How Does Stress Affect Working Memory in Obsessive-Compulsive Disorder?

What you need to know

• Stress impaired working memory performance in people with OCD but not in healthy individuals, particularly for more difficult memory tasks
• Under stress, people with OCD showed increased brain activity in regions involved in visual processing, motor control, and goal-directed behavior
• OCD patients failed to show the normal suppression of brain regions involved in self-referential thinking when under stress
• These findings suggest people with OCD may be more vulnerable to the negative effects of stress on cognitive functioning

How stress affects our thinking and memory

We’ve all experienced how stress can make it harder to think clearly or remember things. For people with obsessive-compulsive disorder (OCD), this effect may be even more pronounced. OCD is a mental health condition characterized by unwanted, intrusive thoughts (obsessions) and repetitive behaviors or mental acts (compulsions). People with OCD often report that stress worsens their symptoms and makes it harder to resist compulsions.

To better understand how stress impacts cognitive functioning in OCD, researchers conducted a study comparing people with OCD to healthy individuals on a working memory task under stressful and non-stressful conditions. Working memory refers to our ability to temporarily hold and manipulate information in mind. It’s crucial for many everyday tasks, from following directions to solving problems.

The working memory challenge

The study included 38 people diagnosed with OCD and 55 healthy individuals matched for gender and education level. Participants completed a computer-based working memory task while undergoing functional magnetic resonance imaging (fMRI) to measure their brain activity.

The task involved remembering two numbers and then either:

1. Simply reporting which number was larger or smaller (maintenance)
2. Performing a calculation on one of the numbers before comparing them (manipulation)

To create a stressful condition, participants were told they were competing against another person and received mostly negative feedback about their performance. In the non-stressful condition, there was no competition or feedback.

How stress affected task performance

For the simpler maintenance task, both groups actually performed better under stress - they were more accurate, though slightly slower to respond. However, for the more challenging manipulation task, stress had different effects:

• Healthy individuals maintained their performance under stress
• People with OCD became significantly less accurate when stressed

This suggests that stress may disproportionately impair more complex cognitive processing in people with OCD.

Brain activity differences under stress

The fMRI results revealed some interesting differences in how the brains of people with and without OCD responded to the working memory task under stress:

Healthy individuals

When stressed, healthy participants showed:

• Decreased activity in the medial prefrontal cortex - a region involved in self-referential thinking and mind-wandering
• Decreased activity in the striatum - an area important for learning and decision-making
• Increased activity in the cerebellum - which plays a role in motor control and some cognitive functions

This pattern suggests that under stress, healthy brains may suppress some internal mental processes to focus more on the external task at hand.

OCD participants

In contrast, OCD participants did not show this same pattern of decreased medial prefrontal cortex and striatum activity under stress. Instead, they exhibited:

• Increased activity in the fusiform gyrus - involved in visual processing and face recognition
• Increased activity in the supplementary motor area - important for movement planning and control
• Increased activity in the precentral gyrus - the primary motor cortex
• Increased activity in the caudate - part of the striatum involved in goal-directed behavior

Additionally, OCD participants failed to suppress activity in regions of the default mode network - a set of interconnected brain areas that are typically less active during external tasks. This network is associated with self-referential thinking and mind-wandering.

What do these brain differences mean?

The researchers suggest a few potential interpretations of these findings:

1. Compensatory activation: The increased activity in motor and visual processing regions may reflect the brain working harder to maintain task performance under stress.

2. Impaired stress response: The lack of normal suppression in self-referential thinking regions could indicate that people with OCD have difficulty shifting mental resources away from internal processes when stressed.

3. Heightened stress sensitivity: The increased activation in regions like the caudate may reflect an exaggerated response to stress in OCD.

Interestingly, the degree of these stress-related brain activity changes was associated with symptom severity in the OCD group. Patients with less severe symptoms showed greater compensatory activation, suggesting they may be better able to adapt to stress.

Conclusions

• Stress appears to have a more detrimental effect on complex working memory performance in people with OCD compared to healthy individuals
• The brains of people with OCD respond differently to stress during cognitive tasks, showing increased activation in some regions but failing to suppress others
• These differences in stress response may contribute to cognitive difficulties and symptom exacerbation in OCD
• Further research is needed to determine if improving stress management could help alleviate cognitive symptoms in OCD

While this study provides valuable insights, it’s important to note some limitations. The sample size was relatively small, and most OCD participants were taking medication, which could influence brain activity. Additionally, the study only examined one type of cognitive task, so the findings may not generalize to all aspects of thinking and memory.

Nonetheless, this research highlights the complex interplay between stress, cognitive functioning, and brain activity in OCD. It suggests that helping people with OCD develop better stress management strategies may be an important component of treatment. Future studies may explore whether stress reduction techniques or cognitive training under mild stress could help build resilience and improve cognitive functioning in OCD.