These non-invasive methods of “seeing” the brain in action may be used individually or combined with one or more others on the list. See how Baycrest scientists are using these technologies in their research.

Electroencephalograpy (EEG) is the oldest brain imaging technology. Multiple electrodes applied to the person’s scalp measure the dynamic pattern of electrical fields in the brain.  Researchers In cognitive neuroscience use EEG technology to study event-related potentials (ERPs)—brain measurements that are associated with a response to a stimulus (i.e., a specific sound, task or thought).

Structural magnetic resonance imaging (MRI) gives doctors and scientists highly refined images of the body's interior without surgery. The technique uses strong magnets and pulses of radio waves to manipulate the natural magnetic properties of hydrogen, primarily in water in the body, creating useful images of organs and soft tissues. MRI is one of the few imaging tools that can “see through” bone (the skull) and deliver high quality pictures of the brain's delicate soft tissue structures. MRI may also provide valuable information when used on people with cognitive or psychological symptoms.

Functional magnetic resonance imaging (fMRI) takes the value of the traditional, rather static structural MRI image to a whole new level. It allows scientists to measure the delivery of oxygen via the blood to various parts of the brain at a given time or over time. It is based on the knowledge that when a region of the brain is activated, there is increased blood flow in this area as well as increased use of oxygen. Functional MRI allows scientists to take a patient through a set of tasks or stimulus, (recalling an event, finger tapping, hearing music, seeing images, smelling a flower), and then see which parts of the brain are activated. By looking at these activation patterns, researchers hope to understand the specific functions of different parts of the brain.

Magnetoencephalography (MEG) This non-invasive technique is used to measure magnetic fields generated by small electrical currents in neurons of the brain. Patients or subjects wear a specialized helmet containing liquid helium, which allows many measurements to be taken throughout the brain at the same time. MEG gives researchers direct information about various kinds of neural activity, along with the location of their sources in the brain.

Eye tracking  Researchers use eye tracking equipment and specialized software to monitor where a person looks, when, and for how long. The movement of the eyes is influenced by what researchers call “bottom-up” information in the image (i.e., the use of black vs. white contrast or specific colors present within a picture).  Eye movements are also influenced by “top-down” information such as task instructions, attention, and memory.  While this is not a brain imaging technology per se, eye tracking may be used with other methods to examine how people process visual information and to measure the quality of their cognitive processing.

Positron emission tomography (PET) ) is a technique that produces detailed images of certain processes in the body. The equipment detects gamma rays emitted indirectly by a “tracer” which has been injected into the person’s blood stream prior to scanning. Three-dimensional images of tracer concentration within the body are then constructed by computer analysis, often using a simultaneous computed tomography (CT) x-ray scan. PET is used by clinicians to diagnose diffuse brain diseases causing dementia. It’s also an important research tool that’s used to map normal human brain functionn.

Transcranial magnetic stimulation (TMS) is a non-invasive technique that uses a rapidly changing magnetic field to induce an electrical current in a localized region of the cerebral cortex.  This is achieved by applying a specialized coil against the person’s scalp just above the forehead. The electromagnet used in TMS creates electric currents that stimulate nerve cells in the region of the brain involved in mood control and depression. The technique allows researchers to study the functioning and interconnections of the human brain. A variant of TMS called repetitive transcranial magnetic stimulation (rTMS) has been tested as a treatment tool for various neurological and psychiatric disorders including migraines, depression and movement disorders.