Due to these mistakes, Alexander temporarily lost his privileges at the hospital and was forced to pay a $3,500 fine to the Virginia Board of Medicine.
The book was a commercial success but also was the subject of scientific criticism in relation to misconceptions about neurology, such as conflating medically induced coma with brain death.
[1][12] In a statement responding to the criticism, Alexander maintained that his representation of the experience was truthful and that he believed in the message contained in his book.
[12] Proof of Heaven was also criticized by scientists, including Sam Harris who described Alexander's NDE account on his blog as "alarmingly unscientific", and that claims of experiencing visions while his cerebral cortex was shut down demonstrated a failure to acknowledge existing brain science with little evidence prove otherwise.
[14] In 2012 Alexander responded to critics in a second Newsweek article,[15] where he said that he vividly remembers having periods of hallucination and explains that there was a massive difference between them and his 'fully immersive' visions of the afterlife.
Alexander presented related lectures around the world in churches, hospitals, medical schools, and academic symposia, besides appearing on TV shows including Super Soul Sunday with Oprah Winfrey.
[16][17] Alexander has also expanded on his NDE in the Congress of Neurological Surgeons[18] and the peer-reviewed Journal of the Missouri State Medical Association.
Alexander framed his observations with quotations from spiritual teachers and paired them with the recent work of scientists with the aim of bridging religion and science.
[23] Alexander's third book, Living in a Mindful Universe: A Neurosurgeon's Journey into the Heart of Consciousness, was coauthored with Karen Newell, cofounder of Sacred Acoustics and published in 2017.