Oliver Sacks Explains the Biology of Hallucinations: “We See with the Eyes, But with the Brain as Well”

We all under­stand that hal­lu­ci­na­tion involves see­ing things that aren’t real­ly there, but what are hal­lu­ci­na­tions them­selves? “They don’t seem to be of our cre­ation. They don’t seem to be under our con­trol. They seem to come from the out­side, and to mim­ic per­cep­tion.” Those words come from Oliv­er Sacks, who would know. We fea­tured a short clip of him dis­cussing what he learned from his per­son­al expe­ri­ence with LSD and amphet­a­mines back in 2012, when his book Hal­lu­ci­na­tions had just come out. He died almost exact­ly three years lat­er — and there­fore just under a year ago — leav­ing behind a body of work from which we all stand to gain much under­stand­ing of the work­ings of the brain, as illu­mi­nat­ed by both its nor­mal and abnor­mal states.

In this 2009 TED Talk on what hal­lu­ci­na­tions reveal about our minds, Sacks tells of his expe­ri­ences with one patient, elder­ly and blind, who kept “see­ing” visions of “peo­ple in East­ern dress, in drapes, walk­ing up and down stairs.” Anoth­er, with lim­it­ed eye­sight, ” said she saw a man in a striped shirt in a restau­rant. And he turned around. And then he divid­ed into six fig­ures in striped shirts, who start­ed walk­ing towards her. And then the six fig­ures came togeth­er again, like a con­certi­na.” Anoth­er, with a small tumor on the occip­i­tal cor­tex, “would see car­toons. These car­toons would be trans­par­ent and would cov­er half the visu­al field, like a screen. And espe­cial­ly she saw car­toons of Ker­mit the Frog.”

Sacks con­nects all this to some­thing called Charles Bon­net syn­drome, first described by the nat­u­ral­ist of that name in 1760. Bon­net’s grand­fa­ther, who’d had cataract surgery (and 18th-cen­tu­ry cataract surgery at that), said he saw things like hand­ker­chiefs and wheels float­ing in midair. These hal­lu­ci­na­tions work dif­fer­ent­ly than psy­chot­ic ones, which “address you. They accuse you. They seduce you. They humil­i­ate you. They jeer at you.” But Charles Bon­net syn­drome pro­duces an expe­ri­ence more like watch­ing a film — a term Sacks’ patients could use to describe it, though obvi­ous­ly nobody could have in Bon­net’s day.

Bon­net, Sacks con­cludes, “won­dered how, think­ing about these hal­lu­ci­na­tions, as he put it, the the­ater of the mind could be gen­er­at­ed by the machin­ery of the brain. Now, 250 years lat­er, I think we’re begin­ning to glimpse how this is done.” Thanks to Sacks’ inspi­ra­tion of suc­ceed­ing gen­er­a­tions of neu­ro­sci­en­tif­ic researchers, that glimpse of how we “see with the eyes, but with the brain as well” will only widen.

Relat­ed Con­tent:

Oliv­er Sacks’ Last Tweet Shows Beethoven’s “Ode to Joy” Mov­ing­ly Flash­mobbed in Spain

This is What Oliv­er Sacks Learned on LSD and Amphet­a­mines

Oliv­er Sacks Con­tem­plates Mor­tal­i­ty (and His Ter­mi­nal Can­cer Diag­no­sis) in a Thought­ful, Poignant Let­ter

Based in Seoul, Col­in Mar­shall writes and broad­casts on cities and cul­ture. He’s at work on a book about Los Ange­les, A Los Ange­les Primer, the video series The City in Cin­e­ma, the crowd­fund­ed jour­nal­ism project Where Is the City of the Future?, and the Los Ange­les Review of Books’ Korea Blog. Fol­low him on Twit­ter at @colinmarshall or on Face­book.

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