The origin of body dysmorphic disorder has been traced to a specific bundle of neurons within the brain that are connected with processing visual information. The finding, if confirmed, could help the development of new treatments for the condition.
Body dysmorphic disorder is generally defined as a person being overly preoccupied with perceived flaws in a particular aspect of their face or body. Symptoms can include a person worrying a lot about their apperance, spending a lot of time looking in mirrors or avoiding them altogether, and obsessive grooming behaviours, such as excessive hair brushing or skin picking. The condition has been linked to genetics, a chemical imbalance in the brain and past trauma, such as bullying.
Previous studies have shown that to those who don鈥檛 have the condition. This causes them to focus on specific details of their appearance rather than seeing the 鈥渂ig picture鈥�, but it wasn鈥檛 clear why this happens.
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To learn more, at the University of Toronto in Canada and his colleagues looked at 17 adults 鈥� two men and 15 women 鈥� who had been diagnosed with body dysmorphic disorder and 21 people 鈥� 6 men and 15 women 鈥� without the condition. Brain scans measured the density of neurons within the pathways that transmit visual information while they were awake but in a resting state.
The researchers found that a bundle of nerve fibres called the vertical occipital fasciculus had a lower density in those with body dysmorphic disorder than in those without the condition, indicating reduced communication along this pathway. This bundle connects the dorsal visual stream 鈥� which processes signals about eye position and attention 鈥� with the ventral visual stream, which is involved in recognising faces and objects.
There were also differences in the densities of the bundle among those with body dysmorphic disorder: the lower the density, the worse their symptoms.
The researchers then used magnetic resonance imaging to measure how the participants鈥� brains responded to seeing photographs of their own faces. They found that those with the condition had altered communication between their dorsal and ventral visual streams when looking at their own faces compared with when looking at scrambled images of their faces. This communication didn鈥檛 change among those who weren鈥檛 diagnosed with body dysmorphic disorder.
鈥淲e鈥檝e assumed for some time that imbalances in visual processing are at least partly responsible for the distressing distortions experienced by people with BDD [body dysmorphic disorder] when they look at their own face,鈥� says at the University of Essex in the UK. This study shows that 鈥渢he imbalances may be attributable to a specific anatomical neuronal bundle鈥�.
鈥淭he findings are exciting because they not only enhance our understanding of BDD, but also open up the possibility of intervention in future,鈥� she says. 鈥淚nterventions that involve stimulating the remaining connections could strengthen the communication between visual processing regions and rebalance overall perception of one鈥檚 own face.鈥�
Feusner says the researchers hope to investigate such interventions once they have replicated their findings. 鈥淲e plan to use the results to inform the development of new treatments, such as perceptual retraining or to help with personalised target selection for non-invasive neuromodulation,鈥� he says.
bioRxiv
