Pairs Of Visual Stimuli Research Articles

DYNAMICS OF THE PARIETAL-OCCIPITAL ALPHA RHYTHM ACTIVITY DURING COMPARISON OF VISUAL STIMULI DURATIONS

This research is aimed at studying the dynamics of the parietal-occipital alpha rhythm in its connection with the process of stimuli duration comparison. EEG study was conducted in which participants (n = 48) were asked to compare pairs of visual stimuli of different durations ranging from 3.2 to 6.4 s. The time-frequency analysis of the EEG was carried out in the range of 8–12 Hz. The power of alpha rhythm increases from the stimulus onset to the middle of its presentation, but then its dynamic depends on the stimulus duration: it further increases for short durations (3.2, 3.6, 4.0 s), stays the same for middle durations (4.4, 4.8, 5.2 s) and decreases for long durations (5.6, 6.0, 6.4 s). The relative decrease of alpha power for long stimuli in relation to the short ones was related to subjective perception of time. The results are discussed from the point of view of the “dual klepsydra” model: it is assumed that alpha rhythm acts as an electrophysiological correlate of the functioning of “neural accumulators” associated with the subjective passage of time.

Prestimulus α/β power in temporal-order judgments: individuals differ in direction of modulation but show consistency over auditory and visual tasks.

The processing of incoming sensory information can be differentially affected by varying levels of α-power in the electroencephalogram (EEG). A prominent hypothesis is that relatively low prestimulus α-power is associated with improved perceptual performance. However, there are studies in the literature that do not fit easily into this picture, and the reasons for this are poorly understood and rarely discussed. To evaluate the robustness of previous findings and to better understand the overall mixed results, we used a spatial TOJ task in which we presented auditory and visual stimulus pairs in random order while recording EEG. For veridical and non-veridical TOJs, we calculated the power spectral density (PSD) for 3 frequencies (5 Hz steps: 10, 15, and 20 Hz). We found on the group level: (1) Veridical auditory TOJs, relative to non-veridical, were associated with higher β-band (20 Hz) power over central electrodes. (2) Veridical visual TOJs showed higher β-band (10, 15 Hz) power over parieto-occipital electrodes (3) Electrode site interacted with TOJ condition in the β-band: For auditory TOJs, PSD over central electrodes was higher for veridical than non-veridical and over parieto-occipital electrodes was lower for veridical than non-veridical trials, while the latter pattern was reversed for visual TOJs. While our group-level result showed a clear direction of prestimulus modulation, the individual-level modulation pattern was variable and included activations opposite to the group mean. Interestingly, our results at the individual-level mirror the situation in the literature, where reports of group-level prestimulus modulation were found in either direction. Because the direction of individual activation of electrodes over auditory brain regions and parieto-occipital electrodes was always negatively correlated in the respective TOJ conditions, this activation opposite to the group mean cannot be easily dismissed as noise. The consistency of the individual-level data cautions against premature generalization of group-effects and suggests different strategies that participants initially adopted and then consistently followed. We discuss our results in light of probabilistic information processing and complex system properties, and suggest that a general description of brain activity must account for variability in modulation directions at both the group and individual levels.

Reward salience but not spatial attention dominates the value representation in the orbitofrontal cortex

The orbitofrontal cortex (OFC) encodes value and plays a key role in value-based decision-making. However, the attentional modulation of the OFC’s value encoding is poorly understood. We trained two monkeys to detect a luminance change at a cued location between a pair of visual stimuli, which were over-trained pictures associated with different amounts of juice reward and, thus, different reward salience. Both the monkeys’ behavior and the dorsolateral prefrontal cortex neuronal activities indicated that the monkeys actively directed their spatial attention toward the cued stimulus during the task. However, the OFC’s neuronal responses were dominated by the stimulus with higher reward salience and encoded its value. The value of the less salient stimulus was only weakly represented regardless of spatial attention. The results demonstrate that reward and spatial attention are distinctly represented in the prefrontal cortex and the OFC maintains a stable representation of reward salience minimally affected by attention.

Distinct Patterns of Automatic and Controlled Incongruent Information Processing in the Human Brain.

It is a fundamental ability to discriminate incongruent information in daily activity. However, the underlying neural dynamics are still unclear. Using stereoelectroencephalography (SEEG), in this study, we investigated the fine-grained and different states of incongruent information processing in patients with refractory epilepsy who underwent intracranial electrode implantation. All patients performed a delayed match-to-sample paradigm in the sequential pairs of visual stimuli (S1 followed by S2). Participants were asked to discriminate whether the relevant feature of S2 was identical to S1 while ignoring the irrelevant feature. The spatiotemporal cortical responses evoked by different conditions were calculated and compared, respectively, in the context of brain intrinsic functional networks. In total, we obtained SEEG recordings from 241 contacts in gray matter. In the processing of irrelevant incongruent information, the activated brain areas included the superior parietal lobule, supramarginal gyrus, angular gyrus, inferior temporal gyrus, and fusiform gyrus. By comparing the relevant incongruent condition with the congruent condition, the activated brain areas included the middle frontal gyrus, superior temporal gyrus, middle temporal gyrus, posterior superior temporal sulcus, and posterior cingulate cortex. We demonstrated the dynamics of incongruent information processing with high spatiotemporal resolution and suggested that the process of automatic detection of irrelevant incongruent information requires the involvement of local regions and relatively few networks. Meanwhile, controlled discrimination of relevant incongruent information requires the participation of extensive regions and a wide range of nodes in the network. Furthermore, both the frontoparietal control network and default mode network were engaged in the incongruent information processing.

Transitive inference in cleaner wrasses (Labroides dimidiatus).

Transitive inference (TI) is the ability to infer unknown relationships from previous information. To test TI in non-human animals, transitive responding has been examined in a TI task where non-adjacent pairs were presented after premise pair training. Some mammals, birds and paper wasps can pass TI tasks. Although previous studies showed that some fish are capable of TI in the social context, it remains unclear whether fish can pass TI task. Here, we conducted a TI task in cleaner wrasses (Labroides dimidiatus), which interact with various client fishes and conspecifics. Because they make decisions based on previous direct and indirect interactions in the context of cleaning interactions, we predicted that the ability of TI is beneficial for cleaner fish. Four tested fish were trained with four pairs of visual stimuli in a 5-term series: A-B+, B-C+, C-D+, and D-E+ (plus and minus denote rewards and non-rewards, respectively). After training, a novel pair, BD (BD test), was presented wherein the fish chose D more frequently than B. In contrast, reinforcement history did not predict the choice D. Our results suggest that cleaner fish passed the TI task, similar to mammals and birds. Although the mechanism underlying transitive responding in cleaner fish remains unclear, this work contributes to understanding cognitive abilities in fish.

Unraveling the Electrophysiological Activity Behind Recognition Memory

Abstract. Traditionally, most event related potential (ERP) studies of memory retrieval have been reported during item-recognition tasks. Those studies lead to two well-known ERP memory components termed FN400 (familiarity) and LPC (recollection). Nevertheless, some critics have raised concerns regarding the actual meaning of that activity since it emerges as the result of contrasting two different memory traces (previously studied vs. seen for the first time), and it is registered after the target presentation. Therefore, they possibly depict operations not related to memory itself but some cognitive processes associated with recognition memory. Based on those critics, we propose an innovative approach to study electrophysiological activity underlying recognition memory. We compared two very similar tasks with only one of them requiring subjects to actively retrieve a “cue-target” pair of visual stimuli from memory, while the other task required subjects to recognize the target stimulus as equal/different to the cue. Because of this experimental manipulation, we assured that active memory retrieval processes take place between the presentation of the cue and the target stimuli for only one of the tasks. As a result, responses upon the targets can give us valuable information regarding ERP components associated with recognition based on memory retrieval. We found three components possibly related to brain computations necessary to achieve correct target recognition. A N200-like component linked to executive functions (inhibition) from frontal cortices, a P300-like component, related to the expectation of the target stimulus, and a P600-like component associated to recognition based on LTM retrieval. These results help us to understand the complexity behind ERP components associated with recognition memory.

Seeing or not Seeing Where Your Hands Are. The Influence of Visual Feedback About Hand Position on the Interaction Between Nociceptive and Visual Stimuli.

Examining the mechanisms underlying crossmodal interaction between nociceptive and visual stimuli is crucial to understand how humans handle potential bodily threats in their environment. It has recently been shown that nociceptive stimuli can affect the perception of visual stimuli, provided that they occur close together in external space. The present study addresses the question whether these crossmodal interactions between nociceptive and visual stimuli are mediated by the visually perceived proximity between the visual stimuli and the limb on which nociceptive stimuli are applied, by manipulating the presence vs. absence of visual feedback about the position of the stimulated limb. Participants performed temporal order judgments on pairs of visual stimuli, shortly preceded by nociceptive stimuli, either applied on one hand or both hands simultaneously. The hands were placed near the visual stimuli and could either be seen directly, seen through a glass barrier, or hidden from sight with a wooden board. Unilateral nociceptive stimuli induced spatial biases to the advantage of visual stimuli presented near the stimulated hand, which were greater in the conditions in which the hands were seen than in the condition in which vision was prevented. Spatial biases were not modulated by the presence of the glass barrier, minimizing the possibility that the differential effect between the vision and no-vision conditions is solely due to the presence of the barrier between the hands and the visual stimuli. These findings highlight the importance of visual feedback for determining spatial mapping between nociceptive and visual stimuli for crossmodal interaction.

High-Speed Videography Reveals How Honeybees Can Turn a Spatial Concept Learning Task Into a Simple Discrimination Task by Stereotyped Flight Movements and Sequential Inspection of Pattern Elements.

Honey bees display remarkable visual learning abilities, providing insights regarding visual information processing in a miniature brain. It was discovered that bees can solve a task that is generally viewed as spatial concept learning in primates, specifically the concept of “above” and “below.” In these works, two pairs of visual stimuli were shown in the two arms of a Y-maze. Each arm displayed a “referent” shape (e.g., a cross, or a horizontal line) and a second geometric shape that appeared either above or below the referent. Bees learning the “concept of aboveness” had to choose the arm of the Y-maze in which a shape–any shape–occurred above the referent, while those learning the “concept of belowness” had to pick the arm in which there was an arbitrary item beneath the referent. Here, we explore the sequential decision-making process that allows bees to solve this task by analyzing their flight trajectories inside the Y-maze. Over 368 h of high-speed video footage of the bees' choice strategies were analyzed in detail. In our experiments, many bees failed the task, and, with the possible exception of a single forager, bees as a group failed to reach significance in picking the correct arm from the decision chamber of the maze. Of those bees that succeeded in choosing correctly, most required a close-up inspection of the targets. These bees typically employed a close-up scan of only the bottom part of the pattern before taking the decision of landing on a feeder. When rejecting incorrect feeders, they repeatedly scanned the pattern features, but were still, on average, faster at completing the task than the non-leaners. This shows that solving a concept learning task could actually be mediated by turning it into a more manageable discrimination task by some animals, although one individual in this study appeared to have gained the ability (by the end of the training) to solve the task in a manner predicted by concept learning.

Does Body Perception Shape Visuospatial Perception?

How we perceive our body is shaped by sensory experiences with our surrounding environment, as witnessed by poor performance in tasks during which participants judge with their hands crossed the temporal order between two somatosensory stimuli, one applied on each hand. This suggests that somatosensory stimuli are not only processed according to a somatotopic representation but also a spatiotopic representation of the body. We investigated whether the perception of stimuli occurring in external space, such as visual stimuli, can also be influenced by the body posture and somatosensory stimuli. Participants performed temporal order judgements on pairs of visual stimuli, one in each side of space, with their hands uncrossed or crossed. In Experiment 1, participants' hands were placed either near or far from the visual stimuli. In Experiment 2, the visual stimuli were preceded, either by 60 ms or 360 ms, by tactile stimuli applied on the hands placed near the visual stimuli. Manipulating the time interval was intended to activate either a somatotopic or a spatiotopic representation of somatic inputs. We did not obtain any evidence for an influence of body posture on visual temporal order judgment, suggesting that body perception is less relevant for processing extrabody stimuli than the reverse.

Investigating the spatial characteristics of the crossmodal interaction between nociception and vision using gaze direction.

The present study investigated the influence of nociceptive stimuli on visual stimuli processing according to the relative spatial congruence between the two stimuli of different sensory modalities. Participants performed temporal order judgments on pairs of visual stimuli, one presented near the hand on which nociceptive stimuli were occasionally applied, the other one either to its left or to its right. The visual hemifield in which the stimulated hand and the near visual stimulus appeared was manipulated by changing gaze direction. The stimulated hemibody and the stimulated visual hemifield were therefore either congruent or incongruent, in terms of anatomical locations. Despite the changes in anatomical congruence, judgments were always biased in favor of the visual stimuli presented near the stimulated hand. This indicates that nociceptive-visual interaction may rely on a realignment of the respective initial anatomical representations of the somatic and retinotopic spaces toward an integrated, multimodal representation of external space.

Identity matching to sample and exclusion performance in elderly with and without neurocognitive disorders

Neurocognitive disorders (NCDs) affect complex processes of stimulus control, such as relational performance. The aims of this study were (a) to compare the performance of older adults with NCD with that of control older adults in generalized identity matching (GI) tests and in responding by exclusion probes and (b) to verify the effect of identity matching training on subsequent GI and exclusion tests, in older adults with NCD. Participants were 24 older adults (aged 60 to 92 years), eight without NCD (control group I [CG I]), and 16 with NCD: CG II, with accurate performance in the GI tests and the experimental group (EG), with low performance in these tests. After exclusion and GI tests with all participants, the EG underwent identity matching training with 3 pairs of visual stimuli, and exclusion and identity matching posttests. All participants of the CG I and CG II presented accurate performance in the tests. Seven of the 8 older adults of the EG achieved the learning criterion in the training and showed some improvement in the GI posttest; however, positive effects of the training were not observed in the exclusion posttests. Teaching procedures for identity matching in older adult patients with NCD can produce positive results; however, it is necessary to understand the relationship between cognitive decline and other relational performances.

Investigating peri-limb interaction between nociception and vision using spatial depth.

In order to adapt behavior to a potentially body damaging threat, it is crucial to coordinate the perception of the location of the threat in external space and that of the location of the potential damage on the body surface. Such ability presupposes interactions between nociceptive stimuli and visual stimuli occurring close to the body. We hypothesized that these interactions would rely on multisensory representations of each limb itself, extending its boundaries slightly into external space, with less influence of the global representation of the body as a whole. In most studies investigating such representations, spatial organization of the somatic and extra-somatic stimuli is made according to an egocentric frame of reference centered on the main axes of the participant's whole body (e.g. the trunk), dissociating the left vs. the right side of space. Here, the contribution of such a body-centered frame was minimized, by placing participants' hands in front of them along their anteroposterior body axis, one at a proximal, the other at a distal location. They performed a temporal order judgment task on pairs of visual stimuli, one delivered close to each hand. Visual stimuli were preceded by nociceptive stimuli applied either on one hand, or on both hands simultaneously (control condition). Results showed that, as compared to the control condition, participants' judgements were biased in favor of the visual stimuli the closest to the stimulated hand, irrespective of their distance from the trunk. This finding supports the idea that the mechanisms underlying nociceptive-visual interactions are based on spatial representations that primarily use the stimulated limb rather than the whole body as a coordinate system.

Orienting attention in visual space by nociceptive stimuli: investigation with a temporal order judgment task based on the adaptive PSI method.

Despite their high relevance for defending the integrity of the body, crossmodal links between nociception, the neural system specifically coding potentially painful information, and vision are still poorly studied, especially the effects of nociception on visual perception. This study investigated if, and in which time window, a nociceptive stimulus can attract attention to its location on the body, independently of voluntary control, to facilitate the processing of visual stimuli occurring in the same side of space as the limb on which the visual stimulus was applied. In a temporal order judgment task based on an adaptive procedure, participants judged which of two visual stimuli, one presented next to either hand in either side of space, had been perceived first. Each pair of visual stimuli was preceded (by 200, 400, or 600ms) by a nociceptive stimulus applied either unilaterally on one single hand, or bilaterally, on both hands simultaneously. Results show that, as compared to the bilateral condition, participants' judgments were biased to the advantage of the visual stimuli that occurred in the same side of space as the hand on which a unilateral, nociceptive stimulus was applied. This effect was present in a time window ranging from 200 to 600ms, but importantly, biases increased with decreasing time interval. These results suggest that nociceptive stimuli can affect the perceptual processing of spatially congruent visual inputs.

Suppressive interactions underlying visually evoked fixational saccades

Small saccades occur frequently during fixation, and are coupled to changes in visual stimulation and cognitive state. Neurophysiologically, fixational saccades reflect neural activity near the foveal region of a continuous visuomotor map. It is well known that competitive interactions between neurons within visuomotor maps contribute to target selection for large saccades. Here we asked how such interactions in visuomotor maps shape the rate and direction of small fixational saccades. We measured fixational saccades during periods of prolonged fixation while presenting pairs of visual stimuli (parafoveal: 0.8° eccentricity; peripheral: 5° eccentricity) of various contrasts. Fixational saccade direction was biased toward locations of parafoveal stimuli but not peripheral stimuli, ∼100–250ms following stimulus onset. The rate of fixational saccades toward parafoveal stimuli (congruent saccades) increased systematically with parafoveal stimulus contrast, and was suppressed by the simultaneous presentation of a peripheral stimulus. The suppression was best characterized as a combination of two processes: a subtractive suppression of the overall fixational saccade rate and a divisive suppression of the direction bias. These results reveal the nature of suppressive interactions within visuomotor maps and constrain models of the population code for fixational saccades.

Arbitrary sounds facilitate visual search for congruent objects

Multisensory correspondences are thought to form through Hebbian-type learning, whereby repeated exposure to coincident auditory and visual signals promotes the formation of auditory-visual associations. Previous research has demonstrated that feature-based multisensory correspondences influence perceptual processing (Iordanescu et al., 2010). For example, when searching for keys among clutter, participants are faster to detect the spatial location of the keys when the characteristic sound of keys jingling is played at the onset of search. It remains unclear, however, whether such facilitation in perceptual processing relies on natural correspondences or whether newly learned associations might similarly facilitate processing. In the present study, we demonstrate that learned arbitrary sounds facilitate visual processing of an associated object, despite the absence of spatial information in the auditory signal. We trained participants to associate two pairs of visual stimuli each with a single arbitrary sound. Visual stimuli consisted of kaleidoscope images that varied in spatial frequency, shape, size, and color. Learning was verified with a two-alternative task in which participants had to correctly match a presented sound to the associated kaleidoscope image. Following training, participants performed a visual search for target kaleidoscopes from one of the previously learned sets with simultaneous presentation of target-congruent or target-incongruent sounds. We demonstrated that a non-spatially informative target-congruent sound speeds visual search to the associated target object. Accuracy did not significantly differ across the two sound congruency conditions and there was no evidence of a speed-accuracy trade-off. These results suggest audiovisual integration may facilitate visual processing and detection by increasing the salience of target objects. Meeting abstract presented at VSS 2013

The temporal resolution of binding brightness and loudness in dynamic random sequences

Purpose. This study investigated the ways in which observers can combine dynamic visual and auditory information. Method. The stimuli were composed of gray disks accompanied by simultaneous bursts of auditory white noise. Three levels of disk brightness and of noise loudness were used to produce 9 different types of audiovisual tokens. On a given trial, 18 tokens (83ms per token) drawn from these 9 token types were presented in random order. Different conditions required participants to try to classify stimulus sequences using various target filters that gave differential weight to the 9 audiovisual token types. In each condition, a probit model was used to measure the attention filter achieved by the participant (the impact exerted on the observer’s judgments by each of the 9 token-types). The model also included terms reflecting potential non-simultaneous "misbindings" across time of auditory and visual components. Results. Participants demonstrated a high degree of strategic flexibility in achieving attention filters that varied widely across tasks, but these filters often deviated strongly from the corresponding target filters. Model fits revealed that misbindings of auditory and visual components that were 83 ms apart influenced judgments with half the strength of simultaneous components. Components that were 167 ms apart did not misbind. Conclusions. The temporal resolution of the binding achieved with these stimuli is higher than is found in tasks requiring the observer to judge the phase with which an alternating pair of visual stimuli matches up with an alternating pair of auditory stimuli (Fujisaki & Nishida, 2010). In correlating loudness and brightness, the space of attention filters that participants are able to achieve is at least three dimensional. Citation: Fujisaki, W & Nishida, S (2010). A common perceptual temporal limit of binding synchronous inputs across different sensory attributes and modalities, Proceedings of the Royal Society of London B: Biological Sciences,277(1692):2281-90. Meeting abstract presented at VSS 2012

Written words supersede pictures in priming semantic access: a P300 study

The dynamic interplay of semantic access during information integration across the verbal and nonverbal domains and sensory modalities is poorly understood. Here, we compared the priming effects of four types of meaningful stimuli (pictures, written words, spoken words, and environmental sounds) on picture and written word targets referring to the same concept in all cases. P3b event-related brain potentials indexed automatic access to semantic memory in the different modalities. As expected, P3b amplitudes were large in the repetition priming condition, but also for word-picture and picture-word visual stimulus pairs. Critically, written word primes resulted in the largest P3b amplitudes whether elicited by written word or picture targets, suggesting a semantic priming supremacy of written words.

Mechanisms of attention for appetitive and aversive outcomes in Pavlovian conditioning

Different mechanisms of attention controlling learning have been proposed in appetitive and aversive conditioning. The aim of the present study was to compare attention and learning in a Pavlovian conditioning paradigm using visual stimuli of varying predictive value of either monetary reward (appetitive conditioning; 10p or 50p) or blast of white noise (aversive conditioning; 97 dB or 102 dB). Outcome values were matched across the two conditions with regard to their emotional significance. Sixty-four participants were allocated to one of the four conditions matched for age and gender. All participants underwent a discriminative learning task using pairs of visual stimuli that signalled a 100%, 50%, or 0% probability of receiving an outcome. Learning was measured using a 9-point Likert scale of expectancy of the outcome, while attention using an eyetracker device. Arousal and emotional conditioning were also evaluated. Dwell time was greatest for the full predictor in the noise groups, while in the money groups attention was greatest for the partial predictor over the other two predictors. The progression of learning was the same for both groups. These findings suggest that in aversive conditioning attention is driven by the predictive salience of the stimulus while in appetitive conditioning attention is error-driven, when emotional value of the outcome is comparable.

Asymmetry of P3 amplitude during oddball tasks reflects the unnaturalness of visual stimuli

This study examined the relationship between the 'naturalness' of a visual stimulus and the event-related potentials measured during an oddball task. The study focused on asymmetry of the P3 amplitude during an oddball task or P3 asymmetry. Participants performed two visual oddball tasks using a pair of stimuli (A and B): one in which A was the target stimulus and B was the standard stimulus and vice versa. The stimuli consisted of natural-unnatural pairs of visual stimuli (e.g. upright-inverted faces, possible-impossible human poses). As a result of comparing the amplitudes of the target stimuli, P3 asymmetry was found in natural-unnatural pairs; that is, their naturalness differentiated the target P3 amplitude: larger P3 to the unnatural target than to the natural one. This study showed that P3 asymmetry reflected unnaturalness and unfamiliarity of visual stimuli.

Evaluation of Objective Uncertainty in the Visual System

The role of sensory systems is to provide an organism with information about its environment. Because sensory information is noisy and insufficient to uniquely determine the environment, natural perceptual systems have to cope with systematic uncertainty. The extent of that uncertainty is often crucial to the organism: for instance, in judging the potential threat in a stimulus. Inducing uncertainty by using visual noise, we had human observers perform a task where they could improve their performance by choosing the less uncertain among pairs of visual stimuli. Results show that observers had access to a reliable measure of visual uncertainty in their decision-making, showing that subjective uncertainty in this case is connected to objective uncertainty. Based on a Bayesian model of the task, we discuss plausible computational schemes for that ability.