Vibratory Stimuli Research Articles

Sonomechanobiology: High frequency cell mechanostimulation

It is well known that cells respond in many different ways to various forms of mechanical cues. To date, however, mechanostimulation has typically been carried out statically or at relatively low frequencies (several Hz), characteristic of the frequencies associated with the motion experienced by cells in their local environment, for example, in the human body (e.g., walking and running). Where higher frequency vibrational mechanotransduction pathways have been investigated, these have primarily been limited to kHz order, and it has generally been suggested that there is no significant advantage in utilising higher frequencies. In a similar manner to observations of new and often nonlinear discoveries when we couple high frequency (10–30 MHz) vibration in the form of surface and hybrid acoustic waves into fluids as well as crystalline materials, we however observe unique and novel phenomena when similar MHz-order vibrational stimuli are transmitted into cells. These include modulation of various ion and piezo channels, and transient, yet reversible, permeabilization of the cell membrane, which have implications for efficient intracellular cytosol delivery, exosome biogenesis, cytoskeletal reorganization and stem cell differentiation, at the same time maintaining very high levels (>95%) in cellular viability.

Real-time tactile biofeedback device use for improving balance control of an adolescent with medulloblastoma

PurposeBiofeedback is used for regulating vestibular adaptation and balance by providing real-time stimulus to the individual during physical activities. This study aimed at (1) developing a wearable device, which tracks balance, counts the number and the direction of balance losses and provides haptic biofeedback through real-time vibration stimulus (2) investigating device efficacy on an adolescent medulloblastoma patient during static and dynamic tasks.Design/methodology/approachA 16-year-old medulloblastoma patient used the device during 10-m walking and single-leg stance tests. The knee joint kinematics and the number and direction of balance losses were recorded for “with” and “without” biofeedback conditions.FindingsThe device helped regulate the knee joint kinematics and reduce the number of balance losses of the medulloblastoma patient. The knee joint movement pattern similarity of the control subject was highly correlated (R2 = 0.997, RMSE = 1.232). Conversely, medulloblastoma patient knee joint movement pattern similarity was relatively weak (R2 = 0.359, RMSE = 18.6) when “with” and “without” biofeedback conditions were compared. The number of balance losses decreased when the medulloblastoma patient was guided with biofeedback.Research limitations/implicationsThe major limitation of this pilot study is the lack of a large and homogeneous number of participants. The medulloblastoma patient used the device while walking after she was given enough time to get used to the tactile biological feedback, so the long-term effect of the device and biofeedback guidance were not investigated. Additionally, the potential desensitization with prolonged use of the device was not evaluated.Practical implicationsBiofeedback reduced the number of balance losses; additionally, the knee joint movement pattern was regulated during static and dynamic tasks. This device can be integrated into the physical therapy of patients with balance, vestibular and postural control impairments.Social implicationsThis is compact and has an easy-to-wear design, patients, who have balance and postural control impairments, can practically use the device during their activities of daily living.Originality/valueThe device promotes physical activity adaptation and regulates gait through continuous and real-time balance control. Its design makes it simple for the user to wear it beneath clothing while using the sensor.

Let’s pulse device assist in cardiopulmonary resuscitation by professionals and laypersons

It is a study whose objective is to describe the electronic circuit project of a stimulus generator device for the execution of chest compressions at the appropriate frequency for cardiopulmonary resuscitation (CPR). The electronic system was designed using a Microchip PIC family microcontroller with programming in the “C” language with connection of the main components and their respective functions and programming. Thus, Let’s pulse consists of a dedicated embedded system accommodated in the form of a bracelet or wristband so that the rescuer can receive stimuli satisfactorily without compromising the execution of CPR. Unlike other devices, it offers real-time luminous, vibratory, sound and musical stimuli. The device has the potential to efficiently assist in maintaining the appropriate frequency of chest compressions during CPR and in training and qualifying rescuers. It is believed that the development of Let’s pulse will contribute significantly to the Unified Health System in increasing the quality of CPR and consequently reducing premature death from cardiac arrest.

Bimodality of auditory receptors in bush-crickets. Сontinued discussion. It's time to experiment.

Continuation of the discussion on the sensitivity of the chordotonal sensilla of the tympanal organ of bush-crickets to vibratory stimuli. We have previously shown that individual receptors registered directly in the tympanal organ perceive vibrations along with sound stimuli. In addition, scolopidia of the crista acustica possess mixed sensitivity, too, as well as receptors of the intermediate organ. The authors of the comment offered their opinion concerning our applied methods as well as our obtained results. In particular, they noted the dissimilarity of our data from the previously obtained data (the 1970s-1990s), mainly in the laboratory of Prof. K. Kalmring, who assumed that only low-frequency receptors, in particular receptors of the intermediate organ, possess mixed sensitivity. At the same time, receptor activity was recorded in the tympanal nerve without morphological identification of receptors (with the exception of one stained neuron in the prothoracic ganglion). We carried out a series of experiments using the method of K. Kalmring and found that it is possible to register several receptors in the tympanal nerve with different reactions during one experiment: to sound only, also both to vibration stimuli and sound. In the latter case, we dealt with low-threshold receptors, which responded to ultrasound, and this with high probability belonged to the crista acustica. Similar data were previously obtained on the bush-cricket Decticus verrucivorus. In this publication, we explain the methodological features of our work and suggest that the loss of sensitivity to vibrations at the level of the tympanal nerve by some auditory receptors may be due to the ephaptic and/or chemical interaction of the tympanal organ receptors with vibroreceptors of the subgenual or other organs. To verify this hypothesis, it is necessary to conduct additional studies, such as physiological, morphological, and immunohistochemical, along the entire vibroacoustic afferent tract, that is, from the peripheral part to the first switches to the corresponding interneurons.

Chronic exposure to environmentally-relevant concentrations of imidacloprid impact survival and ecologically-relevant behaviors of fathead minnow larvae.

Imidacloprid (IM) has emerged as a contaminant of concern in several areas within the United States due to its frequent detections in aquatic ecosystems and pseudo-persistence, posing potential risks to non-target species. Here we summarize our work evaluating the sublethal toxicity of IM to in fathead minnow larvae following chronic exposure beginning just after fertilization. Our in silico analysis and in vivo bioassays suggest that IM has a low binding affinity for the vertebrate nAChR, as expected. However, chronic exposure to ≥ 0.16 µg IM/L reduced survival by 10%, and exposure to ≥ 18 µg IM/L reduced survival by approximately 20-40%. Surviving fish exposed to ≥ 0.16 µg IM/L showed reduced growth, altered embryonic motor activity, and hatched prematurely. Further, a significant proportion of fish exposed to ≥ 0.16 µg IM/L were slower to respond to vibrational stimuli and slower to swim away, indicating a potential for chronic exposure to IM to impair the ability of larvae to escape predation. The adverse health effects observed here indicate that chronic exposure to environmentally-relevant concentrations of IM may elicit sublethal responses that culminate in a significant increase in mortality during early life stages, ultimately translating to reduced recruitment in wild fish populations.

Socket-residuum coupling integrity affects perception of external stimuli: Effects of altering the transtibial interface using vacuum-assisted suspension.

Relative movement between the socket and residual limb can impair function in prosthesis users. It is plausible that, in addition to its mechanical effect, the integrity of the socket-residuum interface influences the ability of an individual to sense tactile cues through the prosthesis. Vacuum-assisted suspension (VAS) has been shown to reduce relative movement at this interface, providing a means to test this premise. The purpose of this pilot study was to assess the effects of altering socket-residuum interface integrity through the VAS pressure level on the thresholds of perception of an externally applied vibration stimulus. Seven unilateral transtibial prosthesis users participated. Socket-residual limb integrity was altered using the VAS subatmospheric (vacuum) pressure level. Vibration perception tests were conducted at low, mid, and high vacuum levels, targeting 0, 8, and 19 in Hg respectively, and performed in partially loaded and fully loaded conditions. Vibration intensity was increased using a dial until participants delivered a verbal signal indicating it was perceptible, and the nominal intensity was recorded. Intensity thresholds decreased (ie, sensitivity increased) from low to high vacuum settings when fully loaded ( P = 0.008). Differences when partially loaded were nonsignificant and variable across participants. This study provides preliminary evidence that altering the integrity between the socket and residual limb by modifying the vacuum level affects sensation related to the external environment experienced through the prosthesis, although translation of these findings to real-world stimuli remains to be tested.

Whole body vibration accelerates the functional recovery of motor nerve components in sciatic nerve-crush injury model rats.

This study aimed to investigate the effect of whole body vibration (WBV) on the sensory and motor nerve components with sciatic nerve injury model rats. Surgery was performed on 21 female Wister rats (6-8 weeks) under intraperitoneal anesthesia. The nerve-crush injuries for the left sciatic nerve were inflicted using a Sugita aneurysm clip. The sciatic nerve model rats were randomly divided into two groups (n=9; control group, n=12; WBV group). The rats in the WBV group walked in the cage with a vibratory stimulus (frequency 50 Hz, 20 min/day, 5 times/wk), while those in the control group walked in the cage without any vibratory stimulus. We used heat stimulation-induced sensory threshold and lumbar magnetic stimulation-induced motor-evoked potentials (MEPs) to measure the sensory and motor nerve components, respectively. Further, morphological measurements, bilateral hind-limb dimension, bilateral gastrocnemius dimension, and weight were evaluated. Consequently, there were no significant differences in the sensory threshold at the injury side between the control and WBV groups. However, at 4 and 6 weeks postoperatively, MEPs latencies in the WBV group were significantly shorter than those in the control group. Furthermore, both sides of the hind-limb dimension at 6 weeks postoperatively, the left side of the gastrocnemius dimension, and both sides of the gastrocnemius weight significantly increased. In conclusion, WBV especially accelerates the functional recovery of motor nerve components in sciatic nerve-crush injury model rats.

Vibrating toothbrush, ice, or topical anesthetic agent to reduce pain of local anesthetic injection in 5- to 12-year-old children undergoing dental procedures — a randomized controlled trial

BackgroundApplication of topical anesthetic agent prior to injection is the most commonly used method to control initial needle penetration pain of local anesthetic injection. Ice and vibration stimulus application are other nonpharmacologic methods used to reduce painful sensations of injection. The present study aims to verify and compare topical anesthetic, ice pretreatment, and electric toothbrush as a vibratory device, to reduce the pain of local anesthetic injections.The study was conducted on children aged 5–12 years, requiring extraction of a maxillary primary tooth. A randomized control trial design was used wherein each child was randomly assigned by permuted block randomization design method to receive either lignocaine 5% as topical anesthetic or ice pretreatment or motorized toothbrush as a vibratory device during local anesthetic injections. Sound, eye, and motor (SEM) scale was used for objective evaluation of pain during injection, and Faces Pain Scale (FPS) was used for subjective evaluation. For statistical analysis, nonparametric test — Kruskal Wallis/ANOVA test for three groups and between two groups Mann–Whitney U-test, was used to compare SEM and FPS values. Level of significance chosen was p < 0.05.ResultsSEM (palatal) and FPS (palatal) scores were slightly higher in topical anesthetic group as compared to ice pretreatment or vibration group, but the differences were not statistically significant. There were no statistically significant differences among SEM (buccal) and FPS (buccal) scores in all the three groups.ConclusionsIce cooling and electric toothbrush-induced vibration were as effective as topical anesthetic for reduction in pain due to injection.Trial registrationThe CTRI number of the trial is CTRI/2021/03/032046.

Sensory Profiling in Classical Ehlers-Danlos Syndrome: A Case-Control Study Revealing Pain Characteristics, Somatosensory Changes, and Impaired Pain Modulation

Pain is one of the most important yet poorly understood complaints in heritable connective tissue disorders (HCTDs) caused by monogenic defects in extracellular matrix molecules. This is particularly the case for the Ehlers-Danlos syndrome (EDS), paradigm collagen-related disorders. This study aimed to identify the pain signature and somatosensory characteristics in the rare classical type of EDS (cEDS) caused by defects in type V or rarely type I collagen. We used static and dynamic quantitative sensory testing and validated questionnaires in 19 individuals with cEDS and 19 matched controls. Individuals with cEDS reported clinically relevant pain/discomfort (Visual Analogue Scale ≥5/10 in 32% for average pain intensity the past month) and worse health-related quality of life. An altered somatosensory profile was found in the cEDS group with higher (P = .04) detection thresholds for vibration stimuli at the lower limb, indicating hypoesthesia, reduced thermal sensitivity with more (P < .001) paradoxical thermal sensations (PTSs), and hyperalgesia with lower pain thresholds to mechanical (P < .001) stimuli at both the upper and lower limbs and cold (P = .005) stimulation at the lower limb. Using a parallel conditioned pain modulation paradigm, the cEDS group showed significantly smaller antinociceptive responses (P-value .005–.046) suggestive of impaired endogenous pain modulation. In conclusion, individuals with cEDS report chronic pain and worse health-related quality of life and present altered somatosensory perception. This study is the first to systematically investigate pain and somatosensory characteristics in a genetically defined HCTD and provides interesting insights into the possible role of the ECM in the development and persistence of pain. PerspectiveChronic pain compromises the quality of life in individuals with cEDS. Moreover, an altered somatosensory perception was found in the cEDS group with hypoesthesia for vibration stimuli, more PTSs, hyperalgesia for pressure stimuli, and impaired pain modulation.

The ndrg2 Gene Regulates Hair Cell Morphogenesis and Auditory Function during Zebrafish Development.

Damages of sensory hair cells (HCs) are mainly responsible for sensorineural hearing loss, however, its pathological mechanism is not yet fully understood due to the fact that many potential deafness genes remain unidentified. N-myc downstream-regulated gene 2 (ndrg2) is commonly regarded as a tumor suppressor and a cell stress-responsive gene extensively involved in cell proliferation, differentiation, apoptosis and invasion, while its roles in zebrafish HC morphogenesis and hearing remains unclear. Results of this study suggested that ndrg2 was highly expressed in the HCs of the otic vesicle and neuromasts via in situ hybridization and single-cell RNA sequencing. Ndrg2 loss-of-function larvae showed decreased crista HCs, shortened cilia, and reduced neuromasts and functional HCs, which could be rescued by the microinjection of ndrg2 mRNA. Moreover, ndrg2 deficiency induced attenuated startle response behaviors to sound vibration stimuli. Mechanistically, there were no detectable HC apoptosis and supporting cell changes in the ndrg2 mutants, and HCs were capable of recovering by blocking the Notch signaling pathway, suggesting that ndrg2 was implicated in HC differentiation mediated by Notch. Overall, our study demonstrates that ndrg2 plays crucial roles in HC development and auditory sensory function utilizing the zebrafish model, which provides new insights into the identification of potential deafness genes and regulation mechanism of HC development.

CERVICAL VESTIBULAR EVOKED MYOGENIC POTENTIALS IN PATIENTS WITHTYPE IIDIABETES MELLITUS

Introduction:Vestibular impairment has been demonstrated in patients with diabetes mellitus. Vestibular evoked myogenic potential (VEMP) is a short latency electromyographic response to sound or vibration stimuli that may reflect otolith organ or related reflex functions. cVEMPs are summation responses recorded from the contracted sternocleidomastoid inresponse to synchronized acoustic stimulation of the ipsilateral ear/saccule.In diabetic patients. Objective: Here, we asses prevalence of vestibular dysfunction by measuring cVEMP findings in patients with diabetes mellitus typeII. Methods: This study was carried out on two groups of subjects including 20 adult subjects with diabetes mellitustypeIIand 20 adult subjectsnon-diabetics, both group their aged ranged from 20-60 years. Results:showed statistically significant difference in cVEMP between diabetes mellitus type 2 control group with increase in latencies of P1 and N1 and decrease in amplitude. Conclusion: In diabetic individuals who are asymptomatic and never complained of vestibular dysfunction, cVEMPsis able to identify these patients.

Respiratory entrainment of the locus coeruleus modulates arousal level to avoid physical risks from external vibration

Slow rocking chairs can easily put people to sleep, while violent shaking, such as during earthquakes, may lead to rapid awakening. However, the influence of external body vibrations on arousal remains unclear. Herein, a computational model of a locus coeruleus (LC)-norepinephrine (NE) system and cardio-respiratory system were used to show that respiratory entrainment of the LC modulates arousal levels, which is an adaptation to avoid physical risks from external vibration. External vibrations of sinusoidal waves with different frequencies ranging from 0.1 to 20 [Hz] were applied to the LC based on the results of previous studies. We found that respiratory entrainment of the LC decreased the breathing rate (BR) and heart rate (HR) to maintain the HR within its normal range. Furthermore, 1:1 phase locking enhanced arousal level while phase-amplitude coupling decreased it for larger vibration stimuli. These findings suggest that respiratory entrainment of the LC might automatically modulate cardio-respiratory system homeostasis and arousal levels for performance readiness (fight/flight or freeze) to avoid physical risks from larger external vibrations.

Fabrication ofShearing‐Motion‐TypeTactile Display Mechanism UsingSMA Thick‐FilmActuators and Coil Springs Array

AbstractA shearing‐motion‐type microelectromechanical system (MEMS) tactile display mechanism was fabricated to provide a shear vibration stimulus to the fingertip. It consisted of shrinking shape memory alloy (SMA) thick‐film actuators and a supporting coil spring array. The SMA actuator array was designed and fabricated using a flash‐evaporated SMA film (10 μm thick) on a mirror‐polished Cu substrate. The coil spring was successfully arrayed on a glass substrate with an SU‐8 circular array pattern. The glass substrate with the coils was bonded to the SMA substrate to complete the shearing‐motion mechanism. During the bonding process, the SMA actuators were initially elongated by the coil springs. The generated amplitude and force of the fabricated mechanism were characterized when the SMA actuator was heated by applying a pulsed current to be shrank by the shape recovery effect. The fabricated shearing‐motion mechanism successfully generated large amplitude of 41 μm (around 80 μm in reciprocal motion) and force of 22 mN at a driving frequency of 1 Hz. At 20 Hz, an amplitude of 23 μm and force of 10 mN were obtained even though they were reduced owing to the low thermal response. At both driving frequencies, the obtained amplitudes and forces seems to be sufficient for tactile stimulation to finger skin. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC.

Study on the Cognitive Characteristics Induced by Changes in the Intensity, Frequency and Duration of Vibratory Stimuli

The purpose of this study is to analyze the cognitive characteristics that can be induced by vibration stimuli at two intensities, three frequencies, and five presentation periods. The experiment was conducted on 20 right-handed adult males, and a subjective evaluation was performed using a questionnaire. Regression analysis was performed to observe the parameters affecting cognitive characteristics according to changes in intensity, frequency, and stimulation duration. The regression analysis results showed that the cognitive characteristics affected by changes in intensity, frequency, and stimulation duration were "heavy", "bold", "thick", and "light". The cognitive characteristics affected by two-variable combinations were "deep", "clear", "vibrating", "dense", "numb", "blunt", "shallow", "fuzzy", and "soft". Cognitive characteristics affected by either intensity, frequency, or stimulation duration were "fast", "pungent", "skinny", "thin", "slow", "ticklish", "tingling", "prickling", "tap", and "rugged". By observing the cognitive characteristics that can be induced by the combination of intensity, frequency, and stimulation duration, we confirmed that in addition to intensity and frequency, the stimulation duration is an important factor that influences the induction of various cognitive characteristics. The results presented in the study can be used to enhance the utility of haptic surfaces for extended reality applications.

Acute Effects of Whole-Body Vibration on Quadriceps Isometric Muscular Endurance in Middle-Aged Adults: A Pilot Study

This study analysed the acute effects of whole-body vibration (WBV) on quadriceps isometric muscular endurance. Fifteen healthy middle-aged males performed an endurance isometric strength test after three different warm-up conditions: static half squat plus WBV (HSV), static half squat without WBV (HS), and control condition (CC). The endurance isometric strength test consisted of 10 maximal isometric contractions held for 4 s and interspersed by 2 s of rest between each repetition. Rate of Perceived Exertion (RPE) was assessed after warm-up (RPE1) and at the end of the testing session (RPE2). During each testing session, participant’s heart rate (HR) was continuously recorded. For each trial, the mean force across the 10 repetitions and fatigue index were evaluated. Mean force was significantly higher (p &lt; 0.01) in CC than in the other two conditions. Both RPE1 and RPE2 were significantly lower (p &lt; 0.01) in CC than HSV and HS condition. Warm-up HR and the mean testing session HR were significantly lower in CC than the other two conditions (p &lt; 0.01). No significant differences were observed in fatigue index between conditions (p &gt; 0.05) or in HR during the endurance protocol. Performing half-squat with or without vibration stimuli does not increase isometric muscular endurance and does not influence fatigue index.

Speed Control of Mobile Robots Using Vibration Stimuli from Bumpy Road Surface

Speed bumps and rumble strips have been introduced into the traffic infrastructure to improve traffic safety. When a vehicle travels on a road where speed bumps and rumble strips are installed, vibration stimuli are transmitted to the driver to encourage control of the speed and position of the vehicle. In this letter, speed bumps are applied to an automated driving system. More precisely, this letter considers the speed control of a mobile robot using vibration stimuli from bumpy road surfaces. We formulated a design problem for a speed control law for a mobile robot and proposed a controller that can adjust the speed according to road surface geometry. The performance of the proposed method was verified via simulation using Unity.

Programmable tactile feedback system for blindness assistance based on triboelectric nanogenerator and self-excited electrostatic actuator

Vibro-tactile devices are highly resistant to interference and perform excellently in noisy environments, rendering them the preferred method for blindness assistance. To construct an effective haptic feedback system, two key elements are required: a highly sensitive vibration actuator and a safe high-voltage power source. In this work, a self-powered tactile feedback system (STFS) is proposed on the basis of triboelectric nanogenerator (TENG) and self-excited electrostatic actuator (SEEA). The performances of the TENG and SEEA have been systematically investigated and optimized to ensure that the former can power the latter to produce sufficient vibration stimuli on the user’s skin. With the help of a programmed switch matrix, a series of practical applications have been demonstrated, including a refreshable Braille system, a haptic navigation interface, and tactile-assisted encrypted communication. The proposed STFS holds the merits of being portable, cost-effective, multifunctional, and high-accurate, demonstrating the great potential to substantially improve the quality of life for visually impaired individuals.

Sleep in the crustacean crayfish.

Sleep is defined as a state of unconsciousness, reduced locomotive activity and rapid awakening, and is well established in mammals, birds, reptiles and teleosts. Commonly, it is also defined with electrical records (electroencephalogram), which are only well established in mammals and to some extent in birds. However, sleep states similar to those of mammals, except for electrical criteria, appear to occur in some invertebrates. Currently, the most compelling evidence of sleep in invertebrates has been obtained in the crayfish. In mammals, sleep is characterized by a brain state that is different from that of wakefulness, which includes a change to slow waves that has not been observed in insects. Herein, we show that the crayfish enters a brain state with a high threshold to vibratory stimuli, accompanied by a form of slow wave activity in the brain, quite different from that of wakefulness. Therefore, the crayfish can enter a state of sleep that is comparable to that of mammals.

Long-term exposure of zebrafish juveniles to carbon nanofibers at predicted environmentally relevant concentrations: Outspreading warns about ecotoxicological risks to freshwater fish

Although carbon-based nanomaterials (CNMs) toxicity has already been demonstrated in some animal models, little is known about the impact of carbon nanofibers (CNFs) on aquatic vertebrates. Thus, we aimed to evaluate the possible effects of long-term exposure of zebrafish (Danio rerio) juveniles (90 days) to CNFs in predicted environmentally relevant concentrations (10 ng/L and 10 μg/L). Our data revealed that exposure to CNFs did not affect the growth and development of the animals, in addition to not having induced locomotor alterations or anxiety-like behavior. On the other hand, we observed that zebrafish exposed to CNFs showed a response deficit to the vibratory stimulus test, alteration in the density of neuromasts recorded in the final ventral region, as well as an increase in thiobarbituric acid reactive substances levels and a reduction in total antioxidant activity, nitric oxide, and acetylcholinesterase activity in the brain. Such data were directly associated with a higher concentration of total organic carbon in the brain, which suggests the bioaccumulation of CNFs. Furthermore, exposure to CNFs induced a picture suggestive of genomic instability, inferred by the increased frequency of nuclear abnormalities and DNA damage in circulating erythrocytes. Although the individual analyses of the biomarkers did not point to a concentration-dependent effect, the principal component analysis (PCA) and the Integrated Biomarker Response Index (IBRv2) indicate a more prominent effect induced by the higher CNFs concentration (10 μg/L). Therefore, our study confirms the impact of CNFs in the studied model (D. rerio) and sheds light on the ecotoxicological risks of these nanomaterials to freshwater fish. Based on the ecotoxicological screening provided by our study, new horizons are opened for investigations into the mechanisms of action of CNFs, which will help understand the magnitude of the impact of these materials on aquatic biota.

Behavior and brain size of larval zebrafish exposed to environmentally relevant concentrations of beta-methylamino-l-alanine.

Harmful algal blooms (HABs) release toxic compounds in water and are increasing in frequency worldwide. The neurotoxin β-methylamino-l-alanine (BMAA) is released by HABs and has garnered much attention over the past 20 years due to its association with human neurodegenerative disorders, but its effects on wildlife are still largely unknown. This study characterized the effects of chronic exposure to environmentally relevant concentrations of BMAA on the behavior and brain size of developing zebrafish (Danio rerio). Zebrafish were continuously exposed to 0, 1, 10, or 100 µg/l waterborne BMAA between 0- and 5-days postfertilization (dpf) before the onset of exogenous feeding. At 5 dpf, locomotion and responses to vibrational and visual stimuli were assessed. Following behavioral testing, larvae body and brain size were measured. Survival between 0 and 5 dpf did not differ between treatments. Moreover, BMAA exposure did not affect thigmotaxis, startle response magnitude, habituation to repeated presentation of vibrational startling stimuli, or relative brain size. A moderate increase in overall activity was observed in larvae exposed to 10 μg/l BMAA under light, but this effect was not seen in dark conditions, indicating that visual processing may have been affected by chronic BMAA exposure. Thus, passive continuous exposure to environmentally relevant concentrations of BMAA prior to first feeding in zebrafish did not affect survival or selected measures used to represent brain development, anxiety, and motor reflexes, but a limited light-dependent effect on locomotion suggests targeted neurotoxicity within the visual system.