Whole-cell recording from Kenyon cells in silkmoths

Neuromorphic sequence learning with an event camera on routes through vegetation

For many robotics applications, it is desirable to have relatively low-power and efficient onboard solutions. We took inspiration from insects, such as ants, that are capable of learning and following routes in complex natural environments using relatively constrained sensory and neural systems. Such capabilities are particularly relevant to applications such as agricultural robotics, where visual navigation through dense vegetation remains a challenging task. In this scenario, a route is likely to have high self-similarity and be subject to changing lighting conditions and motion over uneven terrain, and the effects of wind on leaves increase the variability of the input. We used a bioinspired event camera on a terrestrial robot to collect visual sequences along routes in natural outdoor environments and applied a neural algorithm for spatiotemporal memory that is closely based on a known neural circuit in the insect brain. We show that this method is plausible to support route recognition for visual navigation and more robust than SeqSLAM when evaluated on repeated runs on the same route or routes with small lateral offsets. By encoding memory in a spiking neural network running on a neuromorphic computer, our model can evaluate visual familiarity in real time from event camera footage.

The botanical eurycomanone is a potent growth regulator of the diamondback moth

Eurycomanone is a quassinoid compound that is derived from Eurycoma longifolia, and it is often used as an indicator to evaluate the active ingredients of Eurycoma longifolia. However, Eurycomanone has rarely been reported to have biological activity toward pests. In this study, we evaluated the antifeedant activity of eurycomanone against the diamondback moth(Plutella xylostella), with a non-selective AFC₅₀(the concentration that corresponds to 50% antifeedant action) value and selective AFC₅₀ of 17.5 mg/L and 14.2 mg/L, respectively, which were 2.1-fold (36.9 mg/L) and 2-fold (28.5 mg/L) lower than that of azadirachtin, respectively. In addition, eurycomanone was used to treat the roots of Brassica chinensis L. at a concentration of 100 µg/g for 72 h. The antifeedant index was found to reach 93% by tracking the leaves. After feeding with 20 µg/g eurycomanone, no pupae or eclosion were observed. To explore this mechanism, we used scanning electron microscopy to discover that eurycomanone could prevent the development of taste receptors on the maxillary palp of diamondback moth larvae. Additional electrophysiological measurements showed that eurycomanone exhibited excitatory action to the central taste neurons of diamondback moth and significantly inhibited the GABA_A receptor current. Eurycomanone exhibited significant activity as an antifeedant, inhibited growth and excelled at systemic absorption.

Transient voltage-activated K+ currents in central antennal lobe neurons: cell type-specific functional properties

In this study we analyzed transient voltage-activated K+ currents (IA) of projection neurons and local interneurons in the antennal lobe of the cockroach Periplaneta americana The antennal lobe is the first synaptic processing station for olfactory information in insects. Local interneurons are crucial for computing olfactory information and form local synaptic connections exclusively in the antennal lobe, whereas a primary task of the projection neurons is the transfer of preprocessed olfactory information from the antennal lobe to higher order centers in the protocerebrum. The different physiological tasks of these neurons require specialized physiological and morphological neuronal phenotypes. We asked if and how the different physiological phenotypes are reflected in the functional properties of IA, which is crucial for shaping intrinsic electrophysiological properties of neurons. Whole cell patch-clamp recordings from adult male P. americana showed that all their central antennal lobe neurons can generate IA The current exhibited marked cell type-specific differences in voltage dependence of steady-state activation and inactivation, and differences in inactivation kinetics during sustained depolarization. Pharmacological experiments revealed that IA in all neuron types was partially blocked by α-dendrotoxin and phrixotoxin-2, which are considered blockers with specificity for Shaker- and Shal-type channels, respectively. These findings suggest that IA in each cell type is a mixed current generated by channels of both families. The functional role of IA was analyzed in experiments under current clamp, in which portions of IA were blocked by α-dendrotoxin or phrixotoxin-2. These experiments showed that IA contributes significantly to the intrinsic electrophysiological properties, such as the action potential waveform and membrane excitability.NEW & NOTEWORTHY In the insect olfactory system, projection neurons and local interneurons have task-specific electrophysiological and morphological phenotypes. Voltage-activated potassium channels play a crucial role in shaping functional properties of these neurons. This study revealed marked cell type-specific differences in the biophysical properties of transient voltage-activated potassium currents in central antennal lobe neurons.

A temporal channel for information in sparse sensory coding

BACKGROUND

Sparse codes are found in nearly every sensory system, but the role of spike timing in sparse sensory coding is unclear. Here, we use the olfactory system of awake locusts to test whether the timing of spikes in Kenyon cells, a population of neurons that responds sparsely to odors, carries sensory information to and influences the responses of follower neurons.

RESULTS

We characterized two major classes of direct followers of Kenyon cells. With paired intracellular and field potential recordings made during odor presentations, we found that these followers contain information about odor identity in the temporal patterns of their spikes rather than in the spike rate, the spike phase, or the identities of the responsive neurons. Subtly manipulating the relative timing of Kenyon cell spikes with temporally and spatially structured microstimulation reliably altered the response patterns of the followers.

CONCLUSIONS

Our results show that even remarkably sparse spiking responses can provide information through stimulus-specific variations in timing on the order of tens to hundreds of milliseconds and that these variations can determine the responses of downstream neurons. These results establish the importance of spike timing in a sparse sensory code.

Parallel processing in the honeybee olfactory pathway: structure, function, and evolution

Animals face highly complex and dynamic olfactory stimuli in their natural environments, which require fast and reliable olfactory processing. Parallel processing is a common principle of sensory systems supporting this task, for example in visual and auditory systems, but its role in olfaction remained unclear. Studies in the honeybee focused on a dual olfactory pathway. Two sets of projection neurons connect glomeruli in two antennal-lobe hemilobes via lateral and medial tracts in opposite sequence with the mushroom bodies and lateral horn. Comparative studies suggest that this dual-tract circuit represents a unique adaptation in Hymenoptera. Imaging studies indicate that glomeruli in both hemilobes receive redundant sensory input. Recent simultaneous multi-unit recordings from projection neurons of both tracts revealed widely overlapping response profiles strongly indicating parallel olfactory processing. Whereas lateral-tract neurons respond fast with broad (generalistic) profiles, medial-tract neurons are odorant specific and respond slower. In analogy to “what-” and “where” subsystems in visual pathways, this suggests two parallel olfactory subsystems providing “what-” (quality) and “when” (temporal) information. Temporal response properties may support across-tract coincidence coding in higher centers. Parallel olfactory processing likely enhances perception of complex odorant mixtures to decode the diverse and dynamic olfactory world of a social insect.