Electroencephalography (EEG) and Transcranial Magnetic Stimulation (TMS) are powerful neuroscientific tools used to study brain function, often in combination. EEG measures electrical activity in the brain, while TMS uses magnetic pulses to stimulate or inhibit brain activity.
Electroencephalography (EEG)
EEG is a non-invasive neurophysiological technique that measures electrical activity generated by the brain through electrodes placed on the scalp.
- How it works: Electrodes detect voltage fluctuations resulting from ionic current flows within the neurons of the brain. These fluctuations are amplified and recorded, providing a continuous representation of brain activity.
- What it measures: EEG primarily captures postsynaptic potentials of cortical neurons. Different frequency bands (e.g., alpha, beta, theta, delta) are associated with different brain states and activities.
- Uses:
- Diagnosing and monitoring neurological conditions such as epilepsy, sleep disorders, and brain tumors.
- Studying cognitive processes such as attention, memory, and language.
- Monitoring brain activity during surgery.
- Researching brain function in various populations, from infants to the elderly.
Transcranial Magnetic Stimulation (TMS)
TMS is a non-invasive brain stimulation technique that uses magnetic pulses to induce electrical currents in specific brain regions.
- How it works: A magnetic coil is held over the scalp, and brief pulses of magnetic energy are delivered. These pulses induce electrical currents that can either depolarize neurons (excite) or hyperpolarize neurons (inhibit), depending on the stimulation parameters.
- What it does: TMS can temporarily disrupt or enhance the activity of the targeted brain region. This allows researchers to investigate the causal role of that region in various cognitive and behavioral functions.
- Uses:
- Treating depression, obsessive-compulsive disorder (OCD), and other mental health conditions.
- Mapping brain function (e.g., motor cortex mapping before surgery).
- Investigating the role of specific brain regions in cognitive processes like decision-making, attention, and motor control.
- Rehabilitating motor and cognitive function after stroke or brain injury.
Combining EEG and TMS
The combination of TMS and EEG provides a powerful method for investigating brain function. By stimulating a specific brain region with TMS and simultaneously recording the resulting changes in electrical activity with EEG, researchers can gain insights into the neural circuits involved in various cognitive processes. TMS-EEG allows for the direct manipulation and observation of brain activity, making it a valuable tool for understanding the causal relationships between brain activity and behavior. It allows for the study of the impact of TMS stimulation on specific EEG measures such as event-related potentials (ERPs) and oscillations. As noted in the reference, TMS-EEG allows researchers to both manipulate brain activity and observe the consequences.
In summary, EEG measures brain electrical activity, while TMS modulates brain activity using magnetic pulses. Combined, they offer a powerful approach to studying brain function and treating neurological and psychiatric disorders.
