Overview of Main Brain Imaging Techniques: EEG, MEG, TMS, and fNIRS

The human brain weighs about 1.4 kg yet contains billions of neurons and trillions of synapses, making it the most complex machine; worldwide initiatives such as the U.S., EU, and Japan brain projects aim to map its activity for advances in medicine, cognition, AI, and industry.

Understanding the brain’s cognitive mechanisms is a key focus of brain‑science labs, providing scientific tools to improve education, talent development, and interventions for developmental disorders.

Main Brain Imaging Technologies

EEG: electroencephalography

MEG: magnetoencephalography

TMS: transcranial magnetic stimulation

ECoG: electrocorticography

LFP: local field potential

fNIRS: functional near‑infrared spectroscopy

PET: positron emission tomography

MRI/fMRI: magnetic resonance imaging

These techniques can be distinguished by their temporal and spatial resolution as well as by measurement nature (invasive, non‑invasive, magnetic stimulation, tracer‑based).

EEG (Electroencephalography)

First recorded by Hans Berger in 1929, EEG captures the tiny electrical currents generated by neuronal firing through electrodes on the scalp; it offers high temporal resolution, low cost, portability, and is widely used for monitoring sleep, anesthesia, cognition, and affective computing.

MEG (Magnetoencephalography)

MEG measures the magnetic fields produced by neuronal currents, providing high spatial resolution and minimal distortion by skull; when combined with MRI it enables precise source localization, though it is expensive, requires shielded rooms, and struggles to detect deep‑brain activity.

TMS (Transcranial Magnetic Stimulation)

TMS uses brief magnetic pulses to induce electric currents in cortical neurons, offering a painless, non‑invasive way to modulate brain activity; it serves both as a research tool and a therapeutic technique for psychiatric and neurological disorders.

fNIRS (Functional Near‑Infrared Spectroscopy)

fNIRS exploits the neurovascular coupling that links neuronal activity to changes in oxy‑ and deoxy‑hemoglobin; by emitting and detecting near‑infrared light, it measures cortical blood oxygenation with good temporal resolution, is silent and portable, but has limited spatial resolution.

Conclusion

The article recaps EEG, MEG, TMS, and fNIRS, highlighting each method’s advantages and drawbacks; wearable EEG devices are identified as the most promising for real‑world educational settings, and future articles will explore deeper imaging modalities such as PET and MRI.