Action priming is linked to visual perception in continuous flash suppression.

In spite of the excellent temporal resolution of event-related EEG potentials (ERPs), the overlapping potentials evoked by masked and masking stimuli are hard to disentangle. However, when both masked and masking stimuli consist of pairs of relevant and irrelevant stimuli, one left and one right from fixation, with the side of the relevant element varying between pairs, effects of masked and masking stimuli can be distinguished by means of the contralateral preponderance of the potentials evoked by the relevant elements, because the relevant elements may independently change sides in masked and masking stimuli. Based on a reanalysis of data from which only selected contralateral-ipsilateral effects had been previously published, the present contribution will provide a more complete picture of the ERP effects in a masked-priming task. Indeed, effects evoked by masked primes and masking targets heavily overlapped in conventional ERPs and could be disentangled to a certain degree by contralateral-ipsilateral differences. Their major component, the N2pc, is interpreted as indicating preferential processing of stimuli matching the target template, which process can neither be identified with conscious perception nor with shifts of spatial attention. The measurements showed that the triggering of response preparation by the masked stimuli did not depend on their discriminability, and their priming effects on the processing of the following target stimuli were qualitatively different for stimulus identification and for response preparation. These results provide another piece of evidence for the independence of motor-related and perception-related effects of masked stimuli.

This study addressed the role of motor representations in declarative memory (i.e., semantic and episodic). Based on embodied and grounded theories of cognition, it is often suggested that motor representations contribute to declarative memory. According to the action priming effect, graspable objects are categorised faster when primed by pictures of a congruent hand grip, as motor representations (how to grasp it) and semantic information (what it is) are closely related. Moreover, motor representations may contribute to episodic memory functioning. We immobilised participants' dominant hand for 24 hr to impair their processing of hand-related motor representations. This method is known to elicit rapid updating of cortical hand representations, and a slowdown in cognitive tasks linked to hand-related motor cognition. We expected to observe a decreased action priming effect following short-term hand nonuse. We further predicted that in a subsequent recognition task, objects that had been encoded following congruent action priming would be recognised faster by controls, but not by previously immobilised participants. Results did not show any effect of hand nonuse on action priming, suggesting that motor representations are not a decisive factor for this effect. Nonetheless, prime congruence influenced subsequent recognition. Immobilised participants were slower to recognise objects previously seen with an unrelated hand grip prime compared with a congruent one. This result suggests a contribution of motor representation to declarative memory, in particular when the sensorimotor system has previously been impaired.

Individually different weighting of multiple processes underlies effects of metacontrast masking.

Time course of free-choice priming effects explained by a simple accumulator model

An evolving view in cognitive neuroscience is that the dorsal visual pathway not only plays a key role in visuomotor behavior but that it also contributes functionally to the recognition of objects. To characterize the nature of the object representations derived by the dorsal pathway, we assessed perceptual performance in the context of the continuous flash suppression paradigm, which suppresses object processing in the ventral pathway while sparing computation in the dorsal pathway. In a series of experiments, prime stimuli, which were rendered imperceptible by the continuous flash suppression, still contributed to perceptual decisions related to the subsequent perceptible target stimuli. However, the contribution of the prime to perception was contingent on the prime's structural coherence, in that a perceptual advantage was observed only for targets primed by objects with legitimate 3-D structure. Finally, we obtained additional evidence to demonstrate that the processing of the suppressed objects was contingent on the magnocellular, rather than the parvocellular, system, further linking the processing of the suppressed stimuli to the dorsal pathway. Together, these results provide novel evidence that the dorsal pathway does not only support visuomotor control but, rather, that it also derives the structural description of 3-D objects and contributes to shape perception.

The activation of ageism and aging stereotypes in younger and older adults was investigated by manipulating both the valence and the stereotypicality of trait stimuli. Participants completed a lexical decision task in which the stimulus onset asynchronies (SOAs) between the prime and target stimuli were varied to examine the effects of automatic and controlled processing (300 and 2,000 ms, respectively). Both younger and older adults demonstrated strong stereotype activation for elderly stereotypes but relatively weak activation for young stereotypes. Both younger and older adults also demonstrated a positive bias toward older people, which was not moderated by SOA. These findings suggest that younger and older adults do not differ in their accessibility to aging stereotypes or to their age-based biases, which appear to be positive toward elderly people.

It is typically assumed that perception for action and object recognition are subserved by functionally and neuroanatomically distinct processing streams in the brain. However, recent evidence challenges this classical view and suggests an interaction between both visual processing streams. While previous studies showed an influence of object perception on action-related tasks, we investigated whether action representations facilitate visual object recognition. In order to address this question, two briefly displayed masked objects were sequentially presented, either affording congruent or incongruent motor interactions. We found superior naming accuracy for object pairs with congruent as compared to incongruent motor interactions (Experiment 1). This action priming effect indicates that action representations can facilitate object recognition. We further investigated the nature of the representations underlying this action priming effect. The effect was absent when the prime stimulus was presented as a word (Experiment 2). Thus, the action priming effect seems to rely on action representations specified by visual object information. Our findings suggest that processes of object-directed action influence object recognition.

Visual masking occurs when the perception of a brief target stimulus is affected by a preceding or succeeding mask. The uncoupling of the target and its perception allows an opportunity to investigate the neuronal mechanisms involved in sensory representation and visual perception. To determine whether rats are a suitable model for subsequent studies of the neuronal basis of visual masking, we first demonstrated that decoding of neuronal responses recorded in the primary visual cortex (V1) of anaesthetized rats predicted that orientation discrimination performance should decline when masking stimuli are presented immediately before or after oriented target stimuli. We then trained Long-Evans rats (n = 7) to discriminate between horizontal and vertical target Gabors or gratings. In some trials, a plaid mask was presented at varying stimulus onset asynchronies (SOAs) relative to the target. Spatially, the masks were presented either overlapping or surrounding the target location. In the absence of a mask, all animals could reliably discriminate orientation when stimulus durations were 16 ms or longer. In the presence of a mask, discrimination performance was impaired, but did not systematically vary with SOA as is typical of visual masking. In humans performing a similar task, we found visual masking impaired perception of the target at short SOAs regardless of the spatial or temporal configuration of stimuli. Our findings indicate that visual masking may be difficult to observe in rats as the stimulus parameters necessary to quantify masking will make the task so difficult that it prevents robust measurement of psychophysical performance. Thus, our results suggest that rats may not be an ideal model to investigate the effects of visual masking on perception.

Individual variation in inter-ocular suppression and sensory eye dominance

The authors investigated information processing in schizophrenia by studying 30 paranoid schizophrenic patients and 30 depressed inpatients. The basic methodology relied on tachistoscopic presentation of stimuli. First, the critical stimulus duration needed for identification of a target stimulus was determined. Second, when the target stimulus was followed by a masking stimulus, a measure of speed of information processing was obtained. The schizophrenic patients were imparied on input factors and speed of processing. The authors think it is unlikely that the results were due to medication effect or to gross psychopathology. Their discussion centers on how this two-factor deficit in information processing may result in cognitive disruption and how this study relates to other investigations.

Two experiments were conducted to examine laterality differences and practice effects under various central backward masking conditions. Critical stimulus onset asynchrony (SOA) was determined for subjects on 3 consecutive days using single letters as target stimuli (TS) and a pattern masking stimulus (MS). There was a right visual field (RVF) advantage on Day 1 but no difference between the visual fields on following days. The decline in the RVF advantage appeared to be dependent upon prior experience with laterally located letters, to be independent of initial experience with a particular set of letters, and to be more pronounced for females than for males. In addition, large improvements in performance were found, particularly between the first and second testing sessions. These practice effects were discussed in terms of the possible development of strategies for enhancing TS features or attenuating MS features.

An attempt was made to obtain Ll-shaped masking functions in two metacontrast experiments. Trained Ss judged whether a square test stimulus (TS) was bright or dim. The TS was presented alone or in conjunction with an adjacent pair of square masking stimuli (MS) whose energy equaled the bright TS. The stimulus onset asynchronies (SOA) ranged from 0 to 125 msec. The task minimized the role of apparent movement cues as a reliable basis for judgment. Similar studies have employed TS plus MS vs MS alone as the alternatives, allowing apparent movement to be a cue. Brightness accuracy was a If-shaped function of SOA. This finding is consistent with neural-net models (Weisstein, 1968). However, analysis of Ss' response bias suggested an alternative explanation involving the MS as a comparison stimulus at short SOA. It was concluded that U-shaped masking functions are also consistent with theories based upon independent component processes, e.g., Schurman and Eriksen (1970) and Uttal (1970).

Moving seamlessly between spoken number words and Arabic digits is common in everyday life. In this study, we systematically investigated the correspondence between auditory number words and visual Arabic digits in adults. Auditory number words and visual Arabic digits were presented concurrently or sequentially and participants had to indicate whether they described the same quantity. We manipulated the stimulus onset asynchronies (SOAs) between the two stimuli (Experiment 1: −500 ms to +500 ms; Experiment 2: −200 ms to +200 ms). In both experiments, we found a significant cross-modal distance effect. This effect was strongest for simultaneous stimulus presentation and decreased with increasing SOAs. Numerical distance emerged as the most consistent significant predictor overall, in particular for simultaneous presentation. However, physical similarity between the stimuli was often a significant predictor of response times in addition to numerical distance, and at longer SOAs, physical similarity between the stimuli was the only significant predictor. This shows that SOA modulates the extent to which participants access quantity representations. Our results thus support the idea that a semantic quantity representation of auditory and visual numerical symbols is activated when participants perform a concurrent matching task, while at longer SOAs participants are more likely to rely on physical similarity between the stimuli. We also investigated whether individual differences in the efficiency of the cross-modal processing were related to differences in mathematical performance. Our results are inconclusive about whether the efficiency of cross-format numerical correspondence is related to mathematical competence in adults.

Recent years, researches on ERP-based brain computer interface (BCI) were increasingly popular. Visual and auditory based multimodal stimuli paradigms have attracted more and more attention, while studies on the effect of experimental parameters on system performance of them were rarely reported. This study aims at investigating the effects of stimulus-onset asynchrony (SOA) on audiovisual stimuli based BCI system. Therefore, paradigms with different SOA were conducted with long SOA (1000ms), medium SOA (500ms) and short SOA (200ms) paradigms. Visual stimuli paradigms, auditory stimuli paradigms and audiovisual bimodal stimuli paradigms were also included in the study of SOA effect on BCI system. Fifteen healthy subjects participated in the experiment. We analyzed event-related potential (ERP) of mono-visual paradigm and audiovisual paradigm. Results revealed that SOA has no significant effect discrimination of target and non-target stimuli. We found that there is little difference in the latencies of the early components among distinct paradigms, but the difference is reflected in the amplitude which is mainly related to the type of stimulus. This study could provide theoretical guidance for the design of new paradigms on audiovisual bimodal BCI system.

The underlying specificity of visual object categorization and discrimination can be elucidated by studying different types of repetition priming. Here we focused on this issue in face processing. We investigated category priming (i.e. the prime and target stimuli represent different exemplars of the same object category) and item priming (i.e. the prime and target stimuli are exactly the same image), using an immediate repetition paradigm. Twenty-three subjects were asked to respond as fast and accurately as possible to categorize whether the target stimulus was a face or a building image, but to ignore the prime stimulus. We recorded event-related potentials (ERPs) and reaction times (RTs) simultaneously. The RT data showed significant effects of category priming in both face trials and building trials, as well as a significant effect of item priming in face trials. With respect to the ERPs, in face trials, no priming effect was observed at the P100 stage, whereas a category priming effect emerged at the N170 stage, and an item priming effect at the P200 stage. In contrast, in building trials, priming effects occurred already at the P100 stage. Our results indicated that distinct neural mechanisms underlie separable kinds of immediate repetition priming in face processing.