Difference in anxiety and sensitization of the acoustic startle response between the two inbred mouse strains BALB/cAN and DBA/2N

The inbred mouse strain BALB has been proposed to be an animal model for pathological anxiety. BALB exhibits a stronger acoustic startle response (ASR) than the 'less emotional' inbred strain DBA. Four experiments were conducted to determine whether this strong ASR is due to a higher anxiety level and/or to greater sensitization in BALB than in DBA, with the following results: (1) The ASR to the very first startle stimulus was found to be much stronger in BALB than in DBA, and freezing behavior evoked by startle stimuli was more pronounced in BALB than in DBA. These findings indicate a higher level of anxiety in this strain. (2) ASR amplitudes of BALB initially rose much higher during consecutive startle stimuli and remained at a high level much longer than in DBA. Thereafter, ASR amplitude dropped more slowly and to a lesser degree than in DBA. Startle amplitudes decreased similarly in both strains (strong exponential decrease) only when a low sound pressure level (SPL) was used which elicited approximately the same low ASR in both strains. These results can only be explained by increased sensitization in BALB. (3) The slope of the i/o-function, which represents the relation between sensory input and motor output, was steeper in BALB than in DBA. As it has been shown recently, sensitization increases the slope of the startle i/o-function indicating increased sensitization in BALB. It is discussed, however, whether anxiety also contributes to this effect. (4) Footshocks increased the ASR much less in BALB than in DBA, again showing increased sensitization in BALB. Both a higher level of anxiety and greater sensitization therefore determined the greater strength of the ASR in BALB than in DBA.     

Prepulse Inhibition of Acoustic Startle Reflex as a Function of the Frequency Difference between Prepulse and Background Sounds in Mice

Background

Prepulse inhibition (PPI) depicts the effects of a weak sound preceding strong acoustic stimulus on acoustic startle response (ASR). Previous studies suggest that PPI is influenced by physical parameters of prepulse sound such as intensity and preceding time. The present study characterizes the impact of prepulse tone frequency on PPI.

Methods

Seven female C57BL mice were used in the present study. ASR was induced by a 100 dB SPL white noise burst. After assessing the effect of background sounds (white noise and pure tones) on ASR, PPI was tested by using prepulse pure tones with the background tone of either 10 or 18 kHz. The inhibitory effect was assessed by measuring and analyzing the changes in the first peak-to-peak magnitude, root mean square value, duration and latency of the ASR as the function of frequency difference between prepulse and background tones.

Results

Our data showed that ASR magnitude with pure tone background varied with tone frequency and was smaller than that with white noise background. Prepulse tone systematically reduced ASR as the function of the difference in frequency between prepulse and background tone. The 0.5 kHz difference appeared to be a prerequisite for inducing substantial ASR inhibition. The frequency dependence of PPI was similar under either a 10 or 18 kHz background tone.

Conclusion

PPI is sensitive to frequency information of the prepulse sound. However, the critical factor is not tone frequency itself, but the frequency difference between the prepulse and background tones.     

A computational model for the modulation of the prepulse inhibition of the acoustic startle reflex

The acoustic startle reflex (ASR), a defensive response, is a contraction of the skeletal and facial muscles in response to an abrupt, intense (> 80 db) auditory stimulus, which has been extensively studied in rats and humans. Prepulse inhibition (PPI) of ASR is the normal suppression of the startle reflex when an intense stimulus is preceded by a weak non-starting pre-stimulus. PPI, a measure of sensory motor gating, is impaired in various neuropsychiatric disorders, including schizophrenia, and is modulated by cognitive and emotional contexts such as fear and attention. We have modeled the fear modulation of PPI of ASR based on its anatomical substrates and taking into account data from behaving rats and humans. The model replicates the principal features of both phenomena and predicts underlying neural mechanisms. In addition, the model yields testable predictions.     

Psychophysiological Response Patterns to Affective Film Stimuli

Psychophysiological research on emotion utilizes various physiological response measures to index activation of the defense system. Here we tested 1) whether acoustic startle reflex (ASR), skin conductance response (SCR) and heart rate (HR) elicited by highly arousing stimuli specifically reflect a defensive state and 2) the relation between resting heart rate variability (HRV) and affective responding. In a within-subject design, participants viewed film clips with a positive, negative and neutral content. In contrast to SCR and HR, we show that ASR differentiated between negative, neutral and positive states and can therefore be considered as a reliable index of activation of the defense system. Furthermore, resting HRV was associated with affect-modulated characteristics of ASR, but not with SCR or HR. Interestingly, individuals with low-HRV showed less differentiation in ASR between affective states. We discuss the important value of ASR in psychophysiological research on emotion and speculate on HRV as a potential biological marker for demarcating adaptive from maladaptive responding.     

Impacts of regular and random noise on the behaviour,growth and development of larval Atlantic cod (Gadus morhua)

Anthropogenic noise impacts behaviour and physiology in many species, but responses could change with repeat exposures. As repeat exposures can vary in regularity, identifying regimes with less impact is important for regulation. We use a 16-day split-brood experiment to compare effects of regular and random acoustic noise (playbacks of recordings of ships), relative to ambient-noise controls, on behaviour, growth and development of larval Atlantic cod (Gadus morhua). Short-term noise caused startle responses in newly hatched fish, irrespective of rearing noise. Two days of both regular and random noise regimes reduced growth, while regular noise led to faster yolk sac use. After 16 days, growth in all three sound treatments converged, although fish exposed to regular noise had lower body width–length ratios. Larvae with lower body width–length ratios were easier to catch in a predator-avoidance experiment. Our results demonstrate that the timing of acoustic disturbances can impact survival-related measures during development. Much current work focuses on sound levels, but future studies should consider the role of noise regularity and its importance for noise management and mitigation measures.     

Alterations in Peripheral and Central Components of the Auditory Brainstem Response: A Neural Assay of Tinnitus

Chronic tinnitus, or “ringing of the ears”, affects upwards of 15% of the adult population. Identifying a cost-effective and objective measure of tinnitus is needed due to legal concerns and disability issues, as well as for facilitating the effort to assess neural biomarkers. We developed a modified gap-in-noise (GIN) paradigm to assess tinnitus in mice using the auditory brainstem response (ABR). We then compared the commonly used acoustic startle reflex gap-prepulse inhibition (gap-PPI) and the ABR GIN paradigm in young adult CBA/CaJ mice before and after administrating sodium salicylate (SS), which is known to reliably induce a 16 kHz tinnitus percept in rodents. Post-SS, gap-PPI was significantly reduced at 12 and 16 kHz, consistent with previous studies demonstrating a tinnitus-induced gap-PPI reduction in this frequency range. ABR audiograms indicated thresholds were significantly elevated post-SS, also consistent with previous studies. There was a significant increase in the peak 2 (P2) to peak 1 (P1) and peak 4 (P4) to P1 amplitude ratios in the mid-frequency range, along with decreased latency of P4 at higher intensities. For the ABR GIN, peak amplitudes of the response to the second noise burst were calculated as a percentage of the first noise burst response amplitudes to quantify neural gap processing. A significant decrease in this ratio (i.e. recovery) was seen only at 16 kHz for P1, indicating the presence of tinnitus near this frequency. Thus, this study demonstrates that GIN ABRs can be used as an efficient, non-invasive, and objective method of identifying the approximate pitch and presence of tinnitus in a mouse model. This technique has the potential for application in human subjects and also indicates significant, albeit different, deficits in temporal processing in peripheral and brainstem circuits following drug induced tinnitus.     

Using the Threat Probability Task to Assess Anxiety and Fear During Uncertain and Certain Threat

Fear of certain threat and anxiety about uncertain threat are distinct emotions with unique behavioral, cognitive-attentional, and neuroanatomical components. Both anxiety and fear can be studied in the laboratory by measuring the potentiation of the startle reflex. The startle reflex is a defensive reflex that is potentiated when an organism is threatened and the need for defense is high. The startle reflex is assessed via electromyography (EMG) in the orbicularis oculi muscle elicited by brief, intense, bursts of acoustic white noise (i.e., “startle probes”). Startle potentiation is calculated as the increase in startle response magnitude during presentation of sets of visual threat cues that signal delivery of mild electric shock relative to sets of matched cues that signal the absence of shock (no-threat cues). In the Threat Probability Task, fear is measured via startle potentiation to high probability (100% cue-contingent shock; certain) threat cues whereas anxiety is measured via startle potentiation to low probability (20% cue-contingent shock; uncertain) threat cues. Measurement of startle potentiation during the Threat Probability Task provides an objective and easily implemented alternative to assessment of negative affect via self-report or other methods (e.g., neuroimaging) that may be inappropriate or impractical for some researchers. Startle potentiation has been studied rigorously in both animals (e.g., rodents, non-human primates) and humans which facilitates animal-to-human translational research. Startle potentiation during certain and uncertain threat provides an objective measure of negative affective and distinct emotional states (fear, anxiety) to use in research on psychopathology, substance use/abuse and broadly in affective science. As such, it has been used extensively by clinical scientists interested in psychopathology etiology and by affective scientists interested in individual differences in emotion.     

Prepulse inhibition （PPI） of tactile startle response in recombinant congenic strains of mice： QTL mapping and comparison with acoustic PPI

Prepulse inhibition (PPI) of the startle response is a psychophysiological measure of sensorimotor gating believed to be cross-modal between different sensory systems.We analyzed the tactile startle response (TSR) and PPI of TSR (tPPD,using light as a prepulse stimulus,in the mouse strains A/J and C57BL/6J and 36 recombinant congenic strains derived from them.Parental strains were significantly different for TSR,but were comparable for tPPI.Among the congenic strains,variation for TSR was significant in both genetic backgrounds,but that of tPPI was significant only for the C57BL/6J background.Provisional mapping for loci modulating TSR and tPPI was carded out.Using mapping data from our previous study on acoustic startle responses (ASR) and PPI of ASR (aPPI),no common markers for aPPI and tPPI were identified.However,some markers were significantly associated with both ASR and TSIL at least in one genetic background.These results indicate cross-modal genetic regulation for the startle response but not for PPI,in these mouse strains.     

Exposure to noise pollution across North American passerines supports the noise filter hypothesis

The noise filter hypothesis predicts that species using higher sound frequencies should be more tolerant of noise pollution, because anthropogenic noise is more intense at low frequencies. Recent work analysed continental‐scale data on anthropogenic noise across the USA and found that passerine species inhabiting more noise‐polluted areas do not have higher peak song frequency but have more complex songs. However, this metric of song complexity is of ambiguous interpretation, because it can indicate either diverse syllables or a larger frequency bandwidth. In the latter case, the finding would support the noise filter hypothesis, because larger frequency bandwidths mean that more sound energy spreads to frequencies that are less masked by anthropogenic noise. We reanalysed how passerine song predicts exposure to noise using a more thorough dataset of acoustic song measurements, and showed that it is large frequency bandwidths, rather than diverse syllables, that predict the exposure of species to noise pollution. Given that larger bandwidths often encompass higher maximum frequencies, which are less masked by anthropogenic noise, our result suggests that tolerance to noise pollution might depend mostly on having the high‐frequency parts of song little masked by noise, thus preventing acoustic communication from going entirely unnoticed at long distances.     

Neural evolution in the bat-free habitat of Tahiti: partial regression in an anti-predator auditory system

Noctuid moths endemic to the mountains of Tahiti have evolved in an environment without bats and these insects have lost a defensive behaviour against these predators, the acoustic startle response (ASR). The ASR in noctuid moths is presumed to be activated by a single auditory receptor neuron (A2 cell) and we report that while this cell still exists in endemic species and possesses similar sensitivity thresholds compared to the A2 cell of recently introduced species, it exhibits reduced firing activity to ASR-evoking sounds. This partial neural regression suggests that the evolutionary disappearance of the ASR in these insects is incomplete and that sensoribehavioural integration decays gradually following the removal of stabilizing selective forces.     

The acoustic startle reflex as a tool for assessment of odor environment effects on affective states in laboratory mice

Apart from self and conspecific odors, odors from other species also influence the affective states in laboratory mice (Mus musculus musculus) in their home cages and during experimental procedures, possibly inducing confusion and inconsistency in experimental data. Thus, it is important to detect the types of animal odors associated with housing, husbandry, and laboratory practice that can arouse different types of affective changes in mice. Here, we aimed to test the effectiveness of the acoustic startle reflex (ASR) in detecting changes in the affective states of laboratory mice due to animal-derived-odor as it has a non-zero baseline, and can be enhanced or attenuated by positive or negative affective shifts, respectively. We used ASR to examine the affective changes in mice that were induced by bedding odors and an alarm pheromone. The odor of bedding obtained from the mice’ home cages significantly attenuated the ASR, suggesting positive affective shifts in the test mice, whereas that from bedding obtained from rat cages significantly enhanced the ASR, suggesting negative affective shifts. No significant changes in ASR were observed in mice presented with the odor of bedding obtained from cages of unfamiliar conspecifics. In contrast, there was significant ASR enhancement in mice exposed to volatile components of alarm pheromones trapped in water, suggesting negative affective shifts. Thus, our findings show that ASR may be a valuable tool in assessing the effects of odors on the affective states in laboratory mice.     

Auditory analysis of the sound source approaching and withdrawing: psychoacoustic and neurophysiological correlates

The findings seemed to be based on direction and velocity of modelling the radial sound source shifting in free acoustic field. The threshold and the optimal parameters of the acoustic model imitating the approaching and withdrawing of the sound source shifting in silence and under conditions of noise, were established. A correlation between peak-to-peak amplitudes of the N1-P2 components of auditory EPs and the imitated direction of the sound shifting, was shown. The role of different left and right hemispheres' areas in perception of the radial sound source was analysed. The detector features of the central auditory neurones were shown as a possible mechanism of estimating the sound source approaching and withdrawal.     

Hypnotizability,Hypnosis and Prepulse Inhibition of the Startle Reflex in Healthy Women: An ERP Analysis

A working model of the neurophysiology of hypnosis suggests that highly hypnotizable individuals (HHs) have more effective frontal attentional systems implementing control, monitoring performance, and inhibiting unwanted stimuli from conscious awareness, than low hypnotizable individuals (LHs). Recent studies, using prepulse inhibition (PPI) of the auditory startle reflex (ASR), suggest that HHs, in the waking condition, may show reduced sensory gating although they may selectively attend and disattend different stimuli. Using a within subject design and a strict subject selection procedure, in waking and hypnosis conditions we tested whether HHs compared to LHs showed a significantly lower inhibition of the ASR and startle-related brain activity in both time and intracerebral source localization domains. HHs, as compared to LH participants, exhibited (a) longer latency of the eyeblink startle reflex, (b) reduced N100 responses to startle stimuli, and (c) higher PPI of eyeblink startle and of the P200 and P300 waves. Hypnosis yielded smaller N100 waves to startle stimuli and greater PPI of this component than in the waking condition. sLORETA analysis revealed that, for the N100 (107 msec) elicited during startle trials, HHs had a smaller activation in the left parietal lobe (BA2/40) than LHs. Auditory pulses of pulse-with prepulse trials in HHs yielded less activity of the P300 (280 msec) wave than LHs, in the cingulate and posterior cingulate gyrus (BA23/31). The present results, on the whole, are in the opposite direction to PPI findings on hypnotizability previously reported in the literature. These results provide support to the neuropsychophysiological model that HHs have more effective sensory integration and gating (or filtering) of irrelevant stimuli than LHs.     

Objective measures of emotion related to brand attitude: a new way to quantify emotion-related aspects relevant to marketing

With this study we wanted to test the hypothesis that individual like and dislike as occurring in relation to brand attitude can be objectively assessed. First, individuals rated common brands with respect to subjective preference. Then, they volunteered in an experiment during which their most liked and disliked brand names were visually presented while three different objective measures were taken. Participant's eye blinks as responses to acoustic startle probes were registered with electromyography (EMG) (i) and their skin conductance (ii) and their heart rate (iii) were recorded. We found significantly reduced eye blink amplitudes related to liked brand names compared to disliked brand names. This finding suggests that visual perception of liked brand names elicits higher degrees of pleasantness, more positive emotion and approach-oriented motivation than visual perception of disliked brand names. Also, skin conductance and heart rate were both reduced in case of liked versus disliked brand names. We conclude that all our physiological measures highlight emotion-related differences depending on the like and dislike toward individual brands. We suggest that objective measures should be used more frequently to quantify emotion-related aspects of brand attitude. In particular, there might be potential interest to introduce startle reflex modulation to measure emotion-related impact during product development, product design and various further fields relevant to marketing. Our findings are discussed in relation to the idea that self reported measures are most often cognitively polluted.     

Auditory-evoked evasive manoeuvres in free-flying locusts and moths

We presented free-flying locusts (Locusta migratoria L.) with sounds that varied in temporal structure and carrier frequency as they flew toward a light source in a flight room under controlled temperature and light conditions. Previous studies have shown tethered locusts react more often to trains of 30-kHz pulses than to pulse trains below 10 kHz. Further, this acoustic startle response has been suggested to function in bat-avoidance. We expected free-flying locusts to respond similarly; however, we found locusts responded to all sounds we presented, not just high-frequency, bat-like sounds. Response rates of turns, loops, and dives varied from 6% to 26% but were statistically independent of carrier frequency and/or pulse structure. Free-flying moths and tethered locusts were tested using a subset of our acoustic stimuli under the same temperature and light conditions as the free-flying locusts. Moth responses were carrier frequency dependent as were responses of tethered locusts positioned along the flight path observed in our free-flight trials. All responses were unaffected by a 90% reduction in room light. We conclude that locusts possess an acoustic startle response evocable in free flight, however, free-flying locusts do not show the same discrimination observed in tethered locusts under similar conditions.Abbreviations ASR acoustic startle response - dB SPL decibel sound pressure level (RMS re: 20 Pa)     

Formation of a defensive conditioned reflex to an acoustic stimulus in rabbits after early visual deprivation

The formation of a defensive conditioned reflex to sound has been studied in rabbits raised from birth up to 30 days of life in dark. It was shown that, as compared with control animals of the same age, elaboration of reflex to sound takes place in them in shorter times periods and with less pairings. This corresponds to changes in electrographic manifestations of conditioning: increased amplitude and reduced peak latency of evoked potentials to acoustic stimuli in the auditory and sensorimotor cortical zones. The data obtained testify to enahcned functional activity of the auditory cortex, apparently due to a compensatory enhancement of impulse activity coming from the intact receptors of the auditory apparatus. It has been assumed that the observed functional changes appearing in the cortical end of the signal analyser (auditory zone); in response to sound, following visual deprivation, are a consequence of an early nature training of synaptic structures with regard to perceptionof impulses of acoustic modality.     

The effects of neonatal saline injections on behaviours in DBA/2 male mice

DBA/2 male mice were exposed to the injections of the saline (0.01 ml/g i.p.) on 1-th, 3-th, 5-th, 7-th, 9-th days after birth. Intact males were used as a control group. Adult saline-treated males displayed the increased number of crossed squares, entries in the centre and time spent in the centre during the open "field" test in comparison with intact animals. The time spent in the light compartment of the light-dark box was decreased in saline treated mice compared with intact animals. During the test of acoustic startle response the magnitude of startle reflex and prepulse inhibition didn't change the startle reflex. Saline administration in males did not affect corticosterone basal level. Sexual motivation was revealed to decrease in saline treated males. These data suggest that neonatal administration of saline induced a stable behavioral syndrome in adult DBA/2 male mice: hyperactivity, a decrease of open space fear and simultaneously an increase of some indices of anxiety.     

Ultrasonic startle behavior in bushcrickets (Orthoptera; Tettigoniidae)

1. In the present work, we show that in flight, bushcrickets not previously known to respond to ultrasound alter their flight course in response to ultrasonic stimuli. Such stimuli elicit in flying Neoconocephalus ensiger an extension of the front and middle legs along the body and a rapid closure of all 4 wings (Fig. 1). This is a short latency acoustic startle response to ultrasound, consistent with acoustic startle responses of other insects. 2. The percentage of trials on which acoustic startle responses were elicited was maximum (90%) for sound frequencies ranging from 25 to at least 60 kHz. No acoustic startle response was observed at frequencies of 5 or 10 kHz (Fig. 2). The threshold for the response was roughly 76 dB between 25 to 60 kHz (Fig. 2) and the behavioral latency was 45 ms (Fig. 3). Recordings from flight muscles show that they cease discharging during the acoustic startle response (Fig. 4). 3. The characteristics of the acoustic startle response match those of an auditory interneuron called the T-neuron. The frequency sensitivity of this neuron is greatest for sound frequencies ranging from 13 to 60 kHz (Fig. 6). Moreover, we found that the neuron produces many more spikes to ultrasound (30 kHz) of increasing intensities than to a conspecific communication sound, whose dominant frequency is 14 kHz (Fig. 7).     

Endogenous cortisol suppression with metyrapone enhances acoustic startle in healthy subjects

Previous human studies have shown that excess cortisol sufficient to fully occupy central nervous system (CNS) corticosteroid receptors may reduce startle eye blink. The present study tested whether cortisol depletion and the resulting reduction in activity of CNS corticosteroid receptors has the opposite effect. In a single-blind, placebo-controlled, randomized study, eye blink EMG responses to 105 dB acoustic startle stimuli were assessed in 25 healthy subjects who received oral metyrapone (1500 mg) to suppress endogenous cortisol production, while 24 controls received oral placebo. As expected, metyrapone significantly reduced salivary cortisol, indicating effective endogenous cortisol suppression. Startle eye blink responses were significantly increased in the metyrapone group. Short-term habituation of the startle reflex was not different between groups. Our results suggest that startle is enhanced during depletion of cortisol. This effect may be mediated by CNS mechanisms controlling cortisol feedback.