title: Subliminal versus supraliminal stimuli activate neural responses in anterior cingulate cortex, fusiform gyrus and insula: a meta-analysis of fMRI studies.
abstract: BACKGROUND
  Non-conscious neural activation may underlie various psychological functions in health and disorder. However, the neural substrates of non-conscious processing have not been entirely elucidated. Examining the differential effects of arousing stimuli that are consciously, versus unconsciously perceived will improve our knowledge of neural circuitry involved in non-conscious perception. Here we conduct preliminary analyses of neural activation in studies that have used both subliminal and supraliminal presentation of the same stimulus.
  
  
  METHODS
  We use Activation Likelihood Estimation (ALE) to examine functional Magnetic Resonance Imaging (fMRI) studies that uniquely present the same stimuli subliminally and supraliminally to healthy participants during functional magnetic resonance imaging (fMRI). We included a total of 193 foci from 9 studies representing subliminal stimulation and 315 foci from 10 studies representing supraliminal stimulation.
  
  
  RESULTS
  The anterior cingulate cortex is significantly activated during both subliminal and supraliminal stimulus presentation. Subliminal stimuli are linked to significantly increased activation in the right fusiform gyrus and right insula. Supraliminal stimuli show significantly increased activation in the left rostral anterior cingulate.
  
  
  CONCLUSIONS
  Non-conscious processing of arousing stimuli may involve primary visual areas and may also recruit the insula, a brain area involved in eventual interoceptive awareness. The anterior cingulate is perhaps a key brain region for the integration of conscious and non-conscious processing. These preliminary data provide candidate brain regions for further study in to the neural correlates of conscious experience.
authors.affiliation: Department of Neuroscience, University of Padua, Padova, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Meneguzzo
authors.affiliation: Lab of Action and Body, Department of Psychology, Royal Holloway, University of London, London, UK.
authors.forename: Manos
authors.initials: M
authors.lastname: Tsakiris
authors.affiliation: Department of Neuroscience, Uppsala University, Uppsala, Sweden.
authors.forename: Helgi B
authors.initials: HB
authors.lastname: Schioth
authors.affiliation: Department of Psychiatry and Mental Health, University of Cape Town, Anzio Road, Cape Town, 7995 South Africa.
authors.forename: Dan J
authors.initials: DJ
authors.lastname: Stein
authors.affiliation: Department of Psychiatry and Mental Health, University of Cape Town, Anzio Road, Cape Town, 7995 South Africa.
authors.forename: Samantha J
authors.initials: SJ
authors.lastname: Brooks
keywords: ANterior cingulate cortex; Activation Likelihood Estimation; Fusiform gyrus, Cingulate cortex; Insula; Subliminal; Supraliminal