Does C9orf72 already change parietal EEG before ALS symptoms?
In 87 asymptomatic relatives of C9orf72 ALS patients, carriers and non-carriers scored the same on a Go/NoGo attention task, but carriers showed stronger N2 negativity localized to precuneus and superior parietal cortex.
Source
Altered EEG Response of the Parietal Network in Asymptomatic C9orf72 Carriers
Study at a glance
- Design
- Case-control — Asymptomatic C9orf72 expansion carriers vs related non-carriers; high-density EEG during SART Go/NoGo, linear mixed models with pedigree
- N
- N=87 · 87 asymptomatic family members (37 C9+, 50 C9−) after excluding 12 of 99 recruited relatives
- Population
- Adult asymptomatic relatives of patients with familial C9orf72 ALS (UMC Utrecht, 2020–2024)
- Outcome
- Sensor- and source-space EEG (N2/P3 and response-locked) plus six SART behavioral measures
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What they did
Recorded 128-channel BioSemi EEG at 512 Hz during SART in 37 C9+ and 50 C9− family members, analyzing stimulus-locked N2 (180–350 ms) and P3 (300–600 ms) plus response-locked ±100 ms windows with pedigree-aware linear mixed models.
What they found
No group difference on six SART metrics. During N2, C9+ carriers had a larger negative potential at central sensors; source analysis localized this to bilateral precuneus and superior parietal regions, with response-locked data implicating the same posterior network.
The limits
What it doesn't show
Cross-sectional EEG cannot prove these parietal changes predict conversion to ALS/FTD, and groups were not age-matched until sensitivity analyses; it is not a treatment or diagnostic-accuracy trial.
Key terms
- C9orf72 repeat expansion
- Hexanucleotide expansion that is the most common genetic cause of ALS in people of European ancestry.
- SART
- Sustained Attention to Response Task: a Go/NoGo paradigm engaging frontoparietal and motor networks.
- N2 / P3
- Stimulus-locked EEG windows 180–350 ms (N2) and 300–600 ms (P3) used in this analysis.
- Precuneus
- Medial parietal region where C9+ carriers showed increased source activity.
- AFM
- Asymptomatic family members: no clinical motor neuron signs, bulbar dysfunction, or cognitive impairment.
- Linear mixed model
- Group comparison that included familial pedigree to handle relatedness.
Flashcards
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Common questions
How many asymptomatic relatives were analyzed?
87 (37 C9+ and 50 C9−) from 99 recruited family members.
Did SART accuracy differ by genotype?
No—groups did not differ on any of six SART performance measures.
Where was the EEG difference localized?
Bilateral precuneus and superior parietal regions during the N2.
What EEG system was used?
BioSemi Active Two, 128 electrodes, sampled at 512 Hz.
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