Scientists at the Sudha Gopalakrishnan Brain Centre at the Indian Institute of Technology, Madras, have produced what they describe as the world's most detailed three-dimensional atlas of the human brainstem at cellular resolution. This digital map, combining more than 500 tissue sections from foetal, childhood, and adult brains, has been made freely available online, offering a universal resource for neuroscientists, neurologists, and neurosurgeons worldwide. Shubha Tole, an Indian neuroscientist at the Tata Institute of Fundamental Research, noted this project 'puts India at the international table,' highlighting the global nature of scientific advancement.
Built from high-resolution microscope images rather than costlier molecular techniques, the project, called Anchor, creates a detailed three-dimensional map of the brainstem. It identifies more than 200 clusters of brain cells and nerve pathways. Eight chemical markers help distinguish different cell types within this complex structure.
The brainstem occupies only a sliver of the brain, yet it keeps people alive by linking the brain to the spinal cord. It controls essential functions like breathing, heartbeat, sleep, wakefulness, and movement. The atlas links two worlds that have largely remained separate: medical imaging, which shows the brain as a whole, and cellular pathology, which reveals it one cell at a time.
A Global Endeavor
Rebecca Folkerth, affiliated with Harvard Medical School and New York University, collaborated with the SGBC team. She stated, 'As a neuropathologist, I begin by examining an entire brain with the naked eye before looking at small pieces under the microscope.' Folkerth added that for Alzheimer's disease, they may examine only 15 to 20 sections, a mere fraction of a percent of the whole organ. She also said, 'What the Indian centre has created is essentially what I dreamed of early in my career - to have brain scans match the brain's microscopic anatomy.'
The atlas lets users zoom from the whole brainstem seen on MRI down to individual neurons while maintaining their precise spatial relationships. Its applications could extend beyond anatomy to Parkinson's disease, stroke, Alzheimer's disease, and sudden infant death syndrome, or SIDS. Partha Mitra, a brain scientist at the New York-based Cold Spring Harbor Laboratory who has worked with SGBC, said detailed brain atlases like this could have a 'transformative impact' on the study of neurological disease by revealing, cell by cell, how brains affected by conditions such as Alzheimer's or autism differ from healthy ones. He also said they could help explain how infections, including Covid-19, trigger long-term neurological damage.
Using brain stroke as an example, Folkerth said the atlas has uncovered new features that could help doctors preserve brain tissue that is injured but not yet beyond repair, potentially improving patient outcomes. Other scientists say the atlas could also help neurosurgeons navigate the brainstem more safely.
Charting the Human Condition
Around 20 scientists spent 18 months at SGBC manually analysing more than 200 brain sections, combining MRI scans, microscopic anatomy, and 3D reconstruction into a single digital atlas. The centre now brings together more than 200 researchers, engineers, and technicians working with collaborators around the world. Mohanasankar Sivaprakasam, who heads the SGBC, said scientists have mapped the brains of several animal species in remarkable detail, but the human brain remains comparatively under-charted because detailed studies of human brain tissue are scarce.
Mitra said MRI-based atlases capture the brain's broad structure but not individual cells, while histological atlases map its architecture at cellular resolution using microscopic images of tissue slices. He noted that newer molecular approaches go a step further by identifying the precise identity of each cell. Scientists still know remarkably little about how the brain's roughly 20,000 proteins are distributed across different regions and cell types, calling that a frontier likely to define the next generation of brain mapping. Folkerth said, 'Every brain,' is 'a treasure chest of new knowledge.'
The SGBC now plans to image more than 100 whole human brains across different stages of life and neurological disorders, including Alzheimer's disease and dementia. This will create a reference library that could reveal how disease reshapes the brain cell-by-cell. The new atlas will not solve the mysteries of the human brain, but by giving scientists a far more detailed map, it may help them ask - and eventually answer - better questions.