It takes two—coincidence coding within the dual olfactory pathway of the honeybee

Abstract

To rapidly process biologically relevant stimuli, sensory systems have developed a broad variety of coding mechanisms like parallel processing and coincidence detection. Parallel processing (e.g., in the visual system), increases both computational capacity and processing speed by simultaneously coding different aspects of the same stimulus. Coincidence detection is an efficient way to integrate information from different sources. Coincidence has been shown to promote associative learning and memory or stimulus feature detection (e.g., in auditory delay lines). Within the dual olfactory pathway of the honeybee both of these mechanisms might be implemented by uniglomerular projection neurons (PNs) that transfer information from the primary olfactory centers, the antennal lobe (AL), to a multimodal integration center, the mushroom body (MB). PNs from anatomically distinct tracts respond to the same stimulus space, but have different physiological properties, characteristics that are prerequisites for parallel processing of different stimulus aspects. However, the PN pathways also display mirror-imaged like anatomical trajectories that resemble neuronal coincidence detectors as known from auditory delay lines. To investigate temporal processing of olfactory information, we recorded PN odor responses simultaneously from both tracts and measured coincident activity of PNs within and between tracts. Our results show that coincidence levels are different within each of the two tracts. Coincidence also occurs between tracts, but to a minor extent compared to coincidence within tracts. Taken together our findings support the relevance of spike timing in coding of olfactory information (temporal code).

Social Complexity and Brain Evolution: Comparative Analysis of Modularity and Integration in Ant Brain Organization

“…Compared to our prior findings in Pheidole [Ilieş et al, 2015], the results of our present study suggest that selection on brain organization differs in these formicine species (Table 1). The utility of our covariance analysis is validated by neuroanatomy: brain regions that were statistically correlated in the present work are known to have functional neural connections in insects [Strausfeld et al, 2009;Martin et al, 2011;Brill et al, 2015;Kinoshita and Homberg, 2017;Seki et al, 2017]. The correlations we identified between MB subregion size (LC and MC; MC and PL), for example, appear to reflect neurobiological organization, given that the LC and the MC receive similar primary sensory inputs, and the underlying afferent projections from the calyces form the PL [Fahrbach, 2006].…”

A subset of broadly responsive Type III taste cells contribute to the detection of bitter, sweet and umami stimuli

“…When either cell population is non-functional there is a severe deficit in the NTS activity that translates into a comparable behavior deficit. This type of synergistic relationship is present in multiple sensory systems (Ala-Laurila & Rieke, 2014, Brill, Meyer et al, 2015, Carr & Konishi, 1990, Gupta, Singh et al, 2016, Joris, Smith et al, 1998, Oertel, Bal et al, 2000, Sakmann, 2017) but to our knowledge, it has not previously been described in the taste system. Future studies are needed to better understand this potential relationship.…”

Mixtures are more salient stimuli in olfaction

“…For instance, information for concentration may be coded by other features of the response, like the portion of activated glomeruli (Stopfer et al, 2003;Strauch et al, 2012), the connectivity between units with plastic synapses (Hopfield, 1991), or by responses at the later part of the olfactory system (Froese et al, 2013). It is also possible that concentration information is encoded by the temporal patterns of input, for instance the response latency of all or a sub-set of units (Hopfield, 1995) or degree of synchrony between firing of different units (Brill et al, 2015). Therefore, the improved identity coding due to more invariant asymptotic response pattern does not necessarily imply a compromise in concentration coding, and it remains an open question how identity and concentration coding may be simultaneously achieved (Hopfield, 1991(Hopfield, ,1995Stopfer et al, 2003, Arnson andHoly, 2013).…”