Cognitive Neuroscience Test 1 Flashcards
Phrenology
Phrenologists look at high level functions localized in specific areas. they look at SPECIFIC areas of the brain and mapping specific functions for specific brain areas
Flouren’s’ Aggregate field theory
The whole brain participates in behavior; there are no specific functions in the specific brain regions
Broca’s Area
speech production (found this through studying damage to the area)
Association cortex
Not sensory or motor
Receive inputs from many areas
Contains cells that may be activated by more than one sensory modality
Specific functional roles
Brodmann areas (what are they; not the specific numbers)
52 distinct areas based on cell structure - multiple cells looked the same so he grouped them together. Even though the areas were only done by how they look and not how they function, it was found that many that look the same, have the same functions- for example, all the cells in Broca’s area look the same so without trying, he showed where Broca’s area wa
Cerebellum
(translation- “little brain”)
The small area hanging off the back of the main brain area
Maintains posture and smooth, coordinated movements
Does not control movement directly
Combines information from sensory inputs describing body position to support smooth coordinate movement
Cerebellum Volume
tells us a lot!
Not strongly related to cortex size
Varied across different species
Species with large cerebellum volume have complex forelimb control (doing things with hands, paws, beaks, etc.)
i.e. some rodents, some large-brained birds, elephants, and some primates
This shows that the cerebellum is important for integrating necessary sensory motor information
Interestingly, dolphins have the largest cerebellum
Default mode network
Set of brain regions that are active when participant is ‘resting’
Not performing a task
These areas become deactivated when participant is performing a task
These areas are involved in memory, future planning, and self referential processing. So, they become active during resting AND tasks that involved these things.
Double dissociation
Patient 1 has damage in Area X and is impaired at Task A but not Task B
Unclear whether Area X is specifically involved in Task A
It is possible that damage to any area causes Task A but not Task B impairment
AND patient 2 has damage in Area Y and is not impaired at Task A but is impaired at Task B
Much more likely that Area X is specifically involved in Task A
Damage to Area Y does not cause Task A impairment
DTI
a technique that detects how water travels along the white matter tracts in the brain
Used for images of axons
Uses traditional MRI scanner
- Sensitive to protons in water rather than tissue
Measures motion of water in axons
- Motion of water is restricted by myelin
- More likely to flow in direction of axon than perpendicular to axon
Can be used to image axons in the brain
Fasciculus
a bundle of axons in the brain
EEG
Electrical potentials from populations of active neurons are measured through the scalp
Disks are placed on the scalp and measure the electric signal coming from the brain. It is flexible- people can move around
Electrical activity changes based on internal state
ERP
Align EEG signal with an external event(Stimulus or response)
- Average over many trials of same type (variation cancels out)
Identify relevant waveforms
- N100 (negatively deflecting waveform occurring 100ms post event onset)- Indicates early stimulus processing
- P300 (positively deflecting waveform occurring 300 ms post event onset- Indicates response to low-probability event)
EEG/ERP pros cons
Pros- have good temporal resolution
Can tell the difference between events that occur 1 ms apart
Cons - poor spatial recognition
Cannot tell where electrical activity is generated
fMRI
Has replaced PET scans for the most part
Similar to MRI
Radio waves perturb proton orientation
When radio waves are turned off, the protons realign with the magnet
Rebound is measured by detectors and produces 1 image.
Difference between MRI and fMRI? Focus on protons in hemoglobin (instead of those in gray/white matter)
Hemoglobin- the oxygen-transport protein in blood
Active areas need blood AND oxygen, so where there is more oxygen, there is more activity. This is why it has replaced PET scans for the most part)
Blood oxygen level dependent (abbreviated BOLD) signal
Good spatial resolution (can distinguish activity locations if they are 1-3 m3 apart)
Has okay temporal resolution (can distinguish activity events that occur 1-2 seconds apart)
A limit- same as MRI, each layered image of the brain takes time.
Functional connectivity
Looking at the connections of the whole brain and how it functions together rather than just one place
Brain areas work together in interconnected networks
- There is a way to examine this with connectivity maps (connectomes) which reveal brain areas that function together
- Maps created by correlating activity in different brain regions over time
This technique requires ‘okay’ spatial and temporal resolution to do well
grey matter
Gray matter volume increases until 6-7 years and then decreases by 5% per decade
Grey matter makes up the outer most layer of the brain
Gray matter is made up of neuronal cell bodies
MEG
Similar to EEG/ERP except measures changes in magnetic fields instead of changes in electricity
MEG traces aligned to event and averaged across trials
Event-related fields (ERFs)
Inverse dipole modeling
Solutions more accurate than for ERP because magnetic fields are not distorted as passing through tissue, skill, and scalp
Good temporal resolution (milliseconds)
Good spatial resolution
Except that locations are modeled rather than observed. Not looking at it, using math to model it
Motor cortex
eh directs movements
MRI
How does this work?
MRI’s measure the distribution of protons in gray/white matter
It does this through magnetic imaging and measuring the difference in timing between protons (we don’t need to know this for tests)
Myelin
Glial cells Create myelin, while Insulates axon
The more insulation, the more efficient transmition is
Nouns vs. verbs
Patients with difficulty processing nominal (noun) information; fine with verbs
Results in difficulty using nouns
Patients with difficulty processing action (verb) information; fine with nouns
Results in difficulty using verbs
Damasio and Tranel (1993)
3 patients with different lesions
Boswell and A.N. have trouble with nouns
K.J. has trouble with verbs
They were asked to describe pictures
Things found from the results
The area where understanding verbs are found in the brain (premotor cortex), is also the area for planning movements.
PET
Measures variation in cerebral blood flow
More active areas in the brain require more blood
Radioactive tracer (isotopes) are injected into the blood stream
The blood flows to active areas of the brain
As isotopes decay, photons are released
Scanner detects the photons and there are more in active areas of the brain
People tend to not like this method. It is invasive
Poor temporal resolution
Takes about 10 minutes for tracer to leave the body, which means you get one image every 10 minutes
Spatial resolution is only okay
Can tell that activity occurred in different locations if locations are ~ 10mm3 apart
Need MRI or CT scan for structure
PET IS NOT USED VERY OFTEN!!
Plasticity
brain’s ability to reorganize and shift
Somatosensory cortex study
Mogilner et al. study - ‘gaining a limb’
Examined finger representations in somatosensory cortex.
How? By stimulating fingers and recording brain activity using MEG (a way to measure brain activity)
They do this in control participants (people who have typical 5 fingered hands)
Experimental participants were people with syndactyly - fingers that have not separated into 5 distinct fingers
Something common in patients with syndactyly is to do a surgery to give people more finger mobility- improves dexterity
So, in this study, they are looking at syndactyly participants before and after surgery is done
Results:
In the brain, the areas for each finger are in the same order as the fingers themselves. There is a tiny chunk of brain dedicated to each specific finger (they are very distinct and do not overlap
For syndactyly participants before surgery, the area of the brain overlap and is not distinct for each area.
After surgery, they get physical therapy and within a week, each finger has a specific area in the brain representing it without overlap
This is a great example of plasticity in the brain. The brain reorganized very fast in order to accommodate for new fingers.
Somatosensory cortex
known for its central role in processing sensory information from various parts of the body
Single dissociation
Patient 1 has damage in Area X and is impaired at Task A but not Task B
Unclear whether Area X is specifically involved in Task A
It is possible that damage to any area causes Task A but not Task B impairment
tDCS
Temporarily increase/decrease cortical excitability
Electrical current sent through scalp between two electrodes
Increases/decreases cortical excitability
Way to temporarily enhance/inhibit function of particular brain area
Primarily affects surface areas
TMS
Temporarily decrease/increase cortical excitability
Used to asses the role of particular brain regions in particular mental functions
Used in clinical settings to help alleviate depression and chronic pain
A way to damage a brain for a given amount of time, but not permanent
Magnetic field passes through the scalp and affects neural processing
Electrical current sent through coil generates field
Depending on timing, frequency, intensity, and angle of stimulation, TMS can be used to:
Decrease cortical excitability
Way to create a temporary “lesion” in particular brain area
Increase cortical excitability
Way to temporarily enhance function of a particular brain area
TMS is similar to neuropsychology research in that:
Brain area is affected and behavior is observed
Performance impaired of improved by stimulation
Control conditions are critical
Include no TMS and other brain areas
Create double dissociation
Can only affect areas on the surface on the brain.
Topographic map
Electrical stimulation of cortex during brain surgery
Patient is awake and conscious
Can report experience
Wernicke’s area
speech comprehension (found this through studying damage to the area)
White matter
White matter volume decreases by age (increases until early 20’s, then begins slowly decreasing)
composed of millions of bundles of axons (nerve fibers) that connect neurons in different brain regions into functional circuits
plasticity- ‘gaining a limb’
‘gaining a limb’
Examined finger representations in somatosensory cortex.
How? By stimulating fingers and recording brain activity using MEG (a way to measure brain activity)
They do this in control participants (people who have typical 5 fingered hands)
Experimental participants were people with syndactyly - fingers that have not separated into 5 distinct fingers
Something common in patients with syndactyly is to do a surgery to give people more finger mobility- improves dexterity
So, in this study, they are looking at syndactyly participants before and after surgery is done
Results:
In the brain, the areas for each finger are in the same order as the fingers themselves. There is a tiny chunk of brain dedicated to each specific finger (they are very distinct and do not overlap
For syndactyly participants before surgery, the area of the brain overlap and is not distinct for each area.
After surgery, they get physical therapy and within a week, each finger has a specific area in the brain representing it without overlap
This is a great example of plasticity in the brain. The brain reorganized very fast in order to accommodate for new fingers.
Plasticity example losing a limb-
Losing a limb
Often when someone losing a limb, they have a ‘phantom limb’ in which they can feel pain associated with a limb that is not there anymore.
The brain doesn’t know that the limb is gone, it just isn’t getting any feedback from it. The brain is extremely slow (years) to let go of that representation of that arm and sometimes it will never let go of it.
On the other hand, with gaining a limb, there is a lot of new information and the brain has to reorganize to accommodate it.
Sometimes when you have lost a an arm, if someone touches your face, you feel it in the phantom arm/hand.
Why? The face and the arm/hand are near each other in the brain and when the arm does not get feedback, it becomes an empty part of the brain. So, the face area of the brain, takes over the arm area of the brain. In fact, this could even mean that the face has more sensitivity because now it has more area of the brain dedicated to it. (this is plasticity)
Mri slices
Different MRI slices
Horizontal
Bottom to top view
Coronal
Front to back view
Sagittal
Side to side view
name all the gyri
- superior frontal gyrus
- middle frontal gyrus
- inferior frontal gyrus
- superior temporal gyrus
- middle temporal gyrus
- inferior temporal gyrus
- precentral gyrus
- postcentral gyrus
name all the sulci
- central sulcus
- lateral sulcus
- longitudinal sulcus
- parietal occipital sulcus
what lobe is in the back
occipital
what lobe is in the front
frontal
what lobe is on the bottom
temporal
what lobe is on the top
parietal
corpus callosum
connects the two hemispheres
arcuate fasciculus
a bundle of axons that connects temporal, parietal, and frontal lobes. at each end is the brocas area/wernikes area
directions of the brain i need to know
lateral, medial, anterior, dorsal, ventral, posterior
lateral view
looking at the side of the brain
medial view
looking at a lateral view of the brain cut in half
anterior view
front of brain view
ventral view
bottom of the brain view
dorsal view
view from the top of the brain
posterior view
view from the back ofo the brain
