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Insects exhibit an astonishing diversity in the design of their ears and the subsequent processing of information within their auditory pathways. The aim of this review is to summarize and compare the present concepts of auditory processing by relating behavioral performance to known neuronal mechanisms. We focus on three general aspects, that is frequency, directional, and temporal processing. The first part compares the capacity (in some insects high) for frequency analysis in the ear with the rather low specificity of tuning in interneurons by looking at Q10dB values and frequency dependent inhibition of interneurons. Since sharpening of frequency does not seem to be the prime task of a set of differently tuned receptors, alternative hypotheses are discussed. Moreover, the physiological correspondence between tonotopic projections of receptors and dendritic organization of interneurons is not in all cases strong. The second part is concerned with directional hearing and thus with the ability for angular resolution of insects. The present concepts, as derived from behavioral performances, for angular resolution versus lateralization and serial versus parallel processing of directional and pattern information can be traced to the thoracic level of neuronal processing. Contralateral inhibition, a mechanism for enhancing directional tuning, appears to be most effective in parallel pathways, whereas in serial processing it may have detrimental effects on pattern processing. The third part, after some considerations of signal analysis in the temporal domain, demonstrates that closely related species often use different combinations of temporal parameters in their recognition systems. On the thoracic level, analysis of temporal modulation functions and effects of inhibition on spiking patterns reveals relatively simple processing, whereas brain neurons may exhibit more complex properties.

The vast majority of animals are poikilotherms, and thus face the problem that the temperature of their nervous systems rather smoothly follows the temperature changes imposed by their environment. Since basic properties of nerve cells, e.g., the time constants of ion channels, strongly depend on temperature, a temperature shift likely affects the processing of the temporal structure of sensory stimuli. This can be critical in acoustic communication systems in which time patterns of signals are decisive for recognition by the receiver. We investigated the temperature dependence of the responses of locust auditory receptors and interneurons by varying the temperature of the experimental animals during intracellular recordings. The resolution of fast amplitude modulations of acoustic signals was determined in a gap detection paradigm. In auditory receptors and local (second order) interneurons, temporal resolution was improved at higher temperatures. This gain could be attributed to a higher precision of spike timing. In a third-order neuron, a rise in temperature affected the interactions of inhibition and excitation in a complex manner, also resulting in a better resolution of gaps in the millisecond range.

Object recognition and classification by sensory pathways is rooted in spike trains provided by sensory neurons. Nervous systems had to evolve mechanisms to extract information about relevant object properties, and to separate these from spurious features. In this review, problems caused by spike train variability and counterstrategies are exemplified for the processing of acoustic signals in orthopteran insects. Due to size limitations of their nervous system we expect to find solutions that are stripped to the computational basics. A key feature of auditory systems is temporal resolution, which is likely limited by spike train variability. Basic strategies to reduce such variability are to integrate over time, or to average across several neurons. The first strategy is constrained by its possible interference with temporal resolution. Grasshoppers do not seem to explore temporal integration much, in spite of the repetitive structure of their songs, which invites for 'multiple looks' at the signal. The benefits of averaging across neurons depend on uncorrelated responses, a factor that may be crucial for the performance and evolution of small nervous systems. In spite of spike train variability the temporal information necessary for the recognition of conspecifics is preserved to a remarkable degree in the auditory pathway.

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Background Acquiring medical knowledge is a key competency for medical students and a lifelong requirement for physicians. Learning techniques can improve academic success and help students cope with stressors. To support students’ learning process medical faculties should know about learning techniques. The purpose of this study is to analyse the preferred learning techniques of female and male as well as junior and senior medical students and how these learning techniques are related to perceived learning difficulties. Methods In 2019, we conducted an online survey with students of the undergraduate, competency-based curriculum of medicine at Charité – Universitätsmedizin Berlin. We chose ten learning techniques of high, moderate and low utility according to Dunlosky et al. (2013) and we asked medical students to rate their preferred usage of those techniques using a 5-point Likert scale. We applied t-tests to show differences in usage between female and male as well as junior and senior learners. Additionally, we conducted a multiple regression analysis to explore the predictive power of learning techniques regarding perceived difficulties. Results A total of 730 medical students (488 women, 242 men, Mage = 24.85, SD = 4.49) use three techniques the most: ‘highlighting’ (low utility), ‘self-explanation’ (moderate utility) and ‘practice testing’ (high utility). Female students showed a significantly higher usage of low-utility learning techniques (t(404.24) = -7.13, p < .001) and a higher usage of high-utility learning techniques (t(728) = -2.50, p < .05) than male students (M = 3.55, SD = .95). Compared to junior students (second to sixth semester; M = 3.65, SD = .71), senior students (seventh semester to final clerkship year; M = 3.52, SD = .73) showed a lower use of low-utility learning techniques (t(603) = 2.15, p < .05). Usage of low-utility techniques is related to more difficulties (β = .08, t(724) = 2.13, p < .05). Usage of moderate-utility techniques is related to less learning difficulties (β = -.13, t(599) = -3.21, p < .01). Conclusions Students use a wide range of low-, moderate- and high-utility learning techniques. The use of learning techniques has an influence on the difficulties perceived by students. Therefore, they could benefit from knowing about and using high-utility learning techniques to facilitate their learning. Faculties should inform their students about effective learning and introduce them to useful learning techniques.