Parieto-occipital approximately 10 Hz activity reflects anticipatory state of visual attention mechanisms

High-density eeg recordings revealed sensory specific modulation of anticipatory parieto-occipital approximately 10 Hz oscillatory activity when visually presented word cues instructed subjects in an intermodal selective attention paradigm. Cueing attention to the auditory features of imminent compound audio-visual stimuli resulted in significantly higher approximately 10 Hz amplitude in the period preceding onset of this stimulus than when attention was cued to the visual features. We propose that this parieto-occipital approximately 10 Hz activity reflects a disengaged visual attentional system in preparation for anticipated auditory input that is attentionally more relevant. Conversely, lower approximately 10 Hz activity during the attend-visual condition may reflect active engagement of parieto-occipital areas in the anticipatory period. These results support models implicating parieto-occipital areas in the directing and maintenance of visual attention.     

Processing of auditory stimuli during auditory and visual attention as revealed by event-related potentials

Auditory event-related brain potentials (ERPs) were recorded during auditory and visual selective attention tasks. Auditory stimuli consisted of frequent standard tones (1000 Hz) and infrequent deviant tones (1050 Hz and 1300 Hz) delivered randomly to the left and right ears. Visual stimuli were vertical line gratings randomly presented on a video monitor at mean intervals of 6 s. During auditory attention, the subject attended to the stimuli in a designated ear and responded to the 1300-Hz deviants occurring among the attended tones. During visual attention, the subject responded to the occasional visual stimuli. ERPs for tones delivered to the attended ear were negatively displaced relative to ERPs elicited by tones delivered to the unattended ear and to ERPs elicited by auditory stimuli during visual attention. This attention effect consisted of negative difference waves with early and late components. Mismatch negativities (MMNs) were elicited by 1300-Hz and 1050-Hz deviants irrespective of whether they occurred among attended or unattended tones. MMN amplitudes were unaffected by attention, supporting the proposal that the MMN is generated by an automatic cerebral discrimination process.     

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)     

The rotatory machines in the history of psychiatry

In this study, we recorded the event-related potentials (ERPs) elicited by stimuli appearing at attended and unattended locations. The voltage amplitudes and latencies of the P1, N1, P2, N2 and P3 visual components showed statistically significant differences in the attended condition with respect to the unattended one. The power spectral density of the EEG following stimulus onset was calculated. The difference between the spectral densities of the attended and unattended conditions was computed. Statistically significant differences were found in the decrease of alpha (9-11 Hz) and the increase of beta (15-17 Hz) frequencies during the attention condition with respect to the unattended condition. These results suggest that the arrival of a visual stimulus during the attended condition generates a complex reorganization of neuronal activity in both time and frequency domains.     

The gradient of spatial auditory attention in free field: an event-related potential study

Young adult subjects attended selectively to brief noise bursts delivered in free field via a horizontal array of seven loudspeakers spaced apart by 9 degrees of angle. Frequent "standard" stimuli (90%) and infrequent "target/deviant" stimuli (10%) of increased bandwidth were delivered at a fast rate in a random sequence equiprobably from each speaker. In separate runs, the subjects' task was to selectively attend to the leftmost, center, or rightmost speaker and to press a button to the infrequent "target" stimuli occurring at the designated spatial location. Behavioral detection rates and concurrently recorded event-related potentials (ERPs) indicated that auditory attention was deployed as a finely tuned gradient around the attended sound source, thus providing support for gradient models of auditory spatial attention. Furthermore, the ERP data suggested that the spatial focusing of attention was achieved in two distinct stages, with an early more broadly tuned filtering of inputs occurring over the first 80-200 msec after stimulus onset, followed by a more narrowly focused selection of attended-location deviants that began at around 250 msec and closely resembled the behavioral gradient of target detections.     

Spatio-temporal dynamics of attention to color: evidence from human electrophysiology

This study characterized patterns of brain electrical activity associated with selective attention to the color of a stimulus. Multichannel recordings of event-related potentials (ERPs) were obtained while subjects viewed randomized sequences of checkerboards consisting of isoluminant red or blue checks superimposed on a grey background. Stimuli were presented foveally at a rapid rate, and subjects were required to attend to the red or blue checks in separate blocks of trials and to press a button each time they detected a dimmer target stimulus of the attended color. An early negative ERP component with an onset latency of 50 ms was sensitive to stimulus color but was unaffected by the attentional manipulation. ERPs elicited by attended and unattended stimuli began to diverge after approximately 100 ms following stimulus onset. Inverse dipole modelling of the attended-minus-unattended difference waveform indicated that an initial positive deflection with an onset latency of 100 ms had a source in lateral occipital cortex, while a subsequent negative deflection with an onset at 160 ms had a source in inferior occipito-temporal cortex. Longer-latency attention-sensitive components were localized to premotor frontal areas (onset at 190 ms) and to more anterior regions of the fusiform gyrus (onset at 240 ms). These source localizations correspond closely with cortical areas that were identified in previous neuroimaging studies as being involved in color-selective processing. The present ERP data thus provide information about the time course of stimulus selection processes in cortical areas that subserve attention to color.     

The role of selective attention in the perception of multiple-element stimulus arrays.

To access the role of attention in visual processing, we have recorded single-unit activity from area V4 of visual cortex in macaque monkeys, and the results of these experiments provide a clear demonstration of the relationship between inter-stimulus competition and attention. Specifically, attended stimuli elicit larger responses than ignored stimuli, and these attention effects are increased when: a) the total number of distracting stimuli is increased; b) both attended and ignored stimuli are located inside the neuron's receptive field; and c) the attended and ignored stimuli are presented simultaneously rather than sequentially. We have also examined the role of inter-stimulus competition in human subjects by recording event-related potentials (ERPs), which are electrophysiological responses that can be recorded noninvasively from the scalp. In these experiments, we have found that the attention-sensitive N2pc wave is present when subjects focus attention onto target stimuli when they are surrounded by competing distractor stimuli, but is absent when the competition is eliminated (e.g. by removing the distractors). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effects of between-source discriminability on attended and unattended auditory ERPs

Event-related potentials (ERPs) for tone pips from attended and unattended sources, which varied on discriminability, were compared with ERPs for the same stimuli recorded during performance of a visual task. This comparison revealed that Nd, the negative shift of attended relative to unattended ERPs, consisted of three components: a negativity in the attended ERP from 100 to 270 ms, a positivity in the unattended ERP from 170 ms to the end of the epoch, and a second negativity in the attended ERP from 270 to 700 ms. In general, the later onset of early Nd with more difficult between-source discriminations could be attributed to the later onset of the positivity in unattended ERPs. A number of hypotheses were advanced for the origin of the unattended positivity: the suppression of the later of two negative components in the 100-220-ms range, an enhanced P2 component, an endogenous positivity, or the resolution of a protracted negativity elicited by preceding attended stimuli.     

Input and central processing expressed in ERP and heart rate changes to rare target and rare nontarget stimuli

Whether late positive components of event-related potentials (ERPs) parallel changes in heart rate (HR) indicative of attention/orienting to rare stimuli has been debated. In the present study, a three-stimulus design was used, with rare target, rare nontarget, and frequent standard stimuli delivered under identical conditions except that instructions to subjects described the targets to which subjects should respond but did not describe the nontargets. In Experiment 1, stimuli varied among modalities; in Experiment 2, auditory stimuli were employed. Both ERPs and HR were consistent with automatic processing preceding two stages of controlled processing. Rare stimuli evoked larger parietal P300 and initial HR deceleration than standards. Presumably because of load-reducing effects of long interstimulus intervals, targets and nontargets were not distinguished before a late slow wave and a late phase of HR acceleration. Neither rare stimulus elicited a recognizable frontal P3a.     

Attempts at saving severely ischaemic limbs

The relative efficacy of (1) repeated auditory and somesthetic stimulation for the habituation of cardiac acceleration responses and (2) intramodal and cross-modal stimulation for the dishabituation of cardiac responses was studied in 45 full-term 2-day-old infants. Although the stimuli were equally effective initially, repeated presentation of the somesthetic stimulus had a greater decremental effect than repeated presentation of the auditory stimulus. The stimuli were equally effective in producing dishabituation when in a different modality from that of the habituating stimulus (cross-modal) but not when in the same modality (intramodal). Changes in the locus of stimulation without a change in modality were ineffective for producing dishabituation. The findings indicate the human newborn discriminates auditory and somesthetic inputs effectively and equally but does not discriminate contralateral from ipsilateral stimulation in either modality.     

Analysis of neural interactions explains the activation of occipital cortex by an auditory stimulus

Analysis of neural interactions explains the activation of occipital cortex by an auditory stimulus. J. Neurophysiol. 80: 2790-2796, 1998. Large-scale neural interactions were characterized in human subjects as they learned that an auditory stimulus signaled a visual event. Once learned, activation of left dorsal occipital cortex (increased regional cerebral blood flow) was observed when the auditory stimulus was presented alone. Partial least-squares analysis of the interregional correlations (functional connectivity) between the occipital area and the rest of the brain identified a pattern of covariation with four dominant brain areas that could have mediated this activation: prefrontal cortex (near Brodmann area 10, A10), premotor cortex (A6), superior temporal cortex (A41/42), and contralateral occipital cortex (A18). Interactions among these regions and the occipital area were quantified with structural equation modeling to identify the strongest sources of the effect on left occipital activity (effective connectivity). Learning-related changes in feedback effects from A10 and A41/42 appeared to account for this change in occipital activity. Influences from these areas on the occipital area were initially suppressive, or negative, becoming facilitory, or positive, as the association between the auditory and visual stimuli was acquired. Evaluating the total effects within the functional models showed positive influences throughout the network, suggesting enhanced interactions may have primed the system for the now-expected visual discrimination. By characterizing both changes in activity and the interactions underlying sensory associative learning, we demonstrated how parts of the nervous system operate as a cohesive network in learning about and responding to the environment.     

Event-related potentials during mental imagery

Event-related potentials(ERPs) were measured while subjects were constructing mental images of a letter of the alphabet. Following presentation of an uppercase letter, subjects were asked to form a mental image of the same letter in lower case, and determine whether or not it had an ascending or descending stroke (ascender or descender). ERPs were measured in a passive condition and then compared with the ERPs recorded while the subjects performed the discrimination task. During the discrimination task, negative potentials were observed in left frontal, central and parietal areas around 220 ms after the stimulus onset. These early negative potentials were dominant in the left hemisphere and are probably related to working memory processes in mental image formation.     

Event-related potentials to inspiratory flow-resistive loads in young adults: stimulus magnitude effects

Event-related potentials were recorded to brief presentations of four levels of inspiratory flow-resistive loads in young adults. We labeled the loads according to the level of resistance they provided subjectively: sub-threshold (0.34 cmH2O/l per s), near-threshold (4.01 cmH2O/l per s), intermediate (10.4cmH2O/l per s), and near-occlusion (57.5 cmH2O/l per s). No discernible ERPs were elicited by the undetected, sub-threshold stimulus but late components of the ERP (P2, N2, and P3) were observed to each of the three larger stimuli. They were related, in part, to behavioral judgments obtained during the stimulus periods. Both the latency and amplitude of the ERP components varied systematically as a function of stimulus magnitude, in a manner comparable to that observed in ERP paradigms using auditory and visual stimuli. Thus, the data show that event-related potentials to breathing are sensitive to physiologic effects of resistive loads present at the onset of inspiration. Respiratory ERPs may be used to infer sensory and perceptual responses to increases in airflow resistance and, accordingly, may relate to the perception of airflow obstruction in patient populations.     

The analysis of stimulus probability inside and outside the focus of attention, as reflected by the auditory N? and P? components.

Studied how N? and P? reflect a continuous process of matching inputs to a memory-based probabilistic model of the environment. 12 Ss performed a selective 2-channel auditory frequency discrimination while their evoked responses were registered in the attended and rejected channels. The auditory N? component was suppressed for all stimuli in the rejected channel at all probability levels, suppression being greatest when target stimuli were most probable. The rejected channel responded to reduced stimulus probability with N? augmentation. P? amplitude increased linearly as targets were made rarer, but only in the attended channel. When targets were most frequent, P? amplitude in the attended channel dropped to the same level as P? in the rejected channel. Selective attention is a necessary, but not sufficient condition for a selective P? response. Results indicate that attended inputs are modified selectively on the basis of location and pitch prior to the generation of N?, and information about stimulus probability is processed both inside and outside the focus of attention. Results with respect to P? point to a different probability-sensitive mechanism whose operation is contingent on focal attention. (French abstract) (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Directed attention prolongs the perceived duration of a brief stimulus

Stelmach, Herdman, and McNeil (1994) suggested recently that the perceived duration for attended stimuli is shorter than that for unattended ones. In contrast, the attenuation hypothesis (Thomas & Weaver, 1975) suggests the reverse relation between directed attention and perceived duration. We conducted six experiments to test the validity of the two contradictory hypotheses. In all the experiments, attention was directed to one of two possible stimulus sources. Experiments 1 and 2 employed stimulus durations from 70 to 270 msec. A stimulus appeared in either the visual or the auditory modality. Stimuli in the attended modality were rated as longer than stimuli in the unattended modality. Experiment 3 replicated this finding using a different psychophysical procedure. Experiments 4-6 showed that the finding applies not only to stimuli from different sensory modalities but also to stimuli appearing at different locations within the visual field. The results of all six experiments support the assumption that directed attention prolongs the perceived duration of a stimulus.     

Sustained visual-spatial attention produces costs and benefits in response time and evoked neural activity

This study investigated the simple reaction time (RT) and event-related potential (ERP) correlates of biasing attention towards a location in the visual field. RTs and ERPs were recorded to stimuli flashed randomly and with equal probability to the left and right visual hemifields in the three blocked, covert attention conditions: (i) attention divided equally to left and right hemifield locations; (ii) attention biased towards the left location; or (iii) attention biased towards the right location. Attention was biased towards left or right by instructions to the subjects, and responses were required to all stimuli. Relative to the divided attention condition, RTs were significantly faster for targets occurring where more attention was allocated (benefits), and slower to targets where less attention was allocated (costs). The early P1 (100-140 msec) component over the lateral occipital scalp regions showed attentional benefits. There were no amplitude modulations of the occipital N1 (125-180 msec) component with attention. Between 200 and 500 msec latency, a late positive deflection (LPD) showed both attentional costs and benefits. The behavioral findings show that when sufficiently induced to bias attention, human observers demonstrate RT benefits as well as costs. The corresponding P1 benefits suggest that the RT benefits of spatial attention may arise as the result of modulations of visual information processing in the extrastriate visual cortex.     

Visual slow brain potentials in children with attention deficit disorder

Using a two-stimulus reaction time paradigm, with two separate reward conditions (contingent and noncontingent), we compared slow wave brain potentials (ERPs) in 144 children with attention deficit disorder (ADD) and 30 normal control children. This article reviews the findings during the 900 msec visual warning stimulus. As we had expected, based on ERP work of Forth and Hare (1989) and Raine, Venables and Williams (1990), and on previous work from our own laboratory, the group differences were found in the negative slow wave portions of the ERP complex during the contingent reward condition but not during the noncontingent condition. Aggressive hyperactive subjects with attention deficit disorder (ADDHA) were discriminated from nonaggressive subjects (including control subjects) during the contingent reward condition in the following ways: (1) greater fronto-central negativity (640-900 msec slow wave) and (2) greater right parietal than left parietal negativity (430-750 msec slow wave). All ADD subgroups, when compared to control (CONTR) subjects, showed greater slow wave negativity (700-900 msec) at the midline occipital electrode site during the contingent reward condition. This could be explained in part as an IQ effect on ERPs reflecting the IQ difference between the ADD subgroups and the controls. These slow wave findings seem to relate to attentional problems of these children. They are discussed in terms of a psychobiological model of inhibition/disinhibition and appetitive activation.     

Attentional selection and attentional gradients: an alternative method for studying transient visual-spatial attention

Event-related potential (ERP) effects of transient and sustained non-spatial visual attention were investigated in an experiment where subjects were instructed to attend to the color or form of visual stimuli in order to detect infrequently presented targets with the relevant feature. The to-be-attended feature was either varied in a trial-by-trial fashion (transient attention) or was kept constant for an entire experimental block (sustained attention). Both transient and sustained attention resulted in a larger negativity for attended as compared to unattended stimuli between 200 and 300 ms post-stimulus. This effect was more pronounced for sustained attention than for transient attention and larger for attention to color than for attention directed to stimulus form. In the sustained, but not in the transient attention condition, color attention resulted in larger positivities for attended stimuli between 150 and 200 ms and in the P3 time range. These effects are interpreted as evidence for the existence of non-spatial attentional selection processes that are more effective under sustained than under transient attention conditions and are different from processes of visual-spatial attention. Moreover, the results indicate a special status for sustained attention to stimulus color.     

The mismatch negativity to frequency deviant stimuli during natural sleep

Eight subjects spent a single night in the sleep laboratory. Event-related potentials (ERPs) were recorded during the presentation of two auditory "oddball' stimulus conditions in which tonal frequency was manipulated. In the first condition, 1000 Hz "standard' and 2000 Hz "deviant' tones were presented. In the second condition, the deviant tone was reduced to 1050 Hz. In both conditions, deviant probability was 0.2. Stimuli were presented every 600 ms during wakefulness and stages 2, 4, and REM of sleep. A distinctive N1 wave was visible in both stimulus conditions when the subject was awake. The deviant stimuli elicited a "mismatch negativity' (MMN) that inverted in polarity at the mastoid. In REM sleep, an N1 and a MMN were also elicited in both conditions. In the large deviance condition, the MMN had a slightly attenuated amplitude and was shorter in duration while in the small deviant condition, its peak latency was unusually early. Neither the N1 nor the MMN could be recorded in non-REM sleep.     

Physical abuse amplifies attention to threat and increases anxiety in children.

Two experiments using event-related potentials (ERPs) examined the extent to which early traumatic experiences affect children's ability to regulate voluntary and involuntary attention to threat. The authors presented physically abused and nonabused comparison children with conflicting auditory and visual emotion cues, posed by children's mothers or a stranger, to examine the effect of emotion, modality, and poser familiarity on attention regulation. Relative to controls, abused children overattended to task-relevant visual and auditory anger cues. They also attended more to task-irrelevant auditory anger cues. Furthermore, the degree of attention allocated to threat statistically mediated the relationship between physical abuse and child-reported anxiety. These findings indicate that extreme emotional experiences may promote vulnerability for anxiety by influencing the development of attention regulation abilities. (PsycINFO Database Record (c) 2010 APA, all rights reserved)