How being able to recognise a tune helped to shape humans' brains

Being able to recognise a tune has shaped our brains and make us distinct from our ancestors, scientists have revealed.

The human brain appears uniquely tuned for musical pitch and a study involving primates suggest that speech and music may have shaped our hearing circuits.

Scientists discovered that our brains can ‘hear’ musical sound much better than one of our relatives, the macaque monkey.

The study came about as a bet between two American research doctors, one of whom had done research showing that monkeys and humans see the world in the same way and wagered that sound would be no different.

Being able to recognise a tune has shaped our brains and make us distinct from our ancestors, scientists have revealed. The human brain appears uniquely tuned for musical pitch and a study involving primates suggest that speech and music may have shaped our hearing circuits(stock image)

Dr Bevil Conway who had carried out the visual research on monkeys now set out to prove his colleague Dr Sam Norman-Haignere wrong as they both worked on the aural research.

Conceding defeat, Dr Conway, investigator in the National Institute of Health’s Intramural Research Programme, said: ‘We found that a certain region of our brains has a stronger preference for sounds with pitch than macaque monkey brains.

‘The results raise the possibility that these sounds, which are embedded in speech and music, may have shaped the basic organisation of the human brain.’

Dr Norman-Haignere, a fellow at Columbia University’s Zuckerman Institute for Mind, Brain, and Behaviour added: ‘I told Bevil that we had a method for reliably identifying a region in the human brain that selectively responds to sounds with pitch.’

For the study the researchers played a series of harmonic sounds, or tones, to healthy volunteers and monkeys.

Functional magnetic resonance imaging (fMRI) was used to monitor brain activity in response to the sounds.

The researchers also monitored brain activity in response to sounds of toneless noises that were designed to match the frequency levels of each tone played.

At first glance, the scans looked similar as maps of the auditory cortex of human and monkey brains had similar hotspots of activity regardless of whether the sounds contained tones.

However, when the researchers looked more closely at the data, they found evidence suggesting the human brain was highly sensitive to tones.

The human auditory cortex was much more responsive than the monkey cortex when they looked at the relative activity between tones and equivalent noisy sounds.

The human brain appears uniquely tuned for musical pitch and a study involving primates suggest that speech and music may have shaped our hearing circuits. Scientists discovered that our brains can ‘hear’ musical sound much better than one of our relatives, the macaque monkey, pictured in this stock image)

Dr Conway added: ‘We found that human and monkey brains had very similar responses to sounds in any given frequency range.

‘It’s when we added tonal structure to the sounds that some of these same regions of the human brain became more responsive.

‘These results suggest the macaque monkey may experience music and other sounds differently.

‘In contrast, the macaque’s experience of the visual world is probably very similar to our own. It makes one wonder what kind of sounds our evolutionary ancestors experienced.’

Finally, the researchers saw similar results when they used sounds that contained more natural harmonies for monkeys by playing recordings of macaque calls.

Brain scans showed that the human auditory cortex was much more responsive than the monkey cortex when they compared relative activity between the calls and toneless, noisy versions of the calls.

Dr Conway continued: ‘This finding suggests that speech and music may have fundamentally changed the way our brain processes pitch.

‘It may also help explain why it has been so hard for scientists to train monkeys to perform auditory tasks that humans find relatively effortless.’

The full findings of the study were published in the journal Nature Neuroscience.