Our animal inheritance: Humans perk up their ears, too, when they hear interesting sounds

Date:
July 7, 2020
Source:
Saarland University
Summary:
Many animals move their ears to better focus their attention on a
novel sound. That humans also have this capability was not known
until now. A research team now has demonstrated that we make minute,
unconscious movements of our ears that are directed towards the
sound want to focus our attention on. The team discovered this
ability by measuring electrical signals in the muscles of the
vestigial motor system in the human ear.



FULL STORY ==========================================================================
Many animals, including dogs, cats and various species of monkeys, will
move their ears to better focus their attention on a novel sound. That
humans also have this capability was not known until now. A research
team based in Saarland has demonstrated for the first time that we make
minute, unconscious movements of our ears that are directed towards the
sound want to focus our attention on.

The team discovered this ability by measuring electrical signals in the
muscles of the vestigial motor system in the human ear. The results have
now been published in the journal eLife.


========================================================================== Asking children to 'perk up their ears' means asking them to listen
intently.

Nobody seriously thinks that kids literally move their ears the way that
cats, dogs or horses do. But the fact is, they do, as researchers at the Systems Neuroscience & Neurotechnology Unit (SNNU) have now shown. The
research team, led by Professor Danial Strauss, has shown that the muscles around the ear become active as soon as novel, unusual or goal-relevant
sounds are perceived.

'The electrical activity of the ear muscles indicates the direction
in which the subject is focusing their auditory attention,' says
neuroscientist and computer scientist Strauss. 'It is very likely
that humans still possess a rudimentary orientation system that tries
to control the movement of the pinna (the visible outer part of the
ear). Despite becoming vestigial about 25 million years ago, this system
still exists as a "neural fossil" within our brains,' explains Professor Strauss. The question why pinna orienting was lost during the evolution
of the primate lineage has still not been completely resolved.

The researchers were able to record the signals that control the minute, generally invisible, movements of the pinna using a technique known as
surface electromyography (EMG). Sensors attached to the subject's skin
detected the electrical activity of the muscles responsible for moving
the pinna or altering its shape. Two types of attention were examined. To assess the reflexive attention that occurs automatically when we hear unexpected sounds, the participants in the study were exposed to novel
sounds coming at random intervals from different lateral positions
while they silently read a monotonous text. To test the goal-directed
attention that we show when actively listening, the participants were
asked to listen to a short story coming from one laterally positioned
speaker, while ignoring a 'competing' story from a speaker located on
the opposite side. Both experiments showed that muscle movements in the vestigial pinna-orienting system indicate the direction of the subject's auditory attention.

To better characterize these minute movements of the ear, the team also
made special high-definition video recordings of the subjects during
the experiments. The subtle movements of the ears were made visible by
applying computer-based motion magnification techniques. Depending on
the type of aural stimulus used, the researchers were able to observe
different upward movements of the ear as well as differences in the
strength of the rearward motion of the pinna's upper-lateral edge.

'Our results show that electromyography of the ear muscles offers a simple means of measuring auditory attention. The technique is not restricted to fundamental research, it also has potential for a number of interesting applications," explains Professor Strauss. One area of great practical relevance would be in developing better hearing aids. 'These devices
would be able to amplify the sounds that the wearer is trying to hear,
while suppressing the noises that they are trying to ignore. The device
would function in a way that reflects the user's auditory intention.' The hearing aid would almost instantaneously register and interpret the
electrical activity in the ear muscles. A miniature processor would gauge
the direction the user is trying to direct their attention towards and
then adjust the gain on the device's directional microphones accordingly.

The research project was conducted by researchers at the Systems
Neuroscience & Neurotechnology Unit (SNNU), which is affiliated to
both the Medical Faculty at Saarland University and to the School of Engineering at the University of Applied Sciences in Saarland (htw
saar). External project partners were Dr.

Ronny Hannemann from the hearing aid manufacturer Sivantos GmbH and
Steven A.

Hackley, Professor of Psychology at the University of Missouri-Columbia,
who in 2015 first postulated the existence of a vestigial pinna-orienting system in humans.


========================================================================== Story Source: Materials provided by Saarland_University. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Daniel J Strauss, Farah I Corona-Strauss, Andreas Schroeer, Philipp
Flotho, Ronny Hannemann, Steven A Hackley. Vestigial auriculomotor
activity indicates the direction of auditory attention in
humans. eLife, 2020; 9 DOI: 10.7554/eLife.54536 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200707113337.htm

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