“Know yourself” – since ancient Greek times, people have been trying to reveal the basic mechanisms underlying their own or others’ actions and thoughts. Human brain mapping research began from this motivation to understand the human itself through clarifying neurofunctional mechanisms. Unraveling the complex structures and functions of the brain requires diverse approaches spanning neuroscience, biology, medical science, psychology, engineering, physics, chemistry, mathematics and so on.
In the early 20th century, Brodmann classified the cerebral cortex into 52 areas based on the meticulous observation of their cellular and laminar structures, which leads to the current concept of functional localization theory. In the 1930s, a neurosurgeon, Wilder Penfield, created sensory and motor cortical maps (homunculus) through his human brain electrical stimulation experiments during epilepsy surgery. This mapping technique is still used to preserve critical brain functions during brain tumor surgery. In 1929, Berger and colleagues succeeded in recording electroencephalograms (EEG) using scalp electrodes, and later human functional brain mapping was performed with EEG findings. In the 1960s, moreover, magnetoencephalography (MEG) was developed, and it enabled us to make a more precise functional mapping.
In the 1970s and 1980s, non-invasive brain imaging technologies such as SPECT, PET, and MRI emerged. In particular, brain function mapping research using PET for cerebral blood flow assessment made remarkable progress, bringing innovation as a translational technology connecting brain research and medical care. In the 1980s, transcranial magnetic stimulation (TMS) was developed as a non-invasive brain stimulation method. TMS not only contributed to brain functional mapping and basic brain research but also showed therapeutic potential for mental and neurological disorders through cortical plasticity induction with repetitive stimulation. The 1990s brought the discovery of the blood-oxygen-level-dependent (BOLD) signal and the development of functional MRI (fMRI), enabling visualization of brain activity associated with specific cognitive tasks and sensory stimuli. Additionally, PET technology for detecting brain amyloid accumulation related to dementia pathology was developed, advancing dementia research.
Since 2010, large-scale collection of brain imaging, MEG, genetic, behavioral, and health data has been ongoing through projects such as the U.S. Human Connectome Project (HCP), UK Biobank, and Japan’s Brain/Minds Beyond project (Brain/MINDS Beyond). These large-scale population neuroscience studies are expected to elucidate brain changes across the lifespan, including development and aging, and contribute to understanding pathophysiology, early diagnosis, and novel treatment development for psychiatric disorders, developmental disorders, and neurodegenerative diseases. Other approaches including optical topography, brain decoding methods, low-intensity transcranial ultrasound stimulation (TUS) and animal model brain imaging studies contribute to bridging basic and applied neuroscience from various perspectives. Further technological innovations incorporating AI are promising.
Penfield left us with the universal challenge that “The problem of neurology is to understand man himself.” We aim to unveil human nature and advance the treatment of neurological disorders using the cutting-edge human brain mapping technologies.