Actual Stimulus Research Articles

Prior Information Shapes Perceptual Confidence.

Decisional confidence refers to the subjective evaluation of the accuracy of a decision based on sensory information. While these judgments are typically grounded in the strength of evidence leading to a decision, they are also subjected to influence from top-down factors such as prior expectations. Previous research has highlighted the impact of prior information on decision parameters such as reaction times and decision criteria placement. However, a comprehensive understanding of how prior information shapes confidence ratings is still lacking. In this study, we manipulate prior knowledge by inducing varying levels of target probability expectation (low: 33%, random: 50%, high: 67%) in a perceptual detection task. In each trial both type-1 (detection) and type-2 (confidence) responses were recorded. First, we replicate previous findings, demonstrating that decisional priors impact decision criteria but not task sensitivity. Secondly, we reveal the strong effect that prior expectations exert on type-2 decisions, with this influence being moderated by a congruency effect between the given prior, the actual stimulus presented, and the provided response. Moreover, we find that confidence is higher in correct compared to incorrect responses, with low-probability trials leading to higher confidence judgments in correct choices compared to random and liberal trials. Finally, we unveil that prior-dependent modulation rates in criterion and confidence were positively associated. These results underscore the intricate interplay between prior expectations, decision-making, and confidence levels, demonstrating that what we perceive is not solely a data-driven phenomenon but can be already shaped by the available information about the state of the world.

Choice enhances touch pleasantness

We value what we choose more than what is imposed upon us. Choice-induced preferences are extensively demonstrated using behavioural and neural methods, mainly involving rewarding objects such as money or material goods. However, the impact of choice on experiences, especially in the realm of affective touch, remains less explored. In this study, we specifically investigate whether choice can enhance the pleasure derived from affective touch, thereby increasing its intrinsic rewarding value. We conducted an experiment in which participants were being touched by an experimenter and asked to rate how pleasant their experience of touch was. They were given either a choice or no choice over certain touch stimulus variables which differed in their relevance: some were of low relevance (relating to the colour of the glove that the experimenter would use to touch them), while others were of high relevance (relating to the location on their arm where they would be stroked). Before and during touching, pupillometry was used to measure the level of arousal. We found that having a choice over aspects of tactile stimuli—especially those relevant to oneself—enhanced the pleasant perception of the touch. In addition, having a choice increases arousal in anticipation of touch. Regardless of how relevant it is to the actual tactile stimulus, allowing one to choose may positively enhance a person’s perception of the physical contact they receive.

Tactile localization accuracy at the low back.

Localizing tactile stimulation is an important capability for everyday function and may be impaired in people with persistent pain. This study sought to provide a detailed description of lumbar spine tactile localization accuracy in healthy individuals. Sixty-nine healthy participants estimated where they were touched at nine different points, labelled in a 3 × 3 grid over the lumbar spine. Mislocalization between the perceived and actual stimulus was calculated in horizontal (x) and vertical (y) directions, and a derived hypotenuse (c) mislocalization was calculated to represent the direct distance between perceived and actual points. In the horizontal direction, midline sites had the smallest mislocalization. Participants exhibited greater mislocalization for left- and right-sided sites, perceiving sites more laterally than they actually were. For all vertical values, stimulated sites were perceived lower than reality. A greater inaccuracy was observed in the vertical direction.This study measured tactile localization for the low back utilizing a novel testing method. The large inaccuracies point to a possible distortion in the underlying perceptual maps informing the superficial schema; however, further testing comparing this novel method with an established tactile localization task, such as the point-to-point method, is suggested to confirm these findings.

Analysis and Preliminary Results of a Feedback-Feedforward Controller for Depth of Anesthesia

In a computer-based anaesthesia control system, the depth of hypnosis must be correctly maintained. The regulated variable is the Bispectral Index scale (BIS) controlled via the Propofol drug rate. The anesthesiologist administers Propofol to prevent unwanted fluctuations in the controlled variable during surgical stimulation, which acts as an unmeasurable disturbance on the BIS signal. In this paper, a feedback controller is paired with a feedforward control action. Based on existing clinical protocols, a digitalized disturbance signal that mimics the actual surgical stimulus is employed in the feedforward controller design as a measurable disturbance. To account for the time delay in the BIS measurements, a time delay estimation algorithm is developed and used to estimate the patient time delay. The digitalized disturbance signal is then shifted based on the estimated time delay to ensure a pre-emptive action of the feedforward controller. Two different designs of the feedforward controller are developed. Closed loop simulations considering a nominal patient with and without the feedforward control action are presented and compared. The results show that the surgical stimulus is better tackled using a feedforward control action, even if the actual surgical stimulus is not entirely known.

Mirror-Brush Illusion: Creating Phantom Tactile Percepts on Intact Limbs.

Haptic illusions provide unique insights into how we model our bodies separate from our environment. Popular illusions like the rubber-hand illusion and mirror-box illusion have demonstrated that we can adapt the internal representations of our limbs in response to visuo-haptic conflicts. In this manuscript, we extend this knowledge by investigating to what extent, if any, we also augment our external representations of the environment and its action on our bodies in response to visuo-haptic conflicts. Utilizing a mirror and a robotic brushstroking platform, we create a novel illusory paradigm that presents a visuo-haptic conflict using congruent and incongruent tactile stimuli applied to participants' fingers. Overall, we observed that participants perceived an illusory tactile sensation on their visually occluded finger when seeing a visual stimulus that was inconsistent with the actual tactile stimulus provided. We also found residual effects of the illusion after the conflict was removed. These findings highlight how our need to maintain a coherent internal representation of our body extends to our model of our environment.

Automatic, Early Color-Specific Neural Responses to Object Color Knowledge.

Some familiar objects are associated with specific colors, e.g., rubber ducks with yellow. Whether and at what stage neural responses occur to these color associations remain open questions. We recorded frequency-tagged electroencephalogram (EEG) responses to periodic presentations of yellow-associated objects, shown among sequences of non-periodic blue-, red-, and green-associated objects. Both color and grayscale versions of the objects elicited yellow-specific responses, indicating an automatic activation of color knowledge from object shape. Follow-up experiments replicated these effects with green-specific responses, and demonstrated modulated responses for incongruent color/object associations. Importantly, the onset of color-specific responses was as early to grayscale as actually colored stimuli (before 100ms), the latter additionally eliciting a conventional later response (approximately 140-230ms) to actual stimulus color. This suggests that the neural representation of familiar objects includes both diagnostic shape and color properties, such that shape can elicit associated color-specific responses before actual color-specific responses occur.

L'interaction odeur‐goût et ses effets marketing sur la perception et la consommation des produits diététiques

AbstractThe interaction between smell and taste has been widely confirmed in the literature. Exposure to a congruent olfactory stimulus enhances taste, increases palatability and the desire to eat, and promotes food consumption. In this paper, we use laboratory experiments to show that, in addition to its role in taste enhancement, olfaction also plays a role in taste induction. Using the phenomena of cognitive sensory integration and mental imagery, we explain how exposure to a real odor congruent with the expected taste produces a taste sensation for which there is no real taste stimulus. For example, exposure to the smell of vanillin, which is a sugar‐congruent odor, creates a taste sensation of sweetness, increases palatability and food cravings, and increases consumption of sugar‐free biscuits. The lack of exposure to the actual taste stimulus of sugar does not prevent the taste‐congruent odor from creating a taste sensation of sweetness, an olfactory sweetness. Odors are able to induce a taste sensation for which there is no real taste stimulus. The results of this research have implications for the marketing of dietary foods. Tastefulness, which is reduced by the absence of flavor, can be increased by congruent olfactory stimuli in the environment and have a positive effect on the sales of this product category.

Magnetoencephalography recordings reveal the neural mechanisms of auditory contributions to improved visual detection

Sounds enhance the detection of visual stimuli while concurrently biasing an observer’s decisions. To investigate the neural mechanisms that underlie such multisensory interactions, we decoded time-resolved Signal Detection Theory sensitivity and criterion parameters from magneto-encephalographic recordings of participants that performed a visual detection task. We found that sounds improved visual detection sensitivity by enhancing the accumulation and maintenance of perceptual evidence over time. Meanwhile, criterion decoding analyses revealed that sounds induced brain activity patterns that resembled the patterns evoked by an actual visual stimulus. These two complementary mechanisms of audiovisual interplay differed in terms of their automaticity: Whereas the sound-induced enhancement in visual sensitivity depended on participants being actively engaged in a detection task, we found that sounds activated the visual cortex irrespective of task demands, potentially inducing visual illusory percepts. These results challenge the classical assumption that sound-induced increases in false alarms exclusively correspond to decision-level biases.

Opto-extinction of a threat memory in mice

Memories of past experiences guide future behaviour. Sparse ensembles of neurons, known as engrams, are thought to store memories in the brain. Neurons involved in a particular engram (“engram neurons”) are necessary for subsequent memory expression as memory retrieval is thought to be initiated by an external sensory cue reactivating engram neurons. However, conditions or environments are dynamic, such that future behaviour should be flexible. The role of engrams in mediating flexible behaviour is not understood. Here we examined this question using one type of flexible behaviour, extinction of a threat response. An initially neutral tone is first paired with an aversive footshock such that the tone alone induces defensive freezing. After subsequent repeated tone presentations without the footshock, rodents no longer freeze to the tone. Because the tone cue is thought to reactivate the engram to induce memory retrieval, we examined whether it is possible to induce an extinction-like behavioural effect by optogenetically reactivating the lateral amygdala component of the engram alone (without tone re-exposure). Similar to tone-induced extinction, mice showed decreased freezing to optogenetic stimulation of the lateral amygdala engram in the “extinction training” session. Moreover, “opto-extinguished” mice showed decreased freezing to the tone when subsequently tested for retrieval of the extinction training in the same context, suggesting that the opto-extinction transferred to the actual sensory stimulus. However, unlike tone extinction, in which mice showed renewal of tone-induced freezing when tested in a novel context, opto-extinguished mice continued to show a deficit in tone-induced freezing. Extinction has been characterized as new learning that inhibits the original memory or a phenomenon in which the original memory is "unlearned". Our findings suggest that opto-extinction may silence the original engram to “unlearn” the original memory.

Amygdala and anterior insula control the passage from nociception to pain.

Activation of the spinothalamic system does not always result in a subjective pain perception. While the cerebral network processing nociception is relatively well known, the one underlying its transition to conscious pain remains poorly described. We used intracranial electroencephalography in epileptic patients to investigate whether the amplitudes and functional connectivity of posterior and anterior insulae (PI and AI) and amygdala differ according to the subjective reports to laser stimuli delivered at a constant intensity set at nociceptive threshold. Despite the constant intensity of stimuli, all patients reported variable subjective perceptions from one stimulus to the other. Responses in the sensory PI remained stable throughout the experiment, hence reflecting accurately the stability of the stimulus. In contrast, both AI and amygdala responses showed significant enhancements associated with painful relative to nonpainful reports, in a time window corresponding to the conscious integration of the stimulus. Functional connectivity in the gamma band between these two regions increased significantly, both before and after stimuli perceived as painful. While the PI appears to transmit faithfully the actual stimulus intensity received via the spinothalamic tract, the AI and the amygdala appear to play a major role in the transformation of nociceptive signals into a painful perception.

Pseudo-haptic button for improving user experience of mid-air interaction in VR

Mid-air interaction is one of the promising interaction modalities in virtual reality (VR) due to its merits in naturalness and intuitiveness, but the interaction suffers from the lack of haptic feedback as no force or vibrotactile feedback can be provided in mid-air without extra devices. As a breakthrough to compensate for this insufficiency, the application of pseudo-haptic features which create the visuo-haptic illusion without actual physical haptic stimulus can be explored. Therefore, this study aimed to investigate the effect of four pseudo-haptic features: proximity feedback, protrusion, hit effect, and penetration blocking on user experience for free-hand mid-air button interaction in VR. We conducted a user study on 21 subjects to collect user ratings on various aspects of user experience while users were freely interacting with 16 buttons with different combinations of four features. Results indicated that all investigated features significantly improved user experience in terms of haptic illusion, embodiment, sense of reality, spatiotemporal perception, satisfaction, and hedonic quality. In addition, protrusion and hit effect were more beneficial in comparison with the other two features. It is recommended to utilize the four proposed pseudo-haptic features in 3D user interfaces (UIs) to make users feel more pleased and amused, but caution is needed when using proximity feedback together with other features because it can be distracting. The findings of this study could be helpful for VR developers and UI designers in providing better interactive buttons in the 3D interfaces.

Positive hysteresis in emotion recognition: Face processing visual regions are involved in perceptual persistence, which mediates interactions between anterior insula and medial prefrontal cortex

Facial emotion perception can be studied from the point of view of dynamic systems whose output may depend not only on current input but also on prior history — a phenomenon known as hysteresis. In cognitive neuroscience, hysteresis has been described as positive (perceptual persistence) or negative (fatigue of current percept) depending on whether perceptual switching occurs later or earlier than actual physical stimulus changes. However, its neural correlates remain elusive. We used dynamic transitions between emotional expressions and combined behavioral assessment with functional magnetic resonance imaging (fMRI) to investigate the underlying circuitry of perceptual hysteresis in facial emotion recognition. Our findings revealed the involvement of face-selective visual areas — fusiform face area (FFA) and superior temporal sulcus (STS) — in perceptual persistence as well as the right anterior insula. Moreover, functional connectivity analyses revealed an interplay between the right anterior insula and medial prefrontal cortex, which showed to be dependent on the presence of positive hysteresis. Our results support the hypothesis that high-order regions are involved in perceptual stabilization and decision during perceptual persistence (positive hysteresis) and add evidence to the role of the anterior insula as a hub of sensory information in perceptual decision-making.

Effects of social hierarchy on innate fear‑induced panic responses.

Studies have previously demonstrated a relationship between social status and anxiety disorders such as panic disorder. Repeated episodes of panic attacks do not occur in combination with an actual fear stimulus or stressor. However, social ranking modulates the perception of the social signals of a threat or stressor. The hypothalamic nuclei are well‑known for their role in the elaboration of fear‑induced reactions. The dorsomedial hypothalamus (DMH) and the ventromedial hypothalamic (VMH) nuclei are hypothalamic subnuclei involved in the processing of threatening stimuli‑evoked aversive response and innate fear development. These structures are also located in the medial amygdala‑hypothalamus‑brainstem circuit that modulates innate fear‑induced defensive behaviors. This work aimed to investigate the relationship between social hierarchy and innate fear‑induced panic‑like responses in male rats. In our study, the dominance tube test was used to determine the social hierarchy. Then, DMH/VMH nuclei were unilaterally implanted with a guide cannula. After intra‑DMH/VMH injection of bicuculline (GABAA receptor antagonist), both innate fear induction and differences in dominant/subordinate rats were evaluated by the open field test. Intra‑DMH/VMH bicuculline increased the frequency of defensive immobility, forward escape movements, and crossing behaviors, as well as the duration of defensive immobility and forward escape movements in dominant rats. Subordinate rats showed a higher frequency of defensive attention, defensive immobility, and crossing than dominant rats. Additionally, dominant rats demonstrated a lower duration of defensive attention and defensive immobility than subordinate rats. Dominant rats seemed to adopt a form of innate‑fear characterized by increased proactivity with the environment. In contrast, subordinate rats exhibited a reactive form of innate‑fear characterized by passivity and freezing.

The geographical location, current state and forecasting of development of renewable energy facilities within Lviv region


 
 
 
 Ukraine, as a member of the European Energy Community, has committed itself to achieve a share of 12 % renewables in its final energy generation by 2025 and a share of at least 25 % by 2035 (including all hydropower and thermal energy capacities). In 2019, the share of renewables in electricity generation in Ukraine was only 4 %. Renewables produce 4 % of total electricity production in Lviv region. According to this indicator, the region is the leader in the Western Ukraine. The paper analyzes the geographical location and the current state of renewable energy facilities in the Lviv region and forecasting their further development. As of July 1, 2020, in Lviv region there are 67 renewable energy facilities with a total capacity of over 310 MW. Most of the renewables supply electricity to the integrated energy system at a “green” tariff. They include two wind power plants with a total capacity of 33.9 MW in Staryy Sambir district; 59 industrial solar power plants with a total capacity of over than 275 MW in 15 administrative districts of Lviv region, Boryslav and Chervonohrad cities; two mini hydropower plants with a total capacity of 0.576 MW in Drohobych and Turka districts; three mini heat and electricity production plants running on biomass and producing electricity and thermal energy (Radekhiv heat and electricity production plant with a capacity of 2.4 MW, other heat and electricity production plants with a total capacity of 3.66 MW); one biomass electricity production plant operating in the Eco-Mit LLC pig farm in the village of Batyatychi in Kamianka-Buzka district. In addition, 985 solar electricity production plants at private households were built in 20 administrative districts and 9 cities in the region. Their total capacity is over 19 MW, which is equivalent to average capacity of one industrial solar electricity production plant. The leader in the number of industrial facilities for renewable energy is Yavoriv district, where almost half of the total renewables’ capacity of Lviv region is concentrated. The largest number of solar electricity production plants of private households is located in Pustomyty and Yavoriv districts, and Lviv city, whereas the lowest number in mountainous areas, particular in Turka and Skole districts. As of January 1, 2020, solar energy constituted 70 % of renewable energy in Lviv region. At the same time, according to the Development Strategy of Lviv region for the period of 2021–2027, the largest share in the structure of electricity production belongs to wind energy. The development of renewable energy in Ukraine depends on the rate of “green” tariff. The actual financial stimulus has led to a rapid increase in the share of renewables in total electricity generation in Ukraine and Lviv region in particular. Promising areas for renewable energy in Lviv region are wind and bioenergy developments.
 
 
 

Nerves, Pain and Consciousness

We all experience pain at one time or another. Pain is an essential “alarm bell” that tells us that something is wrong, and a “teacher” that reminds us not to do that same thing again. Usually, pain is felt when a stimulus, such as a pinch or an injury, causes electrical pulses to run along one of the cables of nerve fibers in our body and into the brain where they generate an unpleasant sensory and emotional experience. Sometimes pain occurs without any actual stimulus, such as when nerve fibers have been damaged. An example is the phantom pain that amputees sometimes feel in their missing limb. Certain drugs can stop pain by blocking the electrical pulses before they reach the brain. Other drugs stop pain in a different way, by preventing the brain from reading the pain message carried by the electrical pulses. This article explains what happens in the body when we are hurt, how the brain causes this to be felt as pain and how certain drugs can stop pain.

Multivariate prediction of pain perception based on pre-stimulus activity

The perception of pain is modulated by different processes such as, for example, expectations and attention regarding the upcoming stimulus. Such processes are initiated prior to the actual stimulus and are reflected in ongoing brain activity. Different processes that are by definition also complex in itself are reflected in pre-stimulus activity and therefore the detection of this activity pattern should benefit from a multivariate approach. To identify specific pre-stimulus EEG activity patterns related to subsequent pain perception in humans, we contrasted painful with non-painful sensations delivered at the individual threshold level during EEG measurements. The results of the multivariate EEG analysis revealed a high level of accuracy (group mean 68%) in predicting the pain categorization solely based on pre-stimulus activity. In particular, fronto-central regions and activity in the higher gamma band (60:120 Hz) were of maximal importance for classification. Additional analyses supported the specific role of the pattern of high gamma band activity prior to the stimulus for predicting the behavioral outcome and demonstrated that the informational value embedded in the pre-stimulus activity is nearly as informative as the post-stimulus processing and reflects a specific preparatory state. Further, a close relation between pre- and post-stimulus processing in the high gamma band was observed. These findings support the important role of a multivariate cognitive state prior to stimulus appearance for the emergence of the subjective perception of pain and the functional role of widespread high gamma band activity.

MRI-FI-guided superimposed stimulus-responsive co-assembled liposomes for optimizing transmembrane drug delivery pathways and improving cancer efficacy

Cancer is a serious challenge for humanity and the key to advancing cancer therapy is to increase cellular uptake of drugs. This paper provides a folic acid GFC liposome that relies on magnetic resonance imaging-fluorescence imaging (MRI-FI) to precisely guide the multi-stimulus response at the tumor site. By accurately increasing the concentration of free drug at the tumor site, it promotes the efficient diffusion of small molecule drugs into cells and penetration into solid tumors. Furthermore, based on the stimulus response mechanism of GFC liposomes (dissociation-fusion-rearrangement-fragmentation), we demonstrated that GFC liposomes can optimize the high-energy unfavorable fusion behavior of liposomes with cell membranes. In this way, GFC liposomes can intelligently and efficiently deliver drugs into cells in the form of active endocytosis, spontaneous membrane fusion and diffusion, depending on the actual stimulus response effect. Finally, animal experiments demonstrated the potential of the highly efficient MRI-FI-based GFC carrier with a 9.13-fold tumor suppression efficiency. Herein, this paper highlights the advantages of MRI-FI-guided precise multi-stimulus-controlled release and high uptake rate strategies to provide ingenious and concise ideas for precise and efficient cancer therapy.

Neural models for the cross-species recognition of dynamic facial expressions

Dynamic facial expression recognition is an essential skill of primate communication. While the neural mechanisms to recognize static facial expressions has been extensively investigated, they remain largely unclear for dynamic facial expressions. We studied plausible neural encoding mechanisms, exploiting highly controlled and realistic stimulus sets generated by computer graphics, which are also used in electrophysiological experiments. METHODS: Combining mechanisms from physiologically plausible neural models for the recognition of dynamic bodies (Giese & Poggio, 2003), static faces (Giese & Leopold, 2005) and architectures from computer vision (Simonyan et al., 2014), we devised models for the recognition of dynamic facial expressions. The first model is example-based, and encodes dynamic expressions as temporal sequences of snapshots, exploiting a sequence-selective recurrent neural network. The second model exploits norm-referenced encoding, where face-space neurons are tuned to the differences between the actual stimulus frame and a reference face, the neutral facial expression. The dynamic expressions are recognized by differentiating the responses of these face-space neurons. We tested the models with high-quality human and monkey avatars, animated with motion capture data from both species, controlling expression by motion morphing. RESULTS: Both models recognize reliably dynamic facial expressions of humans and monkeys. However, the predicted behaviour of face-tuned neurons is very different for both models. The norm-referenced model shows a highly gradual, almost linear dependence of the neuron activity with the expressivity of the stimuli, while the neurons in the example-based model show very limited capability of generalization to expressions with varying strength. We also explored if the models explain the human capability of humans to recognize human expressions on monkey faces (Taubert et al. 2020). CONCLUSIONS: The two physiologically plausible models accomplish the recognition of dynamic faces and make distinguishable predictions for physiological experiments, where norm-referenced encoding might support transfer of expression recognition across different head shapes.

Pupillometry in auditory multistability.

In multistability, a constant stimulus induces alternating perceptual interpretations. For many forms of visual multistability, the transition from one interpretation to another (“perceptual switch”) is accompanied by a dilation of the pupil. Here we ask whether the same holds for auditory multistability, specifically auditory streaming. Two tones were played in alternation, yielding four distinct interpretations: the tones can be perceived as one integrated percept (single sound source), or as segregated with either tone or both tones in the foreground. We found that the pupil dilates significantly around the time a perceptual switch is reported (“multistable condition”). When participants instead responded to actual stimulus changes that closely mimicked the multistable perceptual experience (“replay condition”), the pupil dilated more around such responses than in multistability. This still held when data were corrected for the pupil response to the stimulus change as such. Hence, active responses to an exogeneous stimulus change trigger a stronger or temporally more confined pupil dilation than responses to an endogenous perceptual switch. In another condition, participants randomly pressed the buttons used for reporting multistability. In Study 1, this “random condition” failed to sufficiently mimic the temporal pattern of multistability. By adapting the instructions, in Study 2 we obtained a response pattern more similar to the multistable condition. In this case, the pupil dilated significantly around the random button presses. Albeit numerically smaller, this pupil response was not significantly different from the multistable condition. While there are several possible explanations–related, e.g., to the decision to respond–this underlines the difficulty to isolate a purely perceptual effect in multistability. Our data extend previous findings from visual to auditory multistability. They highlight methodological challenges in interpreting such data and suggest possible approaches to meet them, including a novel stimulus to simulate the experience of perceptual switches in auditory streaming.

Statistical Mechanical Foundation of Weber–Fechner Laws

Even though the phenomenological relations between perception and stimulus have been firmly established, a theoretical argument for Weber's and Fechner's law in terms of relevant models or from statistical physics is largely missing. We present such a discussion in terms of response theory for nonequilibrium systems, where the induced displacement or current, which stands for the perceived stimulus, crucially depends on the change in time-symmetric reactivities. Stationary nonequilibria may indeed generate extra currents by changing the dynamical activity. The argument finishes by understanding how the extra dynamical activity logarithmically encodes the actual stimulus.