Picture what life would be like if you couldn't picture things. Say someone puts a lump of clay in front of you and wants you to sculpt whatever you want, but you can't construct an image in your mind of what you want to make so you can't sculpt.

Or maybe your reading Harry Potter and the Sorcerer's Stone for the very first time but all the descriptive scenes are lost on you - that first portrayal of Hogwarts, the skin or the troll or the look of the Quidditch pitch - you can't picture what the words are describing.

Or maybe your significant other calls you and you realize you don't know what they look like.

All of these things are symptoms of a neurological condition that has recently been described for the very first time and is now undergoing it's first major study. It's called aphantasia, the inability to visualize things in your imagination.

It's almost the opposite of pareidolia - a phenomenon we talked about a couple weeks ago. Pareidolia is just a trick that the mind plays on most of us when we see things that aren't there, like a face in a pancake or a tiny woman on Mars.

But aphantasia is like the reverse where a patient lacks the so-called 'mind's eye'. Accounts of the condition go back more than a hundred years but it was only named and identified last month by Dr. Adam Zeman, a neurologist at the University of Exeter, after media coverage of one of his studies revealed that the phenomenon may be more common than anyone thought.

Recently, Zeman published a case study about a patient who awoke from heart surgery and found that he no longer had the ability to picture things in his mind. 

Discover magazine then profiled Zeman's work and soon he was contacted by nearly two dozen people who said they had the same symptoms as the heart patient. But most of them didn't know that there was anything different about them until they read about his research.

One subject, a 25 year old man from Ontario was not only unable to picture things in his mind, he can't conjure up smells or sounds or tastes or any other sensations without experiencing them directly.

Another patient, a physician in Wales, has no visual memory and can't remember what objects or people look like until she sees them again.

Now this is where I'd normally talk about what causes aphantasia but of course we don't know because it was just identified a month ago.

The process of visualization is very complex because it involves most of the major areas of the brain so it's hard to pin down where a syndrome like this might start.

The act of seeing is processes by the Occipital lobe at the back of your head for example but whether or not you perceive, recognize or remember what you see depends on a number of other parts including the Parietal and Temperol lobes.

Now that Zeman has enough subjects to study he'll be analyzing their sensory skills, their histories and even their dreams at night to see how their brains can tell them about people, places and things without being able to imagine them.

And this research is especially timely because we recently lost one of the most famous figures in neurology and the study of perception.

Dr. Oliver Sacks died on August 30th of cancer and we didn't want this week to pass without acknowledging what he taught us about the science of the mind.

For forty years Sacks was a professor of neurology and psychiatry at the Albert Einstein College of Medicine in New York and spent the rest of his career at Columbia University.

But unlike most other scientist we tell you about here, Sacks didn't do much laboratory research. He was kicked out of the first lab he worked in in the 1960s because he kept losing samples and breaking equipment.

So instead he began seeing patient and there he discovered the type of research that would frame his career: the case study. 

He's remembered for writing books about people with rare and seemingly bizarre condition like "The Man Who Mistook His Wife for a Hat", a book about a brilliant concert pianist who couldn't recognize faces, including that of his own wife.

But more often he wrote about conditions as common place as migraines and colorblindness. He wrote about how people who can't hear experience the world in their own way and what life is like for a man who was born blind and suddenly becomes able to see.

And Sacks's investigations into conditions like Tourette's and Asperger's syndromes that - at the time he wrote about them - were practically unknown are now are now, thanks impart to his clear and sympathetic portrayal, better understood, better diagnosed and less stigmatized.

Essentially Oliver Sacks did to the human brain what Carl Sagan did for space, he clarified misconceptions, dispelled fears and inspired wonder in all of us and we will miss him.

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