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PSY260H1 Lecture Notes - White Matter, Frontal Lobe, Phineas Gage

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Daniela Polombo

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-most direct way is to measure brain is electrical activity; electrical activity when neurons
are firing action potentials (different concentrations of ions are changing)
-haemodynamic don’t measure electrical activity directly, measures changes in blood flow
and oxygenation of blood flow
Eye movement monitoring:
- can measure cognitive processes as they occur
- non invasive, shines IR light in eye and measure reflectiveness
- can see where people are looking, how long they are looking (duration of fixation),
can look at number of transitions between regions, look at pupil diameter
- the way you view familiar places is different from the way you view no familiar faces
- when familiar with the face you look more at the eyes
- young people who have intact memories become more efficient in viewing faces
- Example: study visiospatial memories; look at cognitive processes when learning
memories, and matching. Healthy people will make eye movements back to the
location of object 1 when they see object 2, older adults don’t do that
- trying to teach older adults this method to see if it can improve memory
Lecturer’s Study
- correlation; people who looked back at locations that were studied did better and
were more likely to get the trial correct
- use eye movements to encode memory
- CT provides info of grey matter but it’s low resolution, cheaper
- MRI gives a finer, spatial resolution
- look at tracks of activity between brain regions
MRI and Memory
- in the 87 year old has larger ventricles
- less grey and white matter in the old brain (more holes)
- hippocampus is hit and the frontal lobe
- voxel-based morphometry: quantitative metric used to measure differences in
grey and white matter in the brain, automated method for understanding changes in
the brain
- takes an average brain and morph each individual subject’s brain into the template
to make comparisons across different people and group
- MRI is very expensive
Phineas Gage
- everything in the brain is connected, will damage white matter track therefore will
affect all the other systems it communicates with after getting a head injury
- allows scientists to track metabolism in the brain
- takes a long time to take a full photo (good for resting brain)
- expensive
- Example: put people in the PET scanner and measured glucose metabolism and
measured working memory (part of short-term, remembering someone’s phone
number for a few seconds to put into your phone)
- working memory engages the frontal lobes
Magnetoencephalography (MEG)
- two components of axon potential
- as electrical current flows in the brain, have a magnetic field that flows around it
and MEG can measure with
- if neurons are firing more together (can happen cyclically)
- when it happens cyclically it causes changes in brain oscillation, some are slower
and some are faster
- slower and faster ones are associated with different phases of sleep and cognition
- Example: scan individuals in MEG machine (same as the eye movement task) and
analyzed how much the brain is expressing the oscillatory patterns, interested in the
theta frequency oscillation, tried to see if there was an increase in theta as they look
at more objects
- difficult to study things with high temporal precision
- can measure really small areas
- want to know where in the brain something occurs use fMRI