title: Effect of Mild Thyrotoxicosis on Performance and Brain Activations in a Working Memory Task.
abstract: OBJECTIVE
  Disturbed levels of thyroid hormones are associated with neuropsychiatric disorders, including memory impairments. The aim of this study was to evaluate effects of mild induced thyrotoxicosis on working memory and its neural correlates.
  
  
  METHODS
  Twenty-nine healthy, male subjects with normal thyroid state participated in the study. Functional MRI was acquired during a working memory task (n-back task) before and after ingesting 250 μg L-thyroxin per day for a period of eight weeks. In addition, neuropsychological tests were performed.
  
  
  RESULTS
  In the hyperthyroid condition the subjects showed slower reaction times, but a higher accuracy in the 0-back version of the memory tasks. Fewer differences between euthyroid and hyperthyroid state were seen for the more difficult conditions of the n-back task. FMRI revealed effects of difficulty in the parahippocampal gyrus, supplementary motor area, prefrontal cortex, anterior cingulate cortex, posterior cerebellum, rolandic operculum and insula (p<0.05, FWE corrected). When comparing euthyroid and hyperthyroid condition in relation to task-induced activation, differences of activation were found in the right prefrontal cortex as well as in the right parahippocampal area. In the psychological assessment, the alerting effect in the Attention Network Task (ANT) and four out of five parameters of the auditory verbal learning test (AVLT) showed an increase from euthyroid to hyperthyroid state.
  
  
  CONCLUSIONS
  It can be concluded that even a short-term intake of thyroid hormones leads to an activation of brain areas associated with working memory and to an improvement of accuracy of working memory tasks.
authors.affiliation: Department of Neurology, University of Lübeck, 23538, Lübeck, Germany.
authors.forename: Anna
authors.initials: A
authors.lastname: Göbel
authors.affiliation: Department of Neurology, University of Lübeck, 23538, Lübeck, Germany.
authors.forename: Marcus
authors.initials: M
authors.lastname: Heldmann
authors.affiliation: Department of Neurology, University of Lübeck, 23538, Lübeck, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Göttlich
authors.affiliation: Department of Internal Medicine I, University of Lübeck, 23538, Lübeck, Germany.
authors.forename: Anna-Luise
authors.initials: AL
authors.lastname: Dirk
authors.affiliation: Department of Internal Medicine I, University of Lübeck, 23538, Lübeck, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Brabant
authors.affiliation: Department of Neurology, University of Lübeck, 23538, Lübeck, Germany.
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Münte
mesh_terms: D000328:Adult; D001921:Brain / Q000000981:diagnostic imaging / Q000187:drug effects / Q000503:physiopathology*; D004334:Drug Administration Schedule; D059907:Functional Neuroimaging; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008570:Memory, Short-Term / Q000187:drug effects / Q000502:physiology*; D008875:Middle Aged; D009483:Neuropsychological Tests; D011930:Reaction Time / Q000187:drug effects / Q000502:physiology; D013971:Thyrotoxicosis / Q000503:physiopathology*; D013974:Thyroxine / Q000008:administration & dosage / Q000494:pharmacology; D055815:Young Adult
chemical_list: D013974:Thyroxine