[4] Barres is also known for his pioneering activism for equal opportunity in science, often citing his experiences as both a male and female scientist.

In studying pathology reports, he noticed a correlation between neural degeneration and irregular patterns of glial cells in the brain and, intrigued, resigned his residency to pursue research in neuroscience at Harvard Medical School.

[14] His research involved study of mammalian glial cells of the central nervous system (CNS), including the exploration of their function and development.

[15][16][19] Some of his earliest works focussed on vertebrate nervous system development, including how and why many neurons fail to survive shortly after forming connections with their targets.

[20] Additionally, he studied processes such as the prerequisites for and consequences of axon myelination, and the interactions of various signaling molecules such as thyroid-hormone and retinoic acid within the formation of glial cells including oligodendrocytes.

[21][22] Early in his time at Stanford, Barres discovered the importance of glial cells in the formation, development, maturation, and regeneration of neurons.

[24] In the 2010s Barres's research focused on using techniques such as immunopanning, immunohistochemistry, tissue culturing, and patch clamping to: 1) understand the cell-to-cell interactions in the developmental regulation of nodes of Ranvier and myelin sheaths; 2) determine to what extent glial cells play a role in synapse formation and function of synapses; 3) identify the signals that promote retinal ganglia growth and survival, and how such knowledge of these signals could be regenerated post-trauma; 4) identify the functions and developmental mechanisms of gray matter astrocytes.

In these objectives, his lab discovered a number of novel glial signals for the induction of myelination, axonal sodium channel clustering, and synapse formation processes.

While he was presenting as female prior to transitioning, he was excluded at schools from science and mathematics courses he was interested in.

[28][29] After delivering his first seminar as a man, one scientist was overheard to comment, “Ben Barres gave a great seminar today, but his work is much better than his sister’s [believing work published under his deadname to be his sister's] work.”[30] In 2012, he recollected the events of his sex change:[31] When I decided to change sex 15 years ago I didn't have role models to point to.

The alternative choice I seriously contemplated at the time was suicide, as I could not go on as Barbara.Barres was critical of economist Lawrence Summers and others who have claimed that one reason there are fewer women than men in science and engineering professorships might be that fewer women than men had the very high levels of "intrinsic aptitude" that such jobs required.

[33] Barres died on December 27, 2017, some 20 months after being diagnosed with pancreatic cancer,[34] at his home in Palo Alto, California.

[38] He is a co-founder of Annexon Biosciences, Inc., a company making drugs to block neurodegeneration in Alzheimer's and other neurological diseases.