The stabilization of cortical evoked potentials during selective visual attention

The event-related potentials (ERP) to lateralized moving visual stimuli (administered to the right and to the left of the subject) were recorded in six derivations in eight healthy subjects during passive viewing and selective attention to one of the stimuli (the relevant one), which demanded precise and rapid motor reaction. It was shown that during the selective voluntary attention correlation between successive ERP was substantially higher than that under conditions of passive (involuntary) attention, i.e. the ERP in the occipital, parietal, and frontal derivations during voluntary attention were more stable. The less was correlation between the ERP at passive viewing, the greater was the difference between the values of correlation coefficients during selective and passive attention. It is suggested that role of selected attention consists in stabilization of activity of the cortical structures, which are involved in solving the behavioral task.     

Event-related potentials associated with covert orientation of visual attention in Parkinson's disease

Event-related potentials (ERPs) were measured in a group of patients with idiopathic Parkinson's disease and compared with a matched control group during a task involving covert orientation of visual attention. Central warning cues directed attention to the probable location of a lateralized signal that required a button-press response. Parkinson patients had enhanced post-cue P1 (at Oz) and P2 (at Cz) amplitudes, delayed N1 (at Oz) latencies, and diminished CNV amplitudes. Post-target amplitudes were similar to controls, except for an enhanced P1 to invalidly cued targets, and delayed N1 and P3 target latencies. These results indicate that Parkinson patients, in addition to their motor deficits, process spatial cues more effortfully and slowly, have impaired response preparation, and process imperative stimuli more slowly.     

Development of selective attention during visual search.

Monitored eye movements in 8 2nd graders, 8 6th graders, and 8 college students during a search task in which Ss were given different types of information about target location before trial onset. Whereas color cues facilitated search performance in the 2 older groups, form cues were less successful in facilitating search and significantly interfered with search relative to a control condition for the 2nd graders. Both facilitation and interference effects in overall search times were related to number of fixations rather than to average fixation during a trial. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Event-related potentials during memorization of spatial locations in the auditory and visual modalities

Event-related potential (ERP) studies of working memory have used delayed S1-S2 match-to-sample tasks in which S1 is held in memory for comparison with S2. ERP negativities in the S1-S2 interval have been interpreted either in terms of working memory operations, or in terms of general preparatory motor processing. Two experiments (N = 20 each) were carried out to explore the nature of ERP negativities in a visuospatial memory task and in an auditory spatial memory task, respectively. In the experimental condition, subjects had to memorize the location of S1 (S1-memorize) so as to respond whether S2 appeared in the same spatial location (S2-memorize). In the control condition, subjects were requested to ignore S1 (S1-passive), and to respond whether S2 matched or not a target location predetermined at the beginning of the trial block (S2-pressing). Results support the two main conclusions of Martin-Loeches et al. (Electroenceph. clin. Neurophysiol., 1994, 91: 363-373). Firstly, that the encoding into memory of spatial location is associated with an ERP negative wave over the brain areas putatively associated with the processing of sensory information (i.e. right parieto-occipital for the visual task; fronto-central and left temporal areas for the auditory task). Secondly, the P300 does not seem to be an important ERP feature related to spatial location encoding and retaining into memory. Despite the distinct scalp distribution of these memory-related, modality-specific ERP negativities, they also showed a considerable degree of temporal synchronicity across modalities.     

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 elicited by infrequent non-target stimuli in young children of alcoholics: family history and gender differences

The treatment of cognitive communicative impairments that occur due to traumatic brain injury is a relatively new field. There is a need for more empirical evidence supporting the efficacy of cognitive rehabilitation. Fortunately, the number of studies in this area have continued to grow over the past few years. The purpose of this article is to provide current information regarding the assessment of functional outcomes after traumatic brain injury using the theoretical framework of the International Classification of Impairments, Disabilities, and Handicaps (ICIDH), which was developed by the World Health Organization (WHO).     

Feature-specific effects of selective visual attention

Four experiments were conducted to quantify the effect of performing a foveal discrimination task on sensitivity for a peripheral grating. The observer's primary task was to discriminate either the spatial frequency or orientation of successive foveal Gabor patches. On a third of the trials they also performed a secondary task to detect the presence of a near-threshold grating in the periphery. We find that sensitivity for detection of the peripheral grating depends on the similarity of the spatial frequencies and orientations between the foveal and peripheral stimuli. Importantly, sensitivity is also affected by which feature is being discriminated in the central task. Because the detectability of the peripheral grating is different when different features of the central stimuli are discriminated, we suggest that the effects on sensitivity are due to feature-specific attention and not simply to passive interactions between filters with similar tuning properties.     

Probability matching in visual selective attention.

J. Jonides (see record 1981-22746-001) suggested a model to account for shifts of spatial attention in visual search tasks with less than 100% cue validity. This 2-stage probability matching model was subsequently tested by Jonides (see record 1984-08558-001). Reaction time (RT) distribution characteristics provided some support for the model. The present author reanalyzes Jonides's data (including that published in 1981). Analysis showed strong support for the probability matching hypothesis. It is concluded that probability matching is an important strategic characteristic of visual spatial attention. (French abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age-related changes in selective attention and perceptual load during visual search.

Three visual search experiments were conducted to test the hypothesis that age differences in selective attention vary as a function of perceptual load (E. A. Maylor & N. Lavie, 1998). Under resource-limited conditions (Experiments 1 and 2), the distraction from irrelevant display items generally decreased as display size (perceptual load) increased. This perceptual load effect was similar for younger and older adults, contrary to the findings of Maylor and Lavie. Distraction at low perceptual loads appeared to reflect both general and specific inhibitory mechanisms. Under more data-limited conditions (Experiment 3), an age-related decline in selective attention was evident, but the age difference was not attributable to capacity limitations as predicted by the perceptual load theory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Perceptual grouping and visual selective attention

The present study demonstrates that incongruent distractor letters at a constant distance from a target letter produce more response competition and negative priming when they share a target's color than when they have a different color. Moreover, perceptual grouping by means of color, attenuated the effects of spatial proximity. For example, when all items were presented in the same color, near distractors produced more response competition and negative priming than far distractors (Experiment 3A). However, when near distractors were presented in a different color and far distractors were presented in the same color as the target, the response competition x distractor proximity interaction was eliminated and the proximity x negative priming interaction was reversed (Experiment 3B). A final experiment demonstrated that distractors appearing on the same object as a selected target produced comparable amounts of response competition and negative priming whether they were near or far from the target. This suggests that the inhibitory mechanisms of visual attention can be directed to perceptual groups/objects in the environment and not only to unsegmented regions of visual space.     

Event-related potentials in hypertriglyceridemia

Chronic morphine-treated dorsal-root ganglion (DRG) neurons in DRG/spinal cord explant cultures were previously shown to become supersensitive to the excitatory effects of remarkably low concentrations of the opioid agonists, morphine and dynorphin, and the opioid antagonist, naloxone. The present study demonstrates that this opioid excitatory supersensitivity of chronic morphine-treated DRG neurons (1 microM for > 1 week) is retained for periods > 3 months after return to control culture medium. Acute application of femtomolar dynorphin, as well as nanomolar naloxone, to the treated neurons after months in control medium evoked characteristic prolongation of the action potential duration (APD), as occurs in cells tested during or shortly after chronic opioid exposure. The threshold concentrations for eliciting these excitatory effects in naive DRG neurons are > 1000-fold higher. Furthermore, treatment of micromolar morphine-sensitized neurons with 1 nM etorphine (which is a potent excitatory opioid receptor antagonist) for I week prior to return to control medium blocked further expression of opioid excitatory supersensitivity when tested after an additional 1-7 weeks in culture. These results provide a unique in vitro model system for analyses of some of the cellular mechanisms underlying protracted opioid dependence in vivo.     

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.     

Interaction of hypertension and age in visual selective attention performance.

Previous research suggests that some aspects of cognitive performance decline as a joint function of age and hypertension. In this experiment, 51 unmedicated individuals with mild essential hypertension and 48 normative individuals, 18–78 yrs of age, performed a visual search task. The estimated time required to identify a display character and shift attention between display positions increased with age. This attention shift time did not differ significantly between hypertensive and normotensive participants, but regression analyses indicated some mediation of the age effect by blood pressure. For individuals less than 60 yrs of age, the error rate was greater for hypertensive than for normotensive participants. Although the present design could detect effects of only moderate to large size, the results suggest that effects of hypertension may be more evident in a relatively general measure of performance (mean error rate) than in the speed of shifting visual attention. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Auditory and visual capture during focused visual attention.

It is well known that auditory and visual onsets presented at a particular location can capture a person’s visual attention. However, the question of whether such attentional capture disappears when attention is focused endogenously beforehand has not yet been answered. Moreover, previous studies have not differentiated between capture by onsets presented at a nontarget (invalid) location and possible performance benefits occurring when the target location is (validly) cued. In this study, the authors modulated the degree of attentional focus by presenting endogenous cues with varying reliability and by displaying placeholders indicating the precise areas where the target stimuli could occur. By using not only valid and invalid exogenous cues but also neutral cues that provide temporal but no spatial information, they found performance benefits as well as costs when attention is not strongly focused. The benefits disappear when the attentional focus is increased. These results indicate that there is bottom-up capture of visual attention by irrelevant auditory and visual stimuli that cannot be suppressed by top-down attentional control. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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.     

Asymmetries of selective listening and attention switching in children.

Administered a selective listening task to 155 normal right-handed 3–12 yr old children. The stimuli consisted of dichotic digits, ranging from single pairs to strings of 4 pairs/trial. Each S attempted to focus attention on 1 ear for 8 practice trials and 28 test trials before switching attention to the opposite ear. Separate analyses of correct responses and intrusion errors yielded almost identical results: There was a significant right-ear advantage (REA) and a developmental increase in overall performance, but there was no developmental change in degree of asymmetry. The REA increased with increasing list length, but independent analyses for each list length failed to reveal any developmental changes in REA. Listening asymmetry was influenced markedly by the order in which the ears were monitored; Ss of all ages had difficulty in switching attention from right ear to left. Results support the developmental invariance hypothesis of cerebral lateralization and demonstrate that auditory asymmetry is not merely a direct reflection of some fixed structural asymmetry in the brain. (54 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Serial deployment of attention during visual search.

This study examined whether objects are attended in serial or in parallel during a demanding visual search task. A component of the event-related potential waveform, the N2pc wave, was used as a continuous measure of the allocation of attention to possible targets in the search arrays. Experiment 1 demonstrated that the relative allocation of attention shifts rapidly, favoring one item and then another. In Experiment 2, a paradigm was used that made it possible to track the absolute allocation of attention to individual items. This experiment showed that attention was allocated to one object for 100-150 ms before attention began to be allocated to the next object. These findings support models of attention that posit serial processing in demanding visual search tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Event-related correlates of response suppression as indicators of novelty seeking in alcoholics

We examined amplification of the c-met, c-erbB-2, and epidermal growth factor receptor (EGFR) gene in the patients with primary gastric cancer, and compared the data with clinical features in order to clarify the relationship between oncogenic abnormality and clinical features. Oncogene amplifications were examined by slot blot hybridization using DNAs extracted from formalin-fixed and paraffin-embedded tissues of primary gastric cancers. Seven of the seventy cancers (10.0%) had c-met gene amplification, nine (12.9%) had c-erbB-2 gene amplification, and six (8.6%) had EGFR gene amplification, respectively. Eighteen cases (25.7%) exhibited one or multiple oncogene amplification, and two cases (2.9%) exhibited simultaneous amplification of the three genes. The cases with c-met gene amplification tend to show invasive character and were related to peritoneal dissemination. The cases with c-erbB-2 gene amplification were related to lymph node metastasis. The cases with EGFR gene amplification had large tumors and were in highly advanced stage. The survival rate in patients with oncogene amplification was significantly lower than that in patients without amplification. Our data indicated that these genes were related to growth and metastasis of gastric cancer. Furthermore, this study about the three genes suggested that the type of activated gene might decide on the type of metastasis and clinical features.     

Visual selective attention and reading efficiency are related in children

We investigated the relationship between visual selective attention and linguistic performance. Subjects were classified in four categories according to their accuracy in a letter cancellation task involving selective attention. The task consisted in searching a target letter in a set of background letters and accuracy was measured as a function of set size. We found that children with the lowest performance in the cancellation task present a significantly slower reading rate and a higher number of reading visual errors than children with highest performance. Results also show that these groups of searchers present significant differences in a lexical search task whereas their performance did not differ in lexical decision and syllables control task. The relationship between letter search and reading, as well as the finding that poor readers-searchers perform poorly lexical search tasks also involving selective attention, suggest that the relationship between letter search and reading difficulty may reflect a deficit in a visual selective attention mechanisms which is involved in all these tasks. A deficit in visual attention can be linked to the problems that disabled readers present in the function of magnocellular stream which culminates in posterior parietal cortex, an area which plays an important role in guiding visual attention.