St Peters MM, Bruno JP, Sarter M (2010) Mesolimbic-basal forebrain circuitry mediating the motivational activation of attention. Neuroscience 2010 Abstracts 506.12/LLL52. Society for Neuroscience, San Diego, CA.
Summary: Prefrontal circuitry mediating cue detection is modulated by the tonic component of cholinergic activity. Performance-associated increases in tonic cholinergic activity are augmented by demands on the cognitive control of attention. Highest levels of tonic cholinergic activity are observed while animals perform below baseline as a result of, for example, a distractor, but while they remain motivated to stabilize and recover attentional performance. Cortico-mesolimbic-basal forebrain circuitry is thought to mediate such motivated activation of attentional performance. We previously observed that stimulation of ionotropic glutamate receptors in the shell of the nucleus accumbens (NAs) stimulates tonic cholinergic activity in the prefrontal cortex. Here we test the hypothesis that such stimulation benefits attentional performance while distractors evoke cognitive control. Rats were trained in an operant sustained attention task (SAT) before undergoing surgery for implantation of a bilateral guide cannula targeting the NAs or, in separate animals, the core of the NA (NAc). NMDA (0.01-0.15 µg/0.5 µL/hemisphere) or vehicle (0.9% saline) was infused bilaterally into task-performing animals during SAT and the more challenging distractor version (dSAT). For the dSAT, the operant chamber ceiling lights flashed on/off at 0.5 Hz during the middle block of three blocks of trials that constituted a session. NMDA infusions in the NAs, but not into the NAc, significantly improved the animals’ attentional performance in the presence of the distractor. These findings are consistent with the hypothesis that activation of the NAs mediates attentional performance under conditions that require top-down control. The next set of experiments determined whether the effects of NAs activation require the cortical cholinergic system. We infused the immunotoxin 192 IgG saporin into prefrontal or parietal regions, in addition to implantation of guide cannula targeting the NAs. Replicating the initial finding, NAs NMDA infusions enhanced dSAT performance. Both PFC and PPC cholinergic deafferentation prevented this effect of NMDA. These findings suggest that the motivated activation of the cholinergic attention system during demands on top-down control modulates fronto-parietal attention networks to optimize attentional performance.
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