Most people perform daily tasks automatically, such as putting files on a desk, preparing tea before work, or getting dressed in the morning. Sequential behaviours are acts that, notwithstanding minor variations in specifics, follow a predictable order. But these daily tasks may require significantly more mental work than they seem on the surface for about one in 40 persons with obsessive-compulsive disorder (OCD). According to a recent brain imaging study conducted by Brown University researchers, individuals with OCD may appear to be functioning normally and calm on the outside, but their brains are operating in what scientists refer to as "invisible overdrive." 

Under Associate Professor Theresa Desrochers, the work was carried out at Brown's Carney Institute for Brain Science and published in Imaging Neuroscience. Researchers compared the performance of individuals with and without OCD on a structured sequencing task using magnetic resonance imaging (MRI), a scanning technique that reveals which areas of the brain are engaged. In a specific order—colour, colour, shape, shape—participants were asked to identify the colour or shape of various items. In order to complete the assignment, they had to recall the sequence while making snap decisions, which is something the brain does all the time. 

Hannah Doyle, lead author and postdoctoral research researcher in Desrochers' group, explained, "We began investigating OCD because symptoms of the disorder suggest that patients lose track or get stuck where they are while performing sequences." 

In terms of behaviour, OCD participants were as accurate as those without the disorder. There was no visible difference from the outside. MRI scans, however, revealed a different picture. Doyle said that although the individuals' behaviour appeared to be identical, the OCD participants' brains recruited more brain regions than those of the control group. 

The scans revealed elevated activity in areas not typically associated with OCD as well as those related to motor control and decision-making. These included regions spanning the occipital gyrus and temporo-occipital junction, which aid in the recognition and interpretation of visual objects, as well as the middle temporal gyrus, which supports working memory and language processing. Simply put, like a swan swimming gracefully over water while paddling frantically below the surface, the OCD brain seems to summon more support systems to accomplish the same task. 

Desrochers clarified the significance of this discovery in the real world. In a healthcare context, many of the jobs are static. However, people organise information and make judgements by interacting with the world through sequences. Therefore, we're asking people to complete an activity that requires interaction between these many control systems," she stated. 

The results may have an impact on therapeutic approaches, especially transcranial magnetic stimulation (TMS), which stimulates particular brain regions with focused magnetic pulses. About 30 to 40 per cent of patients have demonstrated improvement since TMS was approved by the U.S. Food and Drug Administration in 2018 for the treatment of OCD. According to Nicole McLaughlin, co-author of the study, changing the coil placement to target these recently discovered areas may improve results. "We might end up seeing a greater improvement in symptoms if we reposition coils during TMS treatments to be near these brain regions," she said. 

The possibility that the sequencing job itself could be used as a tool to track the effectiveness of treatment is now being investigated. McLaughlin stated, "We intend to use the task in between treatments." "TMS treatment may be useful for symptom reduction if we begin to observe that OCD patients' brains resemble control participants' when they complete the task." 

The study dispels the myth that OCD is just about being too tidy or constantly washing your hands. Instead, it depicts a hidden neurological strain that science is only now starting to map—a brain that is working harder than it should in order to handle everyday life.