With all the different methods for studying the brain,how does one decide which one to use?

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--There are many different methods for studying the brain.The method one uses often is determined by factors such as the invasiveness of the procedure or the purpose of the study.For example,because it's noninvasive,researchers frequently use EEG in both animal and human experiments.The method has a high temporal resolution ("temporal" refers to time and "resolution" refers to sharpness of image),meaning it can detect very rapid changes in the overall electrical activity of the brain occurring in the range of milliseconds.Even though the EEG is an old method,researchers still use it to study brain activity in normal brains and in brains of individuals afflicted with schizophrenia,epilepsy,and other psychiatric and neurological disorders.But EEGs have a few disadvantages.Because they show averaged activity that reaches the surface of the scalp,they tell us little,if anything,about what's happening inside neurons.Furthermore,EEGs have low spatial resolution,meaning that they aren't especially good for determining where in the brain the action is occurring.
--Although electrical recording and stimulation provided the initial probes to map mind functions onto brain areas,a virtual explosion of brain research occurred with the advent of brain scans,or what we call neuroimaging.Researchers developed imaging methods to meet clinical and research needs unmet by other techniques.Each imaging method offered some advantage over previous methods.As a group,these imaging methods enable us to peer inside the brain or body.
--The CT scan shows much more detail than an individual X-ray.The MRI shows structural detail using a totally different principle.The MRI scanner measures the release of energy from water in biological tissues following exposure to a uniform magnetic field.MRI images are superior to CT scans for detecting soft tissues,such as those in the brain.A brain tumour shows up particularly well on an MRI image because a tumour consists of soft tissue.Neuroscientists interested in thinking and emotion typically don't use CT or MRI scans,except to localize brain damage.Instead,they typically use the functional imaging techniques.
--Positron emission tomography (PET)is a functional imaging technique,which means that it measures changes in the brain's activity levels.PET relies on the fact that neurons,like other cells in the body,increase their uptake of glucose when they're active.PET is an invasive tool that requires the injection of glucose-like molecules attached to radiotracers into the patient.Radiotracers are radioactive,but because they're short-lived,they do little or no harm.The scanner measures where in the brain the most glucose-like molecules are taken up,allowing neuroscientists to figure out which parts of the brain are most active during a psychological task.Clinicians use PET scans to see where brain activity increases when patients,such as those with Parkinson's disease,take a medication.Because PET is invasive,researchers later looked for functional imaging methods that wouldn't require injections of radiotracers.
--The discovery of the blood oxygenation level dependent (BOLD)response enabled the development of the functional MRI,known as fMRI.As neural activity picks up its pace,there's an increase in oxygenated blood in response to increased demand.Because fMRI measures the change in blood oxygen level,it's an indirect correlate of neural activity.Neuroscientists frequently use fMRI to image brain activity.The fMRI relies on magnetic fields,as does MRI.Whereas MRI has a high resolution,fMRI operates at a low resolution so that researchers can snap many scans in rapid succession.Individual fMRI images aren't very sharp,but the method shows changes in brain activity level over time because it creates a series of images.

With All the Different Methods for Studying the Brain,how Does