, tumor, or lesion
people with deficits to identifying a specific person or thing in a picture will probably have damage in what area?
left temporal lobe
people who struggle with naming animals may have damage to what areas?
the left posterolateral and anterolateral temporal region as well as broca’s area
people who have issues naming tools may have damage to what areas?
the inferior sensorimotor cortex and left posterolateral temporal region
Transcortical motor aphasia
non fluent speech but are able to repeat back words and even long sentences
- Lesioned area appears to be involved with word choice
what lesion areas are associated with transcortical motor aphasia?
left dorsolateral frontal cortex, adjacent to Broca’s area (above Broca’s)
what is unique about the English family KE?
included a number of members with severe difficulties with speech
- Single gene is responsible
FOXP2 gene
encodes a transcription factor that controls gene expression
- Could affect many different genes
- FOXP2 is still being studied but it seems less likely that it specifically allowed the evolution of language ⇒ been discarded at this point
