Cognitive Daily

Some potential benefits of nicotine

Madam Fathom has an excellent discussion of nicotine’s effect on the brain and cognitive function. First off, I’ve rarely seen a clearer explanation of how neurons actually work:

Neurons are functionally integrated in expansive neural networks, with each neuron receiving up to thousands of inputs from other neurons. However, the neurons are not actually physically connected to one another; there is a tiny gap that separates neurons, called a synapse.

When a neuron is activated, an electrical pulse (an action potential) travels down its membrane; the neuron is said to “fire” an action potential. When the action potential reaches the end of the neuron, it cannot traverse the synapse, but instead induces the release of chemicals which can. Once liberated from the “pre-synaptic” neuron, these chemicals (called neurotransmitters) navigate across the synapse and bind to specific receptors on the “post-synaptic” neuron. Once bound, the neurotransmitters induce one of many physiological changes: they can make it easier to fire an action potential (“excitatory” neurotransmitters), more difficult to fire an action potential (“inhibitory” neurotransmitters), or modulate the firing rate or other behavioral properties of the cell.

An overwhelming number of pre-synaptic neurons, all of which are sources of neurotransmitters, impinge on a single post-synaptic neuron, yet the latter responds with a binary decision: fire or don’t fire. The cell creates order from this chemical deluge by performing a complex, time-dependent summation of all of its inputs; if it receives a sufficient number of excitatory inputs within a reasonable time window, it will fire an action potential and release its own neurotransmitter, passing the information along the circuit.

Why can’t all science writers be this clear? She goes on to explain how nicotine affects this process:

Each neurotransmitter can bind to a number of complementary receptors. One of the receptors for a neurotransmitter called acetylcholine (ACh) happens to also bind and respond to nicotine, which is not naturally present in the body. Thus when a post-synaptic neuron containing these particular receptors (called nicotinic ACh receptors, or nAChRs) is exposed to nicotine (as in when someone smokes a cigarette), it behaves as if it has been influenced by ACh; i.e. to an individual nAChR, nicotine and ACh are indistinguishable.

The problem, of course, is that while each individual neuron is independently in charge of acetylcholine delivery, nicotine affects the entire brain simultaneously. Depending on the individual brain, this can have positive or negative consequences. Madam Fathom goes on to discuss the current state of research on using nicotine to accentuate those positive consequences, for treatment of Alzheimer’s, Parkinson’s, and other disorders, and explain what needs to be done next.

In my view, giving Madam Fathom a book contract wouldn’t be a bad next step!

Read her whole post.

Comments

  1. #1 Harlan
    April 18, 2007

    An old friend of mine, a medical doctor turned cognitive psychologist, talked about the cognitive benefits of nicotine occasionally. He said if it wasn’t so crazy addictive, it would be a great enhancer of concentration. I’ve also heard of the use of nicotine patches with elderly people as a way to improve failing cognitive function.

    And yes, that’s a pretty clear description of how neurons work. I’ve always found the words “pre-synaptic” and “post-synaptic” a little confusing, though. “Pre” and “post” refer to time, but “synapse” refers to space. So you need to work through the metaphor to figure out what the terms mean. I don’t have any better suggestions, though….

  2. #2 avi
    April 18, 2007

    Clear writing usually doesn’t go unnoticed :-)

  3. #3 Libby
    April 18, 2007

    I chew nicotine gum on occasion to aid with concentration, as my ADD is unmedicated due to unavoidable med interactions. It helps somewhat. I just don’t chew it more than two days in a row or three days out of seven, even during exams, having vivid memories of the scened from Bounce where Gwyneth Paltrow lit up a cigarette as part of her effort to wean herself off the gum. At least I needn’t fear new behavioral addiction — I became attached to chewing gum well over a decade ago.

  4. #4 Gary
    April 18, 2007

    The terms pre-synaptic and post-synaptic refer to the direction of transmission in the neurons. Individual neurons only conduct or “flow” in one direction. Pre-synaptic is upstream and post-synaptic is downstream.

  5. #5 Alan Kellogg
    April 18, 2007

    Well actually she’s a bit behind in her neurons. There are some synapses when dendrite and axon merge. This usually happens with thoes connections where there is a ton of traffic. A factoid I picked up while ambling about the web. A good site on neural anatomy may have further information on the subject.

    There was also something about two way traffic, but that I’m not as sure of.

  6. #6 Lizzie
    April 18, 2007

    Thank you for the kind words, Dave!

    And yeah, Alan, it’s true that there are exceptions to synaptic transmission as I described it. I focused on chemical synapses, as these are relevant to nicotine, but electrical synapses also exist and I didn’t mean to be misleading. I’m making a note of it on my post…thanks for pointing it out.

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