Nanobiology Notes

Neurotransmitters - molecular messages

You often hear about neurotransmitters in the news and in science magazines in a kind of off-hand way that assumes everyone must surely know what these things are. But, um, what are they, exactly?

From Sandra Ackerman's book "Discovering the Brain": To be recognized as a neurotransmitter, a chemical compound must satisfy six conditions: It must be

synthesized in the neuron, stored there, released in sufficient quantity to bring about some physical effect; when administered experimentally, the compound must demonstrate the same effect that it brings about in living tissue; there must be receptor sites specific to this compound on the postsynaptic membrane, as well as a means for shutting off its effect, either by causing its swift decomposition or by reuptake, absorbing it back into the cell.

OK, well, what about hormones? They're chemical messengers too - how are hormones different from neurotransmitters? A hormone, by definition, is a compound produced by an endocrine…

It ain't what you don't know that gets you into trouble. It's what you know for sure that just ain't so.

-- Mark Twain

So far, most of the posts in this blog have been focused on building a 'bottom-up' understanding of how the brain works - from how DNA works up to how individual neurons work. Lots of good science to base all of this stuff on. It is difficult to go further 'up the stack' in this way, however. How do neurons work together to do useful things? How are small-scale networks of neurons structured and how do the neurons interact in order for us to do simple things like rhythmically tap a finger?

Are we there yet?
Every decade or two the scientific community gets wildly optimistic that we will be able to fully understand how cognition works and be able to replicate the process in some non-biological system. It's been named many things over the years - cybernetics, artificial intelligence, computational intelligence, cognitive computing (see http://en.wikipedia.org/wiki/Artificial_intelligence for a nice overview). And yet, with all of the money tha…

Looking at Sound

Lately I've been listening a lot to Kate Bush's album Aerial - beautiful, wonderful stuff. The album cover is interesting too - the 'islands' that are reflected in the water are actually the amplitude envelope of a recording of some birds singing.

This idea of 'looking at sound' in different ways has been something I've really enjoyed exploring over the last several years. To help visualize the harmonics in a piece of music, I wrote a program a while back that analyses the frequency content of a sound waveform and creates a spectrogram (spectrum over time) of it, colour coding the intensity levels of each frequency.

I think I've found the bird song shown on the cover - it's 2:25 from the start of the song 'Aerial'. Here's what its spectrogram looks like:

The parallel contour lines that are stacked one on top of each other are the harmonics of the bird song. (A synthesizer's been added to the recording, which has changed the amplitue…

Beta Rhythm (Music of the Mind)

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