The influence of sound

14 Mar 2019 | Back to News, Publications and Annual Reports

There was good news two weeks ago for the fight against depression and obsessive-compulsive neuroses. This article (in Dutch) on the online knowledge platform Nationale Zorggids (National Care Guide) describes how scientists have managed to change brain activity in monkeys, 'meaning that ultrasound could possibly be used to treat depression and other brain disorders in the future'.

Researchers conducted tests involving macaques. They discovered that ultrasound was able to penetrate the brain much further than the stimulation methods currently being used to treat depression and obsessive-compulsive disorders. 'The sound waves act on the amygdala, which is a region in the brain related to emotions. The result is that the connection between this region and other parts of the brain is weakened. This could result in fewer depressive symptoms.'

Research areas

It should be noted that BPRC was not involved in this research. Depression and obsessive-compulsive neuroses are not research areas we study. Obviously, this does not mean that researchers cannot use findings from other fields. To this end, we are in daily contact with other research bodies, hospitals, universities and zoos. For example, researchers from outside BPRC make good use of our biobank, the largest biobank for non-human primate cells and tissue in Europe.

Stimuli for the senses

At BPRC, sound does not play a direct role in research, although it is an important theme for the living environment. This has everything to do with the attention we pay to 'enriching' the living environment. This relates to much more than just food and toys. 'Our animals have eyes and ears, so auditory and visual enrichment is also an important aspect,' says animal keeper Marlies. 'It's important for them to perceive things. This comes naturally to monkeys. You have to provide them with stimuli for their senses.'

With regard to sound, common marmosets are the first that come to mind for Marlies. They are able to produce whistling and chattering sounds, as well as ultrasonic ones. 'As a result, they may be bothered by certain equipment that produces sound that we humans cannot even hear, similar to rats and mice. High or low-pitched sounds could be at wavelengths that interfere with their communication, with stress as a result.'

Constant sound of radio

The monkeys at BPRC are used to hearing music as a background sound, from seven in the morning to seven in the evening. It's always played at the same low volume. They have never known otherwise. Marlies: 'Our animal keepers can switch stations, but can't change the volume. One time the radio fell silent, and it was suddenly quiet as a grave. The animals immediately became a bit upset and refused to accept food.'

It turns out, however, that rhesus macaques do not have a sense of rhythm, according to research described in this recently published book (Dutch).

Musical blanket

Music has another function as well. 'By nature, monkeys are social animals who live in groups. The size of the group we keep here is quite large, of course. The music can also help alleviate their constant awareness of other animals or of the animal keepers. Constantly being able to hear the others can cause stress. Music muffles everything a bit and this plays a clear role in their welfare. It's literally a musical blanket.'