Human Brain Prefers Pitch

Our study is looking at the brain
mechanisms that are thought to support auditory pitch perception and compares
those mechanisms between old-world macaque monkeys and humans. Just to
compare how the brains of these two species handle sound signals. And we
discovered that the monkeys have very different mechanisms in their brains — a
very different organization for handling sounds that that we associate with pitch.
So in a nutshell, what we found is that humans have a very strong bias in their
cortex. Their brain responds very strongly to sounds that have a pitch
quality to them compared to sounds that don’t. On the other hand, monkeys don’t. Monkeys seem to respond to sounds with pitch about the same — if not maybe a
little worse — than the way their brains respond to sounds with noise. I think the
nicest example was provided by my colleague and co-author on the paper,
Sam Norman-Haignere, who describes, breaks down the pitch component and the noise
component of speech. So when we speak we have both those noise components and
the pitch components and you can isolate the two in whispering. (Sound whispering).
In whispering you eliminate all of the pitch components and you just have the
kind of broadband noise component here. And there are lots of
aspects of human behavior that depend on pitch. Most notably language
communication and music, which are in some sense we think of as two uniquely
human abilities. So we tested this by using a non-invasive technique called
fMRI or functional magnetic resonance imaging. We can use that as a measure of
brain activity. Importantly, the sounds that we used were matched in frequency
so the low-level cue that is just the frequency component was matched for the
pitched sounds and the non pitch sounds. The easy way to think about
this is I can define a noise stimulus at any given
frequency range. Like I could (low noise) versus (high noise). Those would be a low and a high
frequency noise. The pitch version of it might be “a” (hums) and so I’ve got two
different stimuli there, either pitch stimuli or noise stimuli — and I can match
them in terms of the the efficacy of those stimuli to drive the auditory
system itself — that is, the frequency component. This could mean that the monkeys
experience of the auditory world is very different from our own. It’s known that lots of
animals use/have vocal sounds that make pitch and respond to pitched sounds. Birds and even macaque monkey calls — their vocalizations often have a pitch
component to them. So we used a an algorithm that allowed us to take
macaque vocalizations. We recorded macaque vocalizations and parsed-out
pitch components and the noise components and then when we presented
those stimuli. Which presumably the macaque monkeys are very familiar with
we saw yet again that the humans showed a preference much greater preference for
the pitched versions of the stimuli compared to the noise versions of the
stimuli compared to the monkeys. So even then, the monkey showed a little
preference for the pitched versions of the stimuli. But the difference between
the pitch and the noise was much higher in humans versus monkeys, which sort of
suggests that you know the humans are more sensitive to the pitch quality of
the macaque vocalizations than the macaques are themselves. What happens when you compare the sounds
that have pitch — that is the ones that have these peaks — and the ones that don’t
have pitch within every given frequency range? And there the pattern results was
just totally different between the species. So in humans you see a lot of
parts of the brain — that’s these this orange pattern — you see a lot of parts of
the brain where that show a lot of a greater activation to the sounds with
pitch. In the macaque monkeys, you can see there’s nothing. If anything, the macaque
monkey show a tiny little speck of blue, which shows that their brains responded
more strongly to the sounds with noise than the sounds with pitch. (noise and pitch sounds) Ow ow ow ow ow ow ow ow ow ow ow ow ow ow ow ow ow ow ow ow ow ow ow ow.

2 thoughts on “Human Brain Prefers Pitch

  1. Thank you for your information. I have multiple sclerosis and I’m doing everything I can to heal and this is going to help me with my research.

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