Unimodal Effects Research Articles

Effects of rhythmic auditory stimulation on vision: Oscillations in performance can be enhanced, but not induced.

A variety of reports suggest that rhythmic auditory stimulation can entrain visual perception, inducing perceptual oscillations as a function of time relative to the auditory rhythm. These effects have, to date, been reported only for stimulation frequencies at and below 3 Hz. Here we investigate the effects of rhythmic auditory stimulation on the detection of masked visual targets when this stimulation occurs at frequencies to which the visual system has been shown to entrain (8-12 Hz). Across four experiments, we found no consistent evidence of poststimulation modulations in performance induced by 8.5, 10.6, or 12.1 Hz auditory stimulation. This absence of a consistent auditory-to-visual effect was paralleled by an absence of unimodal effects (oscillations in auditory performance) following 12.1 Hz auditory stimulation. In a fifth experiment, we found that although auditory stimulation alone did not induce oscillations in visual performance, auditory stimulation did enhance the effects of concurrent visual stimulation. Notably, this enhancement did not require synchronous presentation of stimuli. These observations are consistent with recent reports that passive auditory stimulation beyond 5 Hz induces neither auditory perceptual oscillations nor visual cortical oscillations and suggest limits to the extent of cross-modal entrainment. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Effect of Indoor Temperature and Glazing with Saturated Color on Visual Perception of Daylight

ABSTRACT This paper presents the combined effect of indoor temperature (19 °C, 22 °C, and 26 °C) and colored glazing (blue, orange, and neutral) on visual perception of daylight. Experiments were performed in an office-like test room, in which 75 participants were fully immersed under visual and thermal stimuli. Findings are discussed in terms of cross-modal effects of indoor temperature on visual perception, as well as of unimodal effects of glazing color on visual perception, investigated in terms of color of light and visual environment evaluations. Results show the presence of cross-modal effects of indoor temperature on visual perception of both the visual environment and the color of light. Indoor temperature affected the visual environment evaluation as, first, brightness comfort resulted higher at lower temperatures, and second, the light was associated to warmth adjectives more often at higher temperatures. On the other hand, indoor temperature influenced the color of light evaluation as, only at lower temperatures, daylight tinted by the blue glazing was considered less pleasant and less comfortable, and was chosen less often over the daylight tinted by the orange glazing. In terms of unimodal effect of colored glazing on visual perception, results indicate that the neutral glazing was always preferred over the two colored ones, probably due to the use of saturated colors. The orange glazing, however, was associated with the most relaxing and warmest daylight. These findings have important implications regarding the use of glazing with saturated colors in buildings and expand our understanding of temperature–color interaction – so far investigated only with electric light – to daylight evaluations.

Electrocortical responses associated with attention bias to fearful facial expressions and auditory distress signals

Understanding how emotional stimuli across auditory and visual sensory domains interact and influence multimodal attentional mechanisms is important to understanding how humans prioritize and isolate emotionally-laden stimuli in a continual stream of sensory information that occurs in everyday life. While multimodal emotional human-relevant stimuli have been used in the past, this study is one of the first to look at how human-generated threat-related sounds (e.g., screams) interact with human-generated visual cues of threat (fearful facial expressions) to determine whether these converging sources of threat are represented by either combined or isolated enhancements of visual attention as measured with event-related potential (ERP) components related to attention: the N170, N2, and N2pc. Using the dot-probe task, this study demonstrates that converging sources of multimodal audiovisual threat interact to modulate the N170 ERP component such that auditory distress signals widen the spotlight of attention beyond the contralateral enhancement elicited by the fearful face cue. Multimodal facilitation was neither observed on the N2pc nor the anterior N2. Rather, separate unimodal effects were observed on these ERP components.

Forecast models of coffee leaf rust symptoms and signs based on identified microclimatic combinations in coffee-based agroforestry systems in Costa Rica

Coffee leaf rust is a polycyclic disease that causes severe epidemics impacting yield over several years. For this reason, since the 1960s, more than 20 models have been developed to predict different indicators of the disease's development and help manage it. In existing models, standardized periods of influence of the meteorological predictors of the disease are determined a priori, based on strong assumptions. However, the appearance of a symptom or sign can be influenced by complex combinations of meteorological variables acting at different times and for different durations. In our study, we monitored a total of 5400 coffee leaves during a year and a half, in different agroforestry systems, in order to detect the onset dates of the disease symptoms, such as lesion emergence, and signs, such as sporulation and infectious area increase. In these agroforestry systems, we also recorded microclimate. We statistically identified the complex combinations of microclimatic variables responsible for changes in lesion status to construct three models predicting lesion emergence probability, lesion sporulation probability and growth of its infectious area. Our method allowed the identification of different microclimatic variables that fit well with the knowledge about the coffee leaf rust biology. Minimum air temperature from 20 to 18 days before a lesion emergence explained the status change from healthy to emergence of visible lesion, possibly because the short germination phase is stimulated by low temperatures. We also found a unimodal effect of rainfall over a period of 10 days, 33 days before lesion emergence, with a maximum at 10 mm. Below this threshold, uredospore dispersal is efficient, increasing the lesion appearance probability; above this threshold, wash-off effects on uredospores probably occurs, decreasing the probability of lesion emergence. In addition, we identified microclimatic variables whose influence on coffee leaf rust had not been described before. These variables are likely to be involved in the internal development phases of the disease in the coffee leaves: (1) unimodal effects of maximum air temperature in different periods on sporulation and infectious area growth (2) positive and unimodal effects of rainfall in different periods on sporulation and (3) a negative effect of leaf thermal amplitude in different periods on lesion emergence, sporulation and infectious area growth. Although these models do not provide predictors of the level of disease attack, such as incidence, they provide valuable information for warning systems and for mechanistic model development. These models could also be used to forecast risks of infection, sporulation and infectious area growth and help optimize treatment recommendations.

Influence of indoor temperature and daylight illuminance on visual perception

This paper details the results of an experimental study investigating the combined effect of indoor temperature (19 ℃, 23 ℃ and 27 ℃) and horizontal illuminances (∼140 lx, ∼610 lx and ∼1440 lx) on visual perception, with daylight as the only source of light. The goal is to evaluate the cross-modal effect of temperature and the unimodal effect of daylight illuminances on the visual perception of daylight. A 3 × 3 mixed-design experiment was conducted in an office-like test room with 84 participants. Results show that cross-modal effects of indoor temperature on visual perception occurred: Temperature influenced the perceived warmth of daylight, and temperature interacted with daylight illuminance as the high illuminance was considered more pleasant, was better evaluated and was more often chosen than the low one only in a thermally comfortable condition. In terms of unimodal effects, differences in visual comfort evaluations were substantial only between the low and the other two illuminances, suggesting that visual comfort did not increase with illuminance above an already comfortable threshold. Moreover, perceived brightness under the high daylight illuminance was lower than that reported in past studies under a comparable electric light illuminance, leading to the hypothesis that high illuminances might be more tolerated in a naturally-lit environment compared to a space illuminated with electric light. Findings advance the understanding of occupant perceptions of daylit environments and suggest that, together with visual factors, thermal conditions should be considered in visual perception investigations.

Temperature drives Zika virus transmission: evidence from empirical and mathematical models.

Temperature is a strong driver of vector-borne disease transmission. Yet, for emerging arboviruses we lack fundamental knowledge on the relationship between transmission and temperature. Current models rely on the untested assumption that Zika virus responds similarly to dengue virus, potentially limiting our ability to accurately predict the spread of Zika. We conducted experiments to estimate the thermal performance of Zika virus (ZIKV) in field-derived Aedes aegypti across eight constant temperatures. We observed strong, unimodal effects of temperature on vector competence, extrinsic incubation period and mosquito survival. We used thermal responses of these traits to update an existing temperature-dependent model to infer temperature effects on ZIKV transmission. ZIKV transmission was optimized at 29°C, and had a thermal range of 22.7°C–34.7°C. Thus, as temperatures move towards the predicted thermal optimum (29°C) owing to climate change, urbanization or seasonality, Zika could expand north and into longer seasons. By contrast, areas that are near the thermal optimum were predicted to experience a decrease in overall environmental suitability. We also demonstrate that the predicted thermal minimum for Zika transmission is 5°C warmer than that of dengue, and current global estimates on the environmental suitability for Zika are greatly over-predicting its possible range.

The area–heterogeneity tradeoff applied to spatial protection of rockfish (Sebastes spp.) species richness

AbstractThe “area–heterogeneity tradeoff” hypothesis predicts unimodal effects of habitat heterogeneity on species richness, implying that habitats with intermediate heterogeneity may be priority for spatial protection. Alternatively, if heterogeneity effects are positive, then protecting the most heterogeneous habitats may take precedence. We tested for unimodal effects of habitat heterogeneity on the species density (area‐corrected richness) of rockfishes (Sebastes spp.): long‐lived, benthic fishes vulnerable to overexploitation. Inconsistent with predictions, topographic structural complexity had a strong linear effect on species density; other heterogeneity measures had weaker, positive effects and the only unimodal effect (depth range) was weak. The clear implication is that, to protect the highest density of rockfish species, marine protected areas should include the most topographically complex substrates. Our results can also help refine and test species distribution models needed to inform spatial planning where in situ surveys are lacking. The area–heterogeneity tradeoff generates useful predictions for which support may be context‐dependent.

Strong and nonlinear effects of fragmentation on ecosystem service provision at multiple scales

Human actions, such as converting natural land cover to agricultural or urban land, result in the loss and fragmentation of natural habitat, with important consequences for the provision of ecosystem services. Such habitat loss is especially important for services that are supplied by fragments of natural land cover and that depend on flows of organisms, matter, or people across the landscape to produce benefits, such as pollination, pest regulation, recreation and cultural services. However, our quantitative knowledge about precisely how different patterns of landscape fragmentation might affect the provision of these types of services is limited. We used a simple, spatially explicit model to evaluate the potential impact of natural land cover loss and fragmentation on the provision of hypothetical ecosystem services. Based on current literature, we assumed that fragments of natural land cover provide ecosystem services to the area surrounding them in a distance-dependent manner such that ecosystem service flow depended on proximity to fragments. We modeled seven different patterns of natural land cover loss across landscapes that varied in the overall level of landscape fragmentation. Our model predicts that natural land cover loss will have strong and unimodal effects on ecosystem service provision, with clear thresholds indicating rapid loss of service provision beyond critical levels of natural land cover loss. It also predicts the presence of a tradeoff between maximizing ecosystem service provision and conserving natural land cover, and a mismatch between ecosystem service provision at landscape versus finer spatial scales. Importantly, the pattern of landscape fragmentation mitigated or intensified these tradeoffs and mismatches. Our model suggests that managing patterns of natural land cover loss and fragmentation could help influence the provision of multiple ecosystem services and manage tradeoffs and synergies between services across different human-dominated landscapes.

Spatial patterns and predictors of trophic control in marine ecosystems.

A key question in ecology is under which conditions ecosystem structure tends to be controlled by resource availability vs. consumer pressure. Several hypotheses derived from theory, experiments and observational field studies have been advanced, yet a unified explanation remains elusive. Here, we identify common predictors of trophic control in a synthetic analysis of 52 observational field studies conducted within marine ecosystems across the Northern Hemisphere and published between 1951 and 2014. Spatial regression analysis of 45 candidate variables revealed temperature to be the dominant predictor, with unimodal effects on trophic control operating both directly (r(2) = 0.32; P < 0.0001) and indirectly through influences on turnover rate and quality of primary production, biodiversity and omnivory. These findings indicate that temperature is an overarching determinant of the trophic dynamics of marine ecosystems, and that variation in ocean temperature will affect the trophic structure of marine ecosystems through both direct and indirect mechanisms.

Influence of starfish grazing on lagoonal microalgal communities: non-competitive mechanisms for unimodal effects on diversity

We quantified the effects of grazing by the starfish Parvulastra (=Patiriella) exigua on microalgal assemblages in a lagoon on the South African west coast. This starfish is common on rocky shores in South Africa and Australia, but rarely occurs on soft sediments. Although grazing is well known to be a dominant structuring agent of marine systems, the influence of grazing starfish is poorly documented. Our results indicate that at natural densities, P. exigua plays an important role in structuring soft-sediment microalgal assemblages, having no significant effect on microalgal bio- mass, but reducing microalgal abundance probably through consumption. Interestingly, concentra- tions of extracellular polymeric substances (EPS) increased with densities of P. exigua, indicating a potentially important ecological role of this starfish in enhancing carbohydrate levels on the sediment either through mucus addition or stimulation of bacterial biomass. Taxonomic richness and diversity of microalgae showed classical hump-shaped responses to increasing starfish density. Our findings are discussed in the context of the intermediate disturbance hypothesis, which proposes that distur- bance promotes diversity at intermediate intensities by eliminating dominant species and allowing poor competitors to co-exist. We also present evidence for a mechanism based on non-competitive interactions to explain the promotive effects of this starfish on microalgal diversity, arising from the ability of this species to enhance sedimentary EPS levels. Our results collectively indicate that P. exigua plays an important role in regulating diversity and richness of microalgal assemblages and concur with previous assertions that this starfish plays an underestimated role in structuring intertidal systems.

Attending to visual or auditory motion affects perception within and across modalities: An event-related potential study

The present event-related potential (ERP) study examined the role of dynamic features in multisensory binding. It was tested whether endogenous attention to the direction of motion affects processing of visual and auditory stimuli within and across modalities. Human participants perceived horizontally moving dot patterns and sounds that were presented either continuously (standards) or briefly interrupted (infrequent deviants). Their task was to detect deviants moving in a particular direction within a primary modality, but to detect all deviants irrespective of their motion direction within the secondary modality. Attending to the direction of visual motion resulted in a broad selection negativity (SN) starting at about 200 ms post-stimulus onset, and attending to the direction of auditory motion resulted in a positive difference wave at 150 ms that was followed by a broad negativity starting at about 200 ms (unimodal effects). Moreover, dot patterns moving in a direction that was attended within audition were detected faster and more accurately than oppositely moving stimuli and elicited a cross-modal SN wave. Corresponding cross-modal behavioural and ERP results were obtained for sounds moving in a direction that was attended within vision. Unimodal and cross-modal ERP attention effects partially differed in their scalp topography. The present study shows that dynamic features (direction of motion) may be used to link input across modalities and demonstrates for the first time that these multisensory interactions take place as early as about 200 ms after stimulus onset.

Attending to visual or auditory motion affects perception within and across modalities: an event‐related potential study

The present event-related potential (ERP) study examined the role of dynamic features in multisensory binding. It was tested whether endogenous attention to the direction of motion affects processing of visual and auditory stimuli within and across modalities. Human participants perceived horizontally moving dot patterns and sounds that were presented either continuously (standards) or briefly interrupted (infrequent deviants). Their task was to detect deviants moving in a particular direction within a primary modality, but to detect all deviants irrespective of their motion direction within the secondary modality. Attending to the direction of visual motion resulted in a broad selection negativity (SN) starting at about 200 ms post-stimulus onset, and attending to the direction of auditory motion resulted in a positive difference wave at 150 ms that was followed by a broad negativity starting at about 200 ms (unimodal effects). Moreover, dot patterns moving in a direction that was attended within audition were detected faster and more accurately than oppositely moving stimuli and elicited a cross-modal SN wave. Corresponding cross-modal behavioural and ERP results were obtained for sounds moving in a direction that was attended within vision. Unimodal and cross-modal ERP attention effects partially differed in their scalp topography. The present study shows that dynamic features (direction of motion) may be used to link input across modalities and demonstrates for the first time that these multisensory interactions take place as early as about 200 ms after stimulus onset.

Preparatory states in crossmodal spatial attention: spatial specificity and possible control mechanisms.

We used event-related functional magnetic resonance imaging to study the neural correlates of endogenous spatial attention for vision and touch. We examined activity associated with attention-directing cues (central auditory pure tones), symbolically instructing subjects to attend to one hemifield or the other prior to upcoming stimuli, for a visual or tactile task. In different sessions, subjects discriminated either visual or tactile stimuli at the covertly attended side, during bilateral visuotactile stimulation. To distinguish cue-related preparatory activity from any modulation of stimulus processing, unpredictably on some trials only the auditory cue was presented. The use of attend-vision and attend-touch blocks revealed whether preparatory attentional effects were modality-specific or multimodal. Unimodal effects of spatial attention were found in somatosensory cortex for attention to touch, and in occipital areas for attention to vision, both contralateral to the attended side. Multimodal spatial effects (i.e. effects of attended side irrespective of task-relevant modality) were detected in contralateral intraparietal sulcus, traditionally considered a multimodal brain region; and also in the middle occipital gyrus, an area traditionally considered purely visual. Critically, all these activations were observed even on cue-only trials, when no visual or tactile stimuli were subsequently presented. Endogenous shifts of spatial attention result in changes of brain activity prior to the presentation of target stimulation (baseline shifts). Here, we show for the first time the separable multimodal and unimodal components of such preparatory activations. Additionally, irrespective of the attended side and modality, attention-directing auditory cues activated a network of superior frontal and parietal association areas that may play a role in voluntary control of spatial attention for both vision and touch.

Modelling short-term responsive adjustments in particle clearance rate among bivalve suspension-feeders: separate unimodal effects of seston volume and composition in the scallop Chlamys farreri

Suspension-feeding behaviour in the scallop Chlamys farreri of 72±1 mm shell length was studied in response to wide variations in the amount and composition of suspended seston. Clearance rates (CR; l h −1) with which scallops removed all particles larger than 3.9 μm equivalent spherical diameter varied over an order of magnitude, initially increasing to maxima in separate unimodal relations with different measures of dietary abundance that included total particulate volume (VOL; mm 3 l −1), total particulate mass (TPM; mg l −1), particulate organic mass (POM; mg l −1), particulate organic carbon (POC; mg l −1) and chlorophyll a (CHL; μg l −1), before declining with further increases in seston concentration. Most variance in CR was associated with VOL (47%), compared with TPM (29%), POM (32%), POC (29%), PON (27%) and CHL (20%). This suggests morphological limits to feeding behaviour, as adjustments in CR were primarily dependent upon total seston volume, rather than any gravimetric measure of abundance. Nevertheless, stepwise regression indicated that VOL and CHL together accounted for as much as 58% of the variance in CR; more than for VOL alone ( p<0.001), and more than twice that explained by gravimetric measures of TPM, POM or CHL. The associated relation was best described by a combination of two unimodal curves, predicting that CR increased with food availability to a maximum of 7.1 l h −1 g −1 when VOL was 2.0 mm 3 l −1 and CHL was 5.3 μg l −1, before declining with further increases in either VOL or CHL. Response curves differed according to particle type. Most evidently, compared with silt-enriched diets, natural seawater contained about the same total chlorophyll l −1, but with much lower average volume, with the result that maximal CR was significantly higher in natural seawater. These findings establish highly flexible regulation of CR. They also indicate that to understand regulatory responses in feeding to a mixed suspension of different particles, it is necessary to measure the separate significant influences of particle volume and seston composition, when the range of experimental conditions must span the lower extreme of naturally occurring concentrations. We impress how our findings help to reconcile hitherto apparent differences between previous reports of bivalve suspension-feeding behaviour.