Integration Window Research Articles

The influence of performance on action-effect integration in sense of agency.

Sense of agency refers to the subjective feeling of being able to control an outcome through one's own actions or will. Prior studies have shown that both sensory processing (e.g., comparisons between sensory feedbacks and predictions basing on one's motor intentions) and high-level cognitive/constructive processes (e.g., inferences based on one's performance or the consequences of one's actions) contribute to judgments of sense of agency. However, it remains unclear how these two types of processes interact, which is important for clarifying the mechanisms underlying sense of agency. Thus, we examined whether performance-based inferences influence action-effect integration in sense of agency using a delay detection paradigm in two experiments. In both experiments, participants pressed left and right arrow keys to control the direction in which a moving dot was travelling. The dot's response delay was manipulated randomly on 7 levels (0-480ms) between the trials; for each trial, participants were asked to judge whether the dot response was delayed and to rate their level of agency over the dot. In Experiment 1, participants tried to direct the dot to reach a destination on the screen as quickly as possible. Furthermore, the computer assisted participants by ignoring erroneous commands for half of the trials (assisted condition), while in the other half, all of the participants' commands were executed (self-control condition). In Experiment 2, participants directed the dot as they pleased (without a specific goal), but, in half of the trials, the computer randomly ignored 32% of their commands (disturbed condition) rather than assisted them. The results from the two experiments showed that performance enhanced action-effect integration. Specifically, when task performance was improved through the computer's assistance in Experiment 1, delay detection was reduced in the 480-ms delay condition, despite the fact that 32% of participants' commands were ignored. Conversely, when no feedback on task performance was given (as in Experiment 2), the participants reported greater delay when some of their commands were randomly ignored. Furthermore, the results of a logistic regression analysis showed that the threshold of delay detection was greater in the assisted condition than in the self-control condition in Experiment 1, which suggests a wider time window for action-effect integration. A multivariate analysis also revealed that assistance was related to reduced delay detection via task performance, while reduced delay detection was directly correlated with a better sense of agency. These results indicate an association between the implicit and explicit aspects of sense of agency.

Integrating speech in time depends on temporal expectancies and attention

Sensory information that unfolds in time, such as in speech perception, relies on efficient chunking mechanisms in order to yield optimally-sized units for further processing. Whether or not two successive acoustic events receive a one-unit or a two-unit interpretation seems to depend on the fit between their temporal extent and a stipulated temporal window of integration. However, there is ongoing debate on how flexible this temporal window of integration should be, especially for the processing of speech sounds. Furthermore, there is no direct evidence of whether attention may modulate the temporal constraints on the integration window. For this reason, we here examine how different word durations, which lead to different temporal separations of sound onsets, interact with attention. In an Electroencephalography (EEG) study, participants actively and passively listened to words where word-final consonants were occasionally omitted. Words had either a natural duration or were artificially prolonged in order to increase the separation of speech sound onsets. Omission responses to incomplete speech input, originating in left temporal cortex, decreased when the critical speech sound was separated from previous sounds by more than 250 msec, i.e., when the separation was larger than the stipulated temporal window of integration (125–150 msec). Attention, on the other hand, only increased omission responses for stimuli with natural durations. We complemented the event-related potential (ERP) analyses by a frequency-domain analysis on the stimulus presentation rate. Notably, the power of stimulation frequency showed the same duration and attention effects than the omission responses. We interpret these findings on the background of existing research on temporal integration windows and further suggest that our findings may be accounted for within the framework of predictive coding.

A multi-second adaptive integration process underlies sound texture perception

Temporally homogenous sound textures—as produced by rain, fire or insect swarms—are thought to be represented with time-average statistics measured from early auditory representations. We explored the averaging process involved in sound texture perception using “texture steps”—stimuli whose statistics changed at some point in time. We reasoned that judgments should be biased by the stimulus history included in the averaging process. Listeners were presented with two sounds, a texture step and a probe texture (with constant statistics). Listeners were asked to compare the endpoint of the texture step to the probe and to select the sound that was most similar to a familiar reference texture. Judgments were biased by the presence of a step 1 second prior to the stimulus endpoint, but the bias was reduced when the step occurred 2.5 seconds from the endpoint. In addition, the bias was substantially larger for textures whose statistics were less homogenous (ocean waves) than textures whose statistics were more homogenous (rain). The results suggest a texture integration process operating over several seconds, but whose integration window is adapted to the homogeneity of the sound signal, averaging over longer periods of time for more variable textures.

Temporal synchrony and audiovisual integration of speech and object stimuli in autism

BackgroundIndividuals with Autism Spectrum Disorders (ASD) have been shown to have multisensory integration deficits, which may lead to problems perceiving complex, multisensory environments. For example, understanding audiovisual speech requires integration of visual information from the lips and face with auditory information from the voice, and audiovisual speech integration deficits can lead to impaired understanding and comprehension. While there is strong evidence for an audiovisual speech integration impairment in ASD, it is unclear whether this impairment is due to low level perceptual processes that affect all types of audiovisual integration or if it is specific to speech processing. MethodHere, we measure audiovisual integration of basic speech (i.e., consonant-vowel utterances) and object stimuli (i.e., a bouncing ball) in adolescents with ASD and well-matched controls. We calculate a temporal window of integration (TWI) using each individual’s ability to identify which of two videos (one temporally aligned and one misaligned) matches auditory stimuli. The TWI measures tolerance for temporal asynchrony between the auditory and visual streams, and is an important feature of audiovisual perception. ResultsWhile controls showed similar tolerance of asynchrony for the simple speech and object stimuli, individuals with ASD did not. Specifically, individuals with ASD showed less tolerance of asynchrony for speech stimuli compared to object stimuli. In individuals with ASD, decreased tolerance for asynchrony in speech stimuli was associated with higher ratings of autism symptom severity. ConclusionsThese results suggest that audiovisual perception in ASD may vary for speech and object stimuli beyond what can be accounted for by stimulus complexity.

Effects of Aging in Multisensory Integration: A Systematic Review.

Multisensory integration (MSI) is the integration by the brain of environmental information acquired through more than one sense. Accurate MSI has been shown to be a key component of successful aging and to be crucial for processes underlying activities of daily living (ADLs). Problems in MSI could prevent older adults (OA) to age in place and live independently. However, there is a need to know how to assess changes in MSI in individuals. This systematic review provides an overview of tests assessing the effect of age on MSI in the healthy elderly population (aged 60 years and older). A literature search was done in Scopus. Articles from the earliest records available to January 20, 2016, were eligible for inclusion if assessing effects of aging on MSI in the healthy elderly population compared to younger adults (YA). These articles were rated for risk of bias with the Newcastle-Ottawa quality assessment. Out of 307 identified research articles, 49 articles were included for final review, describing 69 tests. The review indicated that OA maximize the use of multiple sources of information in comparison to YA (20 studies). In tasks that require more cognitive function, or when participants need to adapt rapidly to a situation, or when a dual task is added to the experiment, OA have problems selecting and integrating information properly as compared to YA (19 studies). Additionally, irrelevant or wrong information (i.e., distractors) has a greater impact on OA than on YA (21 studies). OA failing to weigh sensory information properly, has not been described in previous reviews. Anatomical changes (i.e., reduction of brain volume and differences of brain areas’ recruitment) and information processing changes (i.e., general cognitive slowing, inverse effectiveness, larger time window of integration, deficits in attentional control and increased noise at baseline) can only partly explain the differences between OA and YA regarding MSI. Since we have an interest in successful aging and early detection of MSI issues in the elderly population, the identified tests form a good starting point to develop a clinically useful toolkit to assess MSI in healthy OA.

Beyond the Peak - Tactile Temporal Discrimination Does Not Correlate with Individual Peak Frequencies in Somatosensory Cortex.

The human sensory systems constantly receive input from different stimuli. Whether these stimuli are integrated into a coherent percept or segregated and perceived as separate events, is critically determined by the temporal distance of the stimuli. This temporal distance has prompted the concept of temporal integration windows or perceptual cycles. Although this concept has gained considerable support, the neuronal correlates are still discussed. Studies suggested that neuronal oscillations might provide a neuronal basis for such perceptual cycles, i.e., the cycle lengths of alpha oscillations in visual cortex and beta oscillations in somatosensory cortex might determine the length of perceptual cycles. Specifically, recent studies reported that the peak frequency (the frequency with the highest spectral power) of alpha oscillations in visual cortex correlates with subjects’ ability to discriminate two visual stimuli. In the present study, we investigated whether peak frequencies in somatosensory cortex might serve as the correlate of perceptual cycles in tactile discrimination. Despite several different approaches, we were unable to find a significant correlation between individual peak frequencies in the alpha- and beta-band and individual discrimination abilities. In addition, analysis of Bayes factor provided evidence that peak frequencies and discrimination thresholds are unrelated. The results suggest that perceptual cycles in the somatosensory domain are not necessarily to be found in the peak frequency, but in other frequencies. We argue that studies based solely on analysis of peak frequencies might thus miss relevant information.

POm Thalamocortical Input Drives Layer-Specific Microcircuits in Somatosensory Cortex.

Higher-order thalamic nuclei, such as the posterior medial nucleus (POm) in the somatosensory system or the pulvinar in the visual system, densely innervate the cortex and can influence perception and plasticity. To systematically evaluate how higher-order thalamic nuclei can drive cortical circuits, we investigated cell-type selective responses to POm stimulation in mouse primary somatosensory (barrel) cortex, using genetically targeted whole-cell recordings in acute brain slices. We find that ChR2-evoked thalamic input selectively targets specific cell types in the neocortex, revealing layer-specific modules for the summation and processing of POm input. Evoked activity in pyramidal neurons from deep layers is fast and synchronized by rapid feedforward inhibition from GABAergic parvalbumin-expressing neurons, and activity in superficial layers is weaker and prolonged, facilitated by slow inhibition from GABAergic neurons expressing the 5HT3a receptor. Somatostatin-expressing GABAergic neurons do not receive direct input in either layer and their spontaneous activity is suppressed during POm stimulation. This novel pattern of weak, delayed, thalamus-evoked inhibition in layer 2 suggests a longer integration window for incoming sensory information and may facilitate stimulus detection and plasticity in superficial pyramidal neurons.

Walking to a multisensory beat

Living in a complex and multisensory environment demands constant interaction between perception and action. In everyday life it is common to combine efficiently simultaneous signals coming from different modalities. There is evidence of a multisensory benefit in a variety of laboratory tasks (temporal judgement, reaction time tasks). It is less clear if this effect extends to ecological tasks, such as walking. Furthermore, benefits of multimodal stimulation are linked to temporal properties such as the temporal window of integration and temporal recalibration. These properties have been examined in tasks involving single, non-repeating stimulus presentations. Here we investigate the same temporal properties in the context of a rhythmic task, namely audio-tactile stimulation during walking. The effect of audio-tactile rhythmic cues on gait variability and the ability to synchronize to the cues was studied in young adults. Participants walked with rhythmic cues presented at different stimulus-onset asynchronies. We observed a multisensory benefit by comparing audio-tactile to unimodal stimulation. Moreover, both the temporal window of integration and temporal recalibration mediated the response to multimodal stimulation. In sum, rhythmic behaviours obey the same principles as temporal discrimination and detection behaviours and thus can also benefit from multimodal stimulation.

Dendritic GIRK Channels Gate the Integration Window, Plateau Potentials, and Induction of Synaptic Plasticity in Dorsal But Not Ventral CA1 Neurons.

Studies comparing neuronal activity at the dorsal and ventral poles of the hippocampus have shown that the scale of spatial information increases and the precision with which space is represented declines from the dorsal to ventral end. These dorsoventral differences in neuronal output and spatial representation could arise due to differences in computations performed by dorsal and ventral CA1 neurons. In this study, we tested this hypothesis by quantifying the differences in dendritic integration and synaptic plasticity between dorsal and ventral CA1 pyramidal neurons of rat hippocampus. Using a combination of somatic and dendritic patch-clamp recordings, we show that the threshold for LTP induction is higher in dorsal CA1 neurons and that a G-protein-coupled inward-rectifying potassium channel mediated regulation of dendritic plateau potentials and dendritic excitability underlies this gating. By contrast, similar regulation of LTP is absent in ventral CA1 neurons. Additionally, we show that generation of plateau potentials and LTP induction in dorsal CA1 neurons depends on the coincident activation of Schaffer collateral and temporoammonic inputs at the distal apical dendrites. The ventral CA1 dendrites, however, can generate plateau potentials in response to temporally dispersed excitatory inputs. Overall, our results highlight the dorsoventral differences in dendritic computation that could account for the dorsoventral differences in spatial representation.SIGNIFICANCE STATEMENT The dorsal and ventral parts of the hippocampus encode spatial information at very different scales. Whereas the place-specific firing fields are small and precise at the dorsal end of the hippocampus, neurons at the ventral end have comparatively larger place fields. Here, we show that the dorsal CA1 neurons have a higher threshold for LTP induction and require coincident timing of excitatory synaptic inputs for the generation of dendritic plateau potentials. By contrast, ventral CA1 neurons can integrate temporally dispersed inputs and have a lower threshold for LTP. Together, these dorsoventral differences in the threshold for LTP induction could account for the differences in scale of spatial representation at the dorsal and ventral ends of the hippocampus.

Enlarged temporal integration window in schizophrenia indicated by the double-flash illusion

ABSTRACTIntroduction: In the present study we were interested in the processing of audio-visual integration in schizophrenia compared to healthy controls. The amount of sound-induced double-flash illusions served as an indicator of audio-visual integration. We expected an altered integration as well as a different window of temporal integration for patients.Methods: Fifteen schizophrenia patients and 15 healthy volunteers matched for age and gender were included in this study. We used stimuli with eight different temporal delays (stimulus onset asynchronys (SOAs) 25, 50, 75, 100, 125, 150, 200 and 300 ms) to induce a double-flash illusion. Group differences and the widths of temporal integration windows were calculated on percentages of reported double-flash illusions.Results: Patients showed significantly more illusions (ca. 36–44% vs. 9–16% in control subjects) for SOAs 150–300. The temporal integration window for control participants went from SOAs 25 to 200 whereas for patients integration was found across all included temporal delays. We found no significant relationship between the amount of illusions and either illness severity, chlorpromazine equivalent doses or duration of illness in patients.Conclusions: Our results are interpreted in favour of an enlarged temporal integration window for audio-visual stimuli in schizophrenia patients, which is consistent with previous research.

ENDOR with band-selective shaped inversion pulses

Electron Nuclear DOuble Resonance (ENDOR) is based on the measurement of nuclear transition frequencies through detection of changes in the polarization of electron transitions. In Davies ENDOR, the initial polarization is generated by a selective microwave inversion pulse. The rectangular inversion pulses typically used are characterized by a relatively low selectivity, with full inversion achieved only for a limited number of spin packets with small resonance offsets. With the introduction of pulse shaping to EPR, the rectangular inversion pulses can be replaced with shaped pulses with increased selectivity. Band-selective inversion pulses are characterized by almost rectangular inversion profiles, leading to full inversion for spin packets with resonance offsets within the pulse excitation bandwidth and leaving spin packets outside the excitation bandwidth largely unaffected. Here, we explore the consequences of using different band-selective amplitude-modulated pulses designed for NMR as the inversion pulse in ENDOR. We find an increased sensitivity for small hyperfine couplings compared to rectangular pulses of the same bandwidth. In echo-detected Davies-type ENDOR, finite Fourier series inversion pulses combine the advantages of increased absolute ENDOR sensitivity of short rectangular inversion pulses and increased sensitivity for small hyperfine couplings of long rectangular inversion pulses. The use of pulses with an almost rectangular frequency-domain profile also allows for increased control of the hyperfine contrast selectivity. At X-band, acquisition of echo transients as a function of radiofrequency and appropriate selection of integration windows during data processing allows efficient separation of contributions from weakly and strongly coupled nuclei in overlapping ENDOR spectra within a single experiment.

Tolerance for audiovisual asynchrony is enhanced by the spectrotemporal fidelity of the speaker’s mouth movements and speech

ABSTRACTWe examined the relationship between tolerance for audiovisual onset asynchrony (AVOA) and the spectrotemporal fidelity of the spoken words and the speaker’s mouth movements. In two experiments that only varied in the temporal order of sensory modality, visual speech leading (exp. 1) or lagging (exp. 2) acoustic speech, participants watched intact and blurred videos of a speaker uttering trisyllabic words and nonwords that were noise vocoded with 4-, 8-, 16- and 32-channels. They judged whether the speaker’s mouth movements and the speech sounds were in-sync or out-of-sync. Individuals perceived synchrony (tolerated AVOA) on more trials when the acoustic speech was more speech-like (8-channels and higher vs. 4-channels), and when visual speech was intact than blurred (exp. 1 only). These findings suggest that enhanced spectrotemporal fidelity of the audiovisual (AV) signal prompts the brain to widen the window of integration promoting the fusion of temporally distant AV percepts.

Dyslexics' faster decay of implicit memory for sounds and words is manifested in their shorter neural adaptation.

Dyslexia is a prevalent reading disability whose underlying mechanisms are still disputed. We studied the neural mechanisms underlying dyslexia using a simple frequency-discrimination task. Though participants were asked to compare the two tones in each trial, implicit memory of previous trials affected their responses. We hypothesized that implicit memory decays faster among dyslexics. We tested this by increasing the temporal intervals between consecutive trials, and by measuring the behavioral impact and ERP responses from the auditory cortex. Dyslexics showed a faster decay of implicit memory effects on both measures, with similar time constants. Finally, faster decay of implicit memory also characterized the impact of sound regularities in benefitting dyslexics' oral reading rate. Their benefit decreased faster as a function of the time interval from the previous reading of the same non-word. We propose that dyslexics' shorter neural adaptation paradoxically accounts for their longer reading times, since it reduces their temporal window of integration of past stimuli, resulting in noisier and less reliable predictions for both simple and complex stimuli. Less reliable predictions limit their acquisition of reading expertise.

Oxygen and carbon metabolism of Zostera muelleri across a depth gradient – Implications for resilience and blue carbon

There is growing interest in the role that seagrasses play as ‘blue carbon’ stores or sinks, and their potential to offset rising CO2 levels in the atmosphere. This study measured primary aspects of the carbon balance (biomass, community metabolism, dissolved organic carbon [DOC] fluxes, seston trapping) across the depth gradient in a Zostera muelleri meadow during the seasonal biomass minimum and maximum. Over the annual estimation, the meadow was neither a sink nor source of carbon, with inputs of seston (∼58% of total inputs) balanced by exports of wrack and DOC. The carbon sink represented by wrack export depends on the nature of the environment where the wrack accumulates; if it reaches subtidal sediments it will largely be remineralised over the annual cycle, whereas between 14 and 26% of the wrack may be preserved if the material is exported to terrestrial environments. The fate of DOC exuded by seagrasses is unknown due to a lack of knowledge about its composition and lability; however, a number of lines of evidence suggest that a large fraction of DOC is mineralised. The net community metabolism (NCM) of the meadow was balanced, indicating that photosynthetic O2 production balanced community respiration and/or the reoxidation of reduced compounds (sulphur and iron) in the rhizosphere. We suggest that a balanced NCM may be the preferred state for Zostera spp. and may limit their occurrence in environments where plants cannot balance the respiratory demand exerted by seston inputs. There was a close coupling between metabolism and biomass, which in turn is forced by antecedent light over the preceding 120 days (the time integration window for antecedent light that best predicted biomass). Increased metabolism with depth and seasonal variation in light is accompanied by a decrease in the above ground:below ground biomass ratio (AGB:BGB). This trend is suggested to be a morphological adaptation that balances the competing requirements of maintaining a neutral plant carbon balance across enrichment and light gradients. Our results suggest that Zostera muelleri may be most important as a ‘blue carbon’ store (i.e. carbon stored as biomass standing stock), which is therefore vulnerable to degradation if seagrasses are lost.

A General Audiovisual Temporal Processing Deficit in Adult Readers With Dyslexia.

Because reading is an audiovisual process, reading impairment may reflect an audiovisual processing deficit. The aim of the present study was to test the existence and scope of such a deficit in adult readers with dyslexia. We tested 39 typical readers and 51 adult readers with dyslexia on their sensitivity to the simultaneity of audiovisual speech and nonspeech stimuli, their time window of audiovisual integration for speech (using incongruent /aCa/ syllables), and their audiovisual perception of phonetic categories. Adult readers with dyslexia showed less sensitivity to audiovisual simultaneity than typical readers for both speech and nonspeech events. We found no differences between readers with dyslexia and typical readers in the temporal window of integration for audiovisual speech or in the audiovisual perception of phonetic categories. The results suggest an audiovisual temporal deficit in dyslexia that is not specific to speech-related events. But the differences found for audiovisual temporal sensitivity did not translate into a deficit in audiovisual speech perception. Hence, there seems to be a hiatus between simultaneity judgment and perception, suggesting a multisensory system that uses different mechanisms across tasks. Alternatively, it is possible that the audiovisual deficit in dyslexia is only observable when explicit judgments about audiovisual simultaneity are required.

The three-second "subjective present": A critical review and a new proposal.

It has been argued that there is a "subjective present" or "experienced moment" of about 3 seconds in duration, involving automatic binding of events into perceptual units on that time scale. Research on topics that have been taken as relevant to this proposal is reviewed. The topics include accuracy in reproduction of stimulus durations, synchronization of behavior with a regular beat, mental rhythmization of a regular beat, time units in behavior, segmentation of observed behavior into meaningful units, time scale of reversals of perception with bistable ambiguous figures, time scale of inhibition of return in visual search, and EEG responses to deviant stimuli in series of repeating stimuli. Most of the research findings were not consistent with the 3 s window hypothesis. The small amount of supportive evidence is better interpreted as effects of specific processing mechanisms, not as showing general temporal integration. The evidence shows that temporal integration occurs on multiple time scales and no particular duration is special, and that windows of temporal integration are defined in terms of information density, not in terms of duration. The subjective present is constructed through local temporal integration on multiple time scales, further integrated into a coherent global representation of what is going on. (PsycINFO Database Record

Oscillatory integration windows in neurons.

Oscillatory synchrony among neurons occurs in many species and brain areas, and has been proposed to help neural circuits process information. One hypothesis states that oscillatory input creates cyclic integration windows: specific times in each oscillatory cycle when postsynaptic neurons become especially responsive to inputs. With paired local field potential (LFP) and intracellular recordings and controlled stimulus manipulations we directly test this idea in the locust olfactory system. We find that inputs arriving in Kenyon cells (KCs) sum most effectively in a preferred window of the oscillation cycle. With a computational model, we show that the non-uniform structure of noise in the membrane potential helps mediate this process. Further experiments performed in vivo demonstrate that integration windows can form in the absence of inhibition and at a broad range of oscillation frequencies. Our results reveal how a fundamental coincidence-detection mechanism in a neural circuit functions to decode temporally organized spiking.

Visual-tactile integration in speech perception: Evidence for modality neutral speech primitives.

Audio-visual [McGurk and MacDonald (1976). Nature 264, 746-748] and audio-tactile [Gick and Derrick (2009). Nature 462(7272), 502-504] speech stimuli enhance speech perception over audio stimuli alone. In addition, multimodal speech stimuli form an asymmetric window of integration that is consistent with the relative speeds of the various signals [Munhall, Gribble, Sacco, and Ward (1996). Percept. Psychophys. 58(3), 351-362; Gick, Ikegami, and Derrick (2010). J. Acoust. Soc. Am. 128(5), EL342-EL346]. In this experiment, participants were presented video of faces producing /pa/ and /ba/ syllables, both alone and with air puffs occurring synchronously and at different timings up to 300 ms before and after the stop release. Perceivers were asked to identify the syllable they perceived, and were more likely to respond that they perceived /pa/ when air puffs were present, with asymmetrical preference for puffs following the video signal-consistent with the relative speeds of visual and air puff signals. The results demonstrate that visual-tactile integration of speech perception occurs much as it does with audio-visual and audio-tactile stimuli. This finding contributes to the understanding of multimodal speech perception, lending support to the idea that speech is not perceived as an audio signal that is supplemented by information from other modes, but rather that primitives of speech perception are, in principle, modality neutral.

The time-limited visual statistician.

The visual system can calculate summary statistics over time. For example, the multiple frames of a movie showing a dynamically changing disk can be collapsed to form a single representation of that disk's mean size. Summary representations of dynamic information may engage online updating processes that establish a running average of the mean by continuously adjusting the persisting representation of the average in tandem with the arrival of incoming information. Alternatively, summary representations may involve subsampling strategies that reflect limitations in the degree to which the visual system can integrate information over time. Observers watched movies of a disk that changed size smoothly at different rates and then reported the disk's average size by adjusting the diameter of a response disk. Critically, the movie varied in duration. Size estimates depended on the duration of the movie. They were constant and fairly accurate for movie durations up to approximately 600 ms, at which point accuracy decreased with increasing duration to imprecise levels by about 1,000 ms. Summary statistics established over time are unlikely to be updated continuously and may instead be restricted by subsampling processes, such as limited temporal windows of integration. (PsycINFO Database Record

Biosonar detection range of mesopelagic patches by spinner dolphins in Hawaii

Spinner dolphins (Stenella longirostris) in the near-shore waters of the Hawaiian islands forage on the mesopelagic boundary community (mbc) of organisms consisting of myctophids, mid-water shrimp, and small squids. They forage at night in a coordinated fashion swimming parallel to shore hunting for patches of prey that they can encircle and herd into a tight three-dimensional patch. A profiler housing a broadband echo-ranger that projected dolphin-like biosonar signals was used to measure the target strength of the mbc. Echoes consisted of a number of highlights bunched together with target strength between -45 and -55 dB based on a dolphin’s integration window of 264 ms. Noise values collected by an autonomous acoustic recorder at midnight in the location where the profiler data were obtained were used to estimate the biosonar detection range of spinner dolphins for mesopelagic patches. The receiving directivity index and the width of the auditory filter for Tursiops trun catus were used to estimate the biosonar detection ranges of Stenella longirostris searching for mbc patches. Using the sonar equation, the biosonar threshold detection range of spinner dolphins was estimated to be approximately 100 plus m, more than sufficient range for the animals to formulate their prey herding behavior.