Early Stages Of Perceptual Processing Research Articles

Dissociable Neural Mechanisms Underlie the Effects of Attention on Visual Appearance and Response Bias.

A prominent theoretical framework spanning philosophy, psychology, and neuroscience holds that selective attention penetrates early stages of perceptual processing to alter the subjective visual experience of behaviorally relevant stimuli. For example, searching for a red apple at the grocery store might make the relevant color appear brighter and more saturated compared with seeing the exact same red apple while searching for a yellow banana. In contrast, recent proposals argue that data supporting attention-related changes in appearance reflect decision- and motor-level response biases without concurrent changes in perceptual experience. Here, we tested these accounts by evaluating attentional modulations of EEG responses recorded from male and female human subjects while they compared the perceived contrast of attended and unattended visual stimuli rendered at different levels of physical contrast. We found that attention enhanced the amplitude of the P1 component, an early evoked potential measured over visual cortex. A linking model based on signal detection theory suggests that response gain modulations of the P1 component track attention-induced changes in perceived contrast as measured with behavior. In contrast, attentional cues induced changes in the baseline amplitude of posterior alpha band oscillations (∼9-12 Hz), an effect that best accounts for cue-induced response biases, particularly when no stimuli are presented or when competing stimuli are similar and decisional uncertainty is high. The observation of dissociable neural markers that are linked to changes in subjective appearance and response bias supports a more unified theoretical account and demonstrates an approach to isolate subjective aspects of selective information processing.SIGNIFICANCE STATEMENT Does attention alter visual appearance, or does it simply induce response bias? In the present study, we examined these competing accounts using EEG and linking models based on signal detection theory. We found that response gain modulations of the visually evoked P1 component best accounted for attention-induced changes in visual appearance. In contrast, cue-induced baseline shifts in alpha band activity better explained response biases. Together, these results suggest that attention concurrently impacts visual appearance and response bias, and that these processes can be experimentally isolated.

On the origin of the Helmholtz’s square illusion: An attentional account

A square filled with parallel horizontal or vertical lines appears perceptually extended in the direction orthogonal to the lines. Here, we suggest that this Helmholtz illusion arises due to changes in spatial attention that entail changes at very early stages of perceptual processing. Three experiments are reported which tested this assumption. In Experiment1 and Experiment2, transient attentional cues were flashed in such a way that they either promoted (congruent condition) or hindered (incongruent condition) the attentional state presumably induced by the target objects. We predicted a decline of the illusion in the incongruent condition compared with the congruent condition. This prediction was confirmed in both experiments. However, the influence of (in)congruent attention cuing on the Helmholtz illusion depended on more sustained distributions of attention as well. An influence of sustained attention on the illusion was confirmed in Experiment 3, in which changes of attentional focus were induced by a secondary task. Overall, the results were consistent with our claim that the origin of the Helmholtz illusion is closely linked to the distribution of spatial attention.

Emotional content overrides spatial attention.

Spatial attention is our capacity to attend to or ignore particular regions of our spatial environment. However, some classes of stimuli may be able to override our efforts to ignore them. Here we assessed the relationship between involuntary attentional capture with emotional images and spatial attention at early stages of perceptual processing. Multiple scenes of unpleasant and neutral content were displayed in rapid serial visual presentation (RSVP) streams that elicited the steady-state visual evoked potential (SSVEP), a neural marker of selective attention at early visual areas. In a spatial cueing task, participants were cued to covertly attend to RSVP streams presented at 4 and 6Hz presentation rates in the left and right visual hemifields. The task was to detect square targets occasionally displayed within the image streams, responding only to those appearing on the cued side. The RSVP streams were always neutral pictures in one visual hemifield but would unpredictably switch from neutral to aversive content in the other visual hemifield. We found that SSVEP amplitude was consistently modulated by a change in emotional valence of image streams, regardless of whether the change in content occurred in the attended or unattended spatial location, reflecting an automatic sensory amplification for affective stimuli. The present data provide further evidence in support that emotional images can attract visual processing resources independently of spatial attention allocation, and are consistent with sustained sensory facilitation of early visual areas through re-entrant feedback projections from higher-order cortical areas involved in the extraction of affective information.

The influence of the cross-modal emotional pre-preparation effect on audiovisual integration.

Previous studies have shown that the cross-modal pre-preparation effect is an important factor for audiovisual integration. However, the facilitating influence of the pre-preparation effect on the integration of emotional cues remains unclear. Therefore, this study examined the emotional pre-preparation effect during the multistage process of audiovisual integration. Event-related potentials (ERPs) were recorded while participants performed a synchronous or asynchronous integration task with fearful or neutral stimuli. The results indicated that, compared with the sum of the unisensory presentation of visual (V) and auditory (A) stimuli (A+V), only fearful audiovisual stimuli induced a decreased N1 and an enhanced P2; this was not found for the neutral stimuli. Moreover, the fearful stimuli triggered a larger P2 than the neutral stimuli in the audiovisual condition, but not in the sum of the combined (A+V) waveforms. Our findings imply that, in the early perceptual processing stage and perceptual fine processing stage, fear improves the processing efficiency of the emotional audiovisual integration. In the last cognitively assessing stage, the fearful audiovisual induced a larger late positive component (LPC) than the neutral audiovisual. Moreover, the asynchronous-audiovisual induced a greater LPC than the synchronous-audiovisual during the 400-550 ms period. The different integration effects between the fearful and neutral stimuli may reflect the existence of distinct mechanisms of the pre-preparation in terms of the emotional dimension. In light of these results, we present a cross-modal emotional pre-preparation effect involving a three-phase emotional audiovisual integration.

Late attentional processes potentially compensate for early perceptual multisensory integration deficits in children with autism: evidence from evoked potentials

Sensory processing deficits and altered long-range connectivity putatively underlie Multisensory Integration (MSI) deficits in Autism Spectrum Disorder (ASD). The present study set out to investigate non-social MSI stimuli and their electrophysiological correlates in young neurotypical adolescents and adolescents with ASD. We report robust MSI effects at behavioural and electrophysiological levels. Both groups demonstrated normal behavioural MSI. However, at the neurophysiological level, the ASD group showed less MSI-related reduction of the visual P100 latency, greater MSI-related slowing of the auditory P200 and an overall temporally delayed and spatially constrained onset of MSI. Given the task design and patient sample, and the age of our participants, we argue that electro-cortical indices of MSI deficits in ASD: (a) can be detected in early-adolescent ASD, (b) occur at early stages of perceptual processing, (c) can possibly be compensated by later attentional processes, (d) thus leading to normal MSI at the behavioural level.

Covert Spatial Attention Speeds Target Individuation.

Covert spatial attention has long been thought to speed visual processing. Psychophysics studies have shown that target information accrues faster at attended locations than at unattended locations. However, with behavioral evidence alone, it is difficult to determine whether attention speeds visual processing of the target or subsequent postperceptual stages of processing (e.g., converting sensory responses into decision signals). Moreover, although many studies have shown that attention can boost the amplitude of visually evoked neural responses, no robust effect has been observed on the latency of those neural responses. Here, we offer new evidence that may reconcile the neural and behavioral findings. We examined whether covert attention influenced the latency of the N2pc component, an electrophysiological marker of visual selection that has been linked with object individuation-the formation of an object representation that is distinct from the background and from other objects in the scene. To this end, we manipulated whether or not human observers (male and female) covertly attended the location of an impending search target. We found that the target evoked N2pc onset ∼20 ms earlier when the target location was cued than when it was not cued. In a second experiment, we provided a direct replication of this effect, confirming that the effect of attention on N2pc latency is robust. Thus, although attention may not speed the earliest stages of sensory processing, attention does speed the critical transition between raw sensory encoding and the formation of individuated object representations.SIGNIFICANCE STATEMENT Covert spatial attention improves processing at attended locations. Past behavioral studies have shown that information about visual targets accrues faster at attended than at unattended locations. However, it has remained unclear whether attention speeds perceptual analysis or subsequent postperceptual stages of processing. Here, we present robust evidence that attention speeds the N2pc, an electrophysiological signal that indexes the formation of individuated object representations. Our findings show that attention speeds a relatively early stage of perceptual processing while also elucidating the specific perceptual process that is speeded.

Circadian misalignment impairs ability to suppress visual distractions.

Evening-type individuals often perform poorly in the morning because of a mismatch between internal circadian time and external social time, a condition recognized as social jet lag. Performance impairments near the morning circadian (~24hr) trough have been attributed to deficits in attention, but the nature of the impairment is unknown. Using electrophysiological indices of attentional selection (N2pc) and suppression (PD ), we show that evening-type individuals have a specific disability in suppressing irrelevant visual distractions. More specifically, evening-type individuals managed to suppress a salient distractor in an afternoon testing session, as evidenced by a PD , but were less able to suppress the distractor in a morning testing session, as evidenced by an attenuated PD and a concomitant distractor-elicited N2pc. Morning chronotypes, who would be well past their circadian trough at the time of testing, did not show this deficit at either test time. These results indicate that failure to filter out irrelevant stimuli at an early stage of perceptual processing contributes to impaired cognitive functioning at nonoptimal times of day and may underlie real-world performance impairments, such as distracted driving, that have been associated with circadian mismatch.

Where is the disadvantage for reduced pronunciation variants in spoken-word recognition? On the neglected role of the decision stage in the processing of word-form variation

ABSTRACTThis study examines the role of the decision stage in the recognition of reduced pronunciation variants, specifically variants produced with nasal flaps (e.g. “counter” produced as “couner”). We investigate whether the previously reported disadvantage for nasally flapped variants is located at an early perceptual processing stage or at a post-perceptual decision stage. Experiment 1 replicates the variant effect with a lexical decision task. Experiment 2 uses the psychological refractory period paradigm, suggesting that the variant effect is located at a stage that requires central processing resources. Experiment 3 employed the shadowing task, indicating a significantly smaller variant effect compared to the lexical decision task. In concert, our results suggest that the disadvantage for nasally flapped variants has at least in part a decisional locus, which challenges representational and perceptual accounts of the effect. A mechanism is discussed that describes how decisional factors could cause the disadvantage for reduced variants.

Human amygdala response to unisensory and multisensory emotion input: No evidence for superadditivity from intracranial recordings

The amygdala is crucially implicated in processing emotional information from various sensory modalities. However, there is dearth of knowledge concerning the integration and relative time-course of its responses across different channels, i.e., for auditory, visual, and audiovisual input. Functional neuroimaging data in humans point to a possible role of this region in the multimodal integration of emotional signals, but direct evidence for anatomical and temporal overlap of unisensory and multisensory-evoked responses in amygdala is still lacking. We recorded event-related potentials (ERPs) and oscillatory activity from 9 amygdalae using intracranial electroencephalography (iEEG) in patients prior to epilepsy surgery, and compared electrophysiological responses to fearful, happy, or neutral stimuli presented either in voices alone, faces alone, or voices and faces simultaneously delivered. Results showed differential amygdala responses to fearful stimuli, in comparison to neutral, reaching significance 100–200 ms post-onset for auditory, visual and audiovisual stimuli. At later latencies, ∼400 ms post-onset, amygdala response to audiovisual information was also amplified in comparison to auditory or visual stimuli alone. Importantly, however, we found no evidence for either super- or subadditivity effects in any of the bimodal responses. These results suggest, first, that emotion processing in amygdala occurs at globally similar early stages of perceptual processing for auditory, visual, and audiovisual inputs; second, that overall larger responses to multisensory information occur at later stages only; and third, that the underlying mechanisms of this multisensory gain may reflect a purely additive response to concomitant visual and auditory inputs. Our findings provide novel insights on emotion processing across the sensory pathways, and their convergence within the limbic system.

Semantic Knowledge Enhances Conscious Awareness of Visual Objects.

It is becoming increasingly established that information from long-term memory can influence early perceptual processing, a finding that is in line with recent theoretical approaches to cognition such as the predictive coding framework. Notwithstanding, the impact of semantic knowledge on conscious perception and the temporal dynamics of such an influence remain unclear. To address this question, we presented pictures of novel objects to participants as the second of two targets in an attentional blink paradigm. We found that associating newly acquired semantic knowledge to objects increased overall conscious detection in comparison to objects associated with minimal knowledge while controlling for object familiarity. Additionally, event-related brain potentials revealed a corresponding modulation beginning 100 msec after stimulus presentation in the P1 component. Furthermore, the size of this modulation was correlated with participant's subjective reports of conscious perception. These findings suggest that semantic knowledge can shape the contents of consciousness by affecting early stages of perceptual processing.

Predictability and probability modulate the neural responses to other’s pain: An event-related potential investigation

Two ERP experiments were designed to explore the effect of predictability (Exp1) and probability (Exp2) on the perception of others’ pain, respectively. In Exp1, we compared the ERP responses to painful and non-painful pictures when they were fully predictable and fully unpredictable. Results revealed that when the valence of the pictures (painful or non-painful) was fully predictable, the amplitudes of N2 and P3 components triggered by the painful pictures were significantly more positive than the amplitudes of N2 and P3 components triggered by the non-painful ones. When the valence of the pictures was fully unpredictable, the amplitudes of N2 and P3 triggered by the painful and the non-painful pictures were comparable. Besides, the P3 amplitude was positively correlated with the scores of empathy trait (i.e., personal distress). In Exp2, the probability of the presentation of a painful picture was manipulated as low (30%), medium (60%) and high (90%). Results showed that with the increase in the probability of a painful picture’s presentation, the amplitude of N2 elicited decreased. No significant effect was observed on P3. These findings indicated that the early perceptual processing stage reflected in N2 was more likely to be a threat-detection stage, while the later stage reflected in P3 may actually be the stage in which participant empathized other’s pain. Moreover, the more expected pain of others induced stronger empathic responses reflected in the P3. To the best of our knowledge, this study offers the very first psychophysical evidence of the predictability and probability’s effect on pain empathy.

Neural Correlates of Emotion Processing in Word Detection Task.

In our previous study, we have proposed a three-stage model of emotion processing; in the current study, we investigated whether the ERP component may be different when the emotional content of stimuli is task-irrelevant. In this study, a dual-target rapid serial visual presentation (RSVP) task was used to investigate how the emotional content of words modulates the time course of neural dynamics. Participants performed the task in which affectively positive, negative, and neutral adjectives were rapidly presented while event-related potentials (ERPs) were recorded from 18 undergraduates. The N170 component was enhanced for negative words relative to positive and neutral words. This indicates that automatic processing of negative information occurred at an early perceptual processing stage. In addition, later brain potentials such as the late positive potential (LPP) were only enhanced for positive words in the 480–580-ms post-stimulus window, while a relatively large amplitude signal was elicited by positive and negative words between 580 and 680 ms. These results indicate that different types of emotional content are processed distinctly at different time windows of the LPP, which is in contrast with the results of studies on task-relevant emotional processing. More generally, these findings suggest that a negativity bias to negative words remains to be found in emotion-irrelevant tasks, and that the LPP component reflects dynamic separation of emotion valence.

Neurophysiological evidence for enhanced tactile acuity in early blindness in some but not all haptic tasks

Previous research assessing the presence of enhanced tactile skills in early-blind (EB) population obtained conflicting results. Most of the studies relied on behavioral measures with which different mechanisms leading to the same outcome go unnoticed. Moreover, the scarce electrophysiological research that has been conducted focused exclusively on the processing of microgeometric properties. To clarify the extent of superior tactile abilities in EBs using high-density multichannel electrophysiological recordings, the present study compared the electrophysiological correlates of EBs and sighted controls (CON) in two tactile discrimination tasks that targeted microgeometric (texture) and macrogeometric (shape) properties. After a restricted exploration (haptic glance), participants judged whether a touched stimulus corresponded to an expected stimulus whose name had been previously presented aurally. In the texture discrimination task, differences between groups emerged at ∼75 ms (early perceptual processing stages) whereas we found no between-group differences during shape discrimination. Furthermore, for the first time, we were able to determine the latency at which EBs started to discriminate micro- (EB: 170 ms; CON: 230 ms) and macrogeometric (EB: 250 ms; CON: 270 ms) properties. Altogether, the results suggest different electrophysiological signatures during texture (but not shape) discrimination in EBs, possibly due to cortical reorganization in occipital areas and their increased connectivity with S1.

Influence of inhibitory tagging (IT) on emotional and cognitive conflict processing: Evidence from event-related potentials.

Inhibitory tagging (IT), a flexible central control mechanism based on the current task goals, reduces the cognitive conflict effect at the cued location by blocking the incompatible stimulus-response (S-R) code. However, it is unknown whether IT has a similar effect on emotional conflict. Thus, we combined the face-word Stroop task with the manipulation of inhibition of return (IOR) and used event-related potential (ERP) technology to simultaneously examine the modulation effect of IT on emotional and cognitive conflict processing. At the cued location, we found that the two types of conflict effect were significantly reduced and that the conflict processing-related N450 effect was absent. Our data further revealed that IT had similar effects on emotional and cognitive conflict processing. Although a negative difference wave (Nd) was found in the time window of 160 and 220ms, which may reflect the impaired early perceptual processing of the target at the cued location, the effect of Nd was not affected by stimulus congruency. These results illustrate that the cueing effect of conflict processing does not arise from the early stage of perceptual processing, but rather results from the blocked S-R code of the distractors due to IT functioning during the later stage of processing.

Effects of valence and arousal on emotional word processing are modulated by concreteness: Behavioral and ERP evidence from a lexical decision task

We investigated whether the effects of valence and arousal on emotional word processing are modulated by concreteness using event-related potentials (ERPs). The stimuli included concrete words (Experiment 1) and abstract words (Experiment 2) that were organized in an orthogonal design, with valence (positive and negative) and arousal (low and high) as factors in a lexical decision task. In Experiment 1, the impact of emotion on the effects of concrete words mainly resulted from the contribution of valence. Positive concrete words were processed more quickly than negative words and elicited a reduction of N400 (300–410ms) and enhancement of late positive complex (LPC; 450–750ms), whereas no differences in response times or ERPs were found between high and low levels of arousal. In Experiment 2, the interaction between valence and arousal influenced the impact of emotion on the effects of abstract words. Low-arousal positive words were associated with shorter response times and a reduction of LPC amplitudes compared with high-arousal positive words. Low-arousal negative words were processed more slowly and elicited a reduction of N170 (140–200ms) compared with high-arousal negative words. The present study indicates that word concreteness modulates the contributions of valence and arousal to the effects of emotion, and this modulation occurs during the early perceptual processing stage (N170) and late elaborate processing stage (LPC) for emotional words and at the end of all cognitive processes (i.e., reflected by response times). These findings support an embodied theory of semantic representation and help clarify prior inconsistent findings regarding the ways in which valance and arousal influence different stages of word processing, at least in a lexical decision task.

Attachment affects social information processing: Specific electrophysiological effects of maternal stimuli

Attachment is critical to each individual. It affects the cognitive-affective processing of social information. The present study examines how attachment affects the processing of social information, specifically maternal information. We assessed the behavioral and electrophysiological responses to maternal information (compared to non-specific others) in a Go/No-go Association Task (GNAT) with 22 participants. The results illustrated that attachment affected maternal information processing during three sequential stages of information processing. First, attachment affected visual perception, reflected by enhanced P100 and N170 elicited by maternal information as compared to others information. Second, compared to others, mother obtained more attentional resources, reflected by faster behavioral response to maternal information and larger P200 and P300. Finally, mother was evaluated positively, reflected by shorter P300 latency in a mother + good condition as compared to a mother + bad condition. These findings indicated that the processing of attachment-relevant information is neurologically differentiated from other types of social information from an early stage of perceptual processing to late high-level processing.

Effect of Cognitive Aging on Working Memory Consolidation

This study was conducted to investigate the hypothesis that the decline in memory consolidation in aging may be determined by the reduction of inhibitory control processes. To this end an Attentional Blink (AB) paradigm was employed. AB effect was more pronounced and lengthened for older adults (60–85 years) than young (18–22 years) and middle aged (45–55 years) groups, which could be due to interference at the perceptual stage itself. The onset of the first target involuntarily captures attentional resources, impairing subsequent target identification due to decrease in inhibitory control. Experiment 2 was conducted manipulating perceptual load in working memory to study interference as a function of load. The effect of load was more pronounced for older and middle-aged adults. The decline in memory consolidation in this group may be due to difficulties in early stages of perceptual processing, inhibitory control and unsuccessful suppression of irrelevant stimuli. These effects were also observed among middle-aged individuals.

Emotional Voice Processing: Investigating the Role of Genetic Variation in the Serotonin Transporter across Development

The ability to effectively respond to emotional information carried in the human voice plays a pivotal role for social interactions. We examined how genetic factors, especially the serotonin transporter genetic variation (5-HTTLPR), affect the neurodynamics of emotional voice processing in infants and adults by measuring event-related brain potentials (ERPs). The results revealed that infants distinguish between emotions during an early perceptual processing stage, whereas adults recognize and evaluate the meaning of emotions during later semantic processing stages. While infants do discriminate between emotions, only in adults was genetic variation associated with neurophysiological differences in how positive and negative emotions are processed in the brain. This suggests that genetic association with neurocognitive functions emerges during development, emphasizing the role that variation in serotonin plays in the maturation of brain systems involved in emotion recognition.

Early and late stages of visual processing in individuals in prodromal state and first episode schizophrenia: An ERP study

BackgroundP300 deficits in schizophrenia patients are well established, especially in the auditory modality. Several studies have also reported P300 abnormalities in schizophrenia in visual tasks, but these findings are inconsistent. Furthermore, reports on P300 in visual modality in prodromal subjects are very limited. While P300 indexes relatively late and complex cognitive functions such as context updating in working memory, sensory-evoked components such as the P1/N1 primarily index early stages of perceptual processing. Several previous studies suggest that P300 reduction in schizophrenia patients may be dissociable from these earlier components. Therefore, in this study, we measured the P300 component as well as the P1/N1 in a visual oddball paradigm in prodromal subjects and first episode schizophrenia patients, and compared them with those of healthy controls. MethodVisual P300 and P1/N1 were obtained from prodromal (PRO, n=23), first episode schizophrenia patients (SZ, n=17), and healthy control subjects (HC, n=31), who silently counted infrequent target stimuli (“X”) amid standard stimuli (“Y”) presented on the screen while 64-channel EEG was recorded. ResultsBoth PRO and SZ subjects showed reduced P300 amplitudes and delayed P300 peak latencies in comparison to control subjects. On the other hand, N1 amplitude was significantly reduced only in SZ but not in PRO. Increased severity of positive symptoms was significantly associated with smaller P300 amplitude in PRO. ConclusionsThese results suggest that visual P300 is affected already at the prodromal stage and could be a marker of the prodromal phase of schizophrenia.

Indiscriminable sounds determine the direction of visual motion

On cross-modal interactions, top-down controls such as attention and explicit identification of cross-modal inputs were assumed to play crucial roles for the optimization. Here we show the establishment of cross-modal associations without such top-down controls. The onsets of two circles producing apparent motion perception were accompanied by indiscriminable sounds consisting of six identical and one unique sound frequencies. After adaptation to the visual apparent motion with the sounds, the sounds acquired a driving effect for illusory visual apparent motion perception. Moreover, the pure tones with each unique frequency of the sounds acquired the same effect after the adaptation, indicating that the difference in the indiscriminable sounds was implicitly coded. We further confrimed that the aftereffect didnot transfer between eyes. These results suggest that the brain establishes new neural representations between sound frequency and visual motion without clear identification of the specific relationship between cross-modal stimuli in early perceptual processing stages.