Probing the working memory system in chronic fatigue syndrome: a functional magnetic resonance imaging study using the n-back task.
OBJECTIVE
Up to 90% of patients with chronic fatigue syndrome (CFS) report substantial cognitive difficulties. However, objective evidence supporting these claims is inconsistent. The present functional magnetic resonance imaging study examined the neural correlates of working memory in patients with CFS compared with controls.


METHODS
Seventeen patients with CFS and 12 healthy control subjects were scanned while performing a parametric version of the n-back task (0-, 1-, 2-, and 3-back).


RESULTS
Both groups performed comparably well and activated the verbal working memory network during all task levels. However, during the 1-back condition, patients with CFS showed greater activation than control subjects in medial prefrontal regions, including the anterior cingulate gyrus. Conversely, on the more challenging conditions, patients with CFS demonstrated reduced activation in dorsolateral prefrontal and parietal cortices. Furthermore, on the 2- and 3-back conditions, patients but not control subjects significantly activated a large cluster in the right inferior/medial temporal cortex. Trend analyses of task load demonstrated statistically significant differences in brain activation between the two groups as the demands of the task increased.


CONCLUSIONS
These results suggest that patients with CFS show both quantitative and qualitative differences in activation of the working memory network compared with healthy control subjects. It remains to be determined whether these findings stay stable after successful treatment.
Caseras
Xavier
X
Unitat de Psicologia Mèdica, Institut de Neurociències, Universitat Autònoma de Barcelona, Barcelona, Spain. x.caseras@iop.kcl.ac.uk
Mataix-Cols
David
D
Giampietro
Vincent
V
Rimes
Katharine A
KA
Brammer
Michael
M
Zelaya
Fernando
F
Chalder
Trudie
T
Godfrey
Emma L
EL
D000328:Adult; D016022:Case-Control Studies; D015673:Fatigue Syndrome, Chronic / Q000150:complications* / Q000378:metabolism* / Q000523:psychology; D005260:Female; D006179:Gyrus Cinguli / Q000378:metabolism; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008568:Memory / Q000502:physiology*; D008875:Middle Aged; D017397:Prefrontal Cortex / Q000378:metabolism; D013647:Task Performance and Analysis