Methods of Brain Research

Imaging techniques allow for the creation of images of the brain and its activity and play a crucial role in brain research. Computed tomography (CT) uses X-rays to obtain detailed cross-sectional images and 3D reconstructions of the brain, but it does not provide information about the functional activity of the brain. Positron emission tomography (PET) uses a radiotracer (contrast agent) to visualize metabolic activity in the brain and create a three-dimensional image. Magnetic resonance imaging (MRI) uses the alignment of hydrogen nuclei along magnetic field lines to generate detailed images, while functional magnetic resonance imaging (fMRI) indirectly uses blood oxygen level dependent (BOLD) changes as a measure of blood flow changes in active brain areas. Electro- and magnetoencephalography (EEG/MEG) are non-invasive methods for measuring the electrical or magnetic activity of the brain and have extremely high temporal, but limited spatial resolution. While EEG is better suited for superficial areas (gyri), MEG can also capture activity in deeper regions (sulci and subcortical) well. Intracranial electroencephalography (iEEG) is an invasive method for measuring brain activity, where electrodes are placed directly on or in the brain to allow for high spatial and temporal resolution, and is often used in the localization of the source of epileptic activity.