Servatius, R J, Tapp, W N, Bergen, M T et al. · Neuroreport · 1998 · DOI
This study tested whether people with ME/CFS have problems with how their brain learns and forms connections between different pieces of information. Researchers measured brain learning using a test where a gentle puff of air is paired with an eye blink stimulus. While ME/CFS patients could hear and feel the stimuli normally, they had difficulty learning to associate the two stimuli together—suggesting their brain's ability to form certain types of connections may be affected.
This research provides objective neurobiological evidence for cognitive dysfunction in ME/CFS by identifying a specific brain-level learning deficit, moving beyond subjective patient reports. The findings suggest that some cognitive symptoms may reflect genuine organic changes in brain function rather than psychiatric causes, validating patient experiences and potentially opening pathways for targeted treatments.
This study does not prove that all cognitive complaints in ME/CFS stem from associative learning deficits—it documents one specific impairment. The findings are correlational and cannot establish whether this deficit causes fatigue or cognitive symptoms, nor can they explain the underlying biological mechanism. Results from a single conditioning task may not generalize to everyday memory, attention, or reasoning problems patients report.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
The first block is for the primary paper and is the citation you should use in research work. The atlas-snapshot line only applies if you are specifically referring to this atlas’s reading of the paper on the date shown.
Primary citation
Servatius, R J, Tapp, W N, Bergen, M T, Pollet, C A, Drastal, S D, Tiersky, L A, et al. (1998). Impaired associative learning in chronic fatigue syndrome.. Neuroreport. https://doi.org/10.1097/00001756-199804200-00036
BibTeX
@article{mecfsatlas-servatius-1998-impaired-associative,
author = {Servatius, R J and Tapp, W N and Bergen, M T and Pollet, C A and Drastal, S D and Tiersky, L A and Desai, P and Natelson, B H},
title = {Impaired associative learning in chronic fatigue syndrome.},
journal = {Neuroreport},
year = {1998},
doi = {10.1097/00001756-199804200-00036},
note = {PubMed: 9601685},
url = {https://www.mecfsatlas.com/evidence/servatius-1998-impaired-associative},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-26. https://www.mecfsatlas.com/evidence/servatius-1998-impaired-associative
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