View from the lab

Noise reduction is an important science – with or without Amy Winehouse living next door.

Amy Winehouse Photo: GETTY IMAGES

The other day I heard that Amy Winehouse has bought the house next door to mine in Camden Town, and plans to set up a recording studio there. My brain lit up at once with concerns about noise.
I discovered in a physiology class long ago that, even at the age of 21, I had lost the ability to hear high notes, presumably because of the time I spent working in the shrieking environment of a power station. We may have missed International Noise Awareness Day (which was last Wednesday), but noise reduction is important – not just for mechanics and musicians but for scientists and doctors, too.
In any context, noise is the same thing: unwanted input from an external source that interferes with a desired signal. One can either hear it (the neighbours’ hi-fi) or see it (the echoes of the Big Bang that make the snowy pattern on an untuned TV).

Noise reduction has become a science. Physics, maths, and computing conspire to filter out unwanted information and lay bare hidden signals.

Astronomers who use the reverberations of the cosmic explosion to understand the universe are plagued by interference from the thermal energy generated by their instruments and by the buzz of waves pulsing from galaxies far away. The much publicised first pictures of the ripples of the Big Bang were largely based on random noise. Now, computers disentangle the problem.

Those trying to understand messages from our inner universe face the same problem. The images of brains in action that pour from a digital scanner are in fact extracted from a raging mass of unwanted information. Many of the messages that emerge are baffling, or even imaginary.

Functional magnetic resonance imaging (or fMRI) uses an intense magnetic field to probe the brain. Sensors pick up shifts in the extent to which slightly magnetic molecules are flipped from one form to another by the massive pulses of energy. When the blood pigment haemoglobin is carrying oxygen, it tends to pick up a charge opposed to the outside force, but when it has lost its burden it does the reverse. The balance shows how much oxygen is being used, and hence how active any part of our grey matter might be.

The method is used to diagnose tumours, follow the course of blood through a heart and much more. Sometimes, though, patterns emerge on the screen that are no more than noise.

Nowhere is that more obvious than when testing responses to emotions, to language and to noise itself. Some brain sections are associated with feelings such as anger and rage (in which structures called the amygdalae, deep in the stem, light up); but when it comes to less potent cultural cues, the story is blurred.

There has been much interest in how the brain responds to music, from nursery rhymes to grand opera, with every genre thought to have its own place in the cranium. Research suggests that both sides of the brain are used, with the left (involved in speech) more interested in songs, rather than simple tunes. When listening to opera, though, music and words seem to be processed by different hemispheres. Teenage brains, apparently, light up in different places when exposed to tunes high in the charts compared to those lower down. Yet another section gets more interested when there is a solid beat. Trained musicians, but not novices, switch off one patch when they are improvising (an art at which Amy Winehouse is a master), and scans of newborn babies, never previously exposed to music, suggest that their right hemisphere is the only one to light up in response.

Cynics, though, accuse the scanners of seeing patterns that are not there: of molecular phrenology. One remarkable experiment appeared to pick up differential activity in the brain of a dead salmon when the creature was shown pictures of human faces with contrasting expressions (the result was described as a red herring).

That’s a fishy tale, but I look forward to discovering which parts of my brain light up when Ms Winehouse moves in. I am pretty sure that it will not be the amygdalae.