Electrophysiological Responses Research Articles

Hebbian learning can explain rhythmic neural entrainment to statistical regularities.

In many domains, learners extract recurring units from continuous sequences. For example, in unknown languages, fluent speech is perceived as a continuous signal. Learners need to extract the underlying words from this continuous signal and then memorize them. One prominent candidate mechanism is statistical learning, whereby learners track how predictive syllables (or other items) are of one another. Syllables within the same word predict each other better than syllables straddling word boundaries. But does statistical learning lead to memories of the underlying words-or just to pairwise associations among syllables? Electrophysiological results provide the strongest evidence for the memory view. Electrophysiological responses can be time-locked to statistical word boundaries (e.g., N400s) and show rhythmic activity with a periodicity of word durations. Here, I reproduce such results with a simple Hebbian network. When exposed to statistically structured syllable sequences (and when the underlying words are not excessively long), the network activation is rhythmic with the periodicity of a word duration and activation maxima on word-final syllables. This is because word-final syllables receive more excitation from earlier syllables with which they are associated than less predictable syllables that occur earlier in words. The network is also sensitive to information whose electrophysiological correlates were used to support the encoding of ordinal positions within words. Hebbian learning can thus explain rhythmic neural activity in statistical learning tasks without any memory representations of words. Learners might thus need to rely on cues beyond statistical associations to learn the words of their nativelanguage. RESEARCH HIGHLIGHTS: Statistical learning may be utilized to identify recurring units in continuous sequences (e.g., words in fluent speech) but may not generate explicit memory forwords. Exposure to statistically structured sequences leads to rhythmic activity with a period of the duration of the underlying units (e.g., words). I show that a memory-less Hebbian network model can reproduce this rhythmic neural activity as well as putative encodings of ordinal positions observed in earlier research. Direct tests are needed to establish whether statistical learning leads to declarative memories for words.

Menthacarin treatment attenuates nociception in models of visceral hypersensitivity.

Chronic visceral hypersensitivity is closely associated with irritable bowel syndrome (IBS), a very common disorder which significantly impairs quality of life, characterized by abdominal pain, and distension. Imaging studies have found that IBS patients show higher metabolic activities and functional differences from normal controls in the anterior cingulate cortex (ACC), in response to visceral pain stimulation. Non-clinical data and clinical data suggest that medicinal products containing essential oils such as peppermint or caraway oil exert beneficial effects on IBS symptoms. We assessed acute and long-term treatment effects of a mixture of peppermint and caraway essential oils (Menthacarin) on brain electrophysiological markers of gut pain sensitivity in two rat models of visceral hypersensitivity. Chronic administration of corticosteroids and acute repeated mechanical hyperstimulation under anesthesia induced hyperalgesia and hypersensitivity, characterized by an increase in electrophysiological excitatory responses of ACC neurons to colorectal distension (CRD) and an increase in the proportion of neurons responding to otherwise subthreshold stimulation, respectively. Long-term, but not acute, oral administration of Menthacarin (60 mg kg-1 day-1) significantly reduced the net excitatory response to CRD in normally responsive control animals and counteracted the development of visceral hyperalgesia and hypersensitivity induced by repeated corticosterone administration and acute mechanical stimulation. The present study shows that, using the CRD method, chronic Menthacarin administration at a clinically relevant dose attenuates the neuronal discharge associated with visceral pain stimuli in the rat ACC, particularly in models of hypersensitivity, suggesting a potential for treating exaggerated visceral pain sensitivity.

Enhanced electrophysiological responses to explicitly predicted and pre-imagined inputs, with confirmation from online decoding with neuro-feedback.

Neural responses to sensory inputs can scale with the likelihood of encountering the input. This is consistent with the predictive coding framework, in that the human brain is expected to be less responsive to predicted inputs. Typically, however, prediction is not explicitly measured. It is inferred from the probability of encountering an event. When an input is explicitly predicted, responses to predicted inputs can be enhanced. Here, we ask if this effect can be ascribed to a generic priming effect, from pre-cogitating about one of two possible inputs. Consistent with this, we find that P300s (a relatively late event-related potential measured with electroencephalography) are greater for explicitly predicted audio and visual inputs, and that this effect cannot be distinguished from a priming effect from pre-imagining audio or visual presentations. Evidence indicates that participants engaged in pre-imagining presentations, as we were able to decode online what type of presentation (audio or visual) they were imagining with a high success rate (approx. 73%), and we encouraged compliance with neuro-feedback regarding this success rate. Our data confirm that human cortex can be more responsive to inputs that have been subject to pre-cogitation-including explicit predictions. This highlights that while anticipatory processes can reduce responding to likely inputs, they can also enhance responding to explicitly predicted inputs.

Antennal olfactory sensitivity and its age‐dependence in the hemimetabolous insect Metcalfa pruinosa

AbstractMetcalfa pruinosa is a highly polyphagous, invasive insect in Europe with the capability of transferring phytoplasma. In the present study, we aim to identify volatile organic compounds that may act as semiochemicals for M. pruinosa. Using a dynamic volatile collection system, volatile organic compounds were collected from Ailanthus altissima, Aristolochia clematitis and Tagetes patula. Compounds were identified using gas chromatography–mass spectrometry. We also tested the electrophysiological responses of M. pruinosa to the collected volatile organic compounds using gas chromatography‐electroantennographic detection. In total, 77 volatile organic compounds were identified, and 29 compounds elicited an electroantennographic response. We analysed responses to volatile organic compounds extracted from Tagetes patula to compare antennal sensitivity between developmental stages and sexes. No differences were found in responders' number or response amplitude between males and females or adults and nymphs for any volatile. Based on the detected compounds, M. pruinosa adult females and males seem to have similar ecological needs in the host habitat. However, when we compared the response amplitudes among compounds, significant differences were found. These differences suggest that (E)‐4,8‐dimethyl‐nonatriene, methyl salicylate, and piperitone could have an important role in M. pruinosa's behaviour. This is the first contribution to M. pruinosa olfaction profile providing a base for future semiochemical‐based pest control tactics.

In situ monolayer patch clamp of acutely stimulated human iPSC-derived cardiomyocytes promotes consistent electrophysiological responses to SK channel inhibition

Human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) represent an in vitro model of cardiac function. Isolated iPSC-CMs, however, exhibit electrophysiological heterogeneity which hinders their utility in the study of certain cardiac currents. In the healthy adult heart, the current mediated by small conductance, calcium-activated potassium (SK) channels (ISK) is atrial-selective. Functional expression of ISK within atrial-like iPSC-CMs has not been explored thoroughly. The present study therefore aimed to investigate atrial-like iPSC-CMs as a model system for the study of ISK. iPSCs were differentiated using retinoic acid (RA) to produce iPSC-CMs which exhibited an atrial-like phenotype (RA-iPSC-CMs). Only 18% of isolated RA-iPSC-CMs responded to SK channel inhibition by UCL1684 and isolated iPSC-CMs exhibited substantial cell-to-cell electrophysiological heterogeneity. This variability was significantly reduced by patch clamp of RA-iPSC-CMs in situ as a monolayer (iPSC-ML). A novel method of electrical stimulation was developed to facilitate recording from iPSC-MLs via In situ Monolayer Patch clamp of Acutely Stimulated iPSC-CMs (IMPASC). Using IMPASC, > 95% of iPSC-MLs could be paced at a 1 Hz. In contrast to isolated RA-iPSC-CMs, 100% of RA-iPSC-MLs responded to UCL1684, with APD50 being prolonged by 16.0 ± 2.0 ms (p < 0.0001; n = 12). These data demonstrate that in conjunction with IMPASC, RA-iPSC-MLs represent an improved model for the study of ISK. IMPASC may be of wider value in the study of other ion channels that are inconsistently expressed in isolated iPSC-CMs and in pharmacological studies.

Separation of Oral Cooling and Warming Requires TRPM8.

Cooling sensations arise inside the mouth during ingestive and homeostasis behaviors. Oral presence of cooling temperature engages the cold and menthol receptor TRPM8 (transient receptor potential melastatin 8) on trigeminal afferents. Yet, how TRPM8 influences brain and behavioral responses to oral temperature is undefined. Here we used in vivo neurophysiology to record action potentials stimulated by cooling and warming of oral tissues from trigeminal nucleus caudalis neurons in female and male wild-type and TRPM8 gene deficient mice. Using these lines, we also measured orobehavioral licking responses to cool and warm water in a novel, temperature-controlled fluid choice test. Capture of antidromic electrophysiological responses to thalamic stimulation identified that wild-type central trigeminal neurons showed diverse responses to oral cooling. Some neurons displayed relatively strong excitation to cold <10°C (COLD neurons) while others responded to only a segment of mild cool temperatures below 30°C (COOL neurons). Notably, TRPM8 deficient mice retained COLD-type but lacked COOL cells. This deficit impaired population responses to mild cooling temperatures below 30°C and allowed warmth-like (≥35°C) neural activity to pervade the normally innocuous cool temperature range, predicting TRPM8 deficient mice would show anomalously similar orobehavioral responses to warm and cool temperatures. Accordingly, TRPM8 deficient mice avoided both warm (35°C) and mild cool (≤30°C) water and sought colder temperatures in fluid licking tests, whereas control mice avoided warm but were indifferent to mild cool and colder water. Results imply TRPM8 input separates cool from warm temperature sensing and suggest other thermoreceptors also participate in oral cooling sensation.

Discovery and properties of novel analogues of the aphid pheromones nepetalactone and nepetalactol.

Pheromones have unique advantages for pest control. Current aphid pheromone research focuses on alarm and sex pheromones. However, practical applications are limited so far, as (E)-β-farnesene has only been investigated to a small extent as an alarm pheromone and only male aphids are targeted by sex pheromones. Previous literature reports electrophysiological responses and repellent behavior of asexual aphids to nepetalactone (1B), therefore our objective was to modify nepetalactone's structure to identify key fragments responsible for repellent effects, as guidance for subsequent modifications and further investigation. In this study, seven derivatives were designed and synthesized based on nepetalactol (1A) and nepetalactone (1B) as lead compounds. Free-choice tests, conducted using cowpea aphids (Aphis craccivora), revealed that the lactone moiety was crucial for the repellent activity, and the removal of the carbonyl group eliminated the repelling effect. Compound (±)1I, an analogue of nepetalactone (1B), demonstrated a significantly higher repellent value than nepetalactone (1B) at three different concentrations, and even at 0.1 mg/mL it maintained a considerable repellent effect (26.5%). Electrostatic potential and density functional theory calculations supported the importance of the carbonyl group for the repellent effects. The newly discovered para-pheromone (±)1I shows improved repellent effects and potential for development as a novel biological control agent. Based on our innovative findings, analogues with improved efficacy and properties can be designed and prepared. Our research contributes to understanding the effects of structural modifications on pheromone activity and properties, which is crucial for exploring novel pheromone-based products for crop protection. © 2024 Society of Chemical Industry.

Exploring the functional profiles of odorant binding proteins crucial for sensing key odorants in the new leaves of coconut palms in Rhynchophorus ferrugineus

The red palm weevil (RPW), Rhynchophorus ferrugineus (Curculionidae: Coleoptera) is a highly destructive global pest of coconut trees, with a preference for laying its eggs on new leaves. Females can identify where to lay eggs by using their sense of smell to detect specific odorants found in new leaves. In this study, we focused on the two odorants commonly found in new leaves by GC–MS: trans, trans-2,4-nonadienal and trans-2-nonenal. Our behavioral assays demonstrated a significant attraction of females to both of these odorants, with their electrophysiological responses being dose-dependent. Furthermore, we examined the expression patterns induced by these odorants in eleven RferOBP genes. Among them, RferOBP3 and RferOBP1768 exhibited the most significant and simultaneous upregulation. To further understand the role of these two genes, we conducted experiments with females injected with OBP-dsRNA. This resulted in a significant decrease in the expression of RferOBP3 and RferOBP1768, as well as impaired the perception of the two odorants. A fluorescence competitive binding assay also showed that both RferOBPs strongly bound to the odorants. Additionally, sequence analysis revealed that these two RferOBPs belong to the Minus-C family and possess four conserved cysteines. Molecular docking simulations showed strong interactions between these two RferOBPs and the odorant molecules. Overall, our findings highlight the crucial role of RferOBP3 and RferOBP1768 in the olfactory perception of the key odorants in coconut palm new leaves. This knowledge significantly improves our understanding of how RPW females locate sites for oviposition and lays the foundation for future research on the development of environmentally friendly pest attractants.

Cognition-Emotion Interaction during L2 Sentence Comprehension: The Correlation of ERP and GSR Responses to Sense Combinations.

This study mainly examined the role of the combination of three senses (i.e., auditory, visual, and tactile) and five senses (i.e., auditory, visual, tactile, olfactory, and gustatory) in the correlation between electrophysiological and electrodermal responses underlying second language (L2) sentence comprehension. Forty subjects did two acceptability judgment tasks, encompassing congruent and semantically/pragmatically incongruent sentences. The event-related potential (ERP) and galvanic skin response (GSR) data for both the target and final words of the sentences were collected and analyzed. The results revealed that there is an interaction between cognitive and emotional responses in both semantically and pragmatically incongruent sentences, yet the timing of the interaction is longer in sentences with pragmatic incongruity due to their complexity. Based on the ERP and GSR correlation results, it was further found that the five-sense combination approach improves L2 sentence comprehension and interest in learning materials yet reduces the level of excitement or arousal. While this approach might be beneficial for some learners, it might be detrimental for those in favor of stimulating learning environments.

Behavioral and electrophysiological responses of cabbage aphids to odors from host plants infested by conspecific and heterospecific herbivores

Behavioral and electrophysiological responses of cabbage aphids to odors from host plants infested by conspecific and heterospecific herbivores

My Perspective: Auditory Evoked Potentials Using Speech

Purpose: The purpose of this tutorial is to clarify the use of speech sounds as stimuli for auditory evoked potentials and how these might contribute to our understanding of speech, language, learning, and hearing disorders. Speech-evoked auditory brainstem responses (ABRs), auditory steady-state responses, auditory middle latency responses, mismatch negativity, P300, cortical onset responses, and the acoustic change complex are reviewed. Method: The author drew upon her scholarship in this area from over 4 decades of research and teaching to summarize the major findings when using speech stimuli to evoke auditory potentials that have been used in clinical contexts. Results: Speech-evoked auditory potentials contribute to our understanding of how the brain processes the acoustic features of speech sounds, providing information that is complementary to psychophysical tests. When psychophysical tests cannot be performed owing to neurodevelopmental immaturity or disability, or cognitive disability, speech-evoked auditory potentials may be used to estimate the benefit of amplification or implantation for speech, language, and hearing. Conclusions: The benefit of using auditory evoked potentials for evaluation is that they provide insight into the brain mechanisms underlying hearing and listening disorders that audiologists aim to treat. While we can use the known correlations between perceptual and electrophysiological responses for “cross-checking” our evaluation results, examining when discrepancies occur is also especially meaningful. For example, the complex ABR reveals subcortical issues in temporal processing that would not be evident in ABRs to clicks or tone bursts, nor in behavioral testing. P300 can document slower neural processing of speech stimuli that may be relevant to the rehabilitation of older adults, even when word recognition scores appear to be congruent with the pure-tone audiogram. In these ways, auditory evoked potentials for speech provide audiologists with tools for demonstrating to clients how their brain responds to speech and opening the conversation for rehabilitation.

Psychophysical and Electrophysiological Parameters of the Auditory Analyzer as Indicators of the Effectiveness of Cochlear Implantation in Children with Bilateral Deafness

Background. The results of rehabilitation of patients with deafness after cochlear implantation (CI) depends on many factors related on both the individual characteristics of the patient and the technical parameters of auditory nerve stimulation — fitting of the CI system processor. Article presents the results of a study of the relationship between psychophysical (subjective) auditory sensations and electrophysiological (objective) responses of the structures of the auditory analyzer to electrical stimulation. Aims — to evaluate the relationship between the electrophysiological responses of the auditory analyzer and the psychophysical parameters of the thresholds of sound perception and speech intelligibility in patients with deafness after CI. Methods. The study involved 88 patients with IV bilateral sensorineural hearing loss, borderline with deafness, aged 6 to 17 years 11 months, among whom 54.5% (n = 48) of girls and 45.5% (n = 40) of boys. Of the patients included in the follow-up, 40% (n = 35) underwent unilateral CI; 60% (n = 53) of children underwent bilateral sequential CI. In our study, slightly more than half of the patients (51.1%) had experience using the CI system for more than 5 years. At the first stage of the study, we studied the relationship between sound perception thresholds (tonal audiometry in a free field) and registered ASSR (auditory steady state response) thresholds in patients with deafness receiving rehabilitation after CI surgery. The relationship between behavioral and electrophysiological (objective) thresholds was assessed by comparing the results of tonal threshold audiometry and the responses received during ASSR registration to acoustic stimulation in a free field. At the second stage, patients with indications for processor fitting (decreased speech intelligibility, uncomfortable sensations) underwent speech audiometry, evoked compound action potentials (ECAP) registration, according to the results of which the parameters of the CI processor were changed. Results. Research data showed the effectiveness of the approach of including the ECAP registration test, followed by the creation of a fitting card and correction of the level of auditory nerve stimulation under the control of speech audiometry in the protocol of fitting the CI processor. Conclusions. The results of the conducted studies allow us to recommend the use of the developed method of objective recording of sound perception thresholds in patients with CI as one of the indicators of the effectiveness of CI in the early period of auditory-speech rehabilitation in patients with undeveloped speech skills and when it is impossible to conduct objective tests accompanied by supra-threshold stimulation of the auditory nerve.

Methylphenidate (Ritalin) affects serotonin signaling differently in young compared to adults. Concomitant behavioral and neuronal recording from dorsal raphe in freely behaving rats

Currently, methylphenidate (MPD) is one of the most commonly prescribed psychostimulants for management and treatment of attention deficit hyperactivity disorder (ADHD). A rise in the consumption of MPD by “ordinary” youth and adults prompted concern regarding the ontogeny effects of acute and chronic MPD exposure. The objective of this study is to concomitantly record behavioral and neuronal activity from the dorsal raphe (DR) nucleus, a major source of serotonergic innervation in the mammalian brain before and following different doses of acute and chronic administration of MPD in freely behaving adolescent (young) and adult rats previously implanted with electrodes in the DR. A wireless recording system over 10 consecutive experimental days was used. Four experimental groups were used: saline, 0.6, 2.5, and 10.0 mg/kg MPD for young and similar groups for adult rats. Animals received one daily MPD injection on experimental days 1-6, followed by three washout days, and then drug rechallenge on experimental day 10 (ED10). 860 DR units were recorded, 356 from adult rats and 504 from young rats. The study provides experimental evidence that the responses to acute and chronic MPD were significantly different between the two age groups. Moreover, the study implies that it is essential to evaluate the electrophysiological responses to a drug based on the animal’s behavioral response to chronic drug exposure and that the DR and serotonin signaling has a significant role in the response to MPD as well as a different role in young as compared to adult rats.

A generative model of electrophysiological brain responses to stimulation.

Each brain response to a stimulus is, to a large extent, unique. However this variability, our perceptual experience feels stable. Standard decoding models, which utilise information across several areas to tap into stimuli representation and processing, are fundamentally based on averages. Therefore, they can focus precisely on the features that are most stable across stimulus presentations. But which are these features exactly is difficult to address in the absence of a generative model of the signal. Here, I introduce genephys, a generative model of brain responses to stimulation publicly available as a Python package that, when confronted with a decoding algorithm, can reproduce the structured patterns of decoding accuracy that we observe in real data. Using this approach, I characterise how these patterns may be brought about by the different aspects of the signal, which in turn may translate into distinct putative neural mechanisms. In particular, the model shows that the features in the data that support successful decoding-and, therefore, likely reflect stable mechanisms of stimulus representation-have an oscillatory component that spans multiple channels, frequencies, and latencies of response; and an additive, slower response with a specific (cross-frequency) relation to the phase of the oscillatory component. At the individual trial level, still, responses are found to be highly variable, which can be due to various factors including phase noise and probabilistic activations.

A generative model of electrophysiological brain responses to stimulation

Each brain response to a stimulus is, to a large extent, unique. However this variability, our perceptual experience feels stable. Standard decoding models, which utilise information across several areas to tap into stimuli representation and processing, are fundamentally based on averages. Therefore, they can focus precisely on the features that are most stable across stimulus presentations. But which are these features exactly is difficult to address in the absence of a generative model of the signal. Here, I introduce genephys, a generative model of brain responses to stimulation publicly available as a Python package that, when confronted with a decoding algorithm, can reproduce the structured patterns of decoding accuracy that we observe in real data. Using this approach, I characterise how these patterns may be brought about by the different aspects of the signal, which in turn may translate into distinct putative neural mechanisms. In particular, the model shows that the features in the data that support successful decoding—and, therefore, likely reflect stable mechanisms of stimulus representation—have an oscillatory component that spans multiple channels, frequencies, and latencies of response; and an additive, slower response with a specific (cross-frequency) relation to the phase of the oscillatory component. At the individual trial level, still, responses are found to be highly variable, which can be due to various factors including phase noise and probabilistic activations.

Decreased phrenic nerve compound muscle action potential, inspiratory muscle strength, and exercise capacity after COVID-19.

Respiratory muscle weakness with higher ventilatory demands were reported even in patients recovering from only mild COVID-19 symptoms. Aim of this study was to assess the function of phrenic nerve and inspiratory respiratory muscle as well as cardiopulmonary exercise capacity in patients with prolonged exertional dyspnea after COVID-19 infection. In this observational exploratory study, electrophysiological examination of the phrenic nerve, inspiratory muscle capacity as well as lung function test, 6-min walk distance (6MWD) and cardiopulmonary exercise test, have been performed in 22 patients post COVID-19 diagnosis (post-CoV). Exercise capacity (peak workload, Wpeak % predicted and peak oxygen uptake, VO2peak % predicted) were significantly affected in the post-CoV patients (61.8 ± 23.3 Wpeak % and 70.9 ± 22.3 VO2peak %). Maximum inspiratory pressure (MIP) was reduced (60.1 ± 25.5 mbar). In 6 of the 22 patients the electrophysiological response of the phrenic nerve was pathologically decreased (reduced compound muscle action potential, CMAP), while nerve conduction velocity (NCV) was normal, which corresponds to reduced muscle fiber contraction capacity. Positive relationships were demonstrated between 6MWD and MIP (rs = 0.88) as well as quality of life questionnaire (CRQ) and MIP (rs = 0.71) only in patients with reduced CMAP. Respiratory muscle weakness and exercise capacity is associated with reduced phrenic nerve CMAP without signs of neuropathy. This indicates that muscle fiber pathology of the diaphragm may be one pathophysiological factor for the prolonged respiratory symptoms after COVID-19 infections.

Genetically engineered HEK cells as a valuable tool for studying electroporation in excitable cells

Electric pulses used in electroporation-based treatments have been shown to affect the excitability of muscle and neuronal cells. However, understanding the interplay between electroporation and electrophysiological response of excitable cells is complex, since both ion channel gating and electroporation depend on dynamic changes in the transmembrane voltage (TMV). In this study, a genetically engineered human embryonic kidney cells expressing NaV1.5 and Kir2.1, a minimal complementary channels required for excitability (named S-HEK), was characterized as a simple cell model used for studying the effects of electroporation in excitable cells. S-HEK cells and their non-excitable counterparts (NS-HEK) were exposed to 100 µs pulses of increasing electric field strength. Changes in TMV, plasma membrane permeability, and intracellular Ca2+ were monitored with fluorescence microscopy. We found that a very mild electroporation, undetectable with the classical propidium assay but associated with a transient increase in intracellular Ca2+, can already have a profound effect on excitability close to the electrostimulation threshold, as corroborated by multiscale computational modelling. These results are of great relevance for understanding the effects of pulse delivery on cell excitability observed in context of the rapidly developing cardiac pulsed field ablation as well as other electroporation-based treatments in excitable tissues.

5-HT2A Receptor Knockout Mice Show Sex-Dependent Differences following Acute Noribogaine Administration.

Noribogaine (noribo) is the primary metabolite from ibogaine, an atypical psychedelic alkaloid isolated from the root bark of the African shrub Tabernanthe iboga. The main objective of this study was to test the hypothesis that molecular, electrophysiological, and behavioral responses of noribo are mediated by the 5-HT2A receptor (5-HT2AR) in mice. In that regard, we used male and female, 5-HT2AR knockout (KO) and wild type (WT) mice injected with a single noribo dose (10 or 40 mg/kg; i.p.). After 30 min., locomotor activity was recorded followed by mRNA measurements by qPCR (immediate early genes; IEG, glutamate receptors, and 5-HT2AR levels) and electrophysiology recordings of layer V pyramidal neurons from the medial prefrontal cortex. Noribo 40 decreased locomotion in male, but not female WT. Sex and genotype differences were observed for IEG and glutamate receptor expression. Expression of 5-HT2AR mRNA increased in the mPFC of WT mice following Noribo 10 (males) or Noribo 40 (females). Patch-clamp recordings showed that Noribo 40 reduced the NMDA-mediated postsynaptic current density in mPFC pyramidal neurons only in male WT mice, but no effects were found for either KO males or females. Our results highlight that noribo produces sexually dimorphic effects while the genetic removal of 5HT2AR blunted noribo-mediated responses to NMDA synaptic transmission.

The greening-causing agent alters the behavioral and electrophysiological responses of the Asian citrus psyllid to a putative sex pheromone

The Asian Citrus Psyllid (ACP), Diaphorina citri, is a vector of the pathological bacterium Candidatus Liberibacter asiaticus (CLas), which causes the most devastating disease to the citrus industry worldwide, known as greening or huanglongbing (HLB). Earlier field tests with an acetic acid-based lure in greening-free, ‘Valencia’ citrus orange groves in California showed promising results. The same type of lures tested in São Paulo, Brazil, showed unsettling results. During the unsuccessful trials, we noticed a relatively large proportion of females in the field, ultimately leading us to test field-collected males and females for Wolbachia and CLas. The results showed high rates of Wolbachia and CLas infection in field populations. We then compared the olfactory responses of laboratory-raised, CLas-free, and CLas-infected males to acetic acid. As previously reported, CLas-uninfected males responded to acetic acid at 1 µg. Surprisingly, CLas-infected males required 50 × higher doses of the putative sex pheromone, thus explaining the failure to capture CLas-infected males in the field. CLas infection was also manifested in electrophysiological responses. Electroantennogram responses from CLas-infected ACP males were significantly higher than those obtained with uninfected males. To the best of our knowledge, this is the first report of a pathogen infection affecting a vector’s response to a sex attractant.

Time-dependent effects of acoustic trauma and tinnitus on extracellular levels of amino acids in the inferior colliculus of rats

Chronic tinnitus is a debilitating condition with very few management options. Acoustic trauma that causes tinnitus has been shown to induce neuronal hyperactivity in multiple brain areas in the auditory pathway, including the inferior colliculus. This neuronal hyperactivity could be attributed to an imbalance between excitatory and inhibitory neurotransmission. However, it is not clear how the levels of neurotransmitters, especially neurotransmitters in the extracellular space, change over time following acoustic trauma and the development of tinnitus. In the present study, a range of amino acids were measured in the inferior colliculus of rats during acoustic trauma as well as at 1 week and 5 months post-trauma using in vivo microdialysis and high-performance liquid chromatography. Amino acid levels in response to sound stimulation were also measured at 1 week and 5 months post-trauma. It was found that unilateral exposure to a 16 kHz pure tone at 115 dB SPL for 1 h caused immediate hearing loss in all the animals and chronic tinnitus in 58 % of the animals. Comparing to the sham condition, extracellular levels of GABA were significantly increased at both the acute and 1 week time points after acoustic trauma. However, there was no significant difference in any of the amino acid levels measured between sham, tinnitus positive and tinnitus negative animals at 5 months post-trauma. There was also no clear pattern in the relationship between neurochemical changes and sound frequency/acoustic trauma/tinnitus status, which might be due to the relatively poorer temporal resolution of the microdialysis compared to electrophysiological responses.