Measuring auditory cortical responses in Tursiops truncatus

Financial support was provided by the Office of Naval Research Code 32 (Mine Countermeasures, Acoustics Phenomenology and Modeling Group), and funded by ONR grants N00014-18-1-2062, N00014-19-1-1223, N00014-18-1-2069, and N00014-20-1-2709.Auditory neuroscience in dolphins has largely focused on auditory brainstem responses; however, such measures reveal little about the cognitive processes dolphins employ during echolocation and acoustic communication. The few previous studies of mid- and long-latency auditory-evoked potentials (AEPs) in dolphins report different latencies, polarities, and magnitudes. These inconsistencies may be due to any number of differences in methodology, but these studies do not make it clear which methodological differences may account for the disparities. The present study evaluates how electrode placement and pre-processing methods affect mid- and long-latency AEPs in (Tursiops truncatus). AEPs were measured when reference electrodes were placed on the skin surface over the forehead, the external auditory meatus, or the dorsal surface anterior to the dorsal fin. Data were pre-processed with or without a digital 50-Hz low-pass filter, and the use of independent component analysis to isolate signal components related to neural processes from other signals. Results suggest that a meatus reference electrode provides the highest quality AEP signals for analyses in sensor space, whereas a dorsal reference yielded nominal improvements in component space. These results provide guidance for measuring cortical AEPs in dolphins, supporting future studies of their cognitive auditory processing.Publisher PDFPeer reviewe

Dolphin echolocation behaviour during active long-range target approaches

Financial support was provided by the US Office of Naval Research Code 32 (Mine Countermeasures, Acoustics Phenomenology & Modeling Group). M.L. and P.T.M. were funded by frame grants from the National Danish Research Council (Det Frie Forskningsråd) and by a Semper Ardens grant from the Carlsberg Foundation. M.L.’s travel expenses were covered by grants from Augustinus Fonden and DAS-Fonden (Danish Acoustical Society, Dansk Akustisk Selskab). F.H.J. was funded by an AIAS-COFUND fellowship from Aarhus Institute of Advanced Studies under the EU's Seventh Framework Programme (Agreement No. 609033).Echolocating toothed whales generally adjust click intensity and rate according to target range to ensure that echoes from targets of interest arrive before a subsequent click is produced, presumably facilitating range estimation from the delay between clicks and returning echoes. However, this click-echo-click paradigm for the dolphin biosonar is mostly based on experiments with stationary animals echolocating fixed targets at ranges below ∼120 m. Therefore, we trained two bottlenose dolphins instrumented with a sound recording tag to approach a target from ranges up to 400 m and either touch the target (subject TRO) or detect a target orientation change (subject SAY). We show that free-swimming dolphins dynamically increase interclick interval (ICI) out to target ranges of ∼100 m. TRO consistently kept ICIs above the two-way travel time (TWTT) for target ranges shorter than ∼100 m, whereas SAY switched between clicking at ICIs above and below the TWTT for target ranges down to ∼25 m. Source levels changed on average by 17log10(target range), but with considerable variation for individual slopes (4.1 standard deviations for by-trial random effects), demonstrating that dolphins do not adopt a fixed automatic gain control matched to target range. At target ranges exceeding ∼100 m, both dolphins frequently switched to click packet production in which interpacket intervals exceeded the TWTT, but ICIs were shorter than the TWTT. We conclude that the click-echo-click paradigm is not a fixed echolocation strategy in dolphins, and we demonstrate the first use of click packets for free-swimming dolphins when solving an echolocation task.Publisher PDFPeer reviewe

The acoustic field on the forehead of echolocating Atlantic bottlenose dolphins (Tursiops truncatus)

Author Posting. © Acoustical Society of America, 2010. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 128 (2010): 1426-1434, doi:10.1121/1.3372643.Arrays of up to six broadband suction cup hydrophones were placed on the forehead of two bottlenose dolphins to determine the location where the beam axis emerges and to examine how signals in the acoustic near-field relate to signals in the far-field. Four different array geometries were used; a linear one with hydrophones arranged along the midline of the forehead, and two around the front of the melon at 1.4 and 4.2 cm above the rostrum insertion, and one across the melon in certain locations not measured by other configurations. The beam axis was found to be close to the midline of the melon, approximately 5.4 cm above the rostrum insert for both animals. The signal path coincided with the low-density, low-velocity core of the melon; however, the data suggest that the signals are focused mainly by the air sacs. Slight asymmetry in the signals were found with higher amplitudes on the right side of the forehead. Although the signal waveform measured on the melon appeared distorted, when they are mathematically summed in the far-field, taking into account the relative time of arrival of the signals, the resultant waveform matched that measured by the hydrophone located at 1 m.This work was supported by the U.S. Office of Naval Research

Track D Social Science, Human Rights and Political Science

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138414/1/jia218442.pd

3 years of liraglutide versus placebo for type 2 diabetes risk reduction and weight management in individuals with prediabetes: a randomised, double-blind trial

Background: Liraglutide 3·0 mg was shown to reduce bodyweight and improve glucose metabolism after the 56-week period of this trial, one of four trials in the SCALE programme. In the 3-year assessment of the SCALE Obesity and Prediabetes trial we aimed to evaluate the proportion of individuals with prediabetes who were diagnosed with type 2 diabetes. Methods: In this randomised, double-blind, placebo-controlled trial, adults with prediabetes and a body-mass index of at least 30 kg/m2, or at least 27 kg/m2 with comorbidities, were randomised 2:1, using a telephone or web-based system, to once-daily subcutaneous liraglutide 3·0 mg or matched placebo, as an adjunct to a reduced-calorie diet and increased physical activity. Time to diabetes onset by 160 weeks was the primary outcome, evaluated in all randomised treated individuals with at least one post-baseline assessment. The trial was conducted at 191 clinical research sites in 27 countries and is registered with ClinicalTrials.gov, number NCT01272219. Findings: The study ran between June 1, 2011, and March 2, 2015. We randomly assigned 2254 patients to receive liraglutide (n=1505) or placebo (n=749). 1128 (50%) participants completed the study up to week 160, after withdrawal of 714 (47%) participants in the liraglutide group and 412 (55%) participants in the placebo group. By week 160, 26 (2%) of 1472 individuals in the liraglutide group versus 46 (6%) of 738 in the placebo group were diagnosed with diabetes while on treatment. The mean time from randomisation to diagnosis was 99 (SD 47) weeks for the 26 individuals in the liraglutide group versus 87 (47) weeks for the 46 individuals in the placebo group. Taking the different diagnosis frequencies between the treatment groups into account, the time to onset of diabetes over 160 weeks among all randomised individuals was 2·7 times longer with liraglutide than with placebo (95% CI 1·9 to 3·9, p<0·0001), corresponding with a hazard ratio of 0·21 (95% CI 0·13–0·34). Liraglutide induced greater weight loss than placebo at week 160 (–6·1 [SD 7·3] vs −1·9% [6·3]; estimated treatment difference −4·3%, 95% CI −4·9 to −3·7, p<0·0001). Serious adverse events were reported by 227 (15%) of 1501 randomised treated individuals in the liraglutide group versus 96 (13%) of 747 individuals in the placebo group. Interpretation: In this trial, we provide results for 3 years of treatment, with the limitation that withdrawn individuals were not followed up after discontinuation. Liraglutide 3·0 mg might provide health benefits in terms of reduced risk of diabetes in individuals with obesity and prediabetes. Funding: Novo Nordisk, Denmark

Exposure amplitude and repetition affect bottlenose dolphin behavioral responses to simulated mid-frequency sonar signals

Thirty bottlenose dolphins (Tursiops truncatus) participated in a controlled exposure study using an acoustic stimulus that consisted of a simulated tactical sonar signal (1-s duration, 3250–3450 Hz). Each dolphin was trained a behavior requiring it to swim across an enclosure, touch a paddle, and return to the starting location. Ten-trial control and exposure sessions were performed with each dolphin. Dolphins were placed into one of five groups, each of which received a 115, 130, 145, 160, 175 or 185 dB re 1 μPa (rms) sound pressure level (SPL) exposure while crossing the enclosure on exposure trials. A canonical correlation analysis was used to determine the set of behavioral responses most interrelated with the independent variables of exposure level, trial number, and age. Responses that significantly contributed to the canonical model were used to create dose– response functions based on the received SPL. Dose–response functions demonstrated a robust relationship between received SPL and the probability of response and indicated rapid habituation to repetitive exposures with received SPL ≤ 160 dB. No habituation was observed at received SPL ≥ 175 dB re 1 μPa and all dolphins refused to participate in trials when the received SPL = 185 dB re 1 μPa. Although bottlenose dolphins may rapidly habituate to sound exposures belowa certain level, particularly if there is food motivation, abandonment of behaviors increases rapidly at received levels ≥ 175 dB re 1 μPa

Research with Navy Marine Mammals Benefits Animal Care, Conservation and Biology

The benefit and ethics of keeping marine mammals in captivity has been a source of debate for several decades. One of the center pieces of the debate is whether there is real benefit to marine mammals as a whole that results from research on captive marine mammals. The Navy Marine Mammal Program (MMP) keeps marine mammals for national defense purposes. However, in nearly 50 years of existence, the MMP has also been a leader in marine mammal research. The results of the research conducted by the MMP has not only benefited the care of marine mammals in captivity, but has directly and indirectly improved our understanding of the behavior, physiology, and ecology ofanimals in the wild. Research conducted with the MMP marine mammal population has produced demonstrable improvements in veterinary care and has lead to some of the earliest advances inproviding guidelines for mitigating the impact of sound on wild marine mammals. Additionally, our understanding of echolocation, diving physiology, and husbandry behaviors has greatly benefited from MMP research. Future and current work conducted by the MMP will continue to add to the knowledge base of marine mammal biology while contributing to their care and conservation

Research with Navy Marine Mammals Benefits Animal Care, Conservation and Biology

The benefit and ethics of keeping marine mammals in captivity has been a source of debate for several decades. One of the center pieces of the debate is whether there is real benefit to marine mammals as a whole that results from research on captive marine mammals. The Navy Marine Mammal Program (MMP) keeps marine mammals for national defense purposes. However, in nearly 50 years of existence, the MMP has also been a leader in marine mammal research. The results of the research conducted by the MMP has not only benefited the care of marine mammals in captivity, but has directly and indirectly improved our understanding of the behavior, physiology, and ecology ofanimals in the wild. Research conducted with the MMP marine mammal population has produced demonstrable improvements in veterinary care and has lead to some of the earliest advances inproviding guidelines for mitigating the impact of sound on wild marine mammals. Additionally, our understanding of echolocation, diving physiology, and husbandry behaviors has greatly benefited from MMP research. Future and current work conducted by the MMP will continue to add to the knowledge base of marine mammal biology while contributing to their care and conservation