Melanopsin photoreception differentially modulates rod-mediated and cone-mediated human temporal vision.

To evaluate the nature of interactions between visual pathways transmitting the slower melanopsin and faster rod and cone signals, we implement a temporal phase summation paradigm in human observers using photoreceptor-directed stimuli. We show that melanopsin stimulation interacts with and alters both rod-mediated and cone-mediated vision regardless of whether it is perceptually visible or not. Melanopsin-rod interactions result in either inhibitory or facilitatory summation depending on the temporal frequency and photoreceptor pathway contrast sensitivity. Moreover, by isolating rod vision, we reveal a bipartite intensity response property of the rod pathway in photopic lighting that extends its operational range at lower frequencies to beyond its classic saturation limits but at the expense of attenuating sensitivity at higher frequencies. In comparison, melanopsin-cone interactions always lead to facilitation. These interactions can be described by linear or probability summations and potentially involve multiple intraretinal and visual cortical pathways to set human visual contrast sensitivity.

Reduced ownership over a virtual body modulates dishonesty.

Although studies suggest that even higher-order functions can be embodied, whether body awareness may bias moral decisions toward (dis)honesty remains underinvestigated. Here, we tested if the Sense of body Ownership (SoO) and the magnitude of monetary rewards influence the tendency to act immorally. Through a virtual body, participants played a card game in which they could lie to others to steal high or low amounts of money. To manipulate SoO, the virtual body was seen and controlled from a first-person perspective, with hands attached or detached, or from a third-person perspective. In third-person perspective, SoO was significantly reduced and more egoistic lies were produced in high reward conditions. Thus, SoO reduction and high monetary reward facilitate dishonest behavior, likely by separating the self from the dishonest actions performed through the disowned body. Because most future interactions will likely occur in a digital metaverse, our results may have crucial societal impact.

Psychometrics of Disembodiment and Its Differential Modulation by Visuomotor and Visuotactile Mismatches.

Altered states of embodiment are fundamental to the scientific understanding of bodily self consciousness. The feeling of disembodiment during everyday activities is common to clinical conditions; however, the direct study of disembodiment in experimental setups is rare compared to the extensive investigation of illusory embodiment of an external object. Using mixed reality to modulate embodiment through temporally mismatching sensory signals from the own body, we assessed how such mismatches affect phenomenal and physiological aspects of embodiment and measured perceptual thresholds for these across multimodal signals. The results of a principal component analysis suggest that multimodal mismatches generally induce disembodiment by increasing the sense of disownership and deafference and decreasing embodiment; however, this was not generally reflected in physiological changes. Although visual delay decreased embodiment both during active movement and passive touch, the effect was stronger for the former. We discuss the relevance of these findings for understanding bodily self plasticity.

Discriminação de velocidades de veículos por observadores parados / Discriminación de velocidades de vehículos por observadores estáticos / Discrimination of vehicle speeds by stationary observers

A percepção de movimento é objeto de estudo da psicofísica, entretanto há poucos estudos em situações naturalísticas ou que utilizam veículos reais. Investigamos como as pessoas percebem a velocidade de veículos em situações naturais. Observadores estáticos foram solicitados a determinar a velocidade de um veículo real em movimento. Os resultados demonstraram acurácia nas estimativas das velocidades dos veículos, independente do sexo do participante e de possuir ou não habilitação. O expoente da função-potência associado a esta dimensão foi de 1,31, mostrando tendência à superestimativa com o aumento da velocidade física, indicando que não há linearidade na percepção de velocidades de veículos por observadores estáticos.

The perception of movement is an object of study of psychophysics, however there are few studies in naturalistic situations or using real vehicles. We investigated how people perceive vehicle speed in natural situations. Static observers were asked to determine the speed of a real moving vehicle. The results showed accuracy in the estimates of vehicle speeds, regardless of the participant's gender and whether or not they are licensed. The exponent of the power-function associated with this dimension was 1.31, showing a tendency to overestimate with increasing physical speed, indicating that there is no linearity in the perception of vehicle speeds by static observers

La percepción del movimiento es objeto de estudio de la psicofísica, sin embargo, existen pocos estudios en situaciones naturalistas o utilizando vehículos reales. Investigamos cómo personas perciben la velocidad del vehículo en situaciones naturales. Se pidió a observadores estáticos que determinaran la velocidad de vehículos en movimiento real. Los resultados mostraron precisión en las estimaciones de la velocidad, independientemente del género del participante y si tiene licencia o no. El exponente de la función de potencia asociado con esta dimensión fue 1.31, mostrando una tendencia a sobreestimar con el aumento de la velocidad física, lo que indica que no existe linealidad en la percepción de la velocidad del vehículo por parte de los observadores estáticos.

Eugenol and carvacrol induce temporally desensitizing patterns of oral irritation and enhance innocuous warmth and noxious heat sensation on the tongue.

Eugenol and carvacrol, from the spices clove and oregano, respectively, are agonists of TRPV3, which is implicated in transduction of warmth and possibly heat pain. We investigated the temporal dynamics of lingual irritation elicited by these agents, and their effects on innocuous warmth and heat pain, using a half-tongue method in human subjects. The irritant sensation elicited by both eugenol and carvacrol decreased across repeated applications at a 1-minute interstimulus interval (self-desensitization) which persisted for at least 10 minutes. Both agents also cross-desensitized capsaicin-evoked irritation. Eugenol and carvacrol significantly increased the magnitude of perceived innocuous warmth (44 °C) for >10 minutes, and briefly (<5 minutes) enhanced heat pain elicited by a 49 °C stimulus. Similar albeit weaker effects were observed when thermal stimuli were applied after the tongue had been desensitized by repeated application of eugenol or carvacrol, indicating that the effect is not due solely to summation of chemoirritant and thermal sensations. Neither chemical affected sensations of innocuous cool or cold pain. A separate group of subjects was asked to subdivide eugenol and carvacrol irritancy into subqualities, the most frequently reported being numbing and warmth, with brief burning, stinging/pricking, and tingle, confirming an earlier study. Eugenol, but not carvacrol, reduced detection of low-threshold mechanical stimuli. Eugenol and carvacrol enhancement of innocuous warmth may involve sensitization of thermal gating of TRPV3 expressed in peripheral warm fibers. The brief heat hyperalgesia following eugenol may involve a TRPV3-mediated enhancement of thermal gating of TRPV1 expressed in lingual polymodal nociceptors.