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We’ve all had moments when something just didn’t seem quite right – perhaps a slightly crooked photo hanging or a book that seems out of place on the shelf. For people with obsessive compulsive disorder (OCD), these feelings are more frequent and intense. In a new study, researchers have found a new way to test these symptoms. They found that patients with OCD-type symptoms reacted faster to disharmonic sounds than to harmonic ones.
“Although many healthy people experience some kind of ‘not-just-right experience’ (NJRE), the term is mostly used in the context of OCD,” says Judith Buse of the Dresden University of Technology in Germany. “While NJRE in healthy people are usually very mild and pretty easy to overcome, NJRE in patients with OCD might be so bothersome, that a someone is not able to go on with the daily routine, because he/she has to rearrange items over and over again.”
Past research has established two motivations behind OCD behavior: one is the wish to reduce a feeling of incompleteness, and the second is the wish to avoid harm. Think of a compulsive hand washer – the behaviors could be driven by the fear of getting sick or by the bothersome feeling that the hands are sticky even if they are clean.
Testing the latter – that feeling of incompleteness – has primarily relied on questionnaires that ask people to self report NJRE. Buse, who works with children and adolescents suffering from OCD, wanted to find an experimental way to test and observe the phenomenon so that she and colleagues can ultimately find the underlying neurological causes. So she turned to the “harmonic expectancy paradigm” developed by Stefan Koelsch of the Free University of Berlin.
In the harmonic expectancy violation paradigm, participants hear several melodies. Most of the melodies end on a chord that sounds makes it harmonic with the preceding chords. But in some cases, the last chord of the melody deviates from the preceding chords, making the it sound disharmonic.
“The first chords serve to build up an expectancy what the last chord will sound like,” Buse explains. “The last chord only sounds ‘harmonic’ or ’disharmonic’ in the context of the whole melody.” And interestingly, she says, even children as young as 5 or 6 years old “implicitly build these harmonic expectancies,” making the paradigm a good candidate for studying OCD in young patients.
To test how this paradigm might work for patients with OCD, Buse and colleagues first looked at healthy adults who varied in their reporting of NJRE and compared how they reacted to disharmonic chord sequences. As published last month in Cognitive Neuroscience, the participants all found the disharmonic sequences unpleasant and incomplete. But there was a clear difference between those participants who reported more NJRE, or symptoms of incompleteness, in day-to day life: Their reaction time to the disharmonic melodies were significantly faster than their reaction times to the harmonic ones.
“People are usually biased in so far as they directly perceive, process, and react faster to stimuli that bother or frightened them – for example, a person with a spider phobia will be pretty fast in detecting the spider in the room,” Buse says. “In a similar way, people, who are bothered by NJRE might be fast in detecting them” and this applies to people who report stronger OCD characteristics.
The next step, she says, is testing the paradigm in patients with OCD and healthy controls – and then determining which brain regions are involved in the faster processing of the disharmonic chord sequences. “We absolutely need studies on patients with OCD to draw conclusions about the disorder,” Buse says. “However, we learned from the study, that NJRE are not only a question of how certain stimuli are evaluated – for example, as bothersome or frightening – but also of how fast certain stimuli are processed.”
-Lisa M.P. Munoz
