bio psych - ch.3.3 research methods

What are the similarities and differences between MRI and fMRI?

Both methods measure the responses of brain chemicals to a magnetic field. MRI shows the anatomy of the brain. The fMRI method shows which brain areas are most active at the moment.

LO2: Examine the effects of stimulating a brain area. Ideally, if damaging some area impairs a behaviour, stimulating that area should enhance the behaviour.

• *Optogenetics* is method of implanting a receptor into a neuron and stimulating it with light, to investigate the functions of a particular type of neuron. --> Development of this method required three steps: 1) Discover or invent a protein that responds to light by producing an electrical current. 2) 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. 3) Develop very thin optical fibers that can shine just the right amount of light onto neurons in a narrowly targeted brain area.

LO4: Correlate brain anatomy with behaviour. Do people with some unusual behaviour also have unusual brains? If so, in what way?

• *Phrenology*: a process of attempting to relate skull anatomy to behaviour. --> Invented by Franz Gall. --> E.g. Gall assumed that certain traits like secretiveness corresponded an area beneath the skull. --> Invalid theory. • *Computerized axial tomography (CT or CAT scan)* is a method of visualizing a living brain by injecting a dye into the blood and placing a person's head into a CT scanner; x-rays are passed through the head and recorded by detectors on the opposite side. --> Helps detect tumours and other structural abnormalities. • *Magnetic resonance imaging (MRI)* method of imaging a living brain by using a magnetic field and a radio frequency field to make atoms with odd atomic weights all rotate in the same direction and then removing those fields and measuring the energy that the atoms release. --> Con: the person must lie motionless in a confining, noisy apparatus.

LO3: Record brain activity during behaviour. We might record changes in brain activity during fighting, sleeping, finding food, solving a problem, or any other behaviour.

• An *electroencephalograph (EEG)* is a device that records electrical activity of the brain through electrodes attached to the scalp. --> Useful for distinguishing between wakefulness and various stages of sleep. It can also help with the diagnosis of epilepsy. --> The same device used for an EEG can also record brain activity in response to a stimulus, in which case we call the results *evoked potentials or evoked responses*. • A *magnetoencephalograph (MEG)* measures the faint magnetic fields generated by brain activity. --> Like EEG, an MEG recording identifies the approximate location of activity. • *Positron-emission tomography (PET)* is a method of mapping activity in a living brain by recording the emission of radioactivity from injected chemicals. • *Functional magnetic resonance imaging (fMRI)* is a modified version of MRI that measures energies based on hemoglobin instead of water. It detects an increase in blood flow to a brain area immediately after an increase in brain activity, and it also detects a slightly slower increase in the percentage of hemoglobin lacking oxygen. --> Less expensive and less risky than PET scans. --> Researchers record brain activity while the subject is reading and during a comparison task and then subtract the brain activity during the comparison task to determine which areas are more active during reading. --> The best way to test our understanding of fMRI results is to see whether the inference we make from a recording matches what someone is actually doing or thinking.

LO1: Examine the effects of brain damage. After damage or temporary inactivation, what aspects of behaviour are impaired?

• Researchers often turn to producing carefully localized damage in laboratory animals. --> An *ablation* is the removal of a brain area, generally with a surgical knife. • Because surgical removal is difficult for tiny structures below the surface of the brain, researchers sometimes make a *lesion*, meaning damage, by means of a *stereotaxic instrument*, a device for the precise placement of electrodes in the brain. --> The researcher anesthetizes an animal, drills a small hole in the skull, inserts the electrode, lowers it to the target, and passes an electrical current just sufficient to damage that area. --> After the death of the animal, someone takes slices of its brain, applies stains, and verifies the actual location of the damage. --> The experimenter produces a sham lesion in a control group, performing all the same procedures except for passing the electrical current. Any behavioural difference between the two groups must result from the lesion and not the other procedures. • *Transcranial magnetic stimulation (TMS)*, the application of magnetic stimulation to a portion of the scalp, can stimulate neurons in the area below the magnet, if the stimulation is sufficiently brief and mild. With stronger stimulation it inactivates the neurons, producing a "virtual lesion" that outlasts the magnetic stimulation itself. --> This procedure enables researchers to study behaviour with some brain area active, then inactive, and then active again.