Chapter 9. Dissociation and Neuroscience (2) the Mechanism of Switching (4)

This diagram shows where switching might occur in the model of dissociation defined by DSM or ICD, but nothing more. There could be some hint about each module’s localization in the brain. Conscious awareness can be located somewhere around prefrontal area or anterior cingulate, while module for the emotion might be located in amygdala and that for body movement in the motor or premotor area, etc. (Okano, 2007, 2009), but they remain largely speculative. What we do not know is how connections among modules in these locations are connected and disconnected. What I would like to do is to move a step forward in understanding or at least speculating the mechanism of switching.
Okano, K (2009 How does dissociation occur? Psychotherapy 35:144-149.[Japanese]
Switching and Necker cube


Necker cube


We could find examples of switching from one state to the next in our ordinary mental activities. One of them is so-called Necker cube. This figure often appears often in the textbook of psychology.
Necker cube by definition is a perspective drawing of the outline of a cube that can induce two perceptions, either a three-dimensional cube orientated upward or a three-dimensional cube orientated downward. The point is that two perceptions do not occur at once. This is an example of so-called “multi-stable perception” where two brain state excluding each other, and it is also called “monocular rivalry”.
If you try it yourself, you might realize that during the time that you take a way of looking at the image, the other way does not occur. The switch from one to the next occurs instantly, with a sensation “now, it switched”. Dissociative switching is quite similar to this “multi-stable perception”, in which different set of neurons forming modules are activated alternately. The fact that two images are never seen simultaneously means that two modules do not activate together, but how ? Perhaps there could be some mechanism to avoid it to happen.

Amit, DJ 1992. Modified by the author

Amit, D.J. (1992)Modeling Brain Function: The World of Attractor Neural Networks. CambridgeUniversity Press, 1992.

I can think of some possible models for this mechanism. One is where the activation of modules acts as an attractor. Neural network consisting module A, for example, has such a low impedance that it gets easily activated and forms a powerful attractor. It would stay until module B gets activated instead. I show a diagram which gives the readers some idea about this model (Figure ##). In this diagram, the “height” of the landscape means the impedance, and points A, B, C, and D are locations of these modules. In this diagram, switching means going beyond the hills in the landscape.
Another possible model is that the excitation of a module inhibits another module. An example is the mechanism of reciprocal inhibition in skeletal muscles. If you turn your palm back and forth quickly, pronator (inward roll) muscle and supinator (outward roll) muscle in your forearm are suppressing each other when activated, so that the movement is performed smoothly.
These two models might be among many neuronal mechanisms which enable dissociative switching to occur, but the detail is largely unknown at this stage.