The attentional blink (AB) is a deficit in conscious perception of the second of two targets if it follows the first within 200-500 msec. The AB phenomenon has been linked to pre-target oscillatory alpha activity. However, this is based on paradigms that use a rapid serial visual presentation (RSVP) stimulus stream in which the targets are embedded. This distracter stream is usually presented at a frequency of 10 Hz and thus generates a steady-state visual-evoked potential (ssVEP) at the center of the alpha frequency band. This makes the interpretation of alpha findings in the AB difficult. To be able to relate these findings either to the presence of the ssVEP or to an effect of endogenously generated alpha activity, we compared AB paradigms with and without different pre-target distracter streams. The distracter stream was always presented at 12 Hz, and power and intertrial phase coherence were analyzed in the alpha range (8-12 Hz). Without a distracter stream alpha power dropped before target presentation, whereas coherence did not change. Presence of a distracter stream was linked to stronger pre-target power reduction and increased coherence, which were both modulated by distracter stream characteristics. With regard to the AB results indicated that, whereas ssVEP-related power tended to be higher when both targets were detected, endogenous alpha power tended to be lower. We argue that the pattern of results indicates that in the pre-target interval several processes act in parallel. The balance between these processes relates to the occurrence of an AB.
The attentional blink (AB) is a deficit in reporting the second (T2) of two targets (T1, T2) when presented in close temporal succession and within a stream of distractor stimuli. The AB has received a great deal of attention in the past two decades because it allows to study the mechanisms that influence the rate and depth of information processing in various setups and therefore provides an elegant way to study correlates of conscious perception in supra-threshold stimuli. Recently evidence has accumulated suggesting that oscillatory signals play a significant role in temporally coordinating information between brain areas. This review focuses on studies looking into oscillatory brain activity in the AB. The results of these studies indicate that the AB is related to modulations in oscillatory brain activity in the theta, alpha, beta, and gamma frequency bands. These modulations are sometimes restricted to a circumscribed brain area but more frequently include several brain regions. They occur before targets are presented as well as after the presentation of the targets. We will argue that the complexity of the findings supports the idea that the AB is not the result of a processing impairment in one particular process or brain area, but the consequence of a dynamic interplay between several processes and/or parts of a neural network.
Positive affect has been associated with improvement in performance in various attentional domains. Negative affect has been associated with narrowing of attention and lowering of performance in attentional tasks. Previous behavioral studies have put forth the diffuse mental state idea as the mechanism of these effects, where attentional resources are more evenly distributed during positive affect and more focused during negative affect. To explore neural correlates of this mechanism, a two-stream rapid serial visual presentation (RSVP) paradigm with centrally presented, overlapping streams was used. Participants attended one of the streams at a time and steady-state visual evoked potentials (ssVEP) in response to the attended and unattended streams were recorded in a positive, negative or neutral affect state. We predicted that in the positive affect condition, ssVEP responses to the attended and the unattended stream would be more alike than in a neutral condition. In the negative affect condition, as an expression of a less diffuse mental state, ssVEP responses were predicted to be more dissimilar. Self-assessments confirmed the effectiveness of the emotional manipulation. In the negative affect condition power was found to be higher than in the neutral condition. However, the modulations in the ssVEP did not reflect the predicted neural correlate of the diffuse mental state mechanism. Thus, the results provide evidence for negative affect modulating attention but suggest that the diffuse mental state is not a spatially oriented phenomenon.
The attentional blink (AB) occurs when the limits of temporal processing are reached. In a typical AB experiment, two targets (T1, T2) are presented within a stream of distracters, and detection of T2 is impaired when presented shortly after T1. Several theories focus on the mechanism underlying this deficit, among them proposals that see the similarity between distracters and targets as a crucial factor. The present study aimed to gain a better understanding of the effect of distracter stream properties on performance in the AB paradigm. A skeletal AB task was combined with a pretarget distracter stream. The presence and familiarity of the distracter stream and its similarityto the targets were manipulated in three separate experiments. The last distracter before T1 was sufficient to impair T1 detection in the standard rapid serial visual presentation (RSVP) paradigm. Second, T2|T1 performance was impaired by an RSVP stream with low target-distracter similarity but unfamiliar stimuli. Finally, a single mask before T1 was shown to impair T2|T1. The results suggest that it is the last distracter before T1, rather than the RSVP stream per se, that impairs T1 detection performance. T2|T1 performance is influenced by a combination of transient attentional capture mechanisms that include but are not limited to target-distracter similarity. Thus, the size of an AB is determined not only by target-distracter similarity but by the overall processing demands of the distracters.
Samenvatting Janson J, Derksen E, Vernooij-Dassen M, Lucassen P, Olde Rikkert M. Dementie: een moeilijk te vertellen diagnose. Een systematisch literatuuronderzoek. Huisarts Wet 2006;49(11):538-43.Inleiding Door de toenemende incidentie van dementie krijgen huisartsen steeds meer te maken met de diagnostiek van deze aandoening. Doel van dit literatuuronderzoek is in kaart te brengen wat de houding en werkwijze van huisartsen is ten aanzien van het meedelen van de diagnose dementie en wat de ervaringen van patie¨nten en mantelzorgers hiermee zijn.Methode Wij zochten met behulp van Cinahl, Psychinfo en MEDLINE naar artikelen en trokken de daarin genoemde referenties na. Twee onderzoekers beoordeelden de artikelen aan de hand van twee criteria: ze moesten over het meedelen van de diagnose dementie in de eerste lijn gaan en Nederlands-of Engelstalig zijn.Resultaat Na selectie van 477 artikelen bleven er 25 over. De sneeuwbalmethode voegde nog 4 artikelen toe. Huisartsen bleken terughoudend in het meedelen van de diagnose; patie¨nten en mantelzorgers ervoeren dit ook. Verder bleek er een verschil te bestaan tussen de opvattingen van artsen en hun praktisch handelen bij het meedelen van de diagnose.Beschouwing Door scholing zou de huisarts meer zekerheid en inzicht kunnen krijgen in het stellen en meedelen van de diagnose dementie en zijn rol daarin. Er is helaas maar weinig onderzoek gedaan dat primair is gericht op het meedelen van de diagnose dementie en de effecten daarvan in de eerste lijn.
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