Continuous Tone Research Articles

Investigation of the processing of ambiguous melodies in the brain by behavioral and neurophysiological experiments

Melody recognition is not a mere succession of pitch and time perception but must be an active process to a make a meaningful line of tones. To investigate this process, we devised a form of illusory melody resembling but different from the ones used in the studies of streaming. A4 and E5 tones are continuously presented while another tone M (middle tone, for example, C5 or C#5) between the two continuous tones is presented intermittently (0.25 s presentation and 0.25 s rest and repeating). One may hear either an illusory continuous melody of repeated ME5 or MA4 depending on the preceding unambiguous phrase of repetition of ME5 or MA4. Assuming that this illusion reflects the active process of melody formation, we investigated 1) the transition time from the primary state (either one of the melody forms) fixed by the leading phrase behaviorally, and 2) possible neural correlates by measuring the MEG (magnetoencephalography) responses to the continuous tones separately by amplitude modulating them with different frequencies. MEG signal was filtered for the two modulation frequencies and the ASSR (auditory steady state responses) were obtained for different experimental conditions. The results so far showed wide variance among subjects but seem promising.

Chord consonance represented in the long-lasting sustained activity in rat auditory cortex

Many sounds in the environment have a rich sound spectrum, which is related to the qualia of the sound such as consonance or dissonance of chords. However, the neural representation of chord consonance is not fully understood. Here, we targeted long-lasting, sustained activities in auditory cortex and investigated whether band-specific power or phase locking value (PLV) represent consonance of the chord consisting of two pure tones. A microelectrode array with 96 recording sites recorded local field potentials (LFPs) in the fourth layer of the auditory cortex of anesthetized rats in response to continuous pure tones and chords. From the LFPs, band-specific powers and PLVs were calculated in 5 bands (theta, 4—8 Hz; alpha, 8—14 Hz; beta, 14—30 Hz; low gamma, 30—40 Hz; high gamma, and 60—80 Hz). Then, differences of band-specific power and PLV (Δpower and ΔPLV) of a chord with respect to those of the higher-frequency composition tone of the chord were compared between consonance and dissonance. Consequently, Δpower was significantly smaller, and ΔPLV was significantly larger for consonance than dissonance, suggesting that the long-lasting, sustained activity in the auditory cortex is modulated according to the complex sound spectrum, such as consonance of the chords.

High-Frequency Binaural Beats Increase Cognitive Flexibility: Evidence from Dual-Task Crosstalk

Increasing evidence suggests that cognitive-control processes can be configured to optimize either persistence of information processing (by amplifying competition between decision-making alternatives and top-down biasing of this competition) or flexibility (by dampening competition and biasing). We investigated whether high-frequency binaural beats, an auditory illusion suspected to act as a cognitive enhancer, have an impact on cognitive-control configuration. We hypothesized that binaural beats in the gamma range bias the cognitive-control style toward flexibility, which in turn should increase the crosstalk between tasks in a dual-task paradigm. We replicated earlier findings that the reaction time in the first-performed task is sensitive to the compatibility between the responses in the first and the second task—an indication of crosstalk. As predicted, exposing participants to binaural beats in the gamma range increased this effect as compared to a control condition in which participants were exposed to a continuous tone of 340 Hz. These findings provide converging evidence that the cognitive-control style can be systematically biased by inducing particular internal states; that high-frequency binaural beats bias the control style toward more flexibility; and that different styles are implemented by changing the strength of local competition and top-down bias.

Mode mixing in shear horizontal ultrasonic guided waves

SH guided waves are used increasingly for non-destructive testing (NDT) applications, particularly for pipes and pipe supports using circumferentially guided wave modes. In practical implementations, it is not always straightforward to ensure single-mode operation and this requires consideration when interpreting results. During shear horizontal (SH) wave generation or SH guided wave interaction with geometrical changes or defects, multiple SH guided wave modes may be produced, depending on the shear wave speed, the frequency of operation, the thickness of the sample and the transducer characteristics. This paper discusses the interference patterns created as the multiple SH modes mix (for both continuous tone generation and short bursts), and the problems caused by the interference patterns on applications such as NDT. In particular, the patterns can lead to defects being missed during an NDT inspection using SH waves, and a way to circumvent this problem is suggested.

Printed Perforated Lampshades for Continuous Projective Images

We present a technique for designing three-dimensional- (3D) printed perforated lampshades that project continuous grayscale images onto the surrounding walls. Given the geometry of the lampshade and a target grayscale image, our method computes a distribution of tiny holes over the shell, such that the combined footprints of the light emanating through the holes form the target image on a nearby diffuse surface. Our objective is to approximate the continuous tones and the spatial detail of the target image to the extent possible within the constraints of the fabrication process. To ensure structural integrity, there are lower bounds on the thickness of the shell, the radii of the holes, and the minimal distances between adjacent holes. Thus, the holes are realized as thin tubes distributed over the lampshade surface. The amount of light passing through a single tube may be controlled by the tube’s radius and by its orientation (tilt angle). The core of our technique thus consists of determining a suitable configuration of the tubes: their distribution across the relevant portion of the lampshade, as well as the parameters (radius, tilt angle) of each tube. This is achieved by computing a capacity-constrained Voronoi tessellation over a suitably defined density function and embedding a tube inside the maximal inscribed circle of each tessellation cell.

Auditory perceptual restoration and illusory continuity correlates in the human brainstem

When noise obstructs portions of target sounds the auditory system fills in missing information, a phenomenon known as auditory restoration or induction. Previous work in animal models demonstrates that neurons in primary auditory cortex (A1) are capable of restoring occluded target signals suggesting that early auditory cortex is capable of inducing continuity in discontinuous signals (i.e., endogenous restoration). Current consensus is that the neural correlates of auditory induction and perceptual restoration emerge no earlier than A1. Moreover, the neural mechanisms supporting induction in humans are poorly understood. Here, we show that in human listeners, auditory brainstem nuclei support illusory auditory continuity well before engagement of cerebral cortex. We recorded brainstem responses to modulated target tones that did or did not promote illusory auditory percepts. Auditory continuity was manipulated by introducing masking noise or brief temporal interruptions in otherwise continuous tones. We found that auditory brainstem responses paralleled illusory continuity by tagging target sounds even when they were occluded by the auditory scene. Our results reveal (i) a pre-attentive, subcortical origin to a presumed cortical function and (ii) that brainstem signal processing helps partially cancel the negative effects of masking by restoring missing portions of auditory objects that are fragmented in the soundscape.

Odors Bias Time Perception in Visual and Auditory Modalities.

Previous studies have shown that emotional states alter our perception of time. However, attention, which is modulated by a number of factors, such as emotional events, also influences time perception. To exclude potential attentional effects associated with emotional events, various types of odors (inducing different levels of emotional arousal) were used to explore whether olfactory events modulated time perception differently in visual and auditory modalities. Participants were shown either a visual dot or heard a continuous tone for 1000 or 4000 ms while they were exposed to odors of jasmine, lavender, or garlic. Participants then reproduced the temporal durations of the preceding visual or auditory stimuli by pressing the spacebar twice. Their reproduced durations were compared to those in the control condition (without odor). The results showed that participants produced significantly longer time intervals in the lavender condition than in the jasmine or garlic conditions. The overall influence of odor on time perception was equivalent for both visual and auditory modalities. The analysis of the interaction effect showed that participants produced longer durations than the actual duration in the short interval condition, but they produced shorter durations in the long interval condition. The effect sizes were larger for the auditory modality than those for the visual modality. Moreover, by comparing performance across the initial and the final blocks of the experiment, we found odor adaptation effects were mainly manifested as longer reproductions for the short time interval later in the adaptation phase, and there was a larger effect size in the auditory modality. In summary, the present results indicate that odors imposed differential impacts on reproduced time durations, and they were constrained by different sensory modalities, valence of the emotional events, and target durations. Biases in time perception could be accounted for by a framework of attentional deployment between the inducers (odors) and emotionally neutral stimuli (visual dots and sound beeps).

Exploiting temporal predictability: Event-related potential correlates of task-supportive temporal cue processing in auditory distraction

The human cognitive system has various functions to enhance performance in tasks requiring responses to stimuli. When potentially occurring stimuli are known, we can establish selective attention sets and ignore task-irrelevant events while attending task-relevant ones. When the stimulation is temporally structured, we can rely on constant temporal relationships between stimulus events to prepare for the task-relevant moments. Most distraction paradigms feature task-irrelevant events which are followed by task-relevant ones within a constant interval, and distraction is induced by randomly replacing some of the standard task-irrelevant events. The constant time interval transforms irrelevant events to task-supportive temporal cues, which are integrated into the task-behavior by the participants. The present study investigated whether distracters could be utilized as temporal cues to support task-related processing in a continuous auditory stimulation paradigm. A continuous tone featuring short and long gaps, and pitch glides was presented. Participants performed a gap duration discrimination task, while ignoring glides. Glides could be presented frequently or rarely. In the informative condition, 80% of the glides predicted the presentation time of the forthcoming gap (400ms), while in the uninformative condition, the occurrence of gaps and glides was independent. Rare glides elicited an enhanced N1, mismatch negativity, and P3 event-related potentials in both informative and uninformative conditions. In informative conditions glides were followed by a contingent negative variation; and rare informative glides elicited an N2b, suggesting that despite triggering distraction-related processes, distracters could be integrated into the task-behavior, and could be utilized as task-supportive cues.

Deep neural network for halftone image classification based on sparse auto-encoder

To restore high quality continuous tone images from each class of halftone images, halftone image fine classification is the key problem. In this paper, a novel feature learning method is proposed for classifying 14 kinds of halftone images produced by the most well-known halftoning algorithms. This study employs the stacked sparse auto-encoders (SAE) trained with unsupervised learning for extracting features of halftone images, and then uses softmax regression with supervised learning for fine-tuning the deep neural network and classifying halftone images. In order to reduce the run-time of deep neural network and improve the image correct classification rate, we propose an effective patch extraction method for testing halftone images by measuring the mean and variance of local entropy in a patch. Halftone image classification is determined by the classification results of all effective patches inside an image via majority voting (MV). The experimental results demonstrate that our proposed method achieves an average correct classification rate (ACCR) of over 99.44% for 14 kinds of halftone images on two public image sets. Compared with state-of-the-art LMS–Bayes and M10–ML methods, the proposed SAE-MV method can distinguish the most categories of halftone images and achieve competitive ACCR, meanwhile, demonstrate better generalization performance.

Blind driving by means of auditory feedback

Driving is a safety-critical task that predominantly relies on vision. However, visual information from the environment is sometimes degraded or absent. In other cases, visual information is available, but the driver fails to use it due to distraction or impairment. Providing drivers with real-time auditory feedback about the state of the vehicle in relation to the environment may be an appropriate means of support when visual information is compromised. In this study, we explored whether driving can be performed solely by means of artificial auditory feedback. We focused on lane keeping, a task that is vital for safe driving. Three auditory parameter sets were tested: (1) predictor time, where the volume of a continuous tone was a linear function of the predicted lateral error from the lane centre 0 s, 1 s, 2 s, or 3 s into the future; (2) feedback mode (volume feedback vs. beep-frequency feedback) and mapping (linear vs. exponential relationship between predicted error and volume/beep frequency); and (3) corner support, in which in addition to volume feedback, a beep was offered upon entering/leaving a corner, or alternatively when crossing the lane centre while driving in a corner. A dead-zone was used, whereby the volume/beep-frequency feedback was provided only when the vehicle deviated more than 0.5 m from the centre of the lane. An experiment was conducted in which participants (N = 2) steered along a track with sharp 90-degree corners in a simulator with the visual projection shut down. Results showed that without predictor feedback (i.e., 0 s prediction), participants were more likely to depart the road compared to with predictor feedback. Moreover, volume feedback resulted in fewer road departures than beep-frequency feedback. The results of this study may be used in the design of in-vehicle auditory displays. Specifically, we recommend that feedback be based on anticipated error rather than current error.

Abstract 18257: A Novel Portable Polyvinylidene Fluoride Based Sensor for Detection of Hemorrhage

Introduction: Hemorrhage (Hem) is one of the leading causes of mortality from trauma, and continuous monitoring for Hem using techniques such as traditional BP, especially in field conditions, poses significant challenges. We have built a portable low-powered noninvasive sensor for continuous vascular tone monitoring to detect significant Hem as an alternative to BP monitoring. The sensor, made of polyvinylidene fluoride (PVDF) material, can sense and record changes in the mechanical properties of arteries due to peripheral vasoconstriction caused by Hem. Methods: Nine pigs underwent Hem by femoral artery bleeding. Systolic arterial pressure (SAP) was used to select 16 instances of significant hemorrhage (SAP>85mmHg pre-Hem and >10mmHg drop in SAP post-Hem). The PVDF signal was measured from the animal’s distal forelimb. A piecewise linear estimation of the PVDF signal was computed using a newly developed Taut String algorithm such that the error was <4% of the signal amplitude. The number of pieces in each period was used as a complexity score (CS) to detect Hem. Results: Arterial BP and the CS derived from the PVDF signal for one subject (Fig), as well as snapshots from the PVDF signal demonstrating morphology changes are shown. Maximum separation between pre- and post-Hem CS was achieved by a threshold of 5.5; 14 instances (87.5%) transitioned from CS≥6 to 5 within 5 minutes of the onset of HS (t0) while the remaining 2 instances transitioned from CS=5 to 3. The average detection delay was 1.95±1.2 min. These changes corresponded to >10mmHg decrease in SAP from baseline. CS improved during subsequent resuscitations. Conclusions: The proposed low-powered portable sensor captures continuous vascular tone and can be used to detect significant Hem in a continuous manner that may offer diagnostic and therapeutic guidance as an alternative to traditional intermittent BP measures. The results indicate that the derived CS can effectively separate the signals pre- and post-Hem.

Color density spectral array of bilateral bispectral index system: Electroencephalographic correlate in comatose patients with nonconvulsive status epilepticus

Purposeto describe the characteristics of the color density spectral array (CDSA) of bilateral bispectral index (b-BIS) monitoring system in patients with comatose nonconvulsive status epilepticus (NCSE). We hypothesized that CDSA could be helpful for monitoring NCSE in critically subjects if continuous EEG (cEEG) is not available. Methodswe retrospectively analyzed comatose patients admitted to our neurological intensive care unit (NICU) from 2011 to 2014 with a diagnosis of definitive NCSE that underwent b-BIS monitoring for at least 24h to guide anesthetic sedation. Clinical, electroencephalography and neuroimaging findings were analyzed. Moreover, all parameters from the b-BIS data including the CDSA were reviewed during periods of NCSE (NCSE pattern) and profound sedation (sedation pattern). Results15 NCSE patients were included. The delay from the diagnosis of NCSE to the onset of b-BIS monitoring was 8 (0.5–31)h and total time of b-BIS monitoring 7.8±6.5 days. CDSA during NCSE pattern was characterized by continuous or intermittent red and dark red tones, spectral edge frequency (SEF) in the delta-theta range, with or without asymmetry and BIS number trend with significant variability. In contrast, CDSA during sedation revealed predominance of orange, yellow, green and occasionally blue tones, SEF in the alpha-beta range, absence of asymmetry and stability of BIS number. Conclusionsb-BIS monitoring system and, in particular, CDSA used by nonexpert NICU personnel may be helpful to follow-up episodes of NCSE, to detect recurrences of nonconvulsive seizures (NCSzs), and to monitor profound anesthetic therapy in comatose patients when cEEG is not available.

Activity in the left auditory cortex is associated with individual impulsivity in time discounting.

Impulsivity dictates individual decision-making behavior. Therefore, it can reflect consumption behavior and risk of addiction and thus underlies social activities as well. Neuroscience has been applied to explain social activities; however, the brain function controlling impulsivity has remained unclear. It is known that impulsivity is related to individual time perception, i.e., a person who perceives a certain physical time as being longer is impulsive. Here we show that activity of the left auditory cortex is related to individual impulsivity. Individual impulsivity was evaluated by a self-answered questionnaire in twelve healthy right-handed adults, and activities of the auditory cortices of bilateral hemispheres when listening to continuous tones were recorded by magnetoencephalography. Sustained activity of the left auditory cortex was significantly correlated to impulsivity, that is, larger sustained activity indicated stronger impulsivity. The results suggest that the left auditory cortex represent time perception, probably because the area is involved in speech perception, and that it represents impulsivity indirectly.

Are auditory steady-state responses a good tool prior to pediatric cochlear implantation?

IntroductionASSR allow frequency-specific evaluation in intensities up to 120dB HL and detection of residual hearing in patients with severe-to-profound hearing loss. Aimto compare ASSR thresholds and behavioral test results in children with suspected severe-to-profound hearing loss. MethodsCross sectional study to compare ASSR and behavioral responses (VRA or audiometry) in 63 pediatric cochlear implant candidates (126 ears) aged between 6 and 72 months. We included children with normal otomicroscopy, absent responses to click-ABR and otoaccoustic emissions. We excluded children with inner ear malformations, auditory neuropathy spectrum disorder or who did not complete VRA or achieve EEG noise<30nV during the ASSR test. Air-conduction ASSR stimuli were continuous sinusoidal tones presented at 0.5, 1, 2 and 4kHz starting at 110dB HL. Behavioral thresholds were acquired with warble tones presented at 0.5, 1, 2 and 4kHz in each ear through insert or head phones at maximum presentation level of 120dB HL. ResultsBehavioral thresholds were obtained in 36.7% (185/504) of all frequencies in all subjects, 9% in intensities >110dB HL. Among 504 ASSR measurements, 53 thresholds were obtained (10.5%). Overall 89.5% of the tested frequencies did not show any response at 110dB HL. Most responses were at 500Hz. Mean differences between behavioral and ASSR thresholds varied from 0.09 to 8.94dB. Twenty-seven comparisons of behavioral and ASSR thresholds were obtained: 12 at 0.5kHz, 9 at 1kHz, 5 at 2kHz and 1 at 4kHz. Absent responses were observed in both tests in 38.1% at 0.5kHz, 52.4% at 1kHz, 74.6% at 2kHz and 81.0% at 4kHz. Specificity was>90% at 1, 2 and 4kHz. In ears with no behavioral response at 120dB HL all ASSR thresholds were in the profound hearing loss range, 90% of them were ≥110dB HL. ConclusionAmong 63 pediatric CI candidates, absent responses to high-intensity ASSR was the major finding (specificity>90%) predicting behavioral thresholds in the profound hearing loss range. These findings can be helpful to confirm the decision for cochlear implantation.

Filling the blanks in temporal intervals: the type of filling influences perceived duration and discrimination performance.

In this work we investigate how judgments of perceived duration are influenced by the properties of the signals that define the intervals. Participants compared two auditory intervals that could be any combination of the following four types: intervals filled with continuous tones (filled intervals), intervals filled with regularly-timed short tones (isochronous intervals), intervals filled with irregularly-timed short tones (anisochronous intervals), and intervals demarcated by two short tones (empty intervals). Results indicate that the type of intervals to be compared affects discrimination performance and induces distortions in perceived duration. In particular, we find that duration judgments are most precise when comparing two isochronous and two continuous intervals, while the comparison of two anisochronous intervals leads to the worst performance. Moreover, we determined that the magnitude of the distortions in perceived duration (an effect akin to the filled duration illusion) is higher for tone sequences (no matter whether isochronous or anisochronous) than for continuous tones. Further analysis of how duration distortions depend on the type of filling suggests that distortions are not only due to the perceived duration of the two individual intervals, but they may also be due to the comparison of two different filling types.

LumeJet &amp;#x2013; Inkless Ultra High Quality Photobook Production

The result of 10 years research, LumeJet is commercializing a new photonic 'inkless' printer, the S200, for ultra high quality photobook production. Similar to Ink Jet &#x2013; but without the inks &#x2013; LumeJet comprises custom designed print heads (moving or static) with multi-LED arrays and special fiber taper optics. Using light, rather than ink, increases throughput and image quality, whilst reducing media costs for image intensive documents. LumeJet is a continuous tone process that can resolve down to 2pt colored text and graphics, which would require at least 10-colours and over 4000dpi with inkjet and toner systems. Applications for LumeJet technology have also been identified in label and package printing and printed electronics.

Auditory and motor contributions to the timing of melodies under cognitive load.

Current theoretical models and empirical research suggest that sensorimotor control and feedback processes may guide time perception and production. In the current study, we investigated the role of motor control and auditory feedback in an interval-production task performed under heightened cognitive load. We hypothesized that general associative learning mechanisms enable the calibration of time against patterns of dynamic change in motor control processes and auditory feedback information. In Experiment 1, we applied a dual-task interference paradigm consisting of a finger-tapping (continuation) task in combination with a working memory task. Participants (nonmusicians) had to either perform or avoid arm movements between successive key presses (continuous vs. discrete). Auditory feedback from a key press (a piano tone) filled either the complete duration of the target interval or only a small part (long vs. short). Results suggested that both continuous movement control and long piano feedback tones contributed to regular timing production. In Experiment 2, we gradually adjusted the duration of the long auditory feedback tones throughout the duration of a trial. The results showed that a gradual shortening of tones throughout time increased the rate at which participants performed tone onsets. Overall, our findings suggest that the human perceptual-motor system may be important in guiding temporal behavior under cognitive load.

Cortical activity associated with the detection of temporal gaps in tones: a magnetoencephalography study.

We used magnetoencephalogram (MEG) in two experiments to investigate spatio-temporal profiles of brain responses to gaps in tones. Stimuli consisted of leading and trailing markers with gaps between the two markers of 0, 30, or 80 ms. Leading and trailing markers were 300 ms pure tones at 800 or 3200 Hz.Two conditions were examined: the within-frequency (WF) condition in which the leading and trailing markers had identical frequencies, and the between-frequency (BF) condition in which they had different frequencies. Using minimum norm estimates (MNE), we localized the source activations at the time of the peak response to the trailing markers. Results showed that MEG signals in response to 800 and 3200 Hz tones were localized in different regions within the auditory cortex, indicating that the frequency pathways activated by the two markers were spatially represented.The time course of regional activity (RA) was extracted from each localized region for each condition. In Experiment 1, which used a continuous tone for the WF 0-ms stimulus, the N1m amplitude for the trailing marker in the WF condition differed depending on gap duration but not tonal frequency. In contrast, N1m amplitude in BF conditions differed depending on the frequency of the trailing marker. In Experiment 2, in which the 0-ms gap stimulus in the WF condition was made from two markers and included an amplitude reduction in the middle, the amplitude in WF and BF conditions changed depending on frequency, but not gap duration.The difference in temporal characteristics betweenWF and BF conditions could be observed in the RA.

Inducible brown adipocytes in subcutaneous inguinal white fat: the role of continuous sympathetic stimulation.

Brown adipocytes (BA) generate heat in response to sympathetic activation and are the main site of nonshivering thermogenesis in mammals. Although most BA are located in classic brown adipose tissue depots, BA are also abundant in the inguinal white adipose tissue (iWAT) before weaning. The number of BA is correlated with the density of sympathetic innervation in iWAT; however, the role of continuous sympathetic tone in the establishment and maintenance of BA in WAT has not been investigated. BA marker expression in iWAT was abundant in weaning mice but was greatly reduced by 8 wk of age. Nonetheless, BA phenotype could be rapidly reinstated by acute β₃-adrenergic stimulation with CL-316,243 (CL). Genetic tagging of adipocytes with adiponectin-CreER(T2) demonstrated that CL reinstates uncoupling protein 1 (UCP1) expression in adipocytes that were present before weaning. Chronic surgical denervation dramatically reduced the ability of CL to induce the expression of UCP1 and other BA markers in the tissue as a whole, and this loss of responsiveness was prevented by concurrent treatment with CL. These results indicate that ongoing sympathetic activity is critical to preserve the ability of iWAT fat cells to express a BA phenotype upon adrenergic stimulation.

Frequency of greatest temporary hearing threshold shift in harbor porpoises (Phocoena phocoena) depends on the noise level.

Harbor porpoises may suffer hearing loss when they are exposed to high level sounds. After exposure for 60 min to a 6.5 kHz continuous tone at average received sound pressure levels (SPLav.re.) ranging from 118 to 154 dB re 1μPa, the temporary hearing threshold shifts (TTSs) of a harbor porpoise were quantified at the center frequency (6.5 kHz), at 0.5, 1.0, and 1.3 octaves above the center frequency (9.2, 13.0, and 16.0 kHz), and at a frequency assumed to be ecologically important for harbor porpoises (125 kHz, the center frequency of their echolocation signals) by means of a psychoacoustic technique. The hearing frequency at which the maximum TTS occurred depended on the SPLav.re. The higher the SPLav.re., the higher the TTS induced at frequencies higher than the exposure frequency; below 148 dB re 1 μPa, the maximum TTS was at 6.5 kHz, whereas above 148 dB re 1 μPa, the maximum TTS was at 9.2 kHz. The hearing threshold of the harbor porpoise for the center frequency of its echolocation signals (125 kHz) was not affected at the highest SPLav.re. to which the animal was exposed.