Neurons send information from one place to another.  One neuron gets information and then it sends it off to another.  Then that neuron may send it even farther along.

    Now that you know how neurons can talk to each other through synapses, and how this synaptic information is turned back into electrical information that the postsynaptic neuron can carry along, all at the cellular level, it is time for you to think along larger lines.  Like, why should one neuron pass on information to the next?  How many neurons give information to how many other neurons?

    Let's consider a sensory neuron that picks up information about touch on your skin.  Its dendrites receive information about touch, and send that information in to the CNS.  What should the CNS do with this information?  What could it be used for?  Here are some ideas:

    Consider all those possible uses of this touch information.  In order for our brains to be able to answer all those questions, the information about the touch from this sensory neuron is going to have to interact with many other neurons, and send the information to many places in our brain.  For example, in order to understand what kind of touch it was, the sensory information needs to be sent to a place in your CNS where it can be compared with other sensory information from your skin-- the deep pressure sensors (Pacinian corpuscles), pain, and temperature-- to know if it was a light touch or a painful touch.  And to know what it was that touched you, the sensory information about touch has to go to the place in your CNS where sensory information comes from your eyes that see the world around you, so we can compare the touch with the items around you.

    Because this sensory information has to go to many places, we can talk about divergence of sensory information.  Divergence just means that one bit of information goes to many places.

    I tried to illustrate this in the figure to your right.  The information from neuron A is sent to many neurons down the line.  Physically, at the cellular level, each neuron sends axonal terminals to multiple neurons.  So neuron A branches to synapse on neurons B through F.  Etc.

    In this manner, one bit of information can get shared at many levels and regions of the nervous system.

    Another concept in information processing is the exact opposite of divergence.  When information from many things all come together to interact on one neuron, convergence has occurred.  When might this happen?  Let's say you are trying to figure out what some particular object in your world is.  You might use your vision, sense of smell, sense of touch, etc., all to finally figure out what that one thing is so that you can say "apple."  All of your senses converged in your brain onto the region that is responsible for putting a name on the object.

    This idea of convergence is illustrated in this figure to the left.   Neuron Z is the final recipient of all the information coming from neurons Q through Y.

Divergence and Convergence happen simultaneously

    Both of these things, divergence and convergence, are happening at the same time.  While some neurons are sending their information out divergently, they are also receiving it convergently.  In this manner, the nervous system can take everything into account, and properly process information.

© 2006 STCC Foundation Press
written by Dawn A. Tamarkin, Ph.D.