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Abstract

Converging evidence from lesion, imaging, and electrophysiology studies suggest that different prefrontal sub-regions play different roles in goal-directed behavior. We have recorded single units and local field potentials (LFP) in the rat prelimbic (PL) and anterior cingulate (CG) cortices during a sustained attention task. The 3-choice serial reaction time task requires a rat to orient toward and divide attention between 3 brief (300 msec duration) light stimuli presented in random order across nose poke holes in an operant conditioning chamber. In 12 rats, single unit phasic responses were analyzed for 4 peri-event time windows: cue onset and correct, incorrect, and premature nose poke responses. We found attention-related phasic responses (at least 3 consecutive 200 msec bins with z-score greater than 2.36) of single units during a 4 sec pre-cue window. On correct trials, 19/111 total units (17.1%) in CG and 9/155 total units (5.8%) in PL exhibited excitatory phasic responses. Inhibitory phasic responses were observed in 14/111 total units (12.6%) in CG and 11/155 total units (7.1%) in PL. On incorrect (poorly attended) trials, fewer units were responsive to the cue and the population response was lower in magnitude. On unattended trials when the rat did not orient to the cues, only 3/111 (2.7%) of CG units and 2/155 (1.3%) of PL units were responsive to the cue. In order to investigate the role of dopamine in modulating the representation of attention in the prefrontal cortex, we administered both vehicle and systemic 0.5 mg/kg methylphenidate 30 min prior to task recordings. We are currently analyzing these recordings to determine if methylphenidate affects the number of attention-related units and the magnitude of the population response. Our results suggest that the CG cortex may represent attention to a greater degree than the PL cortex.