| 1. |
- Haarala, Christian, et al.
(författare)
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Electromagnetic field emitted by 902 MHz phones shows no effects on children's cognitive function
- 2005
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Ingår i: Bioelectromagnetics. - : Wiley-Liss. - 0197-8462 .- 1521-186X. ; 26:S7, s. S144-S150
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Tidskriftsartikel (refereegranskat)abstract
- The present study investigated the potential effects of a standard 902 MHz global system for mobile communication (GSM) mobile phone on 10–14 years old children’s cognitive function. A total of 32 children (16 boys, 16 girls) participated with their own and parental consent. The subjects were 10– 14 years old (mean 12.1 years, SD 1.1). They performed a battery of cognitive tests twice in a counterbalanced order: once while exposed to an active mobile phone and once during exposure to an inactive phone. The tests were selected from those we used earlier with adults. The statistical analyses showed no significant differences between the mobile phone off and on conditions in reaction times and accuracy over all tests or in any single test. It was concluded that a standard mobile phone has no effect on children’s cognitive function as measured by response speed and accuracy. The present results challenge some earlier findings suggesting that the electromagnetic field (EMF) created by an active mobile phone would facilitate cognitive functioning.
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| 2. |
- Koivisto, Mika, et al.
(författare)
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Comparison of event-related potentials in attentional blink and repetition blindness
- 2008
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Ingår i: Brain Research. - : Elsevier B.V.. - 0006-8993 .- 1872-6240. ; 1189, s. 115-126
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Tidskriftsartikel (refereegranskat)abstract
- Attending to the first target in rapid serial visual presentation (RSVP) interferes with processing of the second target so that the participants fail to recognize the second target if the targets are separated by a stimulus onset asynchrony of 200–500 ms. This phenomenon is attentional blink (AB). Repetition blindness (RB) is an additional difficulty to recognize the second occurrence of the same stimulus in RSVP. A controversial issue in studies of both deficits is the processing level at which they occur. To compare the timing and mechanisms of AB and RB directly during the same RSVP stream, we recorded event-related potentials (ERPs) in response to repeated and unrepeated targets. Comparable to earlier ERP studies on visual awareness, the results showed for both types of targets a negative amplitude difference between ERPs to consciously recognized and unrecognized targets during 250-350 ms from stimulus onset, suggesting that both AB and RB are associated with deficits of conscious perception, occurring at earlier stages than access to working memory. However, the perceptual deficit in RB is more severe, which may be related to higher overall negativity in response to repeated targets observed 150–300 ms after stimulus onset, suggesting stronger cortical baseline activation and higher perceptual threshold for repeated targets as compared with unrepeated ones.
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| 3. |
- Koivisto, Mika, et al.
(författare)
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Electrophysiological correlates of visual consciousness and selective attention
- 2007
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Ingår i: NeuroReport. - : Lippincott Williams & Wilkins. - 0959-4965 .- 1473-558X. ; 18:8, s. 753-756
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Tidskriftsartikel (refereegranskat)abstract
- It is not clear whether attention is necessary or not for consciousness. We studied the relationship between attention and consciousness by tracking their electrophysiological correlates. The participants attended to visual targets, ignored nontargets in the prespecified visual field and ignored all stimuli in the opposite field. Visual consciousness was varied by masking. Our results showed that the earliest electrophysiological correlate of consciousness emerged independent of the manipulations of spatial and nonspatial attention. Conversely, the electrophysiological correlate of attention, selection negativity, was elicited regardless of the presence or absence of consciousness. Only the correlates of later, higher-level conscious processes strongly depended on attention. Thus, the electrophysiological brain responses reflecting visual consciousness and attention are initially independent of each other.
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| 4. |
- Koivisto, Mika, et al.
(författare)
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How meaning shapes seeing
- 2007
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Ingår i: Psychological Science. - : Sage Publications. - 0956-7976 .- 1467-9280. ; 18:10, s. 845-849
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Tidskriftsartikel (refereegranskat)abstract
- yInattentional blindness refers to the failure to see an unexpected object that one may be looking at directly when one's attention is elsewhere. We studied whether a stimulus whose meaning is relevant to the attentional goals of the observer will capture attention and escape inattentional blindness. The results showed that an unexpected stimulus belonging to the attended semantic category but not sharing physical features with the attended stimuli was detected more often than a semantically unrelated stimulus. This effect was larger when the unexpected stimuli were words than when they were pictures. The results imply that the semantic relation between the observer's attentional set and the unexpected stimulus plays a crucial role in inattentional blindness: An unexpected stimulus semantically related to the observer's current interests is likely to be seen, whereas unrelated unexpected stimuli are unseen. Attentional selection may thus be driven by purely semantic features: Meaning may determine whether or not one sees a stimulus.
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| 5. |
- Koivisto, Mika, et al.
(författare)
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The earliest electrophysiological correlate of visual awareness?
- 2008
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Ingår i: Brain and Cognition. - : Elsevier Inc.. - 0278-2626 .- 1090-2147. ; 66:1, s. 91-103
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Tidskriftsartikel (refereegranskat)abstract
- To examine the neural correlates and timing of human visual awareness, we recorded event-related potentials (ERPs) in two experiments while the observers were detecting a grey dot that was presented near subjective threshold. ERPs were averaged for conscious detections of the stimulus (hits) and nondetections (misses) separately. Our results revealed that hits, as compared to misses, showed a negativity around 180–350 ms at occipital and posterior temporal sites. It was followed by a positive wave after 400–500 ms, peaking at parietal sites. These correlates were not affected by a manipulation of attention. The early negativity, called ‘visual awareness negativity’ (VAN), may be a general, primary electrophysiological correlate of visual awareness. The present data show that it can be observed in response to appearance of a stimulus in visual awareness and that it generalizes across different manipulations of stimulus visibility.
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| 6. |
- Koivisto, Mika, et al.
(författare)
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The effects of perceptual load on semantic processing under inattention
- 2009
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Ingår i: Psychonomic Bulletin & Review. - : The Psychonomic Society, Inc.. - 1069-9384 .- 1531-5320. ; 16:5, s. 864-868
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Tidskriftsartikel (refereegranskat)abstract
- Inattentional blindness refers to a failure to consciously detect an irrelevant object that appears without any expectation when attention is engaged with another task. The perceptual load theory predicts that task-irrelevant stimuli will reach awareness only when the primary task is of low load, which allows processing resources to spill over to processing task-irrelevant stimuli as well. We studied whether perceptual load has an effect on inattentional blindness for a task-irrelevant stimulus whose meaning is or is not relevant to the attentional goals of the observer. In the critical trial, a word appeared without any expectation in the center of a display of attended pictures. The results showed that, under both high and low load, unexpected words belonging to the attended semantic category were detected more often than semantically unrelated words. These results imply that task-irrelevant stimuli, whose meanings are relevant to the observer’s task, enter awareness irrespective of perceptual load.
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| 7. |
- Koivisto, Mika, et al.
(författare)
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The relationship between awareness and attention : Evidence from ERP responses
- 2009
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Ingår i: Neuropsychologia. - : Elsevier. - 0028-3932 .- 1873-3514. ; 47:13, s. 2891-2899
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Tidskriftsartikel (refereegranskat)abstract
- The relationship between attention and awareness is complex, because both concepts can be understood in different ways. Here we review our recent series of experiments which have tracked the independent contributions of different types of visual attention and awareness to electrophysiological brain responses, and then we report a new experiment focusing on spatial attention, nonspatial selection of objects, and visual consciousness at the same time. The results indicate that the earliest electrophysiological correlate of consciousness, assumed to correlate with “phenomenal consciousness”, was dependent on spatial attention, suggesting that spatial attention is a prerequisite for the internal representations of space that provide the medium for phenomenal experience. The correlate of phenomenal consciousness emerged independent of nonspatial selection of objects, but its later part was modified by it. By contrast, the correlate of access to later conscious processing stages (“reflective consciousness”) that take the selected contents of phenomenal consciousness as input for conceptual thought and working memory, was dependent on both spatial attention and nonspatial selection. These results imply that one should distinguish between different types of attention and different forms of awareness, when describing the relationship between attention and awareness.
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| 8. |
- Koivisto, Mika, et al.
(författare)
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The role of selective attention in visual awareness of stimulus features : Electrophysiological studies
- 2008
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Ingår i: Cognitive, Affective, & Behavioral Neuroscience. - : Psychonomic Society, Inc.. - 1530-7026 .- 1531-135X. ; 8:2, s. 195-210
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Tidskriftsartikel (refereegranskat)abstract
- Attention and awareness are closely related, but the nature of their relationship is unclear. The present study explores the timing and temporal evolution of their interaction with event-related potentials. The participants attended to specific conjunctions of spatial frequency and orientation in masked (unaware) and unmasked (aware) visual stimuli. A correlate of awareness appeared 100-200 msec from stimulus onset similarly to both attended and unattended features. Selection negativity (SN), a correlate of attentional selection, emerged in response to both masked and unmasked stimuli after 200 msec. This double dissociation between correlates of awareness and SN suggests that the electrophysiological processes associated with feature-based attentional selection and visual awareness of features can be dissociated from each other at early stages of processing. In a passive task, requiring no attention to the stimuli, early electrophysiological responses (before 200 msec) related to awareness were attenuated, suggesting that focal attention modulates visual awareness earlier than does selective feature-beased attention.
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| 9. |
- Koivisto, Mika, et al.
(författare)
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The role of unattended distractors in sustained inattentional blindness
- 2008
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Ingår i: Psychological Research. - : Springer. - 0340-0727 .- 1430-2772. ; 72:1, s. 39-48
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Tidskriftsartikel (refereegranskat)abstract
- When participants are attending to a subset of visual targets or events and ignore irrelevant distractors ("selective looking"), they often fail to detect the appearance of an unexpected visual object or event even when the object is visible for several seconds ("sustained inattentional blindness"). An important factor influencing detection rates in selective looking is the attentional set of the participant: the more similar the features of the unexpected object are to the attended ones, the more probably it will be detected. We examined the possible contribution of active ignoring to this similarity effect by studying the role of the distractor objects in sustained inattentional blindness. First we showed the similarity effect for chromatic colors and then we manipulated the similarity of the unexpected object in relation to the distractor objects and did not find any effects. Moreover, we found that inattentional blindness was present even when the displays did not contain any irrelevant to-be-ignored objects. We conclude that attending to target items on the bais of attentional set, but not active ignoring of nontargets items, is sufficient for the occurrence of sustained inattentional blindness.
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| 10. |
- Overgaard, Morten, et al.
(författare)
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The electrophysiology of introspection
- 2006
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Ingår i: Consciousness and Cognition. - : Elsevier. - 1053-8100 .- 1090-2376. ; 15:4, s. 662-672
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Tidskriftsartikel (refereegranskat)abstract
- To study whether the distinction between introspective and non-introspective states of mind is an empirical reality or merely a conceptual distinction, we measured event-related potentials (ERPs) elicited in introspective and non-introspective instruction conditions while the observers were trying to detect the presence of a masked stimulus. The ERPs indicated measurable differences related to introspection in both preconscious and conscious processes. Our data support the hypothesis that introspective states empirically differ from non-introspective states.
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