Cajal's Challenge
Dan Lewis Foundation | Spring 2024

Overcoming the Barriers in Making New Neurons in the Adult Brain: Lessons from Nature


Almost 100 years ago, the father of modern neuroscience Santiago Ramón y Cajal, a Spanish physician, recognized that the injured brain could not repair or regrow damaged neurons. Cajal stated, “In adult centers the nerve paths are something fixed, ended, immutable. Everything may die, nothing may be regenerated. It is key for the science of the future to change, if possible, this decree.”¹ Cajal recognized that for individuals with devastating brain diseases or brain injuries, there was little that could be done to repair or regenerate neurons. He proposed that it was up to future scientists to solve the problem of regeneration. There lies Cajal’s Challenge. 


The Federation of European Neuroscience Societies (FENS) will meet in Vienna from June 25th to 29th, covering all areas of neuroscience from basic to translational. On June 24th, a one-day pre-FENS workshop will be held with 100 young researchers. This one-day meeting, started in 2021, is designed to create a strong and interactive community among young researchers in the fields of neurogenesis and glia to neuron conversion in Europe, the U.S., and beyond. Our vision is to promote the free exchange of ideas and results among the research groups working in this area. Neurogenesis and Glia-to-Neuron conversion is one of the most exciting research fields of our times.

Cajal’s Challenge Speakers:

Alejandro Schinder, PhD

Benedict Berninger, PhD

Don Cleveland, PhD

Enric Llorens, PhD 

Elly Tanaka, PhD

Magdalena Gotz, PhD

Noelia Urban, PhD

Sumru Bayin, PhD

Sofia Grade, PhD

Sven Falk, PhD

For more information and free registration: 

https://roymaimonel.wixsite.com/cajalschalange


1. Ramón y Cajal S.

Degeneration and Regeneration of the Nervous System.

Haffner Publishing Company, New York, NY1926


Two women embrace, comforted. A man watches from a separate chair. Interior, daytime.

What Does “Ambiguous Loss” Mean?

By Hal Lewis • December 5, 2025
My daughter, currently nearing completion of a graduate program in counselling, recently introduced me to the term “ambiguous loss”. This term applies to a loss that is unclear and lacks certainty, leaving family members and close friends feeling stuck because it is so difficult to mourn or find closure. One type of ambiguous loss is when the person is physically present but psychologically absent because their personality, memory, cognition, or emotional connection has been altered. Examples might include a family member with dementia, a progressive disease, a severe emotional disorder, or substantial brain injury. A second type of ambiguous loss is when the person is psychologically present but physically absent. This could include a missing person due to a natural disaster, a long- term incarceration, a kidnapping, or severe estrangement from the family. This type of loss can lead to intense confusion, frozen grief, and a prolonged sense of helplessness.
Marchell smiling, sitting on a couch, holding notebooks

Marchell’s Story

By Dan Lewis Foundation • December 2, 2025
Marchell is an engaging and energetic middle-aged man who was enthusiastic about being interviewed for the DLF newsletter. He is an activist working to promote the rights and well-being of persons in the brain injury community, with a particular emphasis on helping persons with brain injury who are incarcerated or have been released from prison. Marchell is a successful businessman, proud of the company he co-founded--the Association of Young Business Owners (AYBOS), a marketing company in the Denver, Colorado area. He also works for Well Power (Denver’s Mental Health Center system) as a Zero Suicide Certified Peer and Family Specialist.  Marchell is clearly a man on the move to get a lot of positive things done. But this wasn’t always the case. Marchell spent much of his younger adult life incarcerated himself for a variety of crimes including robbery and assault. He had a history of recidivism following multiple releases.