Figure 6. Sensorimotor integration during odor sensing.

A. Humans show rapid modulation of sniff magnitude as a function of odorant concentration. Blue and purple traces show mean intranasal flow rate for low and high concentrations of an odorant; black trace shows the p-value of the difference between the flow rates at each concentration. Sniff flow rates diverge and remain different at 160 msec after inhalation onset. Modified with permission from (Johnson et al., 2003).

B. Rats show similarly rapid changes in sniffing in response to a novel odorant. Red and blue plots show cumulative inhalation count over time during presentations of novel versus familiar (‘learned’) odorants. Black plot shows p-value of the difference between novel and learned trials. Sniff counts diverges significantly at 140 msec after the first inhalation. Modified with permission from (Wesson et al., 2008a).

C. Potential substrates for cortical control of sniffing behavior. Electrical stimulation of infralimbic cortex in an anesthetized rat elicits respiratory changes that closely resemble exploratory sniffing (compare with Figure 4A). Modified with permission from Aleksandrov et al. (2007).

D. Schematic illustrating the potential neural pathways involved in attentional modulation and sensorimotor integration during sniffing. Gray paths indicate the movement of odorant molecules through the nasal cavity; blue paths indicate sensory afferent pathways; red paths indicate centrifugal pathways targeting OB and PC. Dashed lines indicate more speculative connections. See text for references. IL, Infralimbic cortex; Ins, Insular cortex; LC, locus coeruleus; RN, Raphe nuclei; Cb, cerebellum; NTS, nucleus of the solitary tract. Brain template courtesy of A. Puche, Univ. of Maryland.