1,721,059 research outputs found
Continuous dynamics of cooperation and competition in social decision-making
No full textbehavioral observations, continuous trajectories, adult human dyads, dynamic social interactions
https://osf.io/56hw7
Human and macaque pairs employ different coordination strategies in a transparent decision game
No full textBehavioral data: choice sequences, reward outcomes and the reaction and movement times, in human-human, rhesus macaque-macaque, and human-macaque dyad
Active Vision: Fixational Eye Movements Help Seeing Space in Time
No full textSummaryThe significance of the miniature eye movements that we make during visual fixation has been intensely debated for the last 80 years. Recent studies have revealed that these motions of the eyes fulfill an important functional role: helping to extract useful information from natural scenes
Active Vision: Microsaccades Direct the Eye to Where It Matters Most
No full textSummaryEven in the most sensitive part of human retina, the fovea, perception is not uniform. To compensate for such non-uniformity, tiny fixational microsaccades direct the optimal foveal locus to relevant parts of the fixated scene, similarly to larger exploratory saccades but on a miniature scale
Reply to: The linearity and selectivity of neuronal responses in awake visual cortex, Chen et al. (2009)
No full textBrain repair using electrical stimulation of healthy nodes
No full textA method and system of compensating for a damaged brain node is disclosed. The damaged node is determined by techniques such as fMRI or neural recording. A healthy node that can compensate for the function of the damaged node is determined. A stimulating electrode is placed on at least one functioning node to bypass the activity from the damaged node to compensate for a missing node. The functioning node is then stimulated to compensate for the damaged node
Dorsal pulvinar inactivation leads to spatial selection bias without perceptual deficit
No full textAbstract The dorsal pulvinar has been implicated in visuospatial attentional and perceptual confidence processing. Pulvinar lesions in humans and monkeys lead to spatial neglect symptoms, including an overt spatial saccade bias during free choices. However, it remains unclear whether disrupting the dorsal pulvinar during target selection that relies on a perceptual decision leads to a perceptual impairment or a more general spatial orienting and choice deficit. To address this question, we reversibly inactivated the unilateral dorsal pulvinar by injecting GABA-A agonist THIP while two macaque monkeys performed a color discrimination saccade task with varying perceptual difficulty. We used Signal Detection Theory and simulations to dissociate perceptual sensitivity (d-prime) and spatial selection bias (response criterion) effects. We expected a decrease in d-prime if dorsal pulvinar affects perceptual discrimination and a shift in response criterion if dorsal pulvinar is mainly involved in spatial orienting. After the inactivation, we observed response criterion shifts away from contralesional stimuli, especially when two competing stimuli in opposite hemifields were present. Notably, the d-prime and overall accuracy remained largely unaffected. Our results underline the critical contribution of the dorsal pulvinar to spatial orienting and action selection while showing it to be less important for visual perceptual discrimination.Hermann und Lilly Schilling-Stiftung für Medizinische Forschung http://dx.doi.org/10.13039/100017694Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659CNMPB Primate Platfor
Saccades and drifts differentially modulate neuronal activity in V1: Effects of retinal image motion, position, and extraretinal influences
No full textIn natural vision, continuously changing input is generated by fast saccadic eye movements and slow drifts. We analyzed effects of fixational saccades, voluntary saccades, and drifts on the activity of macaque V1 neurons. Effects of fixational saccades and small voluntary saccades were equivalent. In the presence of a near-optimal stimulus, separate populations of neurons fired transient bursts after saccades, sustained discharges during drifts, or both. Strength, time course, and selectivity of activation by fast and slow eye movements were strongly correlated with responses to flashed or to externally moved stimuli. These neuronal properties support complementary functions for post-saccadic bursts and drift responses. Local post-saccadic bursts signal rapid motion or abrupt change of potentially salient stimuli within the receptive field; widespread synchronized bursts signal occurrence of a saccade. Sustained firing during drifts conveys more specific information about location and contrast of small spatial features that contribute to perception of fine detail. In addition to stimulus-driven responses, biphasic extraretinal modulation accompanying saccades was identified in one third of the cells. Brief perisaccadic suppression was followed by stronger and longer-lasting enhancement that could bias perception in favor of saccade targets. These diverse patterns of neuronal activation underlie the dynamic encoding of our visual world
Modeling V1 complex cells in alert monkeys
No full textCortical complex cells are usually described as nonlinear energy operators that sum squared outputs of quadrature pairs of linear subunits, responding to drifting sinusoidal gratings with unmodulated elevation of flring rate (F0 harmonic). However, several lines of evidence suggest that the view of complex cells as a uniform class is over-simplifled, since energy models do not capture many complex cell behaviors. In alert monkeys complex cells with strongly overlapping increment and decrement regions exhibit a considerable F1 modulation, and a subset of these cells have a relative modulation (RM=F1/F0) >1. We have also found that most complex cells show profound dependence of the response form (harmonic content), and not only the amplitude, on grating parameters such as spatial and temporal frequency and size, displaying a variety of behaviors ranging from nonlinear unmodulated flring (F0) and frequency doubling (F2) to pseudolinear modulation (F1). One of the parsimonious explanations could be that at least some of these behaviors, e.g. F1 modulation, result from the imbalance of increment and decrement mechanisms such as incomplete spatial overlap and/or difierence in amplitudes of the two regions. We tested this hypothesis using a model that approximates an apparent structure of complex receptive flelds in our data by pooling two linear (increment and decrement) inputs with Gaussian spatial proflle and same biphasic temporal response function. Model cells with various overlaps and amplitude ratios were stimulated with drifting gratings of difierent spatial frequencies. To quantify the measure of spatial (im)balance we computed a product of overlap index and amplitude ratio. In the model, maximal modulation increased with spatial imbalance, and the correlation for the two measures was high (r=-0.86, p0.01) was inconsistent with model predictions. Thus, a static spatial imbalance of increment and decrement mechanisms cannot fully predict the presence of strong F1 harmonic in responses of complex cells. These results and efiects of temporal frequency suggest that temporal properties of input channels and possibly the dynamics of interaction between them play an important role in shaping the responses of complex cells. To account for the response diversity exhibited by complex cells, we are developing more realistic models that also include in∞uences of the surround
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