Neuroscience of Memory: Neuroimaging and Case Studies Flashcards
But what can we use MRI for?
- Important for detecting and monitoring disease (ex:dementia)
- Important for understanding brain
plasticity - driving can change structure of the brain-taxi driver) - Important for demonstrating a “double dissociation,” namely
when two areas are functionally dissociated by two cognitive functions, with each being affected to a lesion to one area but not to the other.
double diassosiation example
- u loose episodic memomory but have no problem with sematic memory
- another patient lost sematic memory but not episodic
DTI
Can be used to image
the white matter
you cant see this in MRI
Different diseases can affect white matter
- traumatic brain deasse
- Lyme deasses
Functional MRI (fMRI) Explained
we mesure changes on blood flow (no brain activity) to understand brain activity-
When neuronal activity increases, there is an increase in oxygenated
haemoglobin but not all of it is absorbed by the neurons
Critically, this increase changes magnetic properties (which can be measured), hence the term blood oxygenation level dependent (BOLD) imaging
Oxygen gets delivered to neurons by
haemoglobin
we measure oxygenation
Functional MRI (fMRI) Explained
- person lays down
- the machine starts
- ask questions or tasks and observe brain activity (oxygen increse in the parts of the brain that are being used )
Functional MRI (fMRI) Explained
- Neurons start firing within less than 1 sec (e.g., every 3 ms!)
- fMRI response ~5 sec
later! - the fmri responses have some delays
- so if u need quick response capture it wont be the rich choice
pros of FMRI
- Good spatial resolution
- Safe
cons
- Indirect (not measuring neural
activity) - Poor temporal resolution (the precision of time intervals in a system or measurement is slower)
- Need to stay still!(hard to scan babies)
fMRI Analytic Approaches
- Examine local activation “blobology”
How active is an entire region in a given state? - Examine “functional connectivity”
How connected are regions in a given state? - Examine “voxel-based patterns”
What is the pattern of activation in a given state? - so we can compare to other reagions
Functional connectivity
Functional connectivity is determined by the amount of correlated neural activity in two brain areas
- extraxct signal across that 10 min(that i want to observe), in one part of the brian the activity of the brain will go up and down. later i observe if another region of the brain have the same up and downess - activity and if yes they are funciotionally connected
example of fMRI Use for Learning and Memory?
- ask to think about their past
- ask about the future
- we compared both
- . result: they have simmilarlies in brain activity
- ameniasia patients had a hard time imagening the past but also the future
another example of fMRI Use for Learning and Memory?
Example discovery: when remembering past events, individuals with “superior memory” showed increased activity in many different brain regions
○ prefrontal cortex, the hippocampus, and other regions
Brain Regions Active During Remembering
you can use fmri to understand individual difers
electroencephalography (EEG)
- is a method for measuring electrical activity in the brain.
- Here, electrodes are placed on the scalp.
- good with temporal and bad with signature (opposit of fmri)
Event-related potential (ERP):
● electroencephalograms (EEGs) from a single individual are averaged over many repetitions of an event
(i.e., repeated stimulus presentation)
● Compared with fMRI, EEG is a simple and inexpensive way to
monitor changes in brain activity
Cognitive neuroscience methods
non- human:
* neuroimaging
* lesion
Recording from Neurons
● Memory is affected not only by which neurons fire but also by how
often the neurons fire
● Neurophysiology: study of the activity and function of neurons
● Example: measure the firing patterns of individual neurons is single-
cell recording (using an implanted electrode to detect electrical activity (spiking) in a single cell (such as a neuron))
Recording from Single Neurons—
implant electros in amonkey and they do a task and is observed
Other Techniques: Changing Neural Activity
● Electromagnetic stimulation of neurons
○ Researchers can use microelectrodes to stimulate neural activity by delivering tiny amounts of electrical current into the brain
○ Used as early as the 1800s to show that neural activity in the motor cortex
produces motor behavior
Electromagnetic Stimulation of Neurons
● Electrical stimulation can lead to changes in cognition
○ Transcranial magnetic stimulation (TMS) changes activity in the cerebral cortex by generating strong magnetic pulses over the skull
- results are short -tem but repetedly can be long term
- can be used is therapeutic intervation for severe depression
How Researchers Change Brain Activity: Biochemical Control of Brain States
● Another method for manipulating neural activity is the use of drugs. These are chemical substances that alter the biochemical functioning
○ Drugs that affect the brain typically change neural activity by altering synaptic transmission
Drugs for Learning and Memory?
● Only few drugs have been developed to affect learning and memory
● More common are drugs that affect memory as a side effect (usually
negative)
