Tracking Cognitive Rigidity in OCD

Five strangers met on the day with nothing in common but a shared interest. Hardware hackathons are harder than most; you cannot wire up an API and call it a demo. Neurotech compounds the difficulty because you need something grounded in the science. You need to understand what an ERN signal looks like before you can start building anything to measure it. First time I have ever read a research paper during a hackathon. That tells you what kind of weekend it was.

What we built

Flextra is a mobile app that pairs EEG signals from a gTec EEG cap with cognitive flexibility tasks. The goal: give clinicians a quantitative window into cognitive rigidity, one of the core features of OCD.

OCD brains produce an amplified error-related negativity (ERN) roughly 80ms after a mistake; your brain’s alarm bell stuck on full volume. The ERN is one of the most replicated findings in OCD neuroscience. Flextra captures that signal during structured tasks and tracks it over time, so changes in rigidity become visible rather than self-reported.

Why it matters

Cognitive rigidity is not just a symptom; it is an endophenotype. First-degree relatives of OCD patients show impaired cognitive flexibility even without a diagnosis. The ERN stays elevated in children with OCD even after successful CBT. Treatment quiets the compulsions, but the underlying signal persists.

The same error-monitoring signature appears across OCD, anxiety, and substance use disorders. A tool that tracks it could serve more than one condition.

Team

• Sorcha — our expert on OCD. I was asking “what can we ship in 24 hours?”; she was asking “what is actually clinically relevant?”
• Sharleen — sacrificed her head and her laptop to the EEG cap so we could chase down ERN responses in the literature together
• Kyran — built the app, then shot a demo video with more taste than most startups manage in months
• Eleni — brought the commercial sense; plus taught me the insane fact that you can genetically modify fruit flies to not need sleep, a talent I sorely envied by Sunday morning

What to read at 3am in a hackathon

Some rabbit holes if the neuroscience caught your eye.

• The “something’s wrong” signal: OCD brains produce an amplified error response (ERN) ~80ms after a mistake. One of the most replicated findings in OCD neuroscience. Endrass & Ullsperger, 2014
• Rigidity runs in families: First-degree relatives of OCD patients show impaired cognitive flexibility even without a diagnosis, suggesting it is an endophenotype. Chamberlain et al., 2007
• Habit over intention: OCD keeps you responding to cues even when the outcome has changed. Gillan et al., 2011
• Treatment does not quiet the alarm: The ERN stays elevated in children with OCD even after successful CBT. Hajcak et al., 2008
• It is transdiagnostic: The same error-monitoring signal appears across OCD, anxiety, and substance use disorder. Riesel et al., 2019