Early Stages Of Perceptual Processing Research Articles

Crossmodal Contextual Effects of Tactile Flankers on the Detection of Visual Targets

It is well known that detection of a central Gabor stimulus is modulated by the presence of collinear flanker stimuli. Target detection is facilitated when flanker stimuli are iso-oriented and aligned with the target at adequate spatial separations, suggesting the involvement of lateral interactions in early visual processing. Can such contextual effects of flankers on the target detection occur in a cross-modal setting (a central visual target and tactile flankers)? To address this, I investigated a variant of the lateral flanker paradigm using the visually presented line targets and tactile flanker lines. The results showed that tactile flankers facilitated the detection of visual target when the tactile flankers were collinear with the visual target, indicating the occurrence of cross-modal contextual modulation between vision and touch. The findings suggest that the integration process could occur at a relatively early perceptual processing stage of perceptual grouping.

Enhancement of perceptual representations by endogenous attention biases competition in response selection

Perception and response selection are core processes in the generation of overt behavior. Selective attention is known to facilitate behavioral performance by altering perceptual processes. It remains unclear, however, whether selective attention can aid the resolution of response conflict, and if so, at what stage of processing this takes place. In two experiments, an endogenous cuing task was combined with a flanker task to assess the interaction of selective attention with response selection. The results of Experiment 1 show that cuing reduces the flanker-congruency effect when the cue and flanker are presented in close temporal proximity to each other. The results of Experiment 2 demonstrate that pre- but not post-cuing the target reduced the congruency effect, showing that selective attention can affect performance, but is ineffective once stimulus processing has proceeded to response selection. Our results provide evidence that selective attention can aid the resolution of response conflict by altering early perceptual processing stages.

Perceptual Load-Dependent Neural Correlates of Distractor Interference Inhibition

BackgroundThe load theory of selective attention hypothesizes that distractor interference is suppressed after perceptual processing (i.e., in the later stage of central processing) at low perceptual load of the central task, but in the early stage of perceptual processing at high perceptual load. Consistently, studies on the neural correlates of attention have found a smaller distractor-related activation in the sensory cortex at high relative to low perceptual load. However, it is not clear whether the distractor-related activation in brain regions linked to later stages of central processing (e.g., in the frontostriatal circuits) is also smaller at high rather than low perceptual load, as might be predicted based on the load theory.Methodology/Principal FindingsWe studied 24 healthy participants using functional magnetic resonance imaging (fMRI) during a visual target identification task with two perceptual loads (low vs. high). Participants showed distractor-related increases in activation in the midbrain, striatum, occipital and medial and lateral prefrontal cortices at low load, but distractor-related decreases in activation in the midbrain ventral tegmental area and substantia nigra (VTA/SN), striatum, thalamus, and extensive sensory cortices at high load.ConclusionsMultiple levels of central processing involving midbrain and frontostriatal circuits participate in suppressing distractor interference at either low or high perceptual load. For suppressing distractor interference, the processing of sensory inputs in both early and late stages of central processing are enhanced at low load but inhibited at high load.

Decoding the neural correlates of consciousness

Multivariate pattern analysis (MVPA) is an emerging technique for analysing functional imaging data that is capable of a much closer approximation of neuronal activity than conventional methods. This review will outline the advantages, applications and limitations of MVPA in understanding the neural correlates of consciousness. MVPA has provided important insights into the processing of perceptual information by revealing content-specific information at early stages of perceptual processing. It has also shed light on the processing of memories and decisions. In combination with techniques to reconstruct viewed images, MVPA can also be used to reveal the contents of consciousness. The development of multivariate pattern analysis techniques allows content-specific and detailed information to be extracted from functional MRI data. This may lead to new therapeutic applications but also raises important ethical considerations.

Time course of affective processing bias in major depression: An ERP study

The current study investigated the time course of the affective processing bias in major depressive disorder (MDD) in a visual three-stimulus semantic oddball task using event-related potentials (ERPs). MDD patients showed decreased P1 latency over right posterior regions to negative relative to positive target stimuli, reflecting a very early onset of the negativity bias in emotional perception. Compared to controls, MDD patients showed enlarged anterior P2 amplitude to positive target stimuli, reflecting an affective bias in the early attentional stages of processing. In addition, MDD patients showed relatively high N2 and reduced P3 amplitudes to negative compared with positive target stimuli, as well as marginally reduced N2 amplitude to positive target stimuli compared with controls. This suggests that the negativity bias also occurs during later strategic evaluation stages. Therefore, the present study extended previous findings by demonstrating that the affective processing bias in MDD begins in the early stages of perceptual processing and continues at later cognitive stages.

Emotional conflict occurs at an early stage: Evidence from the emotional face–word Stroop task

The perceptual processing of emotional conflict was studied using electrophysiological techniques to measure event-related potentials (ERPs). The emotional face–word Stroop task in which emotion words are written in prominent red color across a face was use to study emotional conflict. In each trial, the emotion word and facial expression were either congruent or incongruent (in conflict). When subjects were asked to identify the expression of the face during a trial, the incongruent condition evoked a more negative N170 ERP component in posterior lateral sites than in the congruent condition. In contrast, when subjects were asked to identify the word during a trial, the incongruent condition evoked a less negative N170 component than the congruent condition. The present findings extend our understanding of the control processes involved in emotional conflict by demonstrating that differentiation of emotional congruency begins at an early perceptual processing stage.

The Prior Knowledge of the Reliability of Sensory Cues Affects the Multisensory Integration in the Early Perceptual Processing Stage

According to the statistically optimal integration theory,our brains weigh various sources of sensory information according to their reliabilities during multisensory integration.Recent behavioral studies have proposed that the prior knowledge about the reliability of different modalities can also play an important role in the weighting of different sensory information.The present study aimed to examine whether the prior knowledge affect multisensory integration in the early perceptual processing stage or in the post-perceptual processes stage.Fourteen participants (19-24 years old) were tested when a single letter ("B" or "E") was presented simultaneously in both auditory and visual modalities.The letter was displayed in one of the two colors.In one condition the visual information presented was always (probability of 100%) congruent with auditory information and this is the same for either color presented (equal-probability condition).In another condition,the probability in which the visual and auditory information was congruent was varied.The probability was 100% (high probability,HP) when the visual letter was in one color and the probability was 30% (low probability,HP) when the visual letter was in another color.Therefore different colors were associated with different probability (different-probability condition).The participants were instructed to press the button 1 for letter B and button 2 for letter E regardless of the color of the visual stimuli and regardless of the auditory information.Each participant completed 240 trials during equal-probability condition and 1500 trials (consisting of 5 experimental blocks) during different-probability condition.Significantly different responses to the congruent audiovisual stimuli were found between HP and LP and the difference was only observed during block 4 and block 5 of difference-probability condition.These results suggested the different probabilities of auditory-visual congruency modulate the response time to auditory-visual congruent stimuli,which suggested the prior knowledge regarding the reliability of sensory cues affects the multisensory integration in the early perceptual processing stage.

Working memory enhances visual perception: Evidence from signal detection analysis.

We show that perceptual sensitivity to visual stimuli can be modulated by matches between the contents of working memory (WM) and stimuli in the visual field. Observers were presented with an object cue (to hold in WM or to merely attend) and subsequently had to identify a brief target presented within a colored shape. The cue could be re-presented in the display, where it surrounded either the target (on valid trials) or a distractor (on invalid trials). Perceptual identification of the target, as indexed by A', was enhanced on valid relative to invalid trials but only when the cue was kept in WM. There was minimal effect of the cue when it was merely attended and not kept in WM. Verbal cues were as effective as visual cues at modulating perceptual identification, and the effects were independent of the effects of target saliency. Matches to the contents of WM influenced perceptual sensitivity even under conditions that minimized competition for selecting the target. WM cues were also effective when targets were less likely to fall in a repeated WM stimulus than in other stimuli in the search display. There were no effects of WM on decisional criteria, in contrast to sensitivity. The findings suggest that reentrant feedback from WM can affect early stages of perceptual processing.

Short Article: Attentional Orientation Induced by Temporarily Established Self-Referential Cues

Self-referential stimuli such as self-face surpass other-referential stimuli in capture of attention, which has been attributed to attractive perceptual features of self-referential stimuli. We investigated whether temporarily established self-referential stimuli are different from other-referential cues in guiding voluntary visual attention. Temporarily established self-referential or friend-referential shapes served as central cues in Posner's endogenous cueing task. We found that, relative to friend-referential cues, self-referential cues induced smaller cueing effect (i.e., the difference in reaction times to targets at cued and uncued locations) when the interstimulus interval was short but larger cueing effect when the interstimulus interval was long. Our findings suggest that temporarily established self-referential cues are more efficient to capture reflexive attention at the early stage of perceptual processing and to shift voluntary attention at the later stage of perceptual processing.

Numerical magnitude modulates temporal comparison: An ERP study

Time is believed to be a part of the generalized magnitude system just like space and quantity. Previous research suggests that time perception can be affected by magnitude in some non-temporal dimensions. Here we address two questions. First, could the influence be caused by an abstract magnitude component without perceptual variables? Second, what are the underlying mechanisms of the influence? Participants compared a pair of durations defined by two Arabic digits in a hundreds of milliseconds range. They performed more accurately when the shorter durations were defined by lower numeric value digits (small digits) and the longer durations were defined by higher value digits (large digits) than they did in the reversed condition. Event-Related Potential (ERP) results showed that the CNVs corresponding to the first duration (CNV1), to the second duration (CNV2) and the N1 were all enhanced when durations marked by small digits than that marked by large ones. Combining the electrophysiological data with the behavioral results, we suggest that digits can modulate performance of temporal comparison at the relatively early stage of perceptual processing. One possible explanation of the current results is that selective temporal attention and subsequent expectation may be involved in this modulation.

Implicit learning modulates selective attention at sensory levels of perceptual processing

Electrophysiological evidence suggests that attention can be modulated as early as 100 msec after stimulus presentation. However, it is not clear whether these changes are based primarily on stimulus properties such as perceptual load (i.e., the level of perceptual difficulty), or other properties, such as general attentional set or learned expectations concerning perceptual load. Using event-related potentials, this study examined how implicit learning of perceptual load conditions modulates selective attention at sensory levels of perceptual analysis. The results show significant differences in P1 amplitude recorded over occipital areas of the brain as a function of learned expectations of perceptual load, only when perceptual load could be reliably predicted by the preceding stimuli. Moreover, differences in processing were found when both low and high perceptual load conditions could be predicted. These findings suggest that implicit learning modulates the allocation of attention at early stages of perceptual processing.

Lexical effects on auditory speech perception: An electrophysiological study

Lexical information can bias categorization of an ambiguous phoneme and subsequently evoke a shift in the phonetic boundary. Here, we explored the extent to which this phenomenon is perceptual in nature. Listeners were asked to ignore auditory stimuli presented in a typical oddball sequence in which the standard was an ambiguous sound halfway between /t/ and /p/ embedded in a Dutch word normally ending in /t/ ('vloot', meaning 'fleet') or /p/ ('hoop', meaning 'hope'). As deviant served the non-ambiguous sound /t/ embedded in the same context. The amplitude of the MMN-response, indexing the perceptual difference between the ambiguous sound and unambiguous /t/ was bigger for the p-word 'hoop' than the t-word 'vloot'. This result is taken as an indication that lexical information actually reached down to early perceptual processing stages.

Timbre priming effects and expectation in melody

In this study, participants identified the timbre of pitches when they occurred in isolation, and again when they occurred appended to short melodies. For pitches congruent with the melody, timbre identification generally improved when the pitches were appended to the melody in comparison to when they occurred in isolation. In addition, the amount of improvement was broadly consistent with theoretical accounts of the degree to which the pitches were expected, given the preceding melody. This finding relates both to proposed interactions in processing between pitch and timbre, and to theoretical work regarding melodic expectations. It suggests that melodic expectations can be revealed implicitly, and is consistent with the idea that they operate at a relatively early stage of perceptual processing. In this study, priming effects were shown in listeners without musical training, demonstrating that expectations can develop in response to passive exposure to music, not only in response to formal training.

Does Location Cueing Increase the Efficiency of the Early Stages of Perceptual Processing?

Previous research has shown that precueing a stimulus's location in an otherwise empty field leads to more efficient detection of that stimulus. The experiments reported here sought to determine whether or not such cueing affects the early stages(s) of perception. If cueing affects early perceptual processing, then the effect of cueing should be larger the more difficult the perceptual task; otherwise it should not. Experiment 1 failed to find any facilitation due to cueing, but did find significant inhibition from invalid cues. The size of the inhibition did not differ significantly as a function of perceptual difficulty. Experiment 2 employed a less attention-demanding type of cueing and found significant facilitation as well as inhibition. As in the first experiment, the size of the cueing effect did not differ significantly as a function of difficulty. Experiment 3 used a stronger manipulation of difficulty and obtained essentially the same results. However, there was some tendency for the effect of cueing to be larger in the more difficult condition. Experiment 4 tested the possibility that this tendency occurred because the perceptual task was so difficult it required voluntary eye movements. When the possible role of eye movements was minimized, there was no tendency for the effect of cueing to be larger in the difficult than in the easy condition. In Experiment 5 the possibility of eye movements was reduced even further and again, found no significant interaction between cueing and difficulty. It was concluded that cueing does not facilitate early perceptual processing. Rather, cueing affects the efficiency with which stimuli are selected for further processing from an unlimited capacity perceptual system to a limited capacity system.

Can attention be allocated to sensory modalities?

Three experiments examined the effects of attention allocation to the modalities of vision, audition, and touch. The first two experiments utilized a simultaneous-successive comparison. The simultaneous procedure involved simultaneous monitoring of all three sensory modalities for the presence of a near-threshold stimulus. The successive condition allowed S to give his full attention to each sensory modality in turn. There was no advantage for the successive condition, whether the task consisted of detection of a single stimulus (Experiment I) or detection of the absence of one of many stimuli (Experiment II). Experiment III used a different paradigm to extend these results and bridge the gap between these results, those of Eijkman and Vendrik (1965), and those of Moray (1973a, b). We concluded that selective allocation of attention to sensory modalities does not affect the early stages of perceptual processing.