Research Methods Flashcards
ablation
removal of a brain area, generally with a surgical knife
lesion
dam- age, by means of a stereotaxic instrument,
stereotaxic instrument
a device for the precise placement of electrodes in the brain
sham lesion
performing all the same procedures except for passing the electrical current that would cause the lesion
Transcranial magnetic stimulation (TMS)
the application of magnetic stimulation to a portion of the scalp, can stimulate neurons in the area be- low the magnet, if the stimulation is sufficiently brief and mild
With stronger stimulation it inactivates the neurons, producing a “virtual lesion” that out- lasts the magnetic stimulation itself
optogenetics
sing light to control a limited population of neurons
- protein that responds to light by producing an electrical current
- develop viruses that insert one of these proteins into a certain type of neuron, or even to just one part of the neuron, such as the axon or the dendrites
- develop very thin optical fibers that can shine just the right amount of light onto neu- rons in a narrowly targeted brain area
then you can control the ex- citation or inhibition of one type of neuron in a small brain area with millisecond accuracy
electroencephalograph (EEG)
records electrical activity of the brain through electrodes— ranging from just a few to more than a hundred—attached to the scalp
evoked potentials or evoked responses
same device used for an EEG can also record brain activity in response to a stimulus
magnetoencephalograph (MEG)
in- stead of measuring electrical activity, it measures the faint magnetic fields generated by brain activity
identifies the approximate location of activity to within about a centimeter
Positron-emission tomography (PET)
provides a high- resolution image of activity in a living brain by recording the emission of radioactivity from injected chemicals
- person receives an injection of glucose or some other chemi- cal containing radioactive atom
- person’s head is surrounded by a set of gamma ray detectors
- areas with the most radioactivity are presumably the ones with the most active neurons
Only at research hospitals, coz expensive
functional magnetic resonance imaging (fMRI)
modified version of MRI based on hemo- globin (the blood protein that binds oxygen) instead of water
Hemoglobin with oxygen reacts to a magnetic field differently from hemoglobin without oxygen
When a brain area becomes more active, two relevant changes occur: First, blood vessels dilate to allow more blood flow to the area. Second, as the brain area uses oxygen, the percentage of hemoglobin with oxygen decreases. An fMRI scan responds to both of these processes
usually use a subtraction method taking out the resting state images
The most common form of fMRI is termed fMRI BOLD, where “BOLD” stands for “blood oxygen level-dependent.”
phrenology
Franz Gall
computerized axial tomography,
CT or CAT scan
physician injects a dye into the blood to increase contrast in the image, and then places the person’s head into a CT scanner
X-rays are passed through the head and recorded by detectors on the opposite side.
help detect tumors and other structural abnormalities
magnetic resonance imaging (MRI)
any atom with an odd- numbered atomic weight, such as hydrogen, has an axis of rotation. An MRI device applies a powerful magnetic field (about 25,000 times the magnetic field of the Earth) to align all the axes of rotation, and then tilts them with a brief ra- dio frequency field
When the radio frequency field is turned off, the atomic nuclei release electromagnetic energy as they relax and return to their original axis. By measuring that en- ergy, MRI devices form an image of the brain
the per- son must lie motionless in a confining, noisy apparatus
Methods of Study Summary
