Surface electrodes record and label brain neurons in insects.

We used suction electrodes to reliably record the activity of identified ascending auditory interneurons from the anterior surface of the brain in crickets. Electrodes were gently attached to the sheath covering the projection area of the ascending interneurons and the ringlike auditory neuropil in the protocerebrum. The specificity and selectivity of the recordings were determined by the precise electrode location, which could easily be changed without causing damage to the tissue. Different nonauditory fibers were recorded at other spots of the brain surface; stable recordings lasted for several hours. The same electrodes were used to deliver fluorescent tracers into the nervous system by means of electrophoresis. This allowed us to retrograde label the recorded auditory neurons and to reveal their cell body and dendritic structure in the first thoracic ganglion. By adjusting the amount of dye injected, we specifically stained the ringlike auditory neuropil in the brain, demonstrating the clusters of cell bodies contributing to it. Our data provide a proof that surface electrodes are a versatile tool to analyze neural processing in small brains of invertebrates.NEW & NOTEWORTHY We show that surface suction electrodes can be used to monitor the activity of auditory neurons in the cricket brain. They also allow delivering electrophoretically a fluorescent tracer to label the structure of the recorded neurons and the local neuropil to which the electrode was attached. This new extracellular recording and labeling technique is a versatile and useful method to explore neural processing in invertebrate sensory and motor systems

Two matched filters and the evolution of mating signals in four species of cricket

<p>Abstract</p> <p>Background</p> <p>Male field crickets produce pure-tone calling songs to attract females. Receivers are expected to have evolved a "matched filter" in the form of a tuned sensitivity for this frequency. In addition, the peripheral directionality of field crickets is sharply tuned as a result of a pressure difference receiver. We studied both forms of tuning in the same individuals of four species of cricket, where <it>Gryllus bimaculatus </it>and <it>G. campestris </it>are largely allopatric, whereas <it>Teleogryllus oceanicus </it>and <it>T. commodus </it>occur also sympatrically.</p> <p>Results</p> <p>The sharpness of the sensitivity filter is highest for <it>T. commodus</it>, which also exhibits low interindividual variability. Individual receivers may also vary strongly in the best frequency for directional hearing. In <it>G. campestris</it>, such best frequencies occur even at frequencies outside the range of carrier frequencies of males. Contrary to the predictions from the "matched filter hypothesis", in three of the four species the frequency optima of the two involved filters are not matched to each other, and the mismatch can amount to 1.2 kHz. The mean carrier frequency of the male population is between the frequency optima of both filters in three species. Only in <it>T. commodus </it>we found a match between both filters and the male carrier frequency.</p> <p>Conclusion</p> <p>Our results show that a mismatch between the sensitivity and directionality tuning is not uncommon in crickets, and an observed match (<it>T. commodus</it>) appears to be the exception rather than the rule. The data suggests that independent variation of both filters is possible. During evolution each sensory task may have been driven by independent constraints, and may have evolved towards its own respective optimum.</p

An auditory feature detection circuit for sound pattern recognition.

From human language to birdsong and the chirps of insects, acoustic communication is based on amplitude and frequency modulation of sound signals. Whereas frequency processing starts at the level of the hearing organs, temporal features of the sound amplitude such as rhythms or pulse rates require processing by central auditory neurons. Besides several theoretical concepts, brain circuits that detect temporal features of a sound signal are poorly understood. We focused on acoustically communicating field crickets and show how five neurons in the brain of females form an auditory feature detector circuit for the pulse pattern of the male calling song. The processing is based on a coincidence detector mechanism that selectively responds when a direct neural response and an intrinsically delayed response to the sound pulses coincide. This circuit provides the basis for auditory mate recognition in field crickets and reveals a principal mechanism of sensory processing underlying the perception of temporal patterns.Financial support for the study was provided by the Biotechnology and Biological Sciences Research Council (BB/J01835X/1) and the Isaac Newton Trust (Trinity College, Cambridge).This is the final version of the article. It first appeared from AAAS via http://dx.doi.org/10.1126/sciadv.150032

Product Tests in Virtual Reality: Lessons Learned during Collision Avoidance Development for Drones

Virtual reality (VR) and real-world simulations have become an important tool for product development, product design, and product tests. Product tests in VR have many advantages, such as reproducibility and shortened development time. In this paper, we investigate the virtual testing of a collision avoidance system for drones in terms of economic benefits. Our results show that virtual tests had both positive and negative effects on the development, with the positive aspects clearly predominating. In summary, the tests in VR shorten the development time and reduce risks and therefore costs. Furthermore, they offer possibilities not available in real-world tests. Nevertheless, real-world tests are still important

A small, computationally flexible network produces the phenotypic diversity of song recognition in crickets.

How neural networks evolved to generate the diversity of species-specific communication signals is unknown. For receivers of the signals, one hypothesis is that novel recognition phenotypes arise from parameter variation in computationally flexible feature detection networks. We test this hypothesis in crickets, where males generate and females recognize the mating songs with a species-specific pulse pattern, by investigating whether the song recognition network in the cricket brain has the computational flexibility to recognize different temporal features. Using electrophysiological recordings from the network that recognizes crucial properties of the pulse pattern on the short timescale in the cricket Gryllus bimaculatus, we built a computational model that reproduces the neuronal and behavioral tuning of that species. An analysis of the model's parameter space reveals that the network can provide all recognition phenotypes for pulse duration and pause known in crickets and even other insects. Phenotypic diversity in the model is consistent with known preference types in crickets and other insects, and arises from computations that likely evolved to increase energy efficiency and robustness of pattern recognition. The model's parameter to phenotype mapping is degenerate - different network parameters can create similar changes in the phenotype - which likely supports evolutionary plasticity. Our study suggests that computationally flexible networks underlie the diverse pattern recognition phenotypes, and we reveal network properties that constrain and support behavioral diversity

Matched Filters, Mate Choice and the Evolution of Sexually Selected Traits

Background Fundamental for understanding the evolution of communication systems is both the variation in a signal and how this affects the behavior of receivers, as well as variation in preference functions of receivers, and how this affects the variability of the signal. However, individual differences in female preference functions and their proximate causation have rarely been studied. Methodology/Principal Findings Calling songs of male field crickets represent secondary sexual characters and are subject to sexual selection by female choice. Following predictions from the “matched filter hypothesis” we studied the tuning of an identified interneuron in a field cricket, known for its function in phonotaxis, and correlated this with the preference of the same females in two-choice trials. Females vary in their neuronal frequency tuning, which strongly predicts the preference in a choice situation between two songs differing in carrier frequency. A second “matched filter” exists in directional hearing, where reliable cues for sound localization occur only in a narrow frequency range. There is a strong correlation between the directional tuning and the behavioural preference in no-choice tests. This second “matched filter” also varies widely in females, and surprisingly, differs on average by 400 Hz from the neuronal frequency tuning. Conclusions/Significance Our findings on the mismatch of the two “matched filters” would suggest that the difference in these two filters appears to be caused by their evolutionary history, and the different trade-offs which exist between sound emission, transmission and detection, as well as directional hearing under specific ecological settings. The mismatched filter situation may ultimately explain the maintenance of considerable variation in the carrier frequency of the male signal despite stabilizing selection

An auditory-responsive interneuron descending from the cricket brain: a new element in the auditory pathway.

Crickets receive auditory information from their environment via ears located on the front legs. Ascending interneurons forward auditory activity to the brain, which houses a pattern recognition network for phonotaxis to conspecific calling songs and which controls negative phonotaxis to high-frequency sound pulses. Descending brain neurons, however, which are clearly involved in controlling these behaviors, have not yet been identified. We describe a descending auditory-responsive brain neuron with an arborization pattern that coincides with the ring-like auditory neuropil in the brain formed by the axonal arborizations of ascending and local interneurons, indicating its close link to auditory processing. Spiking activity of this interneuron occurs with a short latency to calling song patterns and the neuron copies the sound pulse pattern. The neuron preferentially responds to short sound pulses, but its activity appears to be independent of the calling song pattern recognition process. It also receives a weaker synaptic input in response to high-frequency pulses, which may contribute to its short latency spiking responses. This interneuron could be a crucial part in the auditory-to-motor transformation of the nervous system and contribute to the motor control of cricket auditory behavior

Interaural intensity differences exhibit optimum functions and determine the degree of lateral steering in no-choice paradigms.

<p>In a single female, the amount of IID provided by the peripheral directionality (A) correlates with the degree of steering (B). (C) On average, the peripheral directionality is tuned to 4.5 kHz, i.e. provides the highest IIDs (blue; mean±SE; N = 20), although optima in single females vary from 4.0 to 5.1 kHz. The lateral steering in no-choice paradigms (red; mean±SE; N = 20) also peaks at 4.5 kHz and exhibits a rather similar optimum function. The correlation of mean values between IIDs and lateral steering (n = 20) is high (D).</p

Tuning of AN1-interneuron and its relevance for the preference of females in two-choice tests.

<p>(A): Variance of tuning curves (red = average tuning; N = 20) in relation to the range of variation of carrier frequencies of male calls (black bar). (B): Tuning of AN1 in a single female and (C) the degree of lateral steering in a two-choice situation towards a calling song at a CF providing the stronger stimulation (right speaker).</p

AN1-tuning is highly predictive for female choice.

<p>(A): Strength of lateral steering towards or away (positive and negative values, respectively) four calling song frequencies of 4 kHz, 4.5 kHz, 5 kHz and 5.5 kHz in a choice with calling songs ranging from 3.5 to 6 kHz. For example, 5 kHz is preferred against all CFs except 4.8 kHz, and a CF of 4 kHz is rejected in all choices except 3.5 kHz (mean±SE; N = 20). (B) The average tuning of AN1 (blue; mean±SE; N = 20) correlates strongly with the behavioural preference (lateral steering towards a CF of 5 kHz in a choice with alternative CFs from 3.5 to 6 kHz, and (C) the degree of lateral steering increases with the intensity difference due to the threshold difference in AN1 for the two alternative CFs.</p