FOUNDATIONS: METHODS AND IMAGING Flashcards
What is an MEG?
MEG measures the magnetic field generated by neurons and is better than EEG for looking at neural activity in brain and measures activity much faster than MRI.
What do researchers study on the mesoscale?
researchers see how smaller regions of the brain communicate along single axons at micrometre or submicrometre resolution. It is like adding in the lanes of highways and local streets.
What does mesoscale mean?
Complex cellular networks in brain regions
What do researhers study in the macroscale?
Detecting how bundles of axon fibres connect large regions together (brain regions and areas)
What do researchers study in the microscale?
Cells in complex cellular networks. Microscale images reveal individual neurons and synapses at resolutions of a few nanometres — akin to a map that shows even footpaths and stepping stones.
What is the nanoscale?
Receptor mosaics within a cell membrane.
What quantity of neurons does the mesoscale look at?
1000-1M neurons
What quantity of neurons does the microscale look at?
1-100s of neurons
What is studied in the microseconds?
Channel openings
What is studied in the milliseconds?
Action potentials
What is studied in the tens of milliseconds?
Perception, motor control, reaction times
What is studied in seconds and above?
Learning
What is studied in years?
Neurodevelopment; diseases such as alzheimers, MS, parkinsons
What is the difference between MRI and fMRI?
MRI is the energy emitted from the ‘spin’ of H atoms in a strong magnetic field.
- fMRI is when localised changes in brain activity are associated with changes in blood oxygenation. fMRI can detect magnetisation changes b/w oxygenated and deoxygenated haemoglobin.
In FMRI what does BOLD stand for?
Blood Oxygen Level Dependent
What is functional connectivity?
Correlation between spatially distinct brain
regions
What applications can we use functional connectivity in?
Looking at how people with schizophrenia are functionally different from siblings
What is an EEG?
Measures potential difference across the head (b/w pairs of electrodes)
- has much better temporal resolution than fMRI
- is done when someone is performing tasks
- inexpensive
- poor spacial resolution
What is temporal resolution?
The amount of time it takes to acquire multiple images one after another in imaging.
e.g. If the TR is 10ms and there are 5 views per segment, the temporal resolution would be 50ms.
What is spacial resolution?
The size of the voxels which is determined by the matrix size, field of view (FOV) and the slice thickness
What is the approximate resting membrane potential?
Approx -65mV
What are the electrodes made from in INTRAcellular recordings?
Saline filled micro pipettes (KCl, NaCl)
What are the electrodes made from in EXTRAcellular recordings ?
Insulated metal
What is Transcranial Magnetic Stimulation?
Induces a change in current flow in localised sections of the brain
What is intracellular microstimulation?
When current is injected into a single cell that changes the membrane potential (similar to a neurotransmitter being released)
What is CT?
Computerised tomography
- X RAY source rotated around the head in plane of ideal cross section
- computer uses relative radiopacity to make an algorithm
What did CT scans reveal?
Gross organisation of gray and white matter AND position of ventricles
What is DTI?
Diffusion Tensor Imaging
- Large visualisation of axons in the brain (connecting of different regions)
- The position of H atoms in H2O can be measure d in brain
What is the name for the imaging method that measures the diffusion of water in the brain over time?
DTI (Diffusion Tensor Imaging)
What can an MRI reveal and what type of signal does it involve?
Involves radio signals and can reveal lesions in brain (tumors and inflammation increase extracellular water)
What is a PET scan?
Positron Emission Tomography
- Looks at blood flow in the brain and metabolism ( like fMRI)
- Radioactive solution containing atoms that emit positrons (e+) is injected in bloodstream
- 19F9 is radio isotop used
In PET scans, how is the positron emission (flourine) used to detect tumors?
- It is attached to 2-deoxyglucose (2-DG- analogue of glucose) in bloodstream
- Migrates to brain
- Metabolically active neurons that use glucose normally take up 2-DG and phosphorylate it so it can’t get out of cell
- Amount of radioactive 2-DG and number of beta+ emissions accumulated in neuron indicate the level of metabolic activity hence tumor growth (high metabolic activity)
What is common (in a general sense) between PET and fMRI scans?
They BOTH look at blood flow in the brain and metabolic activity
What does intracellular recording involve?
Impaling the neuron or axon with microelectrode
- It measures the potential difference between the tip of the INTRACELLULAR ELECTRODE (filled with concentrated KCl solution) and another electrode connected to ground
What do extracellular electrodes contain and what is the purpose of them?
- Electrodes (fine glass capillary with salt solution or metal)are placed NEAR the membrane