Neurophilosophy

Film clip of a split brain patient


This film clip shows Michael Gazzaniga carrying out a behavioural study of a split brain patient named Joe.

The split brain procedure (or corpus callosumectomy) involves severing of the corpus callosum, the bundle of approximately 100 million nerve fibres that connect the two hemispheres of the brain.

The procedure was performed on patients with intractable epilepsy, the idea being that preventing the left and right hemispheres from communicating with each other would stop the abnormal electrical activity associated with epilepsy from spreading across the whole brain.

Split brain patients can lead normal lives but, as this film clip shows, they exhibit bizarre behaviours under experimental conditions as a result of their surgery.

Normally, the left hemisphere of the brain controls, and receives sensory inputs from, the right side of the body, and vice versa (this is known as contralateral control). Thus, visual information entering the left side of the left eye is sent to the right visual cortex, and information from the right side of the right retina is sent to the left visual cortex.

As demonstrated by Joe, information presented to his right visual field does not cross to the left hemisphere. Consequently, Joe cannot say the words presented to his right visual field.

This is because the speech centres are found in the left hemisphere (at least, this is the case for most right-handed people), and the visual information presented on the left side of the screen cannot cross to those parts of the brain involved in speech production. Joe can, however, use his right hand to draw a simple diagram of the object he is unable to name.

(Via Mind Hacks)

Comments

  1. #1 Zachary Tong
    September 17, 2007

    That must be a very surreal feeling for Joe – seeing one shape but drawing another with his left hand. I can’t even imagine what it would feel like. Almost like someone was guiding his hand while drawing, as he has no recollection of ever seeing the left image. Crazy :)

  2. #2 Breton
    September 17, 2007

    I talk about this type of research when I teach cognitive science classes, and I often get questions like #1. I think the better question is along the lines of “what does it feel like to be the left hemisphere of Joe’s brain?” Research like this begins to suggest that consciousness (what ever that means) isn’t a unitary thing in the mind. Thanks for the video link.

  3. #3 Jack Josephy
    September 17, 2007

    its incredible to see that phenomena in action. Its very similar to the blindsight phenomena which I have studied the philisophical and scientiifc implications for quite largely. In response to the first comment made; I don’t think it would really feel like anything. He wouldn’t have any experience as such of drawing the object (other than feeling the pen on the page). It really is a bizare phenomenon and no doubt one with huge implications

  4. #4 Dominique McJeffreys
    May 27, 2009

    You’ve said that:
    “As demonstrated by Joe, information presented to his right visual field does not cross to the left hemisphere. Consequently, Joe cannot say the words presented to his right visual field.”

    However it is information presnted to his left that causes an issue..

    “Joe can, however, use his right hand to draw a simple diagram of the object he is unable to name.”

    He uses his left hand to draw

    Not being a smart-a#$ but it just confused me when i read it

  5. #5 Eric
    May 31, 2010

    Fascinating video.

  6. #6 Rphillips
    November 8, 2010

    Good find! I’m a cognitive science student myself, and Breton, I was wondering if you ever get the question of what it feels like to be a RIGHT hemisphere!

    Too often muteness is confused with unconsciousness, but clearly that’s not the case. When Joe there was drawing the images, his right hemisphere was conscious of the instructions and how to respond to them appropriately, but was unable to speak (or write, I would imagine, given that the linguistic centers are (usually) in the left hemisphere).

    I imagine it must be frustrating for the right brain to be unable to communicate its thoughts/desires, and I wonder how this effects the rest of us, who do have intact corpus callosums (corpus callosi?).