The Idiot Brain by Dean Burnett

Author:Dean Burnett [Dean Burnett]
Language: eng
Format: epub, azw3, mobi, pdf
ISBN: 9780571350834
Publisher: Guardian Faber Publishing
Published: 2016-05-25T16:00:00+00:00

Hearing and touch are linked at a fundamental level. This is something most people don’t know, but think about it; have you ever noticed how incredibly enjoyable it can be to clean out your ear with a cotton bud? Yes? Well, that’s nothing to do with this, I’m just establishing the principle. But the truth is, the brain may perceive touch and hearing completely differently, but the mechanisms it uses to perceive them at all have a surprising amount of overlap.

In the previous section, we looked at smell and taste, and how they often overlap. Admittedly, they do often have similar roles regarding recognising foodstuffs, and can influence each other (smell predominately influencing taste), but the main connection is that smell and taste are both chemical senses. The receptors for taste and smell are triggered in the presence of specific chemical substances, like fruit juice or gummy bears.

By contrast, touch and hearing; what do they have in common? When was the last time you thought something sounded sticky? Or ‘felt’ high-pitched? Never, right?

Actually, wrong. Fans of the louder types of music often enjoy it at a very tactile level. Consider the sound systems you get in clubs, cars, concerts and so forth that amplify the bass element of music so much that it makes your fillings rattle. When it’s powerful enough or of a certain pitch, sound often seems to have a very ‘physical’ presence.

Hearing and touch are both classed as mechanical senses, meaning they are activated by pressure or physical force. This might seem weird, given that hearing is clearly based on sound, but sound is actually vibrations in the air that travel to our eardrum and cause it to vibrate in turn. These vibrations are then transmitted to the cochlea, a spiral-shaped fluid-filled structure, and thus sound travels into our heads. The cochlea is quite ingenious, because it’s basically a long, curled-up, fluid-filled tube. Sound travels along it, but the exact layout of the cochlea and the physics of soundwaves mean the frequency of the sound (measured in hertz, Hz) dictates how far along the tube the vibrations travel. Lining this tube is the organ of Corti. It’s more of a layer than a separate self-contained structure, and the organ itself is covered with hair cells, which aren’t actually hairs, but receptors, because sometimes scientists don’t think things are confusing enough on their own.

These hair cells detect the vibrations in the cochlea, and fire off signals in response. But the hair cells only in certain parts of the cochlea are activated due to the specific frequencies travelling only certain distances. This means that there is essentially a frequency ‘map’ of the cochlea, with the regions at the very start of the cochlea being stimulated by higher-frequency soundwaves (meaning high-pitched noises, like an excited toddler inhaling helium) whereas the very ‘end’ of the cochlea is activated by the lowest-frequency soundwaves (very deep noises, like a whale singing Barry White songs). The areas between these extremes of the cochlea respond to the rest of the spectrum of sounds audible to humans (between 20 Hz and 20,000 Hz).

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