Characterization and Coding of Behaviorally Significant Odor Mixtures

Abstract

Summary For animals to execute odor-driven behaviors, the olfactory system must process complex odor signals and maintain stimulus identity in the face of constantly changing odor intensities [1–5]. Surprisingly, how the olfactory system maintains identity of complex odors is unclear [6–10]. We took advantage of the plant-pollinator relationship between the Sacred Datura (Datura wrightii) and the moth Manduca sexta [11, 12] to determine how olfactory networks in this insect’s brain represent odor mixtures. We combined gas chromatography and neural-ensemble recording in the moth’s antennal lobe to examine population codes for the floral mixture and its fractionated components. Although the floral scent of D. wrightii comprises at least 60 compounds, only nine of those elicited robust neural responses. Behavioral experiments confirmed that these nine odorants mediate flower-foraging behaviors, but only as a mixture. Moreover, the mixture evoked equivalent foraging behaviors over a 1000-fold range in dilution, suggesting a singular percept across this concentration range. Furthermore, neural-ensemble recordings in the moth’s antennal lobe revealed that reliable encoding of the floral mixture is organized through synchronized activity distributed across a population of glomerular coding units, and this timing mechanism may bind the features of a complex stimulus into a coherent odor percept.

Attractiveness of Constitutive and Herbivore-Induced Sesquiterpene Blends of Maize to the Parasitic Wasp Cotesia marginiventris (Cresson)

“…Complex volatile blends are known to play important roles in plant-insect interactions besides attraction of herbivore enemies. In a recent study, Riffell and coworkers investigated the perception and behavioral response of the moth Manduca sexta L. (Lepidoptera: Sphingidae) to the floral volatiles of the Sacred Datura (Datura wrightii (Regel), Solanaceae) (Riffell et al, 2009). Of the over 60 components of the floral scent, many of them terpenes, nine elicited a neural response in the moth, and, among these, four were monoterpenes (linalool, nerol, β-myrcene, and geraniol), and two were sesquiterpene hydrocarbons ((E)-β-caryophyllene and (E,E)-α-farnesene).…”

Graded Encoding of Food Odor Value in theDrosophilaBrain

“…The vast majority of neurons in the early olfactory system of both mammals and invertebrates are broadly tuned, responding to a large range of differing types of odorants Fishilevich and Vosshall, 2005;Wilson and Mainen, 2006;Lin et al, 2006;Kreher et al, 2008;Riffell et al, 2009;Johnson et al, 2010). These nonspecific response profiles mean that individual ORNs or PNs in D. melanogaster that respond to a behaviorally attractive odor can also respond with equal strength to a behaviorally aversive odor Fishilevich and Vosshall, 2005;Kreher et al, 2008;Semmelhack and Wang, 2009).…”

“…Specific subsets of cells at this stage are essential to produce odor-related approach or avoidance behaviors (Suh et al, 2004;Kreher et al, 2008;Semmelhack and Wang, 2009;Ai et al, 2010;Root et al, 2011); but because it is well documented that neurons at this level are broadly tuned Wilson et al, 2004;Fishilevich and Vosshall, 2005;Lin et al, 2006;Kreher et al, 2008;Riffell et al, 2009;Johnson et al, 2010), any specific category or value information representation is likely to emerge only in later stages of the brain.…”

Data-driven honeybee antennal lobe model suggests how stimulus-onset asynchrony can aid odour segregation

“…Airborne odourants distribute in turbulent odour-plumes that fluctuate at multiple temporal scales, spanning from milliseconds to minutes (Murlis et al, 1992;Riffell et al, 2009). In a natural environment the odour-plumes of a variety of odour sources intermingle.…”