Selective involvement of the mid-dorsolateral prefrontal cortex in the coding of the serial order of visual stimuli in working memory.

There is evidence that the primate prefrontal cortex is involved in the monitoring of the order in which stimuli occur. The prefrontal cortical areas, however, involved in the capacity of the human brain to encode and hold "in mind" the precise order of occurrence of a limited number of visual stimuli after a single exposure are not known. Changes in regional cerebral activity were measured with functional magnetic resonance imaging while subjects were coding the precise order of a short sequence of abstract visual stimuli. The results demonstrate the involvement of areas 46 and 9/46, within the mid-dorsolateral subdivision of the prefrontal cortex, in the coding of the precise order of a short sequence of visual stimuli in working memory, consistent with earlier results from monkey lesion studies. The availability of such detailed serial-order information in working memory allows high-level cognitive planning and mental manipulation, functions that depend on prefrontal cortex.