Cog Neuro Lec 3 - Design Experiments: Part 1

Different Brain imaging and equipment used to study structure and function of the brain

what is single-cell recordings for neurophysiology?

electrophysiological methods are used to identify the response characteristic of the cells in the visual cortex.

• basically sticking in an electrode system to see what individual neurons are responding to

• visual cortex example

what is lesion studies?

seeing the effects on an animals after damage to part of the brain

• parietal lobe → reaching behaviour

• good to know reaching and action behaviour but not for language

what is a limitation of single-cell recordings

very specific but we don’t see what else the brain is doing at the same time, higher level cognition

what is a limitation of legion studies?

we cannot see the effects of language in the brain through animals

cognitive neuroimaging

• used for identifying pathophysiology and localizing anatomical and/or function disruptions (medical)

• examining health/impaired brain topography (structure) and examining healthy/altered brain functioning (research)

what is computerized axial tomography (CT)?

pass radiation through the body and measuring how the body absorbs the radiation

• 3D image of the body

limitation of CT?

a lot of radiation

what is a structural magnetic resonance imaging (sMRI)

shows the structure of the body

why is this useful?

• when atoms are in solid like bone, they don’t go very far (low measure of resonance) but in fluid, they will go farther

• incredibly detailed and shows every single level of the brain in every single cut

What is the process of sMRIs?

Process:

• uses a really strong magnetic field to change the position of protons and put all the H atoms into alignment 

• once the atoms are aligned, we knock them out of alignment by releasing a pulse 

• the knocking out of alignment causes the atoms to release a signal/energy from excited energy state (called resonance

• come back into alignment and measure how far they get knocked out of alignment or how long it takes them to line back up

which one is clearer and more defined?

why would you not get an MRI

• ppl with braces bc it distorts the image

• back in the day knee screws or tattoos had iron that would be pulled by the magnet (no longer)

what is in volxel?

how brain space is quantified (volumetric pixels)

• measuring depth

what happens when someone has a brain injury and the brain matter dies?

it gets filled with CSF 

the bigger your hippocampus, the ____ your likelihood to get ptsd

lower (through correlation)

lesion overlap method

common impairment, common damage?

create a heat map and overlap all the brain images to see if there is an overlap in where the legion is and the damage is

• can show where multiple places may be impacted and find the common one to see the core cause

the brain is measured in ____

voxels

what is diffusion tensor imaging (DTI)

looking at the diffusion of water in the brain because water moves in the same way as axons

• therefore seeing the path that water readily moves in on direction vs another in the brain shows the path of axons

what can you use DTI for?

• seeing the effect of axons due to damage

• seeing how axons develop from childhood

why do they shake you up in the MRI scanner for DTI imaging?

to maximize diffusion

what is electroencephalography EEG

• measuring electrical signals on the head

• each electrode creates a recording channel

• more electrodes, more recording channels

what is the difference between temporal resolution and spatial resolution?

temporal: telling you exactly when things are happening (time)

spatial: knowing were the signals are coming from in space (space)

are EEGs better for temporal resolution or spatial resolution

temporal

what is the purpose of EEGs

to tell you exactly what is happening in your head at the exact time

what are event-related potentials (ERP) from EEG data

averaged set of EEG signals to infer mental processes associated with that activity

Crucial importance of many trials, trial averaging

eliminates noise in the brain/third variables

what is the N400 wave for? (EEG)

understands semantic mistakes in speech

what are one of the limitations of EEG

skull, spatial resolution

what is Electrocorticography (ECoG)?

EEG directly on the brain

what is Functional Magnetic Resonance Imaging (fMRI)?

• watching the blood flow in the brain to see brain activity (Neurovascular coupling)

• hemoglobin magnetic properties differ whether oxygenated or deoxygenated

what is the BOLD signal in fMRI?

Blood Oxygenation Level Dependent

• high BOLD signal: active

• low BOLD signal: inactive

• visualizing activators and deactivators

• activators: areas of the brain using the blood

• deactivators: areas of the brain not using the blood

does fMRI have better spatial or temporal resolution

spatial

why is not having good temporal resolution such a problem for fMRI?

you only get to see what area of the brain is using the blood after 6 seconds and only get to see what happens after 1 second of scanning

Subtraction Method

stimulus state - control state = activity due to stimulus

ex. to isolate colour, show image of house with colour, scan, and then again without colour and scan again. See which areas are involved in just colour

what’s a limit of studying lesions in the brain

often times the lesions are large therefore not specific to where it can be cause of certain loss of ability

What is Transcranial Magnetic Stimulation (TMS)

stimulating brain dysfunction

Does TMS have good spatial or temporal resolution

both

study this slide

what are the fundamentals of experimental design?

1. why is this process of interest

2. provide a clear conceptual definition (ie. what is working memory)

3. operational definition (ie. how working memory will be measured in my study)