Our finding that neurons providing perisomatic inhibition in both V1 and MT express m1 AChRs, would lead to the prediction that ACh will modulate the level of synchronous firing, probably in the γ band, in both cortical areas. Non-PV neurons as targets for cholinergic modulation We were unable, on the basis of the data

gathered in this study, Inhibitors,research,lifescience,medical to definitively identify the neuronal class of the large number of non-PV neurons in MT that express the m1 AChR. However based on their sheer numbers (80% of m1 AChR-ir neurons were not PV-ir), our prior report that the proportion of excitatory neurons that express m1 AChRs is higher in the extrastriate cortex (V2) than it is in V1, (Disney et al. 2006), and our unpubl. obs. (A. A. Disney) that a little more than half of the m1 AChR-expressing population in area MT is not immunoreactive

for GABA; this group of cells is likely to be largely comprised of excitatory neurons. Acetylcholine and attention It has been proposed that ACh plays a role in attention Inhibitors,research,lifescience,medical (Everitt and Robbins 1997; Sarter et al. 2005). Most – but not all (Herrero et al. 2008) – of the research implicating ACh release in attention has been Inhibitors,research,lifescience,medical conducted in rodents. At the same time our most sophisticated behavioral models of attention arise from research in macaque monkeys. What role does ACh play in attention in the macaque? Attention has been shown Inhibitors,research,lifescience,medical to alter the gain of neuronal responses throughout the visual pathway of macaques (Motter 1993; Treue and Maunsell 1996; McAdams and Maunsell 1999; Reynolds et al. 2000). ACh has also been found to multiplicatively increase the gain of the ascending visual input to V1 of the

macaque (Disney et al. 2007). Similarly, attention Inhibitors,research,lifescience,medical has been shown to suppress activity in response to task-irrelevant distracters (Moran and Desimone 1985; Reynolds et al. 1999; Sundberg et al. 2009) and to alter the frequency of oscillatory activity in cortical networks (Fries et al. 2001; Chalk et al. 2010). Both of these functions could be enabled through the control of soma-targeting and lateral inhibition. Attention has also Ketanserin been shown to strongly and consistently influence the spiking behavior of narrow-spiking, nonbursting neurons in area V4 (Anderson et al. 2011a) a population that is likely to be largely made up of PV neurons (Kawaguchi and Kubota 1993; Chow et al. 1999; Constantinople et al. 2009; Anderson et al. 2011a). The overall effects of attention on this population of putatively inhibitory neurons are stronger and more consistent than the overall effects of attention on their excitatory neighbors (Mitchell et al. 2007). The common model for attention effects in area V4 proposes that glutamatergic feedback from the frontal eye fields carries a modulating attention Tanespimycin chemical structure signal to V4.