Touching A Nerve: Transient Iatrogenic Sensory Deprivation

ChurchlandThere are many ways to touch a nerve, in the vernacular.  But this book by the godmother of neurophilosophy, Patricia Smith Churchland, speaks to the neural underpinnings of its subtitle: The Self as Brain.  Churchland is located at a nexus of neuroscience, where UCSD meets the Salk Institute in San Diego.  I was captivated when I read her first book on neurophilosophy in the mid ’80s, and even more so by her second book on The Computational Brain in the early ’90s, co-authored with fellow Salk Scientist, Terry Sejnowski.  Whereas Churchland moved heavily into Kantian notions of morals, ethics, and consciousness in terms of the mind as brain tissue, her collaborative work with Sejnowski centered on vision.  Churchland, Ramachandran, and Sejnowski authored a chapter entitled “A Critique of Pure Vision” in 1994 that Sejnowski cites in this recently uploaded video.

Patricia Churchland has enjoyed a long-standing professional collaboration with her husband, Paul Churchland, beautifully documented in a New Yorker Magazine article in 2007.  Paul authored a book in the mid ’90s that was a neurocomputational complement to Patricia’s work.  Taken together, they offer important insights on visual perception in terms of stereopsis and pattern recognition as well as insights into visual-vestibular interactions.  Mapping the brain, as the interdisciplinary group at UCSD/Salk continues to do, is something that will continue in earnest for the foreseeable future.  The U.S. intends to spend millions in supporting ongoing efforts at cortical cartography, and what started as a declaration of 2014 as the year of the brain in Europe in 2014 has now mushroomed into The Age of the Brain, a three year international campaign.

PatriciaWhat touches a nerve about Patrica Churchland’s latest book?  To capture the full flavor you’ll have to read it, but let me give you a snippet.  On page 76 she discusses Charles Bonnet Syndrome, a condition in which patients with visual impairment experience visual hallucinations as a form of perceptually filling-in.  What caught my eye was a parenthetical comment that a patient temporarily using an eye patch may in rare instances also experience hallucinations, but this experience ceases with removal of the  eye patch.  That brought to mind the infographic on amblyopia patching by Rebecca Sherry, together with the Wizard’s observation that de-construction and re-assembly can result in anomalies.


Sue Barry and I have been working on our joint presentation for the ICBO meeting in England in 2014, and Patricia Churchland’s comment rattled my brain.  I will now look at patching in a different way, one that I will call Transient Iatrogenic Sensory Deprivation.  Think about it from two perspectives:

1) The child with amblyopia who has adapted by using that eye as a more sensitive channel for peripheral vision is now lost in space by the patching-induced hemianopia.  While hallucinations might be rare, they are possible, as Churchland notes.  At the very least, it is a very scary proposition for a young child.  That is why, even in attempting to occlude one eye during testing, young children have a visceral reaction in opposition.

2) The patient with ABI who experiencing diplopia may be more disoriented by the cortical, perceptual filling-in of occlusion than she is by inattention to a second image that is constantly present.

All the more reason to limit passive dismantling of the binocular system by occlusion, and work instead toward active rehabilitation.  It takes more than a patch to re-wire a brain.


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