Spatial attention freezes during the attention blink

Brain Research, 2007

In order to investigate the interplay between visuo-spatial attention and central attention, we varied the relative probability (25% vs. 75%) of the responses to lateralized targets in an attentional blink paradigm. When the first target was associated with a less probable response, we observed a larger attentional blink, that is, a general reduction in accuracy for the second target. The efficiency of deployment of spatial attention to the second target was also reduced as a function of the response frequency for the first target. Both the N2pc, an event-related potential (ERP) associated with the deployment of attention in visual space, and the SPCN (sustained posterior contralateral negativity), an ERP associated with the maintenance of information in visual short-term memory, time-locked to T2 were significantly reduced when the first target was associated with a less frequent response.

Psychological Research, 2009

Observers encoded the spatial arrangement of two or three horizontal line segments relative to a square frame presented for 150 ms either in left or right visual field and either above or below the horizontal midline. The target pattern was selected on the basis of colour (red vs. green) from an equivalent distractor pattern in the opposite left-right visual hemifield. After a retention interval of 450 or 650 ms a test pattern was presented at fixation. The task was to decide whether the test was the same as the encoded pattern or different. Selection of the to-be-memorised pattern produced an N2pc response that was not influenced by the number of line segments nor by the length of the retention interval, but that was smaller in amplitude for patterns presented in the upper visual field compared with patterns presented in the lower visual field. A sustained posterior contralateral negativity (SPCN) followed the N2pc. The SPCN was larger for patterns with three line segments than for two, was larger for patterns encoded from lower visual field than from upper visual field, and returned to baseline sooner for the shorter retention interval than for the longer interval. These results, and others, provide an interesting and complex pattern of similarities and differences between the N2pc and SPCN, consistent with the view that N2pc reflects mechanisms of attentional selection whereas the SPCN reflects maintenance in visual short-term memory.

Biological Psychology, 1999

Two experiments were performed in which the effects of selective spatial attention on the ERPs elicited by unilateral and bilateral stimulus arrays were compared. In Experiment 1, subjects received a series of grating patterns. In the unilateral condition these gratings were presented one at a time, randomly to the right or left of fixation. In the bilateral condition, gratings were presented in pairs, one to each side of fixation. In the unilateral condition standard ERP effects of visual spatial attention were observed. However, in the bilateral condition we failed to observe an attention related posterior contralateral positivity (overlapping the P1 and N1 components, latency interval about 100 -250 ms), as reported in several previous studies. In Experiment 2, we investigated whether attention related ERP lateralizations are affected by the task requirement to search among multiple objects in the visual field. We employed a task paradigm identical to that used by Luck et al. (Luck, S.J., Heinze, H.J., Mangun, G.R., Hillyard, S.A., 1990. Visual event-related potentials index focused attention within bilateral stimulus arrays. II. Functional dissociation of P1 and N1 components. Electroencephalogr. Clin. Neurophysiol. 75, 528 -542). Four letters were presented to a visual hemifield, simultaneously to both the attended and unattended hemifields in the bilateral conditions, and to one hemifield only in the unilateral conditions. In a focused attention condition, subjects searched for a target letter at a fixed position, whereas they address: [email protected] (A.A. Wijers) 0301-0511/99/$ -see front matter © 1999 Elsevier Science B.V. All rights reserved. PII: S 0 3 0 1 -0 5 1 1 ( 9 9 ) 0 0 0 0 9 -5 J.J. Lange et al. / Biological Psychology 50 (1999) 203-233 204 searched for the target letter among all four letters in the divided attention condition (as in the experiment of . In the bilateral focused attention condition, only the contralateral P1 was enhanced. In the bilateral divided attention condition a prolonged posterior positivity was observed over the hemisphere contralateral to the attended hemifield, comparable to the results of . A comparison of the ERPs elicited in the focused and divided attention conditions revealed a prolonged 'search related negativity'. We discuss possible interactions between this negativity and attention related lateralizations. The display search negativity consisted of two phases, one phase comprised a midline occipital negativity, developing first over the ipsilateral scalp, while the second phase involved two symmetrical occipitotemporal negativities, strongly resembling the N1 in their topography. The display search effect could be modelled with a dipole in a medial occipital (possibly striate) region and two symmetrical dipoles in occipitotemporal brain areas. We hypothesize that this effect reflects a process of rechecking the decaying information of iconic memory in the occipitotemporal object recognition pathway.

Psychophysiology, 2011

If object-substitution masking (OSM) arises from mask representations replacing target representations, OSM should impede the formation of representations in visual short-term memory (VSTM). We utilized event-related potentials to examine the effect of OSM on target processing. An N2pc was observed on trials with delayed-offset masks, indicating that focused attention was directed to the target. The sustained posterior contralateral negativity (SPCN), an index of VSTM storage, was observed in delayed-offset trials only on trials with correct responses. This supports the hypothesis that inaccurate performance on delayed-offset trials arises from a failure to encode the target in VSTM. On cotermination trials, accuracy was high and neither the N2pc nor SPCN was observed. This indicates that, in the absence of masking, the task was accomplished by maintaining a diffuse attentional state that enabled the joint encoding of the potential target items.

Psychophysiology, 2008

The N2pc component has recently become a popular tool in attention research. To investigate whether this component exclusively reflects attentional target selection, or also prior stages in attentional processing (covert orienting, target-unspecific spatial attention), a spatial cueing procedure was combined with a visual search task. In some blocks, informative cues indicated the side of upcoming singleton targets that were present on most trials among uniform distractors. In other blocks, cues were spatially uninformative, and no preparatory shifts of attention were possible. The N2pc in response to targets was unaffected by this manipulation, showing that this component is not associated with attention shifts. Following informative cues, an attenuated N2pc was elicited by uniform non-target arrays, suggesting that the N2pc may also reflect spatially specific processing of stimulus features at task-relevant locations prior to target selection. Over the past thirty years, the brain mechanisms underlying visual-spatial attention have been studied intensively with event-related brain potential (ERP) measures. Different ERP components have been found to be modulated during spatially selective visual processing, and these components have been linked to different underlying sub-processes of spatial attention. The first type of attention-sensitive ERP effect was uncovered in early ERP studies where participants were instructed to direct their attention to a specific location on the left or right side, and keep it focused for an entire experimental block in order to detect target stimuli at that location (cf., Eason, 1981). Visual stimuli presented within the current focus of spatial attention triggered enhanced sensory-specific visual P1 and N1 components at posterior electrodes. Analogous P1 and N1 amplitude modulations were also observed when attention was manipulated in a trial-by-trial fashion by spatial precues that were presented at the start of each trial (cf. . Because these P1/N1 enhancements for stimuli at attended locations were present irrespective of whether these stimuli were targets or non-targets (e.g., , they are interpreted as reflecting location-specific sensory gating mechanisms in early visual processing that precede the subsequent selection of targets over non-targets. They are assumed to be triggered by top-down signals from higher-order attentional control areas that bias the excitability of visual cortical areas in favour of any sensory input that originates from currently task-relevant locations (cf., Mangun, 1995). Other attention-sensitive ERP modulations found in more recent studies during cued shifts of spatial attention were interpreted as electrophysiological markers of top-down attentional control processes. In these studies, ERP components sensitive to the direction of cued attentional shifts were quantified by comparing ERP waveforms triggered in the interval

Experimental Brain Research, 2008

Brain-based models of visual attention hypothesize that attention-related beneWts aVorded to imperative stimuli occur via enhancement of neural activity associated with relevant spatial and non-spatial features. When relevant information is available in advance of a stimulus, anticipatory deployment processes are likely to facilitate allocation of attention to stimulus properties prior to its arrival. The current study recorded EEG from humans during a centrally-cued covert attention task. Cues indicated relevance of left or right visual Weld locations for an upcoming motion or orientation discrimination. During a 1 s delay between cue and S2, multiple attention-related events occurred at frontal, parietal and occipital electrode sites. DiVerences in anticipatory activity associated with the non-spatial task properties were found late in the delay, while spatially-speciWc modulation of activity occurred during both early and late periods and continued during S2 processing. The magnitude of anticipatory activity preceding the S2 at frontal scalp sites (and not occipital) was predictive of the magnitude of subsequent selective attention eVects on the S2 event-related potentials observed at occipital electrodes. Results support the existence of multiple anticipatory attention-related processes, some with diVering speciWcity for spatial and non-spatial task properties, and the hypothesis that levels of activity in anterior areas are important for eVective control of subsequent S2 selective attention.

Psychophysiology, 2007

A test of the possible functional interaction between mechanisms subserving spatial attention and lexical access was devised by displaying one green and one red string of letters, one to the left and one to the right of fixation, and having participants attend to a target string defined by color while ignoring the other distractor string. The target string for a delayed lexical decision task could be a word or a nonword. The distractor was always a word. When the target was a word, target and distractor were associatively related on half of the trials and not related in the other trials. The event-related potential time-locked to the onset of the letter strings produced an N2pc (a greater negativity at scalp sites contralateral to the target relative to the ipsilateral sites arising at about 170 ms poststimulus). N2pc amplitude was reduced when the words were related relative to when they were not related. The results provide direct, online evidence that the rapid activation of meaning by visual words can influence the efficiency of the deployment of spatial attention.

PLoS ONE, 2012

Three target words (T1, T2, and T3) were embedded in a rapid serial visual presentation (RSVP) stream of non-word distractors, and participants were required to report the targets at the end of each RSVP stream. T2 and T3 were semantically related words in half of the RSVP streams, and semantically unrelated words in the other half of the RSVP streams. Using an identical design, a recent study reported distinct reflections of the T2-T3 semantic relationship on the P2 and N400 components of event-related potentials (ERPs) time-locked to T3, suggesting an early, automatic, source of P2 semantic effects and a late, controlled, source of N400 semantic effects. Here, P2 and N400 semantic effects were examined by manipulating list-wide context. Relative to participants performing in a semantically unbiased context, participants overexposed to filler RSVP streams always including semantically related T2/T3 words reported a dilution of T3-locked P2 semantic effects and a magnification of T3-locked N400 semantic effects. Opposite effects on P2 and N400 ERP components of list-wide semantic context are discussed in relation to recent proposals on the representational status of RSVP targets at processing stages prior to consolidation in visual short-term memory.

International Journal of Psychophysiology, 2015

Visual search and oddball paradigms were combined to investigate memory for to-be-ignored color changes in a group of 12 healthy participants. The onset of unexpected color change of an irrelevant stimulus evoked two reliable ERP effects: a component of the event-related potential (ERP), similar to the visual mismatch negativity response (vMMN), with a latency of 120-160 ms and a posterior distribution over the left hemisphere and Late Fronto-Central Negativity (LFCN) with a latency of 320-400 ms, apparent at fronto-central electrodes and some posterior sites. Color change of that irrelevant stimulus also slowed identification of a visual target, indicating distraction. The amplitude of this color-change vMMN, but not LFCN, indexed this distraction effect. That is, electrophysiological and behavioral measures were correlated. The interval between visual scenes approximated 1 s (611-1629 ms), indicating that the brain's sensory memory for the color of the preceding visual scenes must persist for at least 600 ms. Therefore, in the case of the neural code for color, durable memory representations are formed in an obligatory manner.

Cognitive Brain Research, 1999

A set of five tasks was designed to examine dynamic aspects of visual attention: selective attention to color, selective attention to pattern, dividing and switching attention between color and pattern, and selective attention to pattern with changing target. These varieties of visual attention were examined using the same set of stimuli under different instruction sets; thus differences between tasks cannot be attributed to differences in the perceptual features of the stimuli. ERP data are presented for each of these tasks. A within-task analysis of Ž . different stimulus types varying in similarity to the attended target feature revealed that an early frontal selection positivity FSP was evident in selective attention tasks, regardless of whether color was the attended feature. The scalp distribution of a later posterior Ž . selection negativity SN was affected by whether the attended feature was color or pattern. The SN was largely unaffected by dividing attention across color and pattern. A large widespread positivity was evident in most conditions, consisting of at least three subcomponents which were differentially affected by the attention conditions. These findings are discussed in relation to prior research and the time course of visual attention processes in the brain. q 0926-6410r99r$ -see front matter q 1999 Elsevier Science B.V. All rights reserved.