Research Article: Good vibrations, bad vibrations: Oscillatory brain activity in the attentional blink

Date Published: December 22, 2011

Publisher: University of Finance and Management in Warsaw

Author(s): Jolanda Janson, Cornelia Kranczioch.

http://doi.org/10.2478/v10053-008-0089-x

Abstract

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.

Partial Text

Attention is distributed in time: We are quicker to respond to an event that happens
at the moment in time we expect it or that is in the focus of temporal attention
(Coull, 2004). And yet our ability to
voluntarily distribute attentional resources in time is limited. When two targets
need to be identified amongst a rapid stream of distractor stimuli (see Figure 1a) a deficit for identifying the second
target is evident. The deficit disappears if only the second target needs to be
identified (see Figure 1b). This so-called
attentional blink (AB) is a transitory attention impairment
that is most pronounced when the second target (T2) is presented 200-500 ms after
the first target (T1). It was first reported in 1987 (Broadbent & Broadbent, 1987; Weichselgartner & Sperling, 1987) and received its name 5 years
later from Raymond and colleagues (Raymond, Shapiro,
& Arnell, 1992) who where the first to study it in greater
detail.

Oscillatory brain activity can be characterized by its amplitude, its phase, and its
frequency. The amplitude is defined by the amount of Microvolts (µV) that is
generated, whereas the phase of an oscillation is cyclic and ranges between 0 and 2.
Oscillations can be categorized into five frequency bands: delta (0-4 Hz), theta
(4-8 Hz), alpha (8-12 Hz), beta (12-30 Hz), and gamma (30-80 Hz; Herrmann, Grigutsch, & Busch, 2002) though
the precise frequency boundaries per band are not stringently applied and can vary
from one publication to another. Oscillatory brain activity can be spontaneous or
event-related (Herrmann et al., 2002).
Continuous EEG can be considered to consist largely of a mix of spontaneous
oscillations at different frequencies that change over time (Gutberlet, Jung, & Makeig, 2009). Event-related
oscillations can further be divided into induced and evoked oscillation. Evoked
oscillations are characterized by a high degree of time and phase locking to an
event, whereas induced activity occurs after an event but the onset of this
occurrence and its phase vary in time (Herrmann et
al., 2002). AB research has so far focused on three aspects of
oscillatory brain activity: amplitude, inter-trial phase consistency, and
inter-area phase locking. The following section will give a
short and general description of each of these measures and refer to the AB studies
that used the respective measure.

The picture emerging from the research on oscillatory activity reviewed here shows
that the successful identification of both targets in an AB paradigm relates to a
dynamic interplay of oscillations at different frequencies occurring at different
moments in time. As is illustrated in Figure 4,
even before the first target is shown, AB and no-AB trials differ systematically.
Pre-T1 inter-area phase locking has been suggested to be beneficial to T2
performance in the AB task (Gross et al.,
2004; Kranczioch et al., 2007;
Nakatani et al., 2005). Moreover,
relatively higher alpha power in expectation of an RSVP trial, reduced
distractor-related activity and decreases in both power and synchrony in the alpha
frequency range just before T1 onset have been linked to escaping the AB (Kranczioch et al., 2007; Martens et al., 2006; Slagter
et al., 2009; Wierda et al.,
2010). Differences in oscillatory activity continue after the presentation of
the first target. Around T1 an increase in alpha power becomes apparent in no-AB
trials (Slagter et al., 2009) that lasts
until after T2 presentation (Kranczioch et al.,
2007). The ssVEP response to T1 is reduced in no-AB trials while at the
same time the T2-ssVEP response is enhanced (Keil
& Heim, 2009; Keil et al.,
2006; Kranczioch et al., 2007;
Martens et al., 2006; Wierda et al., 2010). Successful target
detection is furthermore linked to target-related synchronization increases after T1
and T2 in the theta and beta bands (Gross et al.,
2004, 2006; Kranczioch et al., 2007; Slagter et al., 2009) and systematic desynchronization in the beta band
(Gross et al., 2004, 2006).

In a recent extensive review of AB theories and behavioural data, Dux and Marois
(2009) argue that none of the AB models
can account for all the findings in the literature and that therefore the most
likely scenario is that the AB has a multifactorial origin. They leave however open
the possibility that these multiple processes rely on a common capacity-limited
resource, which, however, would again fall short to explain all the findings. Along
similar lines, Hommel and co-workers (2006)
conclude from the neuroscientific evidence that it is unlikely that the AB can be
tracked down to a single cortical structure or system, but that it seems that the AB
arises from the fact that several components have to interact as a network. The
problem is that communication within this network can refer to only one topic at a
time, effectively creating a bottleneck for target processing. The empirical
evidence Hommel and colleagues (2006) could
draw upon at that time suggested that the communication within the network and in
particular the bottleneck are tightly linked to beta band synchronization and
desynchronization during target processing. Research on oscillatory brain activity
in the AB published since then adds to this that task-relevant communication within
the network may also be evident in other frequency bands at varying latencies, and
that a modulation in the AB can occur without an accompanying modulation in beta
activity. Taking a closer look at these recent findings and their interactions with
beta band activity and performance and introducing experimental manipulations of
oscillatory brain activity will not only help to better understand the AB, but also
why the mechanism creating the AB, whatever its nature, can still be bypassed in
conditions that should normally result in blinking the target.

 

Source:

http://doi.org/10.2478/v10053-008-0089-x

 

Leave a Reply

Your email address will not be published.