An event-related potential analysis of extraversion and individual differences in cognitive processing speed and response execution.

Individual differences in cognitive processing speed and response execution were examined in relation to extraversion. Event-related potentials (ERPs) were recorded concurrently with reaction time and movement time (MT) measures as participants (iNn?=?67) performed simple reaction time and stimulus–response compatibility tasks. Slower processing speed for extraverts, as indicated by longer latency of a late positive ERP wave, P3, was only evident in conditions in which stimulus information was in conflict with response selection demands. As previously reported, the salient effect in all conditions of both tasks was faster MT for extraverts, an effect that is indicative of differences in fundamental motor processes. On the simple reaction time task, amplitudes of the N1 component, an early negative ERP wave, were smaller for extraverts than for introverts in response to auditory tones, an effect that affirms the enhanced sensory reactivity of introverts to punctate physical stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The use of biological markers for the study and prevention of chronic degenerative diseases. 1. Definitions, scope of the study and classification

Visual event-related brain potentials (ERPs) were recorded during a running memory task, in which subjects dynamically revised (updated) memory stores, and a control task not requiring maintenance of a changing memory set but utilising identical stimulus sequences and response patterns. In three experiments, ERPs associated with cognitive processes were isolated through subtraction of control potentials from ERPs acquired during updating. We provide evidence that resultant difference ERPs primarily reflected processing or processing control, as opposed to storage. These findings are consistent both with Baddeley's working memory model, which postulates separate storage and control modules, and Morris and Jones' behavioral evidence for specific involvement of Baddeley's central executive in memory updating. In addition, our ERP data indicate that updating requires processes not suggested by Morris and Jones' behavioural studies; possibly control processes engaged to reduce the effects of proactive interference. Overall the data are consistent with the discovery of an ERP correlate of central executive activity.     

Influence of caffeine on information processing stages in well rested and fatigued subjects

The effects of caffeine on different information processing stages were examined by using choice reaction time tasks. Independent variables were stimulus degradation, stimulus-response compatibility, time-uncertainty, state of the subject, and caffeine treatment. The task variables were assumed to affect the following processing stages; encoding, response selection and motor preparation, respectively. A 200 mg dose at the beginning of the experiment and a maintenance dose of 50 mg caffeine or lactose half-way through the session were administered to well rested and fatigued subjects, double-blind and deceptively. Behavioural measurements, event-related potentials (ERPs) and mood questionnaires were used to assess caffeine effects. The data showed that caffeine shortened reaction time. This effect showed an interaction with stimulus degradation and time uncertainty. In addition, ERP results supported the view that caffeine increases cortical arousal and perceptual sensitivity. Stimulating effects of caffeine were mainly located at input and output stages of the information processing system. Central processes were unaffected by caffeine. Fatigued subjects showed larger improvements in performance after caffeine than well-rested subjects. The results also indicated that caffeine effects were not stimulating in all subjects: 6 out of 30 subjects did not show arousing effects of caffeine.     

Identification of emotion in a dichotic listening task: event-related brain potential and behavioral findings

The lateralization of emotion perception has been examined using stimuli in both auditory and visual modalities. Studies using dichotic stimuli have generally supported the hypothesis of right-hemisphere dominance for emotion perception, whereas studies of facial and verbal emotion perception have provided evidence for the right-hemisphere and valence hypotheses. A dichotic target detection task was developed to enable acquisition of event-related potentials (ERP) from subjects engaged in emotion detection. Nonsense syllables (e.g., ba, pa) stated in seven different emotional intonations were dichotically presented to 24 young adults, in a target detection task during four separate blocks (target emotions: happiness, interest, anger, or sadness). Accuracy and reaction time and ERP measures were also collected. ERPs were recorded from 14 scalp electrodes with a nose reference and quantified for N100, sustained negativity, late positivity, and slow wave. Significantly greater left- than right-ear accuracy was obtained for the identification of target prosodic emotion. Hemispheric asymmetries of N100 and sustained negativity were found, with left-hemisphere amplitudes greater than right-hemisphere amplitudes. These ERP asymmetries were not significantly correlated with the left-ear dichotic advantage and may be related more to early phonetic processing than to emotion perception. Since the behavioral evidence supports the right-hemisphere hypothesis for emotion perception, behavioral and ERP asymmetries evident in this task reflect separable patterns of brain lateralization.     

A random-walk model of accuracy and reaction time applied to three experiments on pigeon visual discrimination.

A random-walk model of visual discrimination is described and applied to reaction time (RT) distributions from three discrete-trial experiments with pigeons. Experiment 1 was a two-choice hue discrimination task with multiple hues. Choice percentages changed with hue discriminability; RTs were shortest for the least and most discriminable stimuli. Experiments 2 and 3 used go/no-go hue discriminations. Blocks of sessions differed in reward probability associated with a variable red stimulus in Experiment 2 and with a constant green stimulus in Experiment 3. Changes in hue had a large effect on response percentage and a small effect on RT; changes in reward shifted RT distributions on the time axis. The “random-walk, pigeon” model applied to these data is closely related to Ratcliff's diffusion model (Ratcliff, 1978; Ratcliff & Rouder, 1998). Simulations showed that stimulus discriminability affected the speed with which evidence accumulated toward a response threshold, in line with comparable effects in human subjects. Reward probability affected bias, modeled as the amount of evidence needed to reach one threshold rather than the other. The effects of reward probability are novel, and their isolation from stimulus effects within the decision process can guide development of a broader model of discrimination. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Luminance and spatial attention effects on early visual processing

Event-related potentials (ERPs) were recorded from healthy subjects in response to unilaterally flashed high and low luminance bar stimuli presented randomly to left and right field locations. Their task was to covertly and selectively attend to either the left or right stimulus locations (separate blocks) in order to detect infrequent shorter target bars of either luminance. Independent of attention, higher stimulus luminance resulted in higher ERP amplitudes for the posterior N95 (80-110 ms), occipital P1 (110-140 ms), and parietal N1 (130-180 ms). Brighter stimuli also resulted in shorter peak latency for the occipital N1 component (135-220 ms); this effect was not observed for the N1 components over parietal, central or frontal regions. Significant attention-related amplitude modulations were obtained for the occipital P1, occipital, parietal and central N1, the occipital and parietal P2, and the parietal N2 components; these components were larger to stimuli at the attended location. In contrast to the relatively short latencies of both spatial attention and luminance effects, the first interaction between luminance and spatial attention effects was observed for the P3 component to the target stimuli (350-750 ms). This suggests that interactions of spatial attention and stimulus luminance previously reported for reaction time measures may not reflect the earliest stages of sensory/perceptual processing. Differences in the way in which luminance and attention affected the occipital P1, occipital N1 and parietal N1 components suggest dissociations among these ERPs in the mechanisms of visual and attentional processing they reflect.(ABSTRACT TRUNCATED AT 250 WORDS)     

Precueing spatial S-R correspondence: Is there regulation of expected response conflict?

Four experiments investigated the ability to prepare for the level of forthcoming stimulus-response correspondence in choice-response tasks. In a Simon task, participants responded to the color of spatially variable stimuli with spatially variable responses. Participants were given advance information about whether a forthcoming stimulus-response event would be spatially corresponding, neutral, or spatially noncorresponding. Reliable cues decreased reaction times (RTs) in the corresponding conditions of 2- and 3-choice tasks, decreased RTs in noncorresponding conditions of a 2-choice task but not in a 3-choice task, and left RTs in neutral conditions unaffected. The pattern of results suggests that participants used reliable cues for responding to the nominally irrelevant stimulus location if the correct response could be inferred from location (attention switching). By contrast, the lack of cueing effects on performance in noncorresponding conditions of 3-choice tasks suggests that participants cannot use cues for changing the attentional weights of processing channels for different stimulus dimensions (gating). In summary, gating may be involved in the regulation of experienced response conflict, but the present results suggest that it is not involved in the regulation of expected (i.e., predicted) response conflict. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Nucleus basalis magnocellularis and attention: Effects of muscimol infusions.

The basal forebrain is important in cognitive processing. Most studies have focused on the importance of this area in mnemonic processing. However, the nucleus basalis magnocellularis (NBM), which is a major component of the basal forebrain, may also be involved in attentional processes. Attention can influence the sensitivity of perceptual processes, as assessed by discriminability, or the selection of response strategies, as assessed by bias. This experiment examined whether temporary inactivation of the NBM, using the gamma-aminobutyric acid (GABA) agonist muscimol, would interfere with attention. Each rat was tested in a 2-choice reaction time (RT) task in which stimulus frequency was varied. RT and error rate increased, and discriminability decreased following muscimol infusions into the NBM. Bias was unchanged. The pattern of results provides evidence that the NBM is important in attention, and this influence of the NBM acts primarily on perceptual aspects of attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

What's in a location? Comparing object-based and space-based models of feature integration in visual search.

What is the unit of selection for feature integration in visual search: location or perceptual object? Feature integration theory (A. Treisman, 1988) asserts that it is location. Two alternative models are put forward and tested in a series of 4 experiments using a special conjunctive search task In this task, each stimulus item consists of 2 overlapping forms (perceptual objects). In general, the search was more efficient when the search features were linked to the same perceptual object than when they were linked to different perceptual objects at the same stimulus location. This same-object advantage, however, was shown to depend on stimulus discriminability and density, grouping strength, and hierarchical object structure. The results support a hierarchical object-based model, with important implications for feature integration, visual search, late versus early selection, and object-based versus space-based views of attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Task-set reconfiguration and perceptual processing: Behavioral and electrophysiological evidence.

Oriet and Jolic?ur (2003) proposed that an endogenous task-set reconfiguration process acts as a hard bottleneck during which even early perceptual processing is impossible. We examined this assumption using a psychophysiological approach. Participants were required to switch between magnitude and parity judgment tasks within a predictable task sequence while event-related potentials (ERPs) were recorded. Stimulus contrast and response stimulus interval (RSI) were manipulated. Behavioral data demonstrated typical task switch costs that decreased as RSI increased. However, whereas ERP analysis of visual ERP component latencies sensitively revealed the contrast effect, a switch-specific postponement of perceptual processing during task-set reconfiguration at short RSIs was not observed. The present findings indicate that the process of task-set reconfiguration does not constitute a hard bottleneck that delays perceptual processing. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Alcohol and cognitive control: Implications for regulation of behavior during response conflict.

Alcohol intoxication often leads to dysregulated behavior in contexts characterized by conflict between prepotent response tendencies and incompatible alternative responses. Recent research has identified 2 components of an anterior executive attention system that are essential for adaptive behavior when response conflict exists. Event-related potential (ERP) measures of evaluative and regulative cognitive control were collected to determine if impaired executive attention was responsible for observed behavior deficits when intoxicated. Intoxicated participants displayed task performance deficits on incongruent color-naming trials relative to sober controls. Alcohol did not affect P3 magnitude/latency, indicating that timing and integrity of stimulus evaluation remained intact. In contrast, alcohol did reduce frontal components of ERP that index evaluative and regulative cognitive control processes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The impact of stimulus and response variability on S-R correspondence effects.

Six experiments investigated how variability on irrelevant stimulus dimensions and variability on response dimensions contribute to spatial and nonspatial stimulus-response (S-R) correspondence effects. Experiments 1-3 showed that, when stimuli varied in location and number, S-R correspondence effects for location or numerosity occurred when responses varied on these dimensions but not when responses were invariant on these dimensions. These results are consistent with the response-discrimination account, according to which S-R correspondence effects should only arise for a dimension that is used for discriminating between responses in working memory. Experiments 4-6 showed that, when responses varied in location and number, both invariant and variable stimulus number produced correspondence effects in S-R numerosity. In summary, the present results indicate that the usefulness of a particular dimension for response discrimination can be sufficient for producing S-R correspondence effects, whereas variability of a stimulus dimension is not sufficient for producing such effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Autonomic nervous system activity in autistic, schizophrenic, and normal men: Effects of stimulus significance.

Deficits in attention and cognition in autistic children have been attributed to problems in the early stages of stimulus processing and to autonomic dysregulation, but the evidence is conflicting. Our study addressed this problem by recording skin conductance, skin temperature, respiration rate, and heart rate (HR) during (a) a rest period, (b) a series of nonsignal tones, and (c) a simple warned reaction time (RT) task in autistic, schizophrenic, and normal men; we sought to remove extraneous sources of variance by testing only high-functioning autistic men (n?=?13); age?=?18–39). Control subjects were age-matched normal men (n?=?19) and schizophrenic men (n?=?13) not chronically hospitalized. Autistic men had higher respiration rates, lower skin temperature, and higher HR variability at rest than controls. They were not different on other arousal measures or generally in responding to nonsignal tones but had severely impaired tonic and phasic autonomic responses and motor responses in the RT task. Schizophrenic subjects were also impaired but significantly less so in some aspects of responding. The results do not suggest problems in stimulus processing, but there is evidence of autonomic dysregulation and a pronounced inability to mobilize processing resources appropriately, perhaps a common problem with schizophrenia. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Validity and boundary conditions of automatic response activation in the Simon task.

Three experiments were conducted to determine whether spatial stimulus-response compatibility effects are caused by automatic response activation by stimulus properties or by interference between codes during translation of stimulus into response coordinates. The main evidence against activation has been that in a Simon task with hands crossed, responses are faster at the response location ipsilateral to the stimulus though manipulated by the hand contralateral to the stimulus. The experiments were conducted with hands in standard and in crossed positions and electroencephalogram measures showed coactivation of the motor cortex induced by stimulus position primarily during standard hand positions with visual stimuli. Only in this condition did the Simon effect decay with longer response times. The visual Simon effect appeared to be due to specific mechanisms of visuomotor information transmission that are not responsible for the effects obtained with crossed hands or auditory stimuli. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of decreased audibility produced by high-pass noise masking on cortical event-related potentials to speech sounds/ba/and/da

This study investigated the effects of decreased audibility produced by high-pass noise masking on cortical event-related potentials (ERPs) N1, N2, and P3 to the speech sounds /ba/and/da/presented at 65 and 80 dB SPL. Normal-hearing subjects pressed a button in response to the deviant sound in an oddball paradigm. Broadband masking noise was presented at an intensity sufficient to completely mask the response to the 65-dB SPL speech sounds, and subsequently high-pass filtered at 4000, 2000, 1000, 500, and 250 Hz. With high-pass masking noise, pure-tone behavioral thresholds increased by an average of 38 dB at the high-pass cutoff and by 50 dB one octave above the cutoff frequency. Results show that as the cutoff frequency of the high-pass masker was lowered, ERP latencies to speech sounds increased and amplitudes decreased. The cutoff frequency where these changes first occurred and the rate of the change differed for N1 compared to N2, P3, and the behavioral measures. N1 showed gradual changes as the masker cutoff frequency was lowered. N2, P3, and behavioral measures showed marked changes below a masker cutoff of 2000 Hz. These results indicate that the decreased audibility resulting from the noise masking affects the various ERP components in a differential manner. N1 is related to the presence of audible stimulus energy, being present whether audible stimuli are discriminable or not. In contrast, N2 and P3 were absent when the stimuli were audible but not discriminable (i.e., when the second formant transitions were masked), reflecting stimulus discrimination. These data have implications regarding the effects of decreased audibility on cortical processing of speech sounds and for the study of cortical ERPs in populations with hearing impairment.     

Electrophysiological evidence for a shared representational medium for visual images and visual percepts.

Systematic effects of imagery on visual signal detection performance have been used to argue that imagery and the perceptual processing of stimuli interact at some common locus of activity (Farah, 1985). However, such a result is neutral with respect to the question of whether the interaction occurs during modality-specific visual processing of the stimulus. If imagery affects stimulus processing at early, modality-specific stages of stimulus representation, this implies that the shared stimulus representations are visual, whereas if imagery affects stimulus processing only at later, amodal stages of stimulus representation, this implies that imagery involves more abstract, postvisual stimulus representations. To distinguish between these 2 possibilities, we repeated the earlier imagery-perception interaction experiment while recording event-related potentials (ERPs) to stimuli from 16 scalp electrodes. By observing the time course and scalp distribution of the effect of imagery on the ERP to stimuli, we can put constraints on the locus of the shared representations for imagery and perception. An effect of imagery was seen within 200 ms following stimulus presentation, at the latency of the 1st negative component of the visual ERP, localized at the occipital and posterior temporal regions of the scalp, that is, directly over visual cortex. This finding supports the claim that mental images interact with percepts in the visual system proper and hence that mental images are themselves visual representations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Central cholinergic involvement in working memory: Effects of scopolamine on continuous nonmatching and discrimination performance in the rat.

In 4 experiments, male Sprague-Dawley rats (N?=?37) were trained to stable baselines of leverpressing on a variable intertrial interval continuous nonmatching-to-sample schedule (CNM) or on an analogous discrimination schedule. Scopolamine HBr (0.125, 0.25, and 0.50 mg/kg) reduced the accuracy of CNM performance to a similar extent over the 3 intertrial (retention) intervals: 2.5, 5, and 10 sec, indicating that the drug did not affect the time-dependent process of retention in working memory. When baseline levels of performance accuracy were similar in the CNM and discrimination tasks (but stimulus discriminability was greater in the CNM task), scopolamine reduced accuracy equally in the 2 procedures. The effects of scopolamine on the accuracy of noncorrection trial CNM performance were simulated by reducing stimulus discriminability; however, scopolamine disrupted CNM correction trial performance much more than did reductions in stimulus discriminability. It is concluded that scopolamine's effects on working memory are not limited to the possible effects on stimulus discrimination—scopolamine may also affect the retrieval of response rules from reference memory. (52 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The response-signal method reveals age-related changes in object working memory.

Sixteen healthy young adults (ages 18-32) and 16 healthy older adults (ages 67-81) completed a delayed response task in which they saw the following visual sequence: memory stimuli (2 abstract shapes; 3,000 ms), a blank delay (5,000 ms), a probe stimulus of variable duration (one abstract shape; 125, 250, 500, 1,000, or 2,000 ms), and a mask (500 ms). Subjects decided whether the probe stimulus matched either of the memory stimuli; they were instructed to respond during the mask, placing greater emphasis on speed than accuracy. The authors used D. L. Hintzman & T. Curran's (1994) 3-parameter compound bounded exponential model of speed-accuracy tradeoff to describe changes in discriminability associated with total processing time. Group-level analysis revealed a higher rate parameter and a higher asymptote parameter for the young adult group, but no difference across groups in x-intercept. Proxy measures of cognitive reserve (Y. Stern et al., 2005) predicted the rate parameter value, particularly in older adults. Results suggest that in working memory, aging impairs both the maximum capacity for discriminability and the rate of information accumulation, but not the temporal threshold for discriminability. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Event-related brain potential examination of implicit memory processes: Masked and unmasked repetition priming.

The proposition that cortically based perceptual representation systems (PRSs) are responsible for some implicit priming phenomena was examined by using event-related potentials (ERPs) in repetition and masked word priming. Experiment 1 used an explicit recognition task, in which repeated words replicated previous ERP repetition priming effects, whereas masked repetition priming revealed a new ERP effect with a posterior topography. Experiment 2 demonstrated ERP and behavioral priming in a lexical decision task for repetition and masked repetition priming. Topographical mapping of ERP repetition priming effects involved both early and late effects over the right and left anterior regions, whereas masked priming produced only an early ERP effect posteriorly. These results suggest differences between early and late ERP priming effects in terms of explicit recollection. Moreover, a posterior PRS may not be involved in some longer term implicit repetition priming effects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Control over location-based response activation in the Simon task: Behavioral and electrophysiological evidence.

In 4 Simon experiments the authors examined control over 2 routes of sensorimotor processing: response priming in the unconditional route and response selection via the conditional route. The Simon effect diminished as the frequency of noncorresponding trials increased. Location-based response priming was observed only when the stimulus followed a corresponding event but not after a noncorresponding trial. Therefore, the unconditional route appears to be suppressed whenever the task context indicates priming as potentially disadvantageous. Moreover, the task-irrelevant stimulus location was used for response selection as a function of correspondence probability. Although exact repetitions of stimulus-response sequences caused a marked speed-up of responses, this 3rd mechanism is independent of unconditional route suppression and frequency-based adjustments in the conditional route. (PsycINFO Database Record (c) 2010 APA, all rights reserved)