title: Probing the working memory system in chronic fatigue syndrome: a functional magnetic resonance imaging study using the n-back task.
abstract: 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.
authors.affiliation: Unitat de Psicologia Mèdica, Institut de Neurociències, Universitat Autònoma de Barcelona, Barcelona, Spain. x.caseras@iop.kcl.ac.uk
authors.forename: Xavier
authors.initials: X
authors.lastname: Caseras
authors.forename: David
authors.initials: D
authors.lastname: Mataix-Cols
authors.forename: Vincent
authors.initials: V
authors.lastname: Giampietro
authors.forename: Katharine A
authors.initials: KA
authors.lastname: Rimes
authors.forename: Michael
authors.initials: M
authors.lastname: Brammer
authors.forename: Fernando
authors.initials: F
authors.lastname: Zelaya
authors.forename: Trudie
authors.initials: T
authors.lastname: Chalder
authors.forename: Emma L
authors.initials: EL
authors.lastname: Godfrey
mesh_terms: 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