Bjørn Sætrevik

Priming inhibits the right ear advantage in dichotic listening: Implications for auditory laterality

The typical finding in dichotic listening with verbal stimuli is the right ear advantage (REA), indicating a left hemisphere processing superiority, thus making this an effective tool in studying hemispheric asymmetry. It has been shown that the amplitude of the REA can be modulated by instructions to direct attention to left or right side. The current study attempted to modulate the REA by changing the dichotic listening stimulus situation. In Experiment 1, a consonant vowel (CV) syllable prime was presented binaurally briefly before the dichotic stimuli (consisting of two CVs). The prime could be the same as either the left or right ear dichotic stimulus, or it could be a different stimulus. Participants were instructed to report the CV they heard best from the dichotic syllable pair. The traditional REA was found when the prime was different from both dichotic stimuli. When the prime matched the CV in the left half of the subsequent dichotic pair, the REA was increased, while if the prime matched the right half, the REA was reduced. In order to see at which perceptual stage the modulation takes place, in Experiment 2 the prime was visual, presented on a PC screen. The same effect was seen, although the modulation of the REA was weaker. We propose that the memory trace of the prime is a source of interference, and causes cognitive control of attention to inhibit recognition of stimuli similar to recent distractors. Based on previous studies we propose that this inhibition of attention is performed by prefrontal cortical areas. Similarities to the mechanisms involved in negative priming and implications for auditory laterality studies are pointed out.

Attentional biases among pathological gamblers

Pictorial stimuli were presented in a Stroop task paradigm that enabled the recording of attentional bias. The sample comprised 33 pathological slot machine gamblers (PG) and 22 control participants. The design of the study had one between-subjects factor – Group (PGs vs control), and two within-subject factors: (1) Stimulus meaning (win-related gambling stimuli vs neutral stimuli) and (2) Exposure (subliminal vs supraliminal). The results supported the notion that the PG group had an attentional bias towards visual win-related gambling stimuli compared with the control group. Furthermore, the degree of attentional bias among the PG group was moderately negatively correlated with net loss in the week before testing. One possible treatment implication of the findings is to include in-vivo exposure sessions as a supplement to cognitive behavioural therapy for gambling. Future studies could also include non-win gambling-related stimuli and should also comprise non-pathological regular gamblers as an additional control group.

Cognitive conflict and inhibition in primed dichotic listening.

In previous behavioral studies, a prime syllable was presented just prior to a dichotic syllable pair, with instructions to ignore the prime and report one syllable from the dichotic pair. When the prime matched one of the syllables in the dichotic pair, response selection was biased towards selecting the unprimed target. The suggested mechanism was that the prime was inhibited to reduce conflict between task-irrelevant prime processing and task-relevant dichotic target processing, and a residual effect of the prime inhibition biased the resolution of the conflict between the two targets. The current experiment repeated the primed dichotic listening task in an event-related fMRI setting. The fMRI data showed that when the task-irrelevant prime matched the task-relevant targets, activations in posterior medial frontal cortex (pMFC) and in right inferior frontal gyrus (IFG) increased, which was considered to represent conflict and inhibition, respectively. Further, matching trials where the unprimed target was selected showed activation in right IFG, while matching trials where the primed target was selected showed activations in pMFC and left IFG, indicating the difference between inhibition-biased selection and unbiased selection.

Endogenous and Exogenous Control of Attention in Dichotic Listening

Dichotic listening to verbal stimuli results in a right ear advantage (REA), indicating a left hemisphere processing superiority. The magnitude of the REA can be modulated by instructions to direct attention to the left or right ear stimulus. A previous study from our laboratory showed that presenting a prime syllable before the presentation of the dichotic syllables increases reports of the nonprimed syllable, apparently a negative priming effect that inhibits attention to the distracting prime representation. The present study combined attention instruction and priming, making up a 3 x 3 factorial design. The prime stimulus was a single consonant-vowel syllable presented binaurally just before onset of the dichotic consonant-vowel syllables. Results showed that both instructions and priming manipulations had an effect on which dichotic stimulus was selected. There was also a significant interaction between attention instruction and priming manipulation, indicating that the mechanism for instructed attention and the mechanism for negative priming work on the same level of processing.

The “Similarity Index” as an Indicator of Shared Mental Models and Situation Awareness in Field Studies:

The aim of this paper is to present a methodology where the extent of information sharing among team members is used as an indicator of shared mental models (SMM) and situation awareness (SA). Data collection procedures and probe materials are described for two field experiments performed among emergency management teams in the hydrocarbon industry. Methods are suggested for calculating a “similarity index” by comparing a team member’s responses with the average response in the team or with the responses of the team member assumed to be best informed. It is argued that similarity to team average could be a measure of SMM, whereas similarity to the best-informed team member could be argued to be an indicator of SA. The degree of compliance in responding to the probes is reported, as is the degree to which the extent of shared information differed between the probe questions or according to team positions. Lessons learned from the data collection are summarized, and the applicability of the similarity index as a measure of SA is discussed. Some advantages of the current approach are presented, as are challenges and inherent assumptions in future applications of this approach.

The right ear advantage revisited: Speech lateralisation in dichotic listening using consonant–vowel and vowel–consonant syllables

The dichotic listening task is typically administered by presenting a consonant–vowel (CV) syllable to each ear and asking the participant to report the syllable heard most clearly. The results tend to show more reports of the right ear syllable than of the left ear syllable, an effect called the right ear advantage (REA). The REA is assumed to be due to the crossing over of auditory fibres and the processing of language stimuli being lateralised to left temporal areas. However, the tendency for most dichotic listening experiments to use only CV syllable stimuli limits the extent to which the conclusions can be generalised to also apply to other speech phonemes. The current study re-examines the REA in dichotic listening by using both CV and vowel–consonant (VC) syllables and combinations thereof. Results showed a replication of the REA response pattern for both CV and VC syllables, thus indicating that the general assumption of left-side localisation of processing can be applied for both types of stimuli. Further, on trials where a CV is presented in one ear and a VC is presented in the other ear, the CV is selected more often than the VC, indicating that these phonemes have an acoustic or processing advantage.

Updating working memory in aircraft noise and speech noise causes different fMRI activations

The present study used fMRI/BOLD neuroimaging to investigate how visual-verbal working memory is updated when exposed to three different background-noise conditions: speech noise, aircraft noise and silence. The number-updating task that was used can distinguish between “substitution processes,” which involve adding new items to the working memory representation and suppressing old items, and “exclusion processes,” which involve rejecting new items and maintaining an intact memory set. The current findings supported the findings of a previous study by showing that substitution activated the dorsolateral prefrontal cortex, the posterior medial frontal cortex and the parietal lobes, whereas exclusion activated the anterior medial frontal cortex. Moreover, the prefrontal cortex was activated more by substitution processes when exposed to background speech than when exposed to aircraft noise. These results indicate that (a) the prefrontal cortex plays a special role when task-irrelevant materials should be denied access to working memory and (b) that, when compensating for different types of noise, either different cognitive mechanisms are involved or those cognitive mechanisms that are involved are involved to different degrees.

A biased competition model accounts for negative priming in a free choice situation as residual effects of inhibitory conflict resolution

The processing of a stimulus can be facilitated (positive priming) or impeded (negative priming), depending on whether a repeated stimulus has recently been attended or ignored. The current experiment presented consecutive dichotic syllable pairs with instructions to report any syllable from each pair. The results showed that trials which repeated a syllable from the previous trial had increased response times, and the repeated syllable had a decreased likelihood of being selected. This indicates that inhibition is involved when selecting between stimuli, and that the inhibition associated with stimuli has a residual effect on subsequent selection. Closer examination showed that a repeated syllable was more likely to be ignored if the syllable had been ignored rather than attended on the previous presentation, and trials showing this response pattern had faster response times than trials that did not, thus representing an effect similar to negative priming. We suggest that a biased competition network model, in which pathways are made stronger or weaker as a residual effect of selection, can be applied to account for the observed effect. The model has support from other experimental tasks, and in contrast to prominent accounts of negative priming, it focuses on the processing performed by the network rather than on pre-onset selection criteria for processing.The processing of a stimulus can be facilitated (positive priming) or impeded (negative priming), depending on whether a repeated stimulus has recently been attended or ignored. The current experiment presented consecutive dichotic syllable pairs with instructions to report any syllable from each pair. The results showed that trials which repeated a syllable from the previous trial had increased response times, and the repeated syllable had a decreased likelihood of being selected. This indicates that inhibition is involved when selecting between stimuli, and that the inhibition associated with stimuli has a residual effect on subsequent selection. Closer examination showed that a repeated syllable was more likely to be ignored if the syllable had been ignored rather than attended on the previous presentation, and trials showing this response pattern had faster response times than trials that did not, thus representing an effect similar to negative priming. We suggest that a biased competition network model, in which pathways are made stronger or weaker as a residual effect of selection, can be applied to account for the observed effect. The model has support from other experimental tasks, and in contrast to prominent accounts of negative priming, it focuses on the processing performed by the network rather than on pre-onset selection criteria for processing.

Cognitive Conflict in a Syllable Identification Task Causes Transient Activation of Speech Perception Area.

It has previously been shown that task performance and frontal cortical activation increase after cognitive conflict. This has been argued to support a model of attention where the level of conflict automatically adjusts the amount of cognitive control applied. Conceivably, conflict could also modulate lower-level processing pathways, which would be evident as trial-to-trial changes in domain specific activation. The present fMRI experiment used a syllable identification task where conflict is manipulated by presenting recently ignored syllables. Results showed that on trials following a high conflict trial, activation increased primarily in the planum temporale region of the left temporal cortex, an area believed to be involved in syllable discrimination. The experiment thus showed a transient, domain specific attention effect that was modulated on a trial-to-trial basis. We argue that this indicates a self-regulating system where increased levels of conflict directs resources in order to improve performance.

Proactive and reactive sequential effects on selective attention

Sequences of events can affect selective attention either through proactive mechanisms, through reactive mechanisms, or through a combination of the two. The current study examined electrophysiological responses to both prime and target stimuli in a primed dichotic listening task. Each trial presented a distractor prime syllable followed by two simultaneous syllables, and participants were asked to report one of the simultaneous syllables. Trials where the participant reported the non-primed syllable showed more negative event-related potentials at prime presentation, which may indicate inhibition of the prime representation. Trials where the participant reported the primed syllable showed more negative event-related potentials at target presentation, which may indicate cognitive conflict and effortful response selection. In context of current theories, the data suggest that the interplay of a proactive inhibition bias and a reactive potential for conflict is involved in causing sequential effects on selective attention mechanisms.