Task-irrelevant Visual Stimuli Research Articles

Appearing and disappearing stimuli trigger a reflexive modulation of visual cortical activity

From the vast array of stimuli continually inundating our senses, only a very small portion is selected for higher-order processing. This selection is influenced by voluntary and reflexive mechanisms that may act at multiple stages of analysis. Extensive research has revealed that top–down voluntary mechanisms modulate information processing at both “early” (e.g., perceptual) and “late” (e.g., semantic) stages. Bottom–up sensory-driven mechanisms, however, are less well understood. Previous investigations of bottom–up mechanisms may have been influenced by top–down mechanisms because the stimuli were task-relevant and required overt responses. Here, we directly measured bottom–up influences on visual information processing by recording event-related brain potentials (ERP) to sequences of task-irrelevant visual stimuli. We found that abrupt visual events triggered an automatic enhancement of extrastriate visual activity (the P1 ERP component) to subsequent visual stimuli occurring at the same location. In contrast to theories suggesting that the abrupt appearance of a new object is unique in being able to trigger bottom–up effects, we found that disappearing objects triggered the same enhancement of subsequent stimulus processing as did appearing objects. The present data, however, also provide new electrophysiological evidence for a level of analysis in the brain that may be specific to the appearance of new objects. These data thus provide evidence that abruptly appearing objects may evoke specialized processing at certain stages of analysis in the brain but that, despite this difference, appearing and disappearing objects both trigger reflexive mechanisms that bias neural activity in human extrastriate visual cortex.

Attentional distraction of CNV depending on the spatial focus.

To investigate the distraction of spatial attention to the task-irrelevant visual stimuli, contingent negative variation (CNV) was measured by using a forewarned reaction time task in 20 healthy subjects. The lasting emission of light, irrelevant to the CNV task, at each perimetric angle of 15 degrees, 30 degrees or 45 degrees to the fixated point was presented to the subjects. The amplitude of early CNV was small only under the light-emission at the angle of 30 degrees. Our results indicate that attention is distracted even by the lasting, task-irrelevant stimuli and that distraction is dependent on the focusing function of attention.

Temporal dynamics of lateralized ERP components elicited during endogenous attentional shifts to relevant tactile events.

To investigate the temporal dynamics of lateralized event-related brain potential (ERP) components elicited during covert shifts of spatial attention, ERPs were recorded in a task where central visual symbolic cues instructed participants to direct attention to their left or right hand in order to detect infrequent tactile targets presented to that hand, and to ignore tactile stimuli presented to the other hand, as well as all randomly intermingled peripheral visual stimuli. In different blocks, the stimulus onset asynchrony (SOA) between cue and target was 300 ms, 700 ms, or 1,100 ms. Anterior and posterior ERP modulations sensitive to the direction of an attentional shift were time-locked to the attentional cue, rather than to the anticipated arrival of a task-relevant stimulus. These components thus appear to reflect central attentional control rather than the anticipatory preparation of sensory areas. In addition, attentional modulations of ERPs to task-irrelevant visual stimuli were found, providing further evidence for crossmodal links in spatial attention between touch and vision.

Cognitive resource model for the information-processing of task-irrelevant visual stimuli.

In order to elucidate possible factors that effect P3s to task-irrelevant visual stimuli (non-target P3s), we made a normative visual event-related potential study with button-press tasks in four different conditions in which two factors (the number of colors of non-target stimuli, and the shape of the stimuli) were manipulated without any change in task nor target/non-target ratio. The peak distributions of non-target P3s (centrally peaking) were significantly different from those of task-relevant P3s (parietally peaking) in all conditions. The amplitude of non-target P3 decreased as the variety of colors of the non-target stimuli increased. The amplitude of non-target P3 to colored solid circles was larger than that of non-target P3 to colored Stroop stimuli. Between each condition, task- relevant P3 and reaction time showed no significant difference. Both the variety of non-target stimuli and the shape of the stimuli were shown to have effects on the amplitudes of non-target P3s without any alteration in task-relevant P3s. It is suggested that the amplitude behaviors of non-target P3s partly reflect the amount of cognitive resource allocated for each different kind of task-irrelevant visual stimuli.

Neurophysiologic assessment of auditory brain maturation and learning in extremly premature infants

In 47 patients with Down's syndrome who were too retarded to understand a conventional oddball paradigm, we studied event-related potentials (ERPs) by using task-irrelevant visual stimuli. As the patients had expressed interest in Disney cartoons and books, five pictures of Disney characters such as Mickey Mouse or Peter Pan were employed as the rare stimuli, and nine ordinary scenes such as mountains as the frequent stimuli. Five sets were constructed by intermingling each rare picture with nine frequent pictures, and each picture was presented on a TV screen. ERPs to the rare stimuli (N270–P380), which were different from the averaged waveforms to frequent stimuli and electrooculograms (EOGs), were clearly recorded in 35 out of 47 patients. Only 24 of these patients had ERPs using a conventional auditory oddball paradigm. The peak latencies in patients were significantly prolonged relative to age-matched normal controls, probably due to a slowed neural processing. The amplitude in patients was slightly larger than normal controls, probably due to the patients' greater interest or surprise when confronted with the Disney characters.

Do patients with Down's syndrome recognize Mickey Mouse?

In 47 patients with Down's syndrome who were too retarded to understand a conventional oddball paradigm, we studied event-related potentials (ERPs) by using task-irrelevant visual stimuli. As the patients had expressed interest in Disney cartoons and books, five pictures of Disney characters such as Mickey Mouse or Peter Pan were employed as the rare stimuli, and nine ordinary scenes such as mountains as the frequent stimuli. Five sets were constructed by intermingling each rare picture with nine frequent pictures, and each picture was presented on a TV screen. ERPs to the rare stimuli (N270–P380), which were different from the averaged waveforms to frequent stimuli and electrooculograms (EOGs), were clearly recorded in 35 out of 47 patients. Only 24 of these patients had ERPs using a conventional auditory oddball paradigm. The peak latencies in patients were significantly prolonged relative to age-matched normal controls, probably due to a slowed neural processing. The amplitude in patients was slightly larger than normal controls, probably due to the patients' greater interest or surprise when confronted with the Disney characters.

Phasic EEG activities associated with rapid eye movements during REM sleep in man

Human cortical potentials associated with rapid eye movements (REMs) during REM sleep were recorded in 6 normal young adults by using the averaging technique. The potentials were compared with those recorded during voluntary saccades in the waking state in a dark or an illuminated room. A positive potential of relatively long duration with peak latency of about 200 msec and a wide spread bilateral distribution and of highest amplitude in the mid-parietal area appeared only during REM sleep. It is suggested that this positive potential is phasic EEG activity appearing in association with REMs during REM sleep in man. Comparison of this positive potential with P300s induced by task-irrelevant visual stimuli disclosed that they resemble each other. The possibility was discussed that this positive potential occurring in association with REMs during REM sleep is indeed a P300 appearing in response to visual images in dream.

Regional brain activity in dyslexic and control children during reading tasks: Visual probe event-related potentials

Event-related potentials (ERPs) elicited by task-irrelevant visual stimuli were recorded from 34 control and 32 dyslexic 10- to 12-year-old boys while they performed silent and oral reading at two levels of difficulty. All subjects were extensively screened for neurological problems, IQ, and sensory acuity. Specific features of the ERPs were affected in amplitude and latency by the experimental variables: group membership, oral vs. silent reading, difficulty level, and recording site (within and between hemispheres). A specific effect of difficulty on the central and parietal ERP was seen in the dyslexics but not the controls. Different patterns of asymmetry were found for the two groups in silent vs. oral reading at midtemporal placements. A marked asymmetry (R > L) was found at the midtemporal region for both groups.