Interstimulus Interval Effect on Event-Related Potential N270 in a Color Matching Task

Choice overload interferes with early processing and necessitates late compensation: Evidence from electroencephalogram

Having a multitude of choices can be advantageous, yet an abundance of options can be detrimental to the decision-making process. Based on existing research, the present study combined electroencephalogram and self-reported methodologies to investigate the neural mechanisms underlying the phenomenon of choice overload. Behavioural data suggested that an increase in the number of options led to negative evaluations and avoidance of choice tendencies, even in the absence of time pressure. Event-related potential results indicated that the large choice set interfered with the early visual process, as evidenced by the small P1 amplitude, and failed to attract more attentional resources in the early stage, as evidenced by the small amplitude of P2 and N2. However, the LPC amplitude was increased in the late stage, suggesting greater investment of attentional resources and higher emotional arousal. Multivariate pattern analysis revealed that the difference between small and large choice set began at around 120 ms, and the early and late stages were characterised by opposite activation patterns. This suggested that too many options interfered with early processing and necessitate continued processing at a later stage. In summary, both behavioural and event-related potential (ERP) results confirm the choice overload effect, and it was observed that individuals tend to subjectively exaggerate the choice overload effect.

Task Demands Differentially Affect Processing of Intrinsic and Extrinsic Object Features in Working Memory

Some argue that visual working memory operates on integrated object representations. Here, we contend that obligatory feature integration occurs with intrinsic but not extrinsic object features. Working memory for shapes and colors was assessed using a change-detection task with a central test probe, while recording event-related potentials (ERPs). Color was either an intrinsic surface feature of a shape or connected to the shape via a proximal but spatially disjunct extrinsic frame. There were two types of test: The direct test required memory for shape and color; the indirect test required only shape memory. Study-test changes of color were therefore either task-relevant or task-irrelevant. We assessed performance costs and event-related potential (ERP) effects arising from color changes. In the direct test, performance was poorer for extrinsic than intrinsic stimuli; task-relevant color changes elicited enhanced frontal negativity (N2, FN400) for both intrinsic and extrinsic stimuli. In the indirect test, performance costs and ERP effects associated with irrelevant color change were larger for intrinsic than extrinsic stimuli. This suggests intrinsic information is more readily integrated into the working-memory representation and evaluated against the test probe. Findings imply that feature integration is not obligatory under all conditions but influenced by stimulus-driven and task-related focus of attention.

How does the use of simultaneous contrast illusion on product-background color combination nudge consumer behavior? A behavioral and event-related potential study

Color, as one of the most critical visual factors influencing consumer decisions, has been widely used in e-commerce marketing. However, the effects of product-background saturation combination on consumers’ willingness to purchase products with different heaviness attributes (e.g., heaviness-positive products or heaviness-negative products) have not been conclusively determined. The current study demonstrated the effects of product-background saturation combination on product heaviness perception and its downstream consequences. Based on behavioral method, study 1 showed that a patch of color placed in a pale background (the saturation of the background is lower than the saturation of the color patch) was perceived as visually heavier than that in a colorful background (the saturation of the background is higher than the saturation of the color patch). Study 2 applied event-related potentials (ERPs) method to explore the underlying neural mechanisms of how the interactions between the presentation modes and the product types affect consumer decisions. Behaviorally, compared to the colorful background, the pale background would lead to a higher purchase rate for the heaviness-positive products, whereas the opposite results were found for the heaviness-negative products. Furthermore, for both the heaviness-positive and heaviness-negative products, a shorter reaction time would be observed in the pale background condition than in the colorful background condition. Neurophysiologically, the pale background would result in smaller N2 component and larger P3 component compared to the colorful background for the heaviness-positive products, while the reverse held for the heaviness-negative products. Smaller N2 component implies decreased perceptual conflicts and larger P3 component implies increased decision confidence, suggesting that e-retailers should present heaviness-positive products with pale backgrounds and heaviness-negative products with colorful backgrounds.

Feature-based information filtering in visual working memory is impaired in Parkinson's disease

Increasing attention has been given to working memory (WM) impairment in Parkinson's disease (PD) patients. Previous studies revealed that the space-orientated feature-based filtering (target and distractors in distinct locations) was impaired in PD patients. However, the object-orientated feature-based filtering (target and distractor information pertaining to one object) ability in PD patients remains unclear. In this study, we examined the object-orientated feature-based filtering ability of 14 PD patients and 14 healthy controls in a change detection task under EEG monitoring. Participants were asked to remember the colors of two different objects while ignoring their shapes. Critically, the irrelevant feature could be changed in the probe. A failure in complete feature-based filtering would lead to an "irrelevant-change distracting effect," where the change of the irrelevant feature would impair the performance of the target feature, and lead to an enhanced anterior N2. We found that the distracting effect was larger in PD patients than in the control group in terms of d'; however, the N2 amplitude evoked by the irrelevant change was smaller in PD patients than in the control group. These results suggested that the object-orientated feature-based filtering ability was impaired in PD, which might derive from the deficit of their executive control.

Neural adaptation to non-symbolic number and visual shape: an electrophysiological study

Several studies assumed that the analysis of numerical information happens in a fast and automatic manner in the human brain. Utilizing the high temporal resolution of electroencephalography (EEG) in a passive oddball adaptation paradigm, we compared event-related brain potentials (ERPs) evoked by unattended shape changes and unattended numerosity changes. We controlled visual stimulus properties in a stringent manner. Unattended changes in shape elicited significant, gradual adaptation effects in the range of early visual components, indicating the fast and automatic processing of shapes. Changes in numerosity did not elicit significant changes in these early ERP components. The lack of early number-specific effects was qualified by a significant interaction between Shape and Number conditions. Number change elicited gradual ERP effects only on late ERP components. We conclude that numerosity is a higher-level property assembled from naturally correlating perceptual cues and hence, it is identified later in the cognitive processing stream.

Neural processes underlying the"same"-"different" judgment of two simultaneously presented objects--an EEG study

The present study investigated the neural processes underlying “same” and -“different” judgments for two simultaneously presented objects, that varied on one or both, of two dimensions: color and shape. Participants judged whether or not the two objects were “same” or “different” on either the color dimension (color task) or the shape dimension (shape task). The unattended irrelevant dimension of the objects was either congruent (same-same; different-different) or incongruent (same-different). ERP data showed a main effect of color congruency in the time window 190–260 ms post-stimulus presentation and a main effect of shape congruency in the time window 220–280 ms post-stimulus presentation in both color and shape tasks. The interaction between color and shape congruency in the ERP data occurred in a later time window than the two main effects, indicating that mismatches in task-relevant and task-irrelevant dimensions were processed automatically and independently before a response was selected. The fact that the interference of the task-irrelevant dimension occurred after mismatch detection, supports a confluence model of processing.

The neural mechanisms of percept-memory comparison in visual working memory

Researchers have revealed that comparing the perceptual input with the representations stored in visual working memory initiates a rapid attention-shift, which is predominantly triggered by the relevant-feature change. The comprehension of the change contents further necessitates a follow-up comparison that contrasts all the object features regardless of the task relevancy. However, whether such a distinct stage exists and how the process is carried on need further verification. We explored this issue by investigating the underlying neural mechanisms of the percept-memory comparison. By recording EEG, we found that both the task-relevant and -irrelevant feature changes elicited significantly more negative anterior N2 waves (230-340ms) rooting in the anterior cingulate cortex (ACC), and meanwhile activated the frontal theta (5-8Hz, 250-550ms). These results suggest that a distinct comparison stage does exist, which is supported by the anterior N2, ACC and frontal theta.

Dissociated mechanisms of extracting perceptual information into visual working memory

Background

The processing mechanisms of visual working memory (VWM) have been extensively explored in the recent decade. However, how the perceptual information is extracted into VWM remains largely unclear. The current study investigated this issue by testing whether the perceptual information was extracted into VWM via an integrated-object manner so that all the irrelevant information would be extracted (object hypothesis), or via a feature-based manner so that only the target-relevant information would be extracted (feature hypothesis), or via an analogous processing manner as that in visual perception (analogy hypothesis).

Methodology/Principal Findings

High-discriminable information which is processed at the parallel stage of visual perception and fine-grained information which is processed via focal attention were selected as the representatives of perceptual information. The analogy hypothesis predicted that whereas high-discriminable information is extracted into VWM automatically, fine-grained information will be extracted only if it is task-relevant. By manipulating the information type of the irrelevant dimension in a change-detection task, we found that the performance was affected and the ERP component N270 was enhanced if a change between the probe and the memorized stimulus consisted of irrelevant high-discriminable information, but not if it consisted of irrelevant fine-grained information.

Conclusions/Significance

We conclude that dissociated extraction mechanisms exist in VWM for information resolved via dissociated processes in visual perception (at least for the information tested in the current study), supporting the analogy hypothesis.

Attention changes in epilepsy patients following 3-month topiramate or valproate treatment revealed by event-related potential

The present study was designed to reveal changes of cognitive processes in epilepsy (EP) patients with Topiramate (TPM) or Valproate (VPA) treatment using Wechsler Adult Intelligence Scale (WAIS-CR) and event-related potential (ERP). Thirty untreated epilepsy patients were randomly divided into two groups receiving TPM or VPA, respectively. Fifteen healthy volunteers were included as controls. All the patients were examined by WAIS-CR and ERP before and 3 months after drug treatment. Controls were examined by ERP at the time recruited into the study and 3 months later. Unfamiliar grey-scale photographs of faces (front view) were used as stimuli. ERP were recorded at the same time. Mean Intelligence Quotient (IQ) in TPM group decreased after the 3-month treatment (90.40 vs. 81.00, P<0.05). One component of ERP-P300 was smaller in epilepsy patients than controls (P<0.05), but remained unchanged after TPM or VPA treatment (P>0.05). A delayed and smaller N270 was detected in patients compared to controls (P<0.05). After 3 months TPM treatment, it decreased further compared to before treatment (P<0.05). N170 was lower in patient groups, and it became lower after TPM treatment than before. Our results demonstrate that in all epilepsy patients with mild cognitive impairment ERP changes were found. TPM affected the cognitive functions in epilepsy patients reflected by the decreased full-scale intelligence quotient (FIQ). The imperative effects of TPM on visual perception function reflected by N170 were more obvious than that of VPA. Attention reflected by N270 was impaired after TPM treatment.

Antiepileptic Drugs and the Significance of Event-Related Potentials

The authors compared cognitive changes in epilepsy patients with or without antiepileptic drugs using event-related potential (ERP) N270 and P300. The patients were divided into three groups according to treatment type: carbamazepine, valproate acid (VPA), or no treatment. One control group composed of healthy subjects was included. The Mini-Mental State Examination detected no clinical dementia in all subjects. A modified Sternberg paradigm was used as a task when an ERP was recorded. When a stimulus was different from the memorized item (conflict condition), N270 was elicited in both controls and patients. All the three patient groups showed a delayed and smaller N270 than the control group. P300 was elicited when a stimulus was the same one as the memorized item (match condition), and its amplitude decreased in the VPA group. P300 latency did not differ among the four groups. ERP (N270 and P300) was abnormal in patients with epilepsy. These results indicate that antiepileptic drugs, especially VPA, might enhance the impairment of cognitive processing. N270 is more sensitive than P300 in the early detection of minor cognitive impairment in epileptics.

Brain electrical correlates of dimensional weighting: An ERP study

In visual search, there is a reaction time (RT) cost for targets on a given trial if the previous target was defined in a different dimension. According to the "dimension-weighting" account (Müller, Heller, & Ziegler, 1995), limited attentional weight needs to be shifted to the new dimension, resulting in slower RTs. The present study aimed at identifying brain electrical correlates associated with the weight shift. Analyses of ERPs revealed several components to reflect dimension changes whether the task was to detect the target or to identify its defining dimension. N2 amplitudes were more negative whenever the dimension changed. The P3 exhibited latency differences that mirrored RTs in both tasks, but the amplitudes showed no direct relation to stimulus- or response-related processes. Finally, slow-wave amplitudes were enhanced for dimension changes. Taken together, the results provide support for relatively early, perceptual processes underlying dimension change costs.

Event-Related Potential N270 in Detecting Cognitive Impairment in Patients With Transient Ischemic Attack

Latency and amplitude of the visual P300 and N270 were examined in patients with transient ischemic attack (TIA) and in age-matched healthy control subjects to investigate the feasibility of N270 as a clinical examination method to evaluate the cognitive status of patients with TIA. Stimulus pairs with identical (match condition) or different (conflict condition) colors were randomly presented to subjects. Each pair consisted of two sequential stimuli (S1 and S2) that lasted for 300 ms; the onset interval between them was 700 ms. Thirty TIA patients without clinical dementia and 30 age-matched control subjects determined if the two stimuli in a pair had the same color. Subjects were required to press a button in the match condition and another button in the conflict condition. Event-related potentials (ERPs) were recorded from their scalp electrodes at the same time. N270 was evoked by the second stimulus (S2) of the conflict condition in either control subjects or patients. The patient group exhibited a delayed N270 than the control group. TIA patients as a group showed cognitive decline. N270 is an effective index to detect the cognitive impairment of TIA patients.

Various conflicts from ventral and dorsal streams are sequentially processed in a common system

Event-related potentials (ERPs) were recorded in subjects while they were matching two sequentially presented color spots. The two spots might be presented in the same position of the same color, or different colors (color conflict). They might be in different positions of the same color (position conflict), or different colors (color and position conjunction conflicts). Subjects matched the stimuli in three different sessions according to different attention tasks: attending to color, attending to position, or attending to both color and position. A negative one-peak brain potential, N270, was elicited in all the conflict conditions with amplitude enhanced in the task-relevant conflict. Two negative effects, N270 and N400, were recorded when attending to the conjunction conflicts concurrently. Visual spatial information is processed through the dorsal stream, while the feature information is processed through the ventral stream in the brain. The results suggest that all kinds of conflicts might be processed in a common system above the level of the two streams, which processes the conjunction conflict information from ventral and dorsal stream in series.

Event-related potentials elicited by visual stimulus-duration discrimination tasks

Event-related potentials (ERPs) were recorded on subjects who discriminated the stimulus duration of two sequentially presented spots (S1 and S2). Four kinds of trials were included: short-duration match (S1 and S2 lasting 300 ms), short-duration conflict (S1 and S2 lasting 300 ms and 600 ms, respectively), long-duration match (S1 and S2 were 600 ms) and long-duration conflict (S1 and S2 were 600 ms and 900 ms, respectively). When S1 was equal to S2, components of P1, N1, P2, N2 and a delayed late positive component were recorded after the onset of S2. The other three negativities were elicited in both short and long duration conflict conditions. The three negative components peaked at 475, 600 and 900 ms in the short-duration condition, and they peaked at 805, 900 and 1200 ms in the long-duration condition. The first negativity was considered a visual mis-match negativity (vMMN), followed by a delayed N270 reflecting the conflict processing for duration in the brain. The last negativity, similar to N270, possibly reflects the second conflict processing activity evoked by stimulus offset.

The sequential processing of visual feature conjunction mismatches in the human brain

To clarify the brain mechanism for multifeature stimulus comparison, subjects matched the features of two serial visual stimuli in pairs. Stimulus pairs were of four categories: C-S-, color same, shape same (match); C-S+, color same, shape different (shape mismatch); C+S-, color different, shape same (color mismatch); C+S+, color different, shape different (conjunction mismatches). Subjects matched the stimuli in three different sessions according to different attention tasks: attending to color (Ac), attending to shape (As), or attending to both color and shape (Acs). A negative one-peak brain potential, N270, was elicited in all the mismatch conditions with amplitude enhanced in the task-relevant mismatch. Negative potential with two peaks, N270 and N400, appeared when attending to the conjunction mismatches concurrently. The two serial negativities in response to attended feature conjunctions might reflect the temporal different stages for processing conjunction mismatches or conflicts.

Event-related potential N270, a negative component to identification of conflicting information following memory retrieval

OBJECTIVE

N270, an endogenous ERP component of conflict effect, was evoked in previous studies with S1-S2 paradigm. The present experiment is designed to confirm the speculation that this conflict-related negativity could also be elicited by stimulus probes having conflict with a memorized item in a visual post-retrieval comparison task.

METHODS

A Sternberg probe-matching paradigm was modified in the present study. The stimuli consisted of a memory set of 3 different items (simple figures) and a retrieval set of 3 probe figures. Subjects matched each probe to its corresponding item in the memory set. The tasks were designed with different conflict loads of no-conflict, low-conflict and high-conflict in the probe retrieval test.

RESULTS

Probes of no-conflict elicited a major positive going component, P300, with bilateral parietal distribution. Probes of low- and high-conflict evoked N270, while N430 was elicited only in high-conflict condition. N270 was more negative in high-conflict condition than in low-conflict condition. The N270 was right hemispheric prominent in the low-conflict task and remarkably distributed over the right prefrontal areas. On the other hand, both N270 and N430 were distributed bilaterally on the scalp in the high-conflict task.

CONCLUSIONS

The present results demonstrate that the N270 is an index to the conflict identification, while the N430 of the high-conflict task reflects the processing for complex conflicts following probe retrieval. These negativities are related to the processing of conflicts.

Brain potentials elicited by matching global and occluded 3-dimensional contours

Subjects were instructed to match 3-dimensional forms while event-related potentials (ERPs) were recorded to explore the relationship between visual completion and conflict processing. Sequentially presented paired stimuli (S1 and S2) were identical in condition I, while in condition II the images were of the same contour, but S2 contained an invisible portion, and in condition III S1 and S2 were of different contours. Subjects indicated if stimuli were physically identical or contour similar in two separate sessions. Following the onset of S2, ERP components P100, N150, and LPC were recorded in all conditions. N150 was enhanced in condition II in both sessions, and N270 was elicited in conditions II and III. N150 is related to visual completion, while N270 is related to the evaluation of information discrepancy, belonging to independent systems.

The N270 component of the event-related potential reflects supramodal conflict processing in humans

It is unclear whether crossmodal information conflict can initiate the conflict processing system indexed by a component of the event-related potential (ERP) called the N270, which previously has been observed only for visual conflict. ERPs were recorded in ten subjects, while they were engaged in a visual-auditory discrimination task. A visual stimulus of a facial photograph was followed by an auditory stimulus of Chinese syllable [a] or [i], which might be sounded by the same gender of its preceding photograph (gender match) or by different gender (gender conflict). Subjects pressed a button for gender match and another for gender conflict. A prominent N270, similar to that evoked by visual conflicts, was elicited by the auditory stimuli in gender conflict condition. It is likely that N270 reflects the brain activity of a supra-modal conflict processing system.

Event-related potentials in a No-go task involving response-tendency conflict

Event-related potentials (ERPs) were recorded while 13 subjects completed a color discrimination task. In task one, subjects were asked to press a button when the presented stimulus was a red or a green spot (Go stimulus), and inhibited any motor response when the stimulus was a yellow or a white spot (No-go stimulus). In task two, subjects were instructed to count the number of the Go stimuli, not to count the No-go stimuli. In order to investigate the influence of probability on ERP components, two sessions were designed in each task. In session one, the probability of the four kinds of stimuli was equal. In session two, the probability of red, green, yellow, and white were 10%, 10%, 10%, and 70% respectively. An enhanced negative potential in the frontal area was recorded in the 200-400 ms range both following No-go stimuli and following No-count stimuli, which was not influenced by the stimulus probability. The result cast doubt on the interpretation of the frontal negative potential enhancement as reflecting response-inhibition processes. The potential might be related to the information processing of response-tendency conflict rather than the suppression of motor execution.

Cognitive impairment in Parkinson's disease revealed by event-related potential N270

Disturbed cognitive function is a well-recognized feature of idiopathic Parkinson's disease (PD). The aim of this study was to find a susceptive index to reveal the minor cognitive impairment in PD patients. Thirty PD patients without clinical dementia and thirty-four age-matched normal controls performed a matching task while event-related potentials (ERPs) were recorded from their scalp. There were two kinds of stimulus pairs in this study: match condition, the second stimulus (S2) in a pair was identical to the first one (S1); conflict condition, S2 conflicted with S1 in the color attribute. Subjects were required to press a button in the match condition and another button in the conflict condition. A negative ERP component, N270, which was considered to reflect the conflict processing activity in human brain, was evoked by the S2 of the conflict condition. The patient group showed a delayed and smaller N270 than the control group. The prolongation of its peak latency was significant at P3 and P4 electrodes and the reduction of its mean amplitude was significant at P3 electrode. The amplitude of P300 elicited in the match condition was decreased in the patient group at P4 electrode but its latency did not differ from the control group. These results indicate that PD patients as a group showed cognitive decline even in the absence of clinical dementia. N270 is a sensitive index in revealing this minor cognitive impairment.