Potential pathways underlying sensorimotor integration during sniffing are outlined in Figure 6D. However, much of the neural circuitry mediating motor-related control of olfactory processing remains unclear, largely because the premotor control of sniffing is poorly understood. One important structure may be the cerebellum, which is activated during sniffing, may receive olfactory input from PC, and is involved in optimizing motor output

for sensory acquisition in other modalities (Mainland DNA Synthesis inhibitor and Sobel, 2006, Robinson, 1976 and Sobel et al., 1998b). Sniffing is also likely under cortical control: several cortical areas, including the insular and infralimbic cortices, send projections to brainstem nuclei (such as the nucleus of the solitary tract) involved in respiratory pattern generation (Bianchi et al., 1995), and electrical stimulation of insular and infralimbic cortices alters respiration in anesthetized rats and can elicit increases in respiration frequency that mimic exploratory sniff bouts (Alexandrov et al., 2007; Figure 6C). Whether activation of these or other areas modulate NLG919 research buy processing in olfactory areas such as OB and PC remains untested. Classical neuromodulatory pathways likely also play a role in directed attention. For example, cholinergic inputs to visual cortex alter visual responses via muscarinic acetylcholine receptors (Goard and Dan,

2009 and Herrero

et al., 2008), and dopaminergic signaling modulates the top-down control of visual responses by frontal eye field neurons (Noudoost and Moore, 2011). In the olfactory system, cholinergic, noradrenergic, and serotonergic projections all target OB and PC (McLean and found Shipley, 1992) and can modulate olfactory responses (Chaudhury et al., 2009, Petzold et al., 2009 and Shea et al., 2008; Figure 6D). In addition, olfactory cortical areas send strong centrifugal projections to the OB and are hypothesized to modulate odorant processing by affecting the strength of inhibition within the OB network (Strowbridge, 2009). Importantly, several of these areas are activated during sniffing in the absence of odorant, presumably by the airflow-driven, somatosensory component of a sniff (Adrian, 1942, Sobel et al., 1998a and Grosmaitre et al., 2007). Sniff-induced feedback from olfactory cortical areas to OB or PC might thus provide an alternate, “bottom-up” mechanism by which a sniff can modulate olfactory processing. The active control of stimulus sampling and sensory information processing is fundamental to all sensory systems, and investigating sensory function from a perspective of active sensing is important not only for understanding sensation in the behaving animal but also for integrating data obtained with different experimental approaches and at different levels of the nervous system.