title: Neural networks engaged in tactile object manipulation: patterns of expression among healthy individuals.
abstract: BACKGROUND
  Somatosensory object discrimination has been shown to involve widespread cortical and subcortical structures in both cerebral hemispheres. In this study we aimed to identify the networks involved in tactile object manipulation by principal component analysis (PCA) of individual subjects. We expected to find more than one network.
  
  
  METHODS
  Seven healthy right-handed male volunteers (aged 22 to 44 yrs) manipulated with their right hand aluminium spheres during 5 s with a repetition frequency of 0.5-0.7 Hz. The correlation coefficients between the principal component temporal expression coefficients and the hemodynamic response modelled by SPM (ecc) determined the task-related components. To establish reproducibility within subjects and similarity of functional connectivity patterns among subjects, regional correlation coefficients (rcc) were computed between task-related component image volumes. By hierarchically categorizing, selecting and averaging the task-related component image volumes across subjects according to the rccs, mean component images (MCIs) were derived describing neural networks associated with tactile object manipulation.
  
  
  RESULTS
  Two independent mean component images emerged. Each included the primary sensorimotor cortex contralateral to the manipulating hand. The region extended to the premotor cortex in MCI 1, whereas it was restricted to the hand area of the primary sensorimotor cortex in MCI 2. MCI 1 showed bilateral involvement of the paralimbic anterior cingulate cortex (ACC), whereas MCI 2 implicated the midline thalamic nuclei and two areas of the rostral dorsal pons.
  
  
  CONCLUSIONS
  Two distinct networks participate in tactile object manipulation as revealed by the intra- and interindividual comparison of individual scans. Both were employed by most subjects, suggesting that both are involved in normal somatosensory object discrimination.
authors.affiliation: Department of Neurology, Kantonsspital St, Gallen, St, Gallen, Switzerland.
authors.forename: Georg
authors.initials: G
authors.lastname: Kägi
authors.forename: John H
authors.initials: JH
authors.lastname: Missimer
authors.forename: Eugenio
authors.initials: E
authors.lastname: Abela
authors.forename: Rüdiger J
authors.initials: RJ
authors.lastname: Seitz
authors.forename: Bruno J
authors.initials: BJ
authors.lastname: Weder
mesh_terms: D000328:Adult; D004192:Discrimination, Psychological / Q000502:physiology; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D006801:Humans; D008297:Male; D009415:Nerve Net / Q000502:physiology*; D011597:Psychomotor Performance / Q000502:physiology*; D014110:Touch / Q000502:physiology*; D055815:Young Adult