Methods Flashcards
visible light transmission microscopy
- strucutre of the brain
- involves removal, fixation, dehydration, embedding, mictromy, and staining
stains include: nissl (cell bodies), myelin (axon bundles), and golgi (all parts of neuron) - fluorescence: using fluorescent material that is inserted into a tissue to highlight a particular strucutre
fluorescence microscopy
- using fluorescent material that is inserted into a tissue to highlight a particular structure
- can be very specific
- can get different colours to highlight different parts of the neurons
two-photon microscopy
- laser used to emit two photons at the same time
- photons that are emitted from the fluorophore are detected from a sensor
- photons converge at the same time on a single point in the tissue to excite the fluorophore
what are teh ways they deliver dye when the patient is still alive?
- neuron contaning fluorescent dye injected into by the dye delivery instrument
- neurons of a transgenic mouse that contain fluorescent proteins (changed in genetic phetoype so that the neurons already have fluorescent dyes in them)
define electron microscopy
transmission: transmitting the electron through the specimen, tissue can be stained with heavy metals
scanning: electron scans the surface of the tissue block and backscattered e;lectrons are recorded
computer axial tomography (CAT)
- x-ray source emits x-rays that pass through the head
- some can be absorbed depending on the density of the tissue
- x-rays that pass through are recorded to create and image
magnetic resonance imaging (MRI)
- large electromagnet consisting of a coil that conduct electricity
- smaller coils that are perpendicular to the large could will send and receive radio frequencies
- bore of the magnet, where it is the stronger, is where the person body part is placed to be imaged
- involves exciting a H2 atom (alliogning the H atom with the axis of the magnetic field)
- combinations of voxels will cover the entire brain to create a 3D image
diffusion tensor imaging (DTI)
- image of the axonal pathways
- tuning magnet to measure H20 movement
- unconstrained medium –> isotropic movement: water movement in random and all directions
- constrained medium –> anisotropic movement: water movement is biased in direction
lesions
- inactivating/disruption of a regoin of the nervous system to ascertain its function
what are the different technqiues of creating lesions?
permanent: aspiration (sucking out tissue), excitotoxic (chemcial overstimulate = cell death), heat (heated electrode to burn tissue), knife cut (how knife to remove regions)
reversible: chemical and cryogenic (cooling certain areas of the brain to slow down its activity)
stereotaxic surgery
- used on rodent
- aniamls were put in a machine to steady their brains to look at the atlas
- brain atlas: bregma, junction of coronal and sagittal sutures, used as a main landmark)
- localizing the exact area you wanna create the lesion in
- always need to have sham-control group to know if the lesion was the true cause of the behaviour change
define transcranial magnetic stimulation
- applying intense magnetic field to temporarily inactive neurons
-eletrical current flowing to create magnetic field to disrupt the neurons right under the skull
_ repeated TMS can be used for depression and hallucinations
how are single cell and multi-cell recording different?
single cell: electrode is place in head to hit a specific neuron and only that neurons activity will be recorded
multi-cell: same schema with using tiny electrodes but now looking at the ensemble firing in a certain section of the brain
define electroencephalogram (EEG)
- measures electrical activity from surface of the scalp
- good temporal resolution (timing of firing)
- poor spatial resolution (localizing)
- volume conduction: allows the electrical activity to be measures from electrode on the scalp
- electrical signal
define event-related potentials
- work with EEG
- averaging all the signals together from the event to get a proper wave, cancelling out all the noise
define magnetoencephalography (MEG)
- high temporal and bad spatial
- head is surrounded by SQUID device
- tiny magnets that are cooled down to help pick up the magnetic field with the associated brain region
- magnetic signal
define positron emission tomography (PET)
- patient is injected with radioactive substance that is used up by the brain
- brain will use up more of the substance in areas of where it is most active
- photo detectors surround the persons head
- proton from from the radioactive substance will convert into a positron –> positron collides with electron that cause two photons to travel in opposite directions –> phtons collide with detectors to determine location from the timing it took to hit the detector
- good spatial resolution
define functional magnetic resonance imaging (fMRI)
- localize brain activity (good spatial, bad temporal)
- use magnetic resonance imaging
- patient compete tasks in machine and regional cerebral blood flow is measured
- blood oxygenated level dependent signal is used to know how much activity the brain is producing
- most active area = uses most blood (slide 22 of lecture 10)
- stage image before –> image at stimulation - image at rest –> image with the amount of brain activity involved
define electrical brain stimulation (EBS)
- electrodes are implanted in brain with the tip at nucleus accumbens
- can self stimulate to reduce depression
define transcranial direct current stimulation (tDCS)
- anodal: moving from andoe to cathode to depolarize the neurons leading to excitation
- cathodal: moving from cathode to anode to hyperpolarize the neurosn leading to inhibition (basically creating a lesion)
define optogenetics
- ion channels that are open/closed from light
- genes for these channels can be inserted into the brain
- different light colours are put into the brain via optical fibre to influence the channels acitivty
