, 2009). Interestingly, basal forebrain activation also causes a decrease in interneuronal correlation and increase in sensory-driven response reliability in the visual cortex (Figure 3C), and both effects contribute to improved coding of natural scenes (Goard and

Dan, 2009). The strong similarity between the effects of attention and basal forebrain activation again suggests an involvement of the cholinergic system in selective attention. The decrease in interneuronal correlation may be mediated by mAChRs within the cortex Selleck BEZ235 (Goard and Dan, 2009; Metherate et al., 1992), whereas the improved visual responses of single cortical neurons could involve enhanced responses of thalamic neurons (Goard and Dan, 2009), nAChR-dependent augmentation of thalamocortical transmission (Disney et al., 2007),

and/or mAChR-dependent firing rate increase within the cortex (Herrero et al., 2008; Soma et al., 2012). The recent finding that cholinergic activity can be modulated in a task-dependent manner (Parikh et al., 2007) further supports the plausibility of its involvement in attentional modulation. Of course, it is possible that the cholinergic input plays a permissive rather than instructive role. Selective attention is associated with local activity changes in neurons encoding the attended stimuli, but the neuromodulatory systems in general project BIBW2992 datasheet diffusely to multiple brain regions. Although there is some topographical

organization of the basal nearly forebrain projections to the cortex (Zaborszky et al., 1999), whether there is sufficient spatial precision to support the local modulation by selective attention remains unclear. Another candidate pathway is the top-down feedback from higher-order cortical areas, such as the frontal eye field (FEF), to the visual cortical areas (Gregoriou et al., 2009; Moore and Fallah, 2004; Zhou and Desimone, 2011) (Figure 6). Interestingly, firing rate increases in the FEF induced by local application of a dopamine receptor antagonist mimicked the attentional modulation of V4 neuronal responses (Noudoost and Moore, 2011), suggesting that the effect of neuromodulators could also be mediated by activating the cortico-cortical glutamatergic pathways. While selective attention is typically associated with firing rate increase of the relevant neurons, behavioral arousal or task engagement in general does not always lead to enhanced responses. In the barrel cortex, behavioral arousal or engagement in the learning of a new task was found to suppress whisker-evoked responses (Castro-Alamancos, 2004a; Castro-Alamancos and Oldford, 2002). Similarly, smaller responses to brief tactile stimuli were observed in the rat during exploratory whisker movement than during quiet immobility (Fanselow and Nicolelis, 1999).