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235 results for “Stimulus”
Data from: Stimulus discriminability may bias value-based probabilistic learning
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Increasing stimulus similarity drives nonmonotonic representational change in hippocampus
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Data supporting: Synthesis of higher order feature codes through stimulus-specific supra-linear summation
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Number of frogs per pond per night per stimulus
<p class="Standard">In tropical regions, some anuran species "explosively breed", reproducing in massive and highly diverse aggregations during a brief window of time. These aggregations can serve as acoustic beacons, attracting other anurans towards seasonal ponds. We hypothesize that conspecific and heterospecific calls play a role in navigation towards ponds and synchronization of reproduction among species. We simulated a chorus of two species (<i>Trachycephalus coriaceus</i> and <i>Chiasmocleis shudikarensis</i>) with contrasting call characteristics (low-frequency vs. high-frequency) and reproductive strategies (strict pond breeder vs. opportunistic) near known explosive breeding sites and predicted that choruses of <i>T. coriaceus</i> are more attractive to heterospecifics than of <i>C. shudikarensis</i> because the first provides a more reliable indicator of a suitable breeding pond and a better long-distance signal. We found that both choruses attracted conspecific frogs to the playback outside a natural breeding event. As predicted, heterospecifics were attracted only by low-frequency calls of <i>T. coriaceus</i> that breeds exclusively in large ponds, but not by higher-frequency calls of <i>C. shudikarensis</i> that also breeds in small pools not suitable for other species. Our study presents the first experimental evidence that tropical explosive breeding anurans are attracted to conspecific and heterospecific choruses. The contrasting effect of the playback of the two species on heterospecifics suggests that the attractive effect of a chorus depends on the reproductive strategy of both the sender and the receiver. Given the abundance and diversity of communities in tropical ecosystems, the use of heterospecific acoustic cues may prove widespread and requires further investigation.</p>
Data from: Occipital alpha activity during stimulus processing gates the information flow to object-selective cortex
Given the limited processing capabilities of the sensory system, it is essential that attended information is gated to downstream areas, whereas unattended information is blocked. While it has been proposed that alpha band (8–13 Hz) activity serves to route information to downstream regions by inhibiting neuronal processing in task-irrelevant regions, this hypothesis remains untested. Here we investigate how neuronal oscillations detected by electroencephalography in visual areas during working memory encoding serve to gate information reflected in the simultaneously recorded blood-oxygenation-level-dependent (BOLD) signals recorded by functional magnetic resonance imaging in downstream ventral regions. We used a paradigm in which 16 participants were presented with faces and landscapes in the right and left hemifields; one hemifield was attended and the other unattended. We observed that decreased alpha power contralateral to the attended object predicted the BOLD signal representing the attended object in ventral object-selective regions. Furthermore, increased alpha power ipsilateral to the attended object predicted a decrease in the BOLD signal representing the unattended object. We also found that the BOLD signal in the dorsal attention network inversely correlated with visual alpha power. This is the first demonstration, to our knowledge, that oscillations in the alpha band are implicated in the gating of information from the visual cortex to the ventral stream, as reflected in the representationally specific BOLD signal. This link of sensory alpha to downstream activity provides a neurophysiological substrate for the mechanism of selective attention during stimulus processing, which not only boosts the attended information but also suppresses distraction. Although previous studies have shown a relation between the BOLD signal from the dorsal attention network and the alpha band at rest, we demonstrate such a relation during a visuospatial task, indicating that the dorsal attention network exercises top-down control of visual alpha activity.
Data from: Binocular combination of stimulus orientation
When two sine waves that differ slightly in orientation are presented to the two eyes separately, a single cyclopean sine wave is perceived. However, it is unclear how the brain calculates its orientation. Here, we used a signal detection rating method to estimate the perceived orientation when the two eyes were presented with Gabor patches that differed in both orientation and contrast. We found a nearly linear combination of orientation when both targets had the same contrast. However, the binocular percept shifted away from the linear prediction towards the orientation with the higher contrast, depending on both the base contrast and the contrast ratio. We found that stimuli that differ slightly in orientation are combined into a single percept, similarly for monocular and binocular presentation, with a bias that depends on the interocular contrast ratio. Our results are well fitted by gain-control models, and are consistent with a previous study that favoured the DSKL model that successfully predicts binocular phase and contrast combination and binocular contrast discrimination. In this model, the departures from linearity may be explained on the basis of mutual suppression and mutual enhancement, both of which are stronger under dichoptic than monocular conditions.
Data from: Interaction between stimulus contrast and pre-saccadic crowding
Objects that are briefly flashed around the time of saccades are mislocalized. Previously, robust interactions between saccadic perceptual distortions and stimulus contrast have been reported. It is also known that crowding depends on the contrast of the target and flankers. Here, we investigated how stimulus contrast and crowding interact with pre-saccadic perception. We asked observers to report the orientation of a tilted Gabor presented in the periphery, with or without four flanking vertically oriented Gabors. Observers performed the task either following a saccade or while maintaining fixation. Contrasts of the target and flankers were independently set to either high or low, with equal probability. In both the fixation and saccade conditions, the flanked conditions resulted in worse discrimination performance—the crowding effect. In the unflanked saccade trials, performance significantly decreased with target-to-saccade onset for low-contrast targets but not for high-contrast targets. In the presence of flankers, impending saccades reduced performance only for low-contrast, but not for high-contrast flankers. Interestingly, average performance in the fixation and saccade conditions was mostly similar in all contrast conditions. Moreover, the magnitude of crowding was influenced by saccades only when the target had high contrast and the flankers had low contrasts. Overall, our results are consistent with modulation of perisaccadic spatial localization by contrast and saccadic suppression, but at odds with a recent report of pre-saccadic release of crowding.
Data from: One stimulus - two responses: host and parasite life history variation in response to environmental stress
Climate change stressors will place different selective pressures on both parasites and their hosts, forcing individuals to modify their life history strategies and altering the distribution and prevalence of disease. Few studies have investigated whether parasites are able to respond to host stress and respond by varying their reproductive schedules. Additionally, multiple environmental stressors can limit the ability of a host to respond adaptively to parasite infection. This study compared both host and parasite life history parameters in unstressed and drought-stressed environments using the human parasite, Schistosoma mansoni in its freshwater snail intermediate host. Snail hosts infected with the parasite demonstrated a significant reproductive burst during the pre-patent period (fecundity compensation), but that response was absent in a drought-stressed environment. This is the first report of the elimination of host fecundity compensation to parasitism when exposed to additional environmental stress. More surprisingly, we found that infections in drought-stressed snails had significantly higher parasite reproductive outputs than infections in unstressed snails. The finding suggests that climate change may alter the infection dynamics of this human parasite.
Data from: Stimulus background influences phase invariant coding by correlated neural activity
We recently reported that correlations between the activities of peripheral afferents mediate a phase invariant representation of natural communication stimuli that is refined across successive processing stages thereby leading to perception and behavior in the weakly electric fish Apteronotus leptorhynchus (Metzen et al., 2016). Here, we explore how phase invariant coding and perception of natural communication stimuli are affected by changes in the sinusoidal background over which they occur. We found that increasing background frequency led to phase locking, which decreased both detectability and phase invariant coding. Correlated afferent activity was a much better predictor of behavior as assessed from both invariance and detectability than single neuron activity. Thus, our results not only provide further evidence that correlated activity likely determines perception of natural communication signals, but also provide a novel explanation as to why these preferentially occur on top of low frequency as well as low intensity sinusoidal backgrounds.
Data from: Dynamic population codes of multiplexed stimulus features in primate area MT
The middle-temporal area (MT) of primate visual cortex is critical in the analysis of visual motion. Single-unit studies suggest that the response dynamics of neurons within area MT depend on stimulus features, but how these dynamics emerge at the population level, and how feature representations interact, is not clear. Here, we used multivariate classification analysis to study how stimulus features are represented in the spiking activity of populations of neurons in area MT of marmoset monkey. Using Representational Similarity Analysis (RSA) we distinguished the emerging representations of moving grating and dot field stimuli. We show that representations of stimulus orientation, spatial frequency and speed are evident near the onset of the population response, while the representation of stimulus direction is slower to emerge and sustained throughout the stimulus-evoked response. We further found a spatiotemporal asymmetry in the emergence of direction representations. Representations for high spatial frequencies and low temporal frequencies are initially orientation-dependent, while those for high temporal frequencies and low spatial frequencies are more sensitive to motion direction. Our analyses reveal a complex interplay of feature representations in area MT population response that may explain the stimulus-dependent dynamics of motion vision.
Stimulus classification with electrical potential and impedance of living plants: comparing discriminant analysis and deep-learning methods
<p>The physiology of living organisms, such as living plants, is complex and particularly difficult to understand on a macroscopic, organism-holistic level. Among the many options for studying plant physiology, electrical potential and tissue impedance are arguably simple measurement techniques that can be used to gather plant-level information. Despite the many possible uses, our research is exclusively driven by the idea of phytosensing, that is, interpreting living plants’ signals to gather information about surrounding environmental conditions. As ready-to-use plant-level physiological models are not available, we consider the plant as a blackbox and apply statistics and machine learning to automatically interpret measured signals. In simple plant experiments, we expose <em>Zamioculcas zamiifolia</em> and <em>Solanum lycopersicum</em> (tomato) to four different stimuli: wind, heat, red light and blue light. We measure electrical potential and tissue impedance signals. Given these signals, we evaluate a large variety of methods from statistical discriminant analysis and from deep learning, for the classification problem of determining the stimulus to which the plant was exposed. We identify a set of methods that successfully classify stimuli with good accuracy, without a clear winner. The statistical approach is competitive, partially depending on data availability for the machine learning approach. Our extensive results show the feasibility of the blackbox approach and can be used in future research to select appropriate classifier techniques for a given use case. In our own future research, we will exploit these methods to derive a phytosensing approach to monitoring air pollution in urban areas.</p> <p>Data repository for our paper " <em>Stimulus classification with electrical potential and impedance of living plants: comparing discriminant analysis and deep-learning methods</em> ", submitted to the journal Bioinspiration & Biomimetics . Please refer to the paper for more information.</p> <p> </p> <p><strong>Contents of this repository</strong></p> <ul> <li><em>mu_interface:</em> Code for our data collection plant experiments, based on Raspberry Pis and the <a href="http://cybertronica.co/?q=products/phytosensor">Cybertronica phytosensing and phytoactuating system</a>.</li> <li><em>SupplementaryCode</em>: Includes the discriminant analysis classifier, raw datasets, calculated features, test-train split and the corresponding code.</li> <li><em>dl-4-tsc:</em> Deep learning framework developed by <a href="https://doi.org/10.1007/s10618-019-00619-1">Fawaz et. al (Deep learning for time series classification: a review)</a> and adapted to our use case. </li> <li><em>DeepClassifier: </em>Trained deep learning time series classifier.</li> <li><em>classification_results.xlsx: </em>Overview of the results from the deep learning framework (accuracy, precision, recall, training time, confusion matrix) and the achieved accuracies using discriminant analysis with sequential forward section (further evaluation metrics of the discriminant analysis can be found in SupplementaryCode.</li> </ul>
No evidence of neural feature-specific pre-activation during the prediction of an upcoming stimulus
<p>Confusion matrices and decoding accuracy data of the publication "No evidence of neural feature-specific pre-activation during the prediction of an upcoming stimulus". See the publication methods for a detailed description of how these data were derived from the original, downsampled MEG data (available at https://zenodo.org/records/3268713).</p> <p> </p> <p> </p> <p> </p>
Aversive stimulus-tuned responses in the CA1 of the dorsal hippocampus (dataset 9)
<p>Multichannel electrophysiology data for the manuscript with the same title. (2305_20)</p>
Aversive stimulus-tuned responses in the CA1 of the dorsal hippocampus (dataset 11)
<p>Multichannel electrophysiology data for the manuscript with the same title.</p>
Aversive stimulus-tuned responses in the CA1 of the dorsal hippocampus (dataset 7)
<p>Multichannel electrophysiology data for the manuscript with the same title.</p>
Aversive stimulus-tuned responses in the CA1 of the dorsal hippocampus (dataset 4)
<p>Multichannel electrophysiology data for the manuscript with the same title.</p>
Aversive stimulus-tuned responses in the CA1 of the dorsal hippocampus (dataset 10)
<p>Multichannel electrophysiology data for the manuscript with the same title.</p>
Aversive stimulus-tuned responses in the CA1 of the dorsal hippocampus (dataset 2)
<p>Multichannel electrophysiology data for the manuscript with the same title.</p>
Aversive stimulus-tuned responses in the CA1 of the dorsal hippocampus (dataset 5)
<p>Multichannel electrophysiology data for the manuscript with the same title.</p>
Aversive stimulus-tuned responses in the CA1 of the dorsal hippocampus (dataset 12)
<p>Multichannel electrophysiology data for the manuscript with the same title.</p>
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Allen Brain Atlas
Allen Brain Atlas is an Allen Institute collection of brain map atlases, datasets, APIs, and analysis tools covering mouse, human, and non-human primate brain resources.
Annotated Behaviour and Observability Dataset (ABODe)
ABODe is a University of Edinburgh DataShare dataset for behavior classification in group-housed mice using home-cage video, identities, bounding boxes, ground-plate positions, and annotator labels.
DANDI Archive for NWB datasets
DANDI is a BRAIN Initiative archive for publishing and sharing neurophysiology data, including electrophysiology, optophysiology, and behavioral data packaged as NWB and related standards.
International Brain Laboratory public data
The International Brain Laboratory public data releases expose standardized mouse decision-making experiments, including Neuropixels recordings, widefield calcium imaging, behavior, and session metadata accessed through the ONE API.
OpenNeuro
OpenNeuro is a free, open platform for sharing neuroimaging datasets, with public search, dataset pages, and download paths for web, S3, DataLad, and the OpenNeuro CLI.