How Do Brain Activation Patterns Differ Between Hoarding Disorder and OCD During Executive Tasks?

What you need to know

• Hoarding disorder (HD) and obsessive-compulsive disorder (OCD) show different patterns of brain activation during executive function tasks
• People with HD show an impulsive pattern of responding and reduced brain activation during error processing
• People with OCD show increased brain activation during error processing, suggesting heightened error monitoring
• These distinct neural patterns support classifying HD and OCD as separate disorders

Background

Hoarding disorder (HD) is characterized by difficulty discarding possessions and excessive accumulation of objects, regardless of their actual value. While HD was previously considered a subtype of obsessive-compulsive disorder (OCD), it is now classified as a distinct disorder. However, the neurobiological differences between HD and OCD are not well understood.

This study aimed to investigate how brain activation patterns differ between people with HD, OCD, and healthy controls during executive function tasks. Executive functions are cognitive processes that help control behavior, like inhibiting responses, switching between tasks, and monitoring for errors. Understanding differences in these processes could provide insight into the distinct features of HD and OCD.

How was the study conducted?

The researchers recruited 17 people with HD, 18 people with OCD, and 19 healthy controls. All participants completed two computerized tasks while undergoing functional magnetic resonance imaging (fMRI) brain scans:

1. Stop-signal task: Participants had to quickly press buttons in response to shapes on a screen, but inhibit their response when they saw a “stop” signal. This measures response inhibition.

2. Switch-signal task: Similar to the stop-signal task, but participants had to switch their response pattern when they saw a “switch” signal. This measures cognitive flexibility.

The researchers analyzed participants’ performance on the tasks and their brain activation patterns during different components:

• Response inhibition
• Task switching
• Error processing (brain activity when making mistakes)

Key findings

Behavioral differences

• HD group: Showed faster reaction times but made more errors on both tasks compared to OCD and control groups. This suggests an impulsive pattern of responding.

• OCD group: Performed similarly to controls on most measures, but had fewer successful “go” trials on the switch task.

Brain activation differences

Stop-signal task:

• HD group: Showed decreased activation in prefrontal brain regions (dorsolateral prefrontal cortex and dorsomedial prefrontal cortex) during error processing compared to OCD and control groups.

Switch-signal task:

• OCD group: Showed increased activation in the rostral anterior cingulate cortex during error processing compared to HD and control groups.

• HD group: Showed decreased activation in several prefrontal regions (dorsolateral prefrontal cortex, lateral orbitofrontal cortex) during error processing. They also showed increased activation in the lateral orbitofrontal cortex during successful task switching.

What do these findings mean?

The results reveal distinct patterns of brain activation in HD and OCD during executive function tasks:

Hoarding Disorder

People with HD showed an impulsive pattern of responding behaviorally - they responded quickly but made more errors. This was accompanied by reduced brain activation when processing errors.

This pattern suggests people with HD may have difficulty monitoring their performance and adjusting their behavior based on mistakes. The impulsive responding could relate to problems with discarding items - acting quickly without fully processing potential consequences.

The increased orbitofrontal activation during task switching may reflect greater cognitive effort required to successfully shift behavioral patterns. This could relate to difficulty changing engrained habits around acquiring and saving items.

Obsessive-Compulsive Disorder

People with OCD showed increased brain activation in the anterior cingulate cortex during error processing. This region is involved in performance monitoring and detecting conflicts between intended and actual responses.

The heightened activity suggests people with OCD may engage in excessive error monitoring and performance checking. This fits with OCD symptoms like repeated checking behaviors or an intense focus on doing things “perfectly.”

Distinct profiles support separate diagnoses

The clear differences in brain activation patterns provide neurobiological evidence supporting the classification of HD and OCD as separate disorders. While they may share some surface similarities, the underlying brain processes appear to be quite different.

Conclusions

• People with hoarding disorder show an impulsive pattern of responding and reduced brain activation when processing errors during executive tasks
• People with OCD show increased brain activation during error processing, suggesting heightened performance monitoring
• These distinct neural profiles align with and help explain core symptoms of each disorder
• The findings provide neurobiological support for classifying hoarding disorder and OCD as separate conditions

While more research is still needed, these results offer important insights into the brain basis of hoarding and obsessive-compulsive symptoms. Understanding these differences may eventually lead to more targeted treatments for each condition.