A visit to consciousness

Cognition and consciousness. This study shows clearly that consciousness is not necessary to activate cognitive circuitry. Subliminal stimuli show activation of hippocampal (novelty) and prefrontal structures.

The figure shows increased activation in the prefrontal and hippocampal regions during explicit retrieval elicited by subliminally presented primed (Recognized) and unprimed (Unrecognized) stimuli. A majority of stimuli in the primed condition were recognized by the volunteers, while in the unprimed condition, most of the stimuli were unrecognized. The prefrontal activity was unilateral (left middle frontal gyrus) in the unprimed (Unrecognized) condition, and bilateral (left middle frontal and right superior frontal gyri) in the primed (Recognized) condition. Primed stimuli activated the right hippocampus while unprimed stimuli activated the left hippocampus. Histograms show percent change in MR signal intensity in different contrast conditions in the areas of interest: R = Recognized (primed) picture; U = Unrecognized (unprimed) picture; B = Baseline condition; BA = Brodmann's area. Cortical activation elicited by unrecognized stimuliRajendra D Badgaiyan Department of Radiology Harvard Medical School; and Massachusetts General Hospital, Boston, MA 02114, USABehavioral and Brain Functions 2006, 2:17 doi:10.1186/1744-9081-2-17 The electronic version of this article is the complete one and can be found online at: http://www.behavioralandbrainfunctions.com/content/2/1/17