The role of prefrontal cortex in sensory memory and motor preparation: An event-related fMRI study

Delayed response tasks are behavioral paradigms in which subjects must reme mber stimulus attributes across a delay to subsequently perform the appropr iate motor response. Quintana and Fuster (1992), reported that there exist subpopulations of neurons in monkey lateral prefrontal cortex (PFC) whose f iring rates during the delay are tuned to either sensorial attributes of th e stimulus (i.e., involved in sensory memory) or the direction of a postdel ay motor response associated with the stimulus (i.e., involved in motor pre paration). We studied human subjects with an event-related fMRI method that would allow us to test the hypothesis that there are regions within the PF C that are recruited during both motor preparation and sensory memory. Subj ects performed a delayed-response task with two types of trials that either (1) allowed subjects to prepare during a delay period for a specific motor response or (2) required that subjects maintain a sensory attribute (speci fically, color) during a delay period for correct performance postdelay. It was assumed that during the delay periods, the delayed-response trials wou ld engage motor preparation while delayed-match trials would engage sensory memory. Behavioral data supported this assumption. Imaging results support the hypothesis that the PFC is involved in both motor preparation and sens ory memory. Furthermore, no selectivity (in terms of intensity of neural re presentation on the spatial scale of the voxel size <5 mm(3)) for motor pre paration over sensory memory (or vice-versa) was detected within the PFC, T his latter result fails to support a gross anatomical segregation within th e PFC with respect to involvement in these two cognitive processes. (C) 200 0 Academic Press.