Temporal Response Patterns Research Articles

Enacted Clock-Time: How Temporal Agency Structures Strategic Activity

Agents strategizing in a specific context engage in an ongoing process of temporal structuring that regulates, and reflects, their strategic activity (Orlikowski & Yates, 2002). My study attempts to unpack the temporal structuring process to understand the interplay between temporal agency and strategic activity. Using a phenomenological approach (Interpretative Phenomenological Analysis, as per Smith & Osborn, 2008), I investigated the research-oriented strategic activities of a set of doctoral students in different stages of their respective programs at an elite management institute. Consistent with the structuration perspective, I observed dynamism in the temporalities underlying individuals’ strategic activities, characterized by shifting temporal structuring patterns in response to their evolving contexts. Importantly, I found that temporal agents attempt to control their strategic context through enacting temporal discipline. Abstracting from my findings, I propose a process model of temporal enactment that substantiates the role of temporal agency in effecting strategic outcomes. By elaborating the process of temporal structuring, this study contributes at the intersection of temporality and strategy-as-practice literatures.

Recovery: Fast and Slow—Vegetation Response During the 2012–2016 California Drought

AbstractThe 2012–2016 California Drought severely impacted natural vegetation across a wide range of environmental gradient. Although several studies have reported an increase in plant water stress and mortality, the spatiotemporal variations of ecosystem productivity responses and the associated environmental and biological drivers remain unclear. Here, using Enhanced Vegetation Index from the Moderate resolution imaging spectrometer, we found that 45% of the natural ecosystems showed an abrupt change (breakpoint [BP]) in productivity during 2012–2016. There were three major contrasting temporal patterns of productivity responses: (i) a steady increase under higher temperature followed by a decline due to accumulated moisture depletion (high elevation forest) or temperature decrease (high elevation nonforest), (ii) gradual decline during the drought followed by a rapid recovery within 1 year after drought stress was partially relieved, and (iii) both a gradual decline and an abrupt decline. The magnitude of abrupt changes was negatively correlated (r = −0.80, p < 0.001) with initial gradual changes. Overall, changes during BP offset, on average, 57% of the preceding gradual responses. The spatial variability in ecosystem response patterns is driven by both environmental and biological factors. Particularly, for forests, positive BP was driven by increasing rainfall and decreasing temperature, while negative BP was mainly driven by the precipitation anomaly. By 2019, 33% of the natural vegetation have recovered to the level of EVI in 2010. Ecosystem responses to multiyear droughts can influence ecosystem dynamics in a complex pattern. Multiple ecohydrological factors should be considered to understand and predict the long‐term drought impacts on ecosystems.

Variability in strength of byssus attachment and index condition of subtidal mussels during the maximum growth stage

Local environmental conditions can have strong effects on ecophysiological responses in bivalve molluscs. Molluscs must allocate the energetic resources acquired in their habitats to survival and fitness. In this study, we investigated the spatial and temporal patterns of response in relation to byssus strength and soft tissue weight during the maximum growth stage in the subtidal mussel Mytilus galloprovincialis between March and July 2015 in the Ría de Arousa (NW Spain). Mussels growing in high-energy environments secreted stronger byssus than those inhabiting low-energy sites. The integrated values of wave height and food availability for the previous 15 days showed a positive relationship explaining 45% and 9% of total variability in tenacity of the byssus threads. Differences in condition index were greatest between the northern (highest values) and southern sites at the mouth of the ria owing to differences in food availability. Despite similar hydrodynamic energy values, the high food availability in the exposed northern zones supplied sufficient energetic resources for both strong byssus secretion and high CI. Despite lower food availability, high CI values were also reached in mussels in the innermost, sheltered sites, because of the low need for survival with strong attachment. The condition index was positively correlated with temperature and food availability integrated during 45 previous days prior explained a 57% and 13% of total variance, respectively, while wave height explained 2% but with an inverse relationship. Environmental differences between the geographical zones of the estuary modulated byssus secretion functionality affecting the soft tissues status of mussels.

Mapping Specific Mental Content during Musical Imagery.

Humans can mentally represent auditory information without an external stimulus, but the specificity of these internal representations remains unclear. Here, we asked how similar the temporally unfolding neural representations of imagined music are compared to those during the original perceived experience. We also tested whether rhythmic motion can influence the neural representation of music during imagery as during perception. Participants first memorized six 1-min-long instrumental musical pieces with high accuracy. Functional MRI data were collected during: 1) silent imagery of melodies to the beat of a visual metronome; 2) same but while tapping to the beat; and 3) passive listening. During imagery, inter-subject correlation analysis showed that melody-specific temporal response patterns were reinstated in right associative auditory cortices. When tapping accompanied imagery, the melody-specific neural patterns were reinstated in more extensive temporal-lobe regions bilaterally. These results indicate that the specific contents of conscious experience are encoded similarly during imagery and perception in the dynamic activity of auditory cortices. Furthermore, rhythmic motion can enhance the reinstatement of neural patterns associated with the experience of complex sounds, in keeping with models of motor to sensory influences in auditory processing.

Disentangling listening effort and memory load beyond behavioural evidence: Pupillary response to listening effort during a concurrent memory task.

Recent research has demonstrated that pupillometry is a robust measure for quantifying listening effort. However, pupillary responses in listening situations where multiple cognitive functions are engaged and sustained over a period of time remain hard to interpret. This limits our conceptualisation and understanding of listening effort in realistic situations, because rarely in everyday life are people challenged by one task at a time. Therefore, the purpose of this experiment was to reveal the dynamics of listening effort in a sustained listening condition using a word repeat and recall task. Words were presented in quiet and speech-shaped noise at different signal-to-noise ratios (SNR): 0dB, 7dB, 14dB and quiet. Participants were presented with lists of 10 words, and required to repeat each word after its presentation. At the end of the list, participants either recalled as many words as possible or moved on to the next list. Simultaneously, their pupil dilation was recorded throughout the whole experiment. When only word repeating was required, peak pupil dilation (PPD) was bigger in 0dB versus other conditions; whereas when recall was required, PPD showed no difference among SNR levels and PPD in 0dB was smaller than repeat-only condition. Baseline pupil diameter and PPD followed different variation patterns across the 10 serial positions within a block for conditions requiring recall: baseline pupil diameter built up progressively and plateaued in the later positions (but shot up when listeners were recalling the previously heard words from memory); PPD decreased at a pace quicker than in repeat-only condition. The current findings demonstrate that additional cognitive load during a speech intelligibility task could disturb the well-established relation between pupillary response and listening effort. Both the magnitude and temporal pattern of task-evoked pupillary response differ greatly in complex listening conditions, urging for more listening effort studies in complex and realistic listening situations.

Local vegetation and hydroperiod influence spatial and temporal patterns of carbon and microbe response to wetland rehabilitation

Wetlands have a major influence on the global carbon cycle, with capacity to act as carbon ‘sinks’ or ‘sources’. The source-sink capacity of wetlands is governed by microbially-mediated biogeochemical processes, which are furthermore regulated by environmental conditions. With growing interest in nature-based climate solutions, policymakers and resource managers seek information on ways how wetlands can be managed to maximize carbon drawdown. Here, we explored how rehabilitation (i.e., fencing and grazing removal) influences greenhouse gas (GHG) emissions and soil biogeochemistry (microbial communities and soil quality) from semi-arid, rain-filled freshwater wetlands in south-eastern Australia. Specifically, we investigated the carbon and microbes response under major local environmental factors, such as vegetation type (graminoids vs eucalyptus tree) and seasonal hydroperiod (spring vs autumn), across wetlands that are currently used for grazing or cropping and those that have been under fencing rehabilitation for up to 20 years. We found that rehabilitation did not reduce CO2 and CH4 emissions, rather CH4 flux rates were elevated when the wetlands were flooded (spring). Anaerobic conditions from spring waterlogged soils also increased microbial diversity by 2.6-fold, and influenced the relative abundance of putative methane oxidizers (Nitrososphaerales and Mixococcales) and methanogenic archaea (Methanomicrobia, Methanobacteria). Organic matter quality (measured as C:N ratio) was reduced by the removal of grazing pressure in eucalyptus-dominated sites only. Soil quality, influenced by vegetation type, also had a significant impact on relative abundance of putative nitrogen and carbon cyclers. Overall, our results suggest that fencing rehabilitation in semi-arid rain-filled wetlands had a minor impact on microbial dynamics and carbon processes, overshadowed by the influence of the water table and vegetation type. Focusing future research on spatial and temporal patterns of carbon and microbe rehabilitation responses will help managers devise the most effective rehabilitation practice within a particular geographical area.

Housing first, connection second: the impact of professional helping relationships on the trajectories of housing stability for people facing severe and multiple disadvantage

BackgroundDespite the accumulating evidence on the role of professional helping relationships for highly disadvantaged populations, methodological shortcomings have made it difficult to establish a robust relationships-outcomes link. This study sought to establish the impact of professional helping relationships on the trajectories over 24 months of housing stability for 2141 people facing severe and multiple disadvantage using data from the Housing First controlled trial in Canada.MethodThe study used a mixed method design. Latent growth curve and growth mixture models assessed the impact of working alliance across the sample as a whole and within subgroups with different patterns of housing stability. Thematic analysis explored the factors that may affect the quality of working alliances within different subgroups.ResultsThree distinct trajectories of housing stability emerged (i.e., Class 1: “sharp rise, sustained, and decline housing”; Class 2: “hardly any time housed”; Class 3: “high rise, sustained, and decline housing”) with professional helping relationships having different effects in each. The analysis revealed structural and individual circumstances that may explain differences among the classes.ConclusionsThe findings underscore the role of professional helping relationships, as distinct from services, in major interventions for highly disadvantaged populations, and draws new attention to the temporal patterns of responses to both the quality of relationship and targeted interventions.

Analysis of Tree-Ring Chronologies in Coniferous Forests of Southeastern Kazakhstan

The aim of the present research was to study the spatial and temporal patterns in the growth response of spruce to climate change at different altitudes (upper, middle and lower) of mountainous terrain in Southern Kazakhstan. The analysis of the climatic response of the generalized chronologies was carried out by calculating the correlation coefficients (Rs) between the growth indices and monthly precipitations and air temperatures for the period during which the influence of climatic factors on the annual radial increment of wood was possible. This is especially important in cases where there are no assumptions about the possible influence of climatic factors on the growth of woody plants in specific conditions. According to the research, correlation and response analysis shows that the Palmer Drought Severity Index (PDSI) from July 2015 to June 2016 was the main factor limiting the radial growth of Schrenk spruce. The PDSI showed markedly prolonged and rapid hydration from 1980 to 2005 but declined after 2005. There have been three particularly dry years over the past decade (2008, 2014 and 2015). The chronologies have been reconstructed by the PDSI for the last 189 years for the Dzungarian Alatau. A calibration model from 1950 to 2011 explains 42.6% of the actual PDSI variance. The reconstructed PDSI reflects the severe droughts of the 1910s and 1940s that were widespread in the arid zones of Central Asia. The extremely dry years in the 1910s and 1940s are especially noticeable. A ten-year analysis shows that in five periods, i.e., between the years 1830-1840, 1880-1890, 1920-1930, 1950-1960 and 1980-2000, the PDSI increased and decreased in the 1850-1870, 1900-1910, 1940 and 1970 s.

Generalized Additive Mixed Modeling of Longitudinal Tumor Growth Reduces Bias and Improves Decision Making in Translational Oncology

Scientists working in translational oncology regularly conduct multigroup studies of mice with serially measured tumors. Longitudinal data collected can feature mid-study dropouts and complex nonlinear temporal response patterns. Parametric statistical models such as ones assuming exponential growth are useful for summarizing tumor volume over ranges for which the growth model holds, with the advantage that the model's parameter estimates can be used to summarize between-group differences in tumor volume growth with statistical measures of uncertainty. However, these same assumed growth models are too rigid to recapitulate patterns observed in many experiments, which in turn diminishes the effectiveness of their parameter estimates as summary statistics. To address this problem, we generalized such models by adopting a nonparametric approach in which group-level response trends for logarithmically scaled tumor volume are estimated as regression splines in a generalized additive mixed model. We also describe a novel summary statistic for group level splines over user-defined, experimentally relevant time ranges. This statistic reduces to the log-linear growth rate for data well described by exponential growth and also has a sampling distribution across groups that is well approximated by a multivariate Gaussian, thus facilitating downstream analysis. Real-data examples show that this nonparametric approach not only enhances fidelity in describing nonlinear growth scenarios but also improves statistical power to detect interregimen differences when compared with the simple exponential model so that it generalizes the linear mixed effects paradigm for analysis of log-linear growth to nonlinear scenarios in a useful way. SIGNIFICANCE: This work generalizes the statistical linear mixed modeling paradigm for summarizing longitudinally measured preclinical tumor volume studies to encompass studies with nonlinear and nonmonotonic group response patterns in a statistically rigorous manner.

Frequency response areas of neurons in the mouse inferior colliculus. III. Time-domain responses: Constancy, dynamics, and precision in relation to spectral resolution, and perception in the time domain.

The auditory midbrain (central nucleus of inferior colliculus, ICC) receives multiple brainstem projections and recodes auditory information for perception in higher centers. Many neural response characteristics are represented in gradients (maps) in the three-dimensional ICC space. Map overlap suggests that neurons, depending on their ICC location, encode information in several domains simultaneously by different aspects of their responses. Thus, interdependence of coding, e.g. in spectral and temporal domains, seems to be a general ICC principle. Studies on covariation of response properties and possible impact on sound perception are, however, rare. Here, we evaluated tone-evoked single neuron activity from the mouse ICC and compared shapes of excitatory frequency-response areas (including strength and shape of inhibition within and around the excitatory area; classes I, II, III) with types of temporal response patterns and first-spike response latencies. Analyses showed covariation of sharpness of frequency tuning with constancy and precision of responding to tone onsets. Highest precision (first-spike latency jitter < 1 ms) and stable phasic responses throughout frequency-response areas were the quality mainly of class III neurons with broad frequency tuning, least influenced by inhibition. Class II neurons with narrow frequency tuning and dominating inhibitory influence were unsuitable for time domain coding with high precision. The ICC center seems specialized rather for high spectral resolution (class II presence), lateral parts for constantly precise responding to sound onsets (class III presence). Further, the variation of tone-response latencies in the frequency-response areas of individual neurons with phasic, tonic, phasic-tonic, or pauser responses gave rise to the definition of a core area, which represented a time window of about 20 ms from tone onset for tone-onset responding of the whole ICC. This time window corresponds to the roughly 20 ms shortest time interval that was found critical in several auditory perceptual tasks in humans and mice.

Differential temporal response patterns in rat cocaine self-administration studies: The cumulative record dose-response function

Differential temporal response patterns in rat cocaine self-administration studies: The cumulative record dose-response function

Differential temporal response patterns for cocaine or hydrocodone in rat self-administration studies

Differential temporal response patterns for cocaine or hydrocodone in rat self-administration studies

Dynamic Stress Responses and Real-Time Symptoms in Binge-Eating Disorder.

Stress is a dynamic construct that predicts a range of health behaviors and conditions, including binge eating and excess weight. Thus far, there have been limited and inconsistent findings regarding stress responses in binge-eating disorder (BED) and insufficient consideration of temporal patterns of stress responses across the weight spectrum. The present study used ecological momentary assessment (EMA) to examine stress reactivity (i.e., the magnitude of the initial stress response), recovery (i.e., how long the stress response lasts before returning to baseline), and pileup (i.e., accumulation of repeated experiences of stressors and responses over time) as predictors of binge-eating symptoms (BES) and food craving in BED. Adults with BED (N = 115) completed a 7 day EMA protocol assessing stressful events, perceived stress, binge eating, and food craving prior to being randomized to a behavioral intervention. Generalized estimating equations indicated that moments of greater stress pileup predicted greater subsequent BES (within-person effect). Participants with higher perceived stress and pileup reported greater overall BES and craving, and those with better recovery reported higher overall craving (between-person effects). Findings highlight the importance of considering the dynamic nature of stress responses and, particularly, that the accumulation of stress over the day is an important trigger for BES.

Dendroclimatology of sugar maple (Acer saccharum): Climate-growth response in a late-successional species

Sugar maple (Acer saccharum) is a shade-tolerant, late successional dominant species in the North American eastern deciduous forest. The objective of this study was to quantify the relationship between climate and radial growth in sugar maple and to identify spatial and temporal patterns in dendroclimatic response. We used a combination of archived sugar maple tree-ring chronologies and newly sampled sites to calculate dendroclimatic response of sugar maple at 13 sites in the United States and Canada. At all sites, sugar maple growth was significantly correlated to monthly temperature, precipitation, or Palmer Drought Severity Index. However, there were no generalizable patterns in sugar maple’s growth response to climate. Individual sites had unique dendroclimatic responses with respect to: a) which climatic variables were correlated to radial growth; b) what months had significant correlations between climate and radial growth; and c) what years had significant correlations between climate and radial growth. The individualistic dendroclimatic response of sugar maple appears to reflect a plastic response of the species to changes in climate perhaps related to its status as a strong competitor in late-successional forests. This ability to survive a wide range of environmental conditions may bode well for the species persistence under variable future climatic conditions. It also points to the need for more research on late-successional species in examining forest response to potential climate change scenarios because these species may be more resilient than early-successional species.

0540 Insomnia Symptom Trajectories During and Following Combined Treatment for Insomnia and Depression: A Report from the Triad Study

Abstract Introduction Cognitive behavioral therapy for insomnia (CBT-I) reduces insomnia severity among individuals with insomnia and major depressive disorder (MDD). Understanding the long-term trajectories of insomnia symptom severity has the potential to inform optimization of CBT-I in this population. The objectives of this study were to examine trajectories of change in insomnia severity over a 16-week treatment phase and 2-year naturalistic follow-up, and explore correlates of symptom trajectories. Methods 148 adults (age 46.6±12.6, 73.0% female) with insomnia and MDD were randomly assigned to receive depression pharmacotherapy plus seven sessions of either CBT-I or control insomnia therapy. Depression and insomnia severity were assessed via the Hamilton Depression Rating Scale and Insomnia Severity Index at baseline, bi-weekly during treatment, and every 4 months over follow-up. Sleep effort and beliefs about sleep were assessed at baseline, midtreatment, and posttreatment. Results Latent class linear mixed modeling revealed four insomnia response trajectories: 1) Early Sustained-Responders (16%) showed marked improvement early in treatment, sustained over follow-up; 2) Gradual-Responders (36.7%) achieved substantial symptom reduction by posttreatment, sustained over follow-up; 3) Initial-Responders (25.3%) had substantial symptom reduction during treatment but increased in severity over follow-up; and 4) Partial-Responders (20.7%) achieved minimal improvement over treatment, and maintained moderate symptom severity over follow-up. Chi-square analyses revealed that classes did not differ significantly on sex, ethnicity, employment, relationship status, or treatment received (all ps &amp;gt; .05). One-way ANOVAs with Tukey’s HSD, showed that Partial-Responders consistently endorsed higher depressive symptom severity, sleep effort, and unhelpful beliefs about sleep at baseline, throughout treatment, and follow-up (ps &amp;lt; .05). Early Sustained-Responders endorsed lower sleep effort by midtreatment (ps &amp;lt; .01). Conclusion Results suggest four temporal patterns of treatment response and identified clinical correlates. Future work will be needed to determine if addressing sleep effort early in the course of treatment might enhance sustained insomnia outcome. Support MH078924, MH078961, MH079256

Rising to the challenge? Inter-individual variation of the androgen response to social interactions in cichlid fish

The Challenge Hypothesis (Wingfield et al. Am. Nat. 136, 829-846) aims to explain the complex relationship between androgens and social interactions. Despite its well acceptance in the behavioral endocrinology literature, several studies have failed to found an androgen response to staged social interactions. Possible reasons for these inconsistencies are the use of single sampling points that may miss the response peak, and the occurrence of inter-individual variability in the androgen response to social interactions. In this study we addressed these two possible confounding factors by characterizing the temporal pattern of the androgen response to social interactions in the African cichlid, Oreochromis mossambicus, and relating it to inter-individual variation in terms of the individual scope for androgen response (i.e. the difference between baseline and maximum physiological levels for each fish) and behavioral types. We found that the androgen response to territorial intrusions varies between individuals and is related to their scope for response. Individuals that have a lower scope for androgen response did not increase androgens after a territorial intrusion but were more aggressive and exploratory. In contrast males with a higher scope for response had fewer aggressive and exploratory behaviors and exhibited two peaks of KT, an early response 2–15 min after the interaction and a late response at 60–90 min post-interaction. Given that the pharmacological challenge of the Hypothalamic-Pituitary-Gonad axis only elicits the late response, we suggest that these two peaks may be regulated by different physiological mechanisms, with the early response being mediated by direct brain-gonad neural pathways. In summary, we suggest that determining the temporal pattern of the androgen response to social interactions and considering inter-individual variation may be the key to understanding the contradictory results of the Challenge Hypothesis.

Intraoperative Laser Speckle Contrast Imaging For Real-Time Visualization of Cerebral Blood Flow in Cerebrovascular Surgery:\xa0Results From Pre-Clinical Studies

Cerebrovascular surgery can benefit from an intraoperative system that conducts continuous monitoring of cerebral blood flow (CBF). Such a system must be handy, non-invasive, and directly integrated into the surgical workflow. None of the currently available techniques, considered alone, meets all these criteria. Here, we introduce the SurgeON™ system: a newly developed non-invasive modular tool which transmits high-resolution Laser Speckle Contrast Imaging (LSCI) directly onto the eyepiece of the surgical microscope. In preclinical rodent and rabbit models, we show that this system enabled the detection of acute perfusion changes as well as the recording of temporal response patterns and degrees of flow changes in various microvascular settings, such as middle cerebral artery occlusion, femoral artery clipping, and complete or incomplete cortical vessel cautery. During these procedures, a real-time visualization of vasculature and CBF was available in high spatial resolution through the eyepiece as a direct overlay on the live morphological view of the surgical field. Upon comparison with indocyanine green angiography videoangiography (ICG-VA) imaging, also operable via SurgeON, we found that direct-LSCI can produce greater information than ICG-VA and that continuous display of data is advantageous for performing immediate LSCI-guided adjustments in real time.

Direct Comparison of Odor Responses of Homologous Glomeruli in the Medial and Lateral Maps of the Mouse Olfactory Bulb.

Olfactory sensory neurons (OSNs) expressing same-type odorant receptors typically project to a pair of glomeruli in the medial and lateral sides of the olfactory bulbs (OBs) in rodents. This multiple glomerular representation of homologous inputs is considered to have more important functional roles for odor information processing than the redundant backup system. However, a consensus idea is lacking and this hinders interpretation of the phenomenon. In addition, the shared and unique odorant response properties of the homologous glomeruli remain unclear because the majority of medial glomeruli are hidden in the septal OB, and thus it is difficult to directly compare them. OSNs, which express trace amine-associated odorant receptors (TAARs), were recently identified that project to a pair of glomeruli uniquely located in the dorsal OB. In this study, we measured the odorant-induced calcium responses of homologous pairs of TAAR glomeruli simultaneously in anesthetized mice and directly compared their response patterns. We found that they exhibited similar temporal response patterns and could not find differences in onset latency, rise time, decay time, or response amplitude. However, the medial glomeruli had significantly larger respiration-locked calcium fluctuations than the lateral glomeruli. This trend was observed with/without odorant stimulation in postsynaptic neurons of GABAergic, dopaminergic, and mitral/tufted cells, but not in presynaptic olfactory sensory axon terminals. This indicates that, at least in these TAAR glomeruli, the medial rather than the lateral OB map enhances the respiration-locked rhythm and transfers this information to higher brain centers.

Plasticity of barley in response to plant neighbors in cultivar mixtures

AimsCultivar mixtures can increase productivity through complementarity in resource use, but reported results are often conflicting and the role of plasticity in shaping plant-plant interactions is poorly understood. We aim to determine if individual cultivars show different phenotypic responses when grown in a mixture, whether these responses depend on the neighboring cultivar identity, and how they contribute to variations in productivity and nitrogen (N) use.MethodsFive spring barley cultivars were field-grown in pure stands and in mixtures during 2 years. Plant traits related to development, growth, N use, and reproduction were measured to identify temporal patterns of plastic responses to neighboring plants.ResultsPlants in mixtures were shorter and developed slower early in the season, but later on they grew faster and produced more grain than the corresponding pure stands. Some cultivars showed complementary N accumulation only when grown together with specific neighbors. Mechanisms of improved productivity differed between the individual mixtures.ConclusionsPlastic plant-plant interaction between cultivars is an important driver behind the variability in mixing effects. Results contribute to a better understanding of how productivity in cultivar mixtures is affected by plastic adaptation and differentiation of plant traits, depending on the environment created by neighboring genotypes.

Optimising conditions for in vitro fertilization success of Acropora tenuis, A. millepora and Favites colemani corals in northwestern Philippines

Fertilization is a critical life history event and important to population dynamics. Successful fertilization relies on encounters of compatible and viable sperm and eggs. Scleractinian corals that spawn their gametes directly into the water column may experience limitations from sperm dilution and delays in initial sperm-egg encounters that can impact successful fertilization. Notably, the same issues can be experienced when conducting ex situ larval culture. Therefore, experiments were completed using spawned eggs and sperm of the reef corals Acropora tenuis, A. millepora and Favites colemani to determine the optimal ranges of sperm concentrations (<103 to 107 mL−1) and temporal response patterns when crossing of eggs and sperm was delayed (30 min to 10 h). The results showed that sperm concentrations below 103 mL−1 yielded low rates of fertilization for all three species (<30%), but that sperm concentrations at 104 mL−1 resulted in higher rates of fertilization for the Acropora spp. (>65%) and > 90% fertilization rates for F. colemani. Sperm concentrations of 105–107 mL−1 resulted in the highest observed fertilization rates for all three species (>90%). High fertilization rates (>80%) occurred when eggs and sperm were combined after 30 min and up to 2 h after spawning for F. colemani and up to 4 h for A. tenuis and A. millepora gametes. Fertilization rates were significantly reduced (<30%) after a delay of 4 h for F. colemani and after 6 h for the two Acropora species. No fertilization occurred after a 10-h delay in combining gametes for all the tested coral species. Therefore, optimal fertilization success for these coral species rely on sperm densities of ≥104–106 mL−1 and gametes should be combined within two hours after spawning for optimising larval culture.