Obsessive compulsive disorder (OCD) is a disorder characterized by intrusive thoughts and
repetitive, irrational behaviors, for example an obsession with
cleanliness leading to repetitive hand washing, or a fear that something
terrible will happen if they don't check the door dozens of times,
making leaving the house extremely difficult.
A common way of helping treat OCD is to expose people to something
they consider threatening - for example, if their obsession is around
cleanliness, they may be made to touch a toilet seat but then prevented
from washing their hands. However, so-called 'exposure therapy' often
only has limited success and compulsions can return in times of stress.
‘People who suffer from obsessive compulsive disorder are poor at learning the safety of a stimulus, which may contribute to their struggles to overcome compulsive behavior.’
People who suffer from OCD are poorer
at learning about the safety of a stimulus than healthy volunteers,
which may contribute to their struggles to overcome compulsive
behavior, according to new research from the University of Cambridge.
This new research, published today in the Proceedings of the National Academy of Sciences
, may explain why memories about safety don't stick.
In this study, researchers at Cambridge's Behavioural and Clinical
Neuroscience Institute tested 43 OCD patients and 35 matched healthy
volunteers to see how well those people with OCD were able to reverse
their thinking when a previously threatening stimulus became safe and
vice versa, to examine safety versus threat learning as well as
cognitive flexibility, which is thought to be significantly compromised
in patients with OCD.
Volunteers lay in a functional magnetic resonance imaging (fMRI)
scanner, which measures brain activity, while successively being shown
one of two faces: when shown the red face, nothing happened, but when
shown the green face, the volunteer would sometimes receive a mild
electric shock. By measuring changes in skin conductance caused by tiny
amounts of sweat, the researchers were able to see whether the
volunteers learned which stimulus was safe and which threatening.
After a period of time, the researchers swapped the stimuli - now,
the red face was paired with an electric shock while the green face was
The researchers found that while OCD patients were able to learn
initially which stimulus was threatening, they never learned that the
second stimulus was safe - in fact, they seemed to pay little attention
to this safe stimulus. When the stimuli were reversed, participants were
unable to differentiate between the previously threatening stimulus and
the newly threatening stimulus. This was also reflected in their brain
activity - OCD patients showed a lack of activity in an area at the
front of the brain known as the ventromedial prefrontal cortex when
viewing the safe stimulus.
"Our study suggests that something is going wrong in the brains of
people with OCD when they are learning what is safe, and this in turn
affects how they perceive threats under updated circumstances," explains
Dr Annemieke Apergis-Schoute, the study's first author. "This needs to
be taken into consideration when we're developing future therapies to
tackle the disorder. Current exposure therapies may help the patient
take control over their compulsions, but our work suggests that they
might never learn that their compulsions are unnecessary and they may
return in times of stress."
In a second study, published recently in Biological Psychiatry,
Cambridge researchers showed that this cognitive inflexibility might be
in part a result of a lack of 'chatter' between specific brain areas.
The research, led by PhD student Matilde Vaghi, found that poor
connectivity within some of the brain's key networks as measured in an
fMRI scanner while the patient was at rest may account for this
inflexibility. It also may account for OCD patients' poor goal-directed
abilities (where we consciously act with a goal in mind - for example,
when driving home and our route is disrupted, forcing us to take an
unfamiliar route). Both are related to common symptoms of OCD.
The researchers found disrupted connectivity within discrete
frontostriatal circuits - neural pathways that connect the front of the
brain with the basal ganglia (responsible for important functions such
as the control of movement and 'executive functions' such as
decision-making, learning and habit formation). They believe these may
underlie the repetitive behaviours seen in OCD.
Professor Trevor Robbins, Head of Psychology at Cambridge, senior
author on both studies, says: "When we look at this two studies
together, we can see that there is a clear imbalance between key regions
at the front of the brain in people with OCD. These may underlie some
of the symptoms of inflexibility that we commonly see in patients with