Problem 5 Measuring techniques Flashcards
Brain Lesions (What)
o The goal is to discover what functions are performed by different regions of the brain and then to understand how these functions are combined to accomplish particular behaviours
o is not easy to interpret because several brain regions work together for one behaviour
Brain Lesion (HOW)
o A part of the brain gets damaged and the animals behaviour is observed
o A wire goes to the area you want to lesion and then radio frequency produces heat which kills the brain cells around the tip of the wire
o Excitotoxic lesion: Excitatory amino acids which kills the neuron by stimulating them to death
o Injecting a local anaesthetic (temporary lesion)
o Stereotact defines the position for the damaging
Computed Tomography (CT) (What)
o Used for visualizing the brain and other internal structures of the living body
o Structural image
o High spatial resolution
Computed Tomography (CT) (How)
o On one side of the cylinder is an x-ray tube that projects an X-ray beam through the head to an x-ray detector mounted on the other side
o Rotate around the head and taking several X-ray photos while rotating
o Photos getting combined to get a 3D model
Positron Emission Tomography (PET) (What)
o Images of brain activity
o Identifying the distribution in the brain of molecules of interest
o Low spatial resolution
o Add a CT image for orientation
o Able to measure chemical interaction (Neurotransmitter)
Positron Emission Tomography (PET) (How)
o Radioactive fluorodeoxyglucose is injected in an artery in the neck which feeds the ipsilateral hemisphere
o This fluid is similar to glucose so active cells rapidly take it up
o Coloured map of radioactivity
Magnetic Resonance Imaging (MRI) (What)
o Three dimensional diagnosis (structural)
o High-resolution pictures
structural image
Magnetic Resonance Imaging (MRI) (How)
o A structural brain-imaging procedure in which high-resolution images are constructed from the measurement of radio-frequency waves that hydrogen atoms emit as they align with a powerful magnetic field
o Looking at the proton density that is inside the tunnel
o One magnet is rotating around you and a scanner (send receive coil) is around the measured part
Functional MRI (fMRI) (What)
o Produces images representing the increase in oxygen flow in the blood to active areas of the brain
Functional MRI (fMRI) (How)
o Blood contains more oxygen than the cells need so it accumulates in the active area
o Oxygenated blood has magnetic properties (haemoglobin) that influence the radio-frequency waves emitted by the hydrogen atoms in the MRI
o Seeing the part where the oxygenated blood gets deoxygenated so you can see where action happens
o BOLD signal (the blood-oxygen-level-dependent signal) the signal recorded by fMRI
Transcranial magnetic stimulation (TMS) (What)
o Effects of the disruption on cognition and behaviour are assessed o Causation (does not really proof causation)
Transcranial magnetic stimulation (TMS) (How)
o Turns off an area of human cortex by creating a magnetic field under a coil positioned next to the scull
o Creates an artificial refractory period (No AP)
Transcranial direct current stimulation (tDCS) (What)
o The electrical stimulation temporarily increases activity in part of the brain while the effects of the stimulation on cognition and behaviour are assessed
Transcranial direct current stimulation (tDCS) (How)
o is a technique that can be used to stimulate (“turn on”) an area of the cortex by applying an electrical current through two electrodes placed directly on the scalp (triggers AP)
Scalp Electroencephalography (EEG) (What)
o Measure of the gross electrical activity of the brain
o Some kind of EEG waves are associated with particular types of cerebral pathology
o High temporal resolution low spatial resolution (you can only measure on the outside)
o Measures directly the electrical activity
o Source localisation problem
