• Robb G. Best

The "How" of Thinking

On a nuts-and-bolts level, what's happening in your brain when you think? This is one of the hottest topics in neuroscience. Understanding it is considered the mother lode for many brain researchers. Although we have yet to completely unlock the mystery, we have begun to get a glimpse into the brain's architecture.

The brain is composed of billions of neurons, which are essentially microscopic chemical connectors. Neurons operate similarly to the wiring in your home; they are switches that extend power to a whole host of electrical gadgetry.

When excited, neurons send messages back and forth by temporarily hooking up with each other across minute gaps known as synapses. Into these synapses, the neuron attempting to communicate (presynaptic neuron) sends a message to the receiving neuron (postsynaptic neuron) by releasing a chemical called a neurotransmitter. The receiver neuron bridges the gap using proteins known as receptors, and grabs up the neurotransmitter. Picture a runner in a relay race passing the baton to the next runner and you get the rough idea.

There are two kinds of baton passes in play. The first happens when the presynaptic neuron attempts to link up by requesting an audience with a postsynaptic neuron. We call this an excitatory synapse. It’s like when you call your friend to ask if they have time to chat.

Conversely, it might send a message to the postsynaptic neuron to stay silent. We call this an inhibitory synapse, and it's sort of like when you tell you friend to keep something on the down low and not share it with your other friends.

Messages can move across literally thousands of neurons at a time. The kind of neurons, and order of activation is critical to the message's delivery. For example, the simple act of flexing your big toe involves a myriad of sequenced neurons firing properly while other neural pathways governing your surrounding toes stay quiet. This amazing flexibility, enabling neurons to hook and unhook at precisely the right time and place, is known as plasticity.

In some cases, synapses remain active after their respective neurons fire and subsequently lay down a record of their activity. This is how our memories get built.

In his book Brain Bugs, Dean Buonomano, neurobiologist and psychologist, explains that the role of neurons as part of memory formation was discovered in the early 1970’s. “Tim Bliss and Terje Lomo observed long-lasting increase in strength at synapses in the hippocampus (a region known to contribute to the formation of new memories) after their pre- and postsynaptic neurons were strongly activated. This phenomenon, called long-term potentiation, was an example of a synaptic memory—those synapse, “remembered,” they had been strongly activated—changes in synaptic strength were at some level the brain’s version of burning information into a DVD.”

So not only do neurons allow for messages to be sent to other parts of the brain and body for activation of thought and control of organs and muscle, but they also store code in the form of memories.

But why do some neurons have the strength to store a memory, like all your lines from your fourth grade Christmas pageant, while other connections are temporary, like flexing your big toe? Canadian psychologist Donald Hebbs formulated a rule first addressing this back in 1949.

Buonomano writes that that the resulting Hebb rule “has come to be paraphrased as “neurons that fire together, wire together.”’ The idea is that neurons activating at the same time increase in strength through mutual activation. It’s kind of like the more you and your friends hang out together, the better you get to know each other and the deeper the bond that’s formed.

And neurons "friending" other neurons is critical. Without these tiny efficient switches constantly hooking up, and sometimes storing code, we would be lost. Not lost in thought of course, because when you take away neurons you take away thinking. And thinking, in a real sense, defines who we are.

Just a thought.

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