The notion of a grandmother cell is that there are specific neurons that represent a specific concept of object, such as your grandmother. Initially this concept was not generally accepted. The primary criticism was that too many cells would be needed to identify each individual face because each orientation, expression, and lighting on the face would be different. Moreover, the appearance of the face would change over time.
However, recent research summarized in a Scientific American Mind article1, not only resurrects the notion of the grandmother cell, but also relates it to the phenomenon of consciousness. This research involves placing electrodes in the brain to measure electrical activity. This procedure is so invasive that it is only justified for medical diagnosis and treatment. Neurons in the medial temporal lobe are the source of many epileptic seizures. This region includes the hippocampus and turns visual and other sensory percepts into memories. Although most neurons respond to categories of objects, a few of the neurons were much more discriminating. One hippocampal neuron responded only to photos of Jennifer Aniston, and not to pictures of other actresses. Moreover, the cell responded to seven different pictures of Jennifer Aniston. They also found cells that responded to images of Mother Theresa, to cute little animals, and to the Pythagorean theorem.
Further research, by a highly creative and painstaking research team, developed a technique for making concepts visible. They took a volunteer patient and recorded from a neuron that responded to images of the actor Josh Brolin (who was in her favorite movie) and to another neuron that fired in response to the scene of Marilyn Monroe standing on a subway grill. The patient looked at a monitor where these two images were superimposed. The activity of the two cells controlled the extent to which she saw Brolin or Monroe in the hybrid image. When the patient focused her thoughts on Brolin, the neuron associated with Brolin fired more strongly. Similarly when the patient focused her thoughts on Monroe, the neuron associated with Monroe fired more strongly. Feedback was arranged such that the more one cell fired relative to the other, the more visible that image became as the competing image faded. The image on the screen kept changing until only Brolin or only Monroe remained on the screen. The patient loved it and felt that she was controlling what she saw, which she was.
We know that we can control what we are thinking about and that corresponding neurons and neural circuits respond. But this is, as far as I know, the first demonstration of this phenomenon. By using and controlling the appropriate memory circuits we are able to build and maintain our minds.
1Koch, C. (2011). Being John Malkovich. Scientific American Mind, March/April, 18-19.
© Douglas Griffith and healthymemory.wordpress.com, 2011. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Douglas Griffith and healthymemory.wordpress.com with appropriate and specific direction to the original content.