Donna Bryce

How are overlapping time intervals perceived? Evidence for a weighted sum of segments model

This study investigated the way in which people time two overlapping intervals. Timing models already proposed in the literature predict different effects of the degree of overlap on each estimate, and empirical findings were compared to these predictions. Two unimodal experiments (in which each to-be-timed interval was a visual stimulus) and one bimodal experiment (in which one to-be-timed interval was auditory and the other visual) were conducted. The estimate of the first interval was either unaffected or decreased, and the estimate of the second interval consistently increased as the intervals were more temporally separated. The only model in the literature that could account for such result patterns is a single pacemaker single accumulator structure with an additional recency weighting (see the weighted sum of segments model). That is, participants appear to segment the two overlapping intervals into three non-overlapping and overlapping segments, time these segments separately, and then combine them to estimate each interval. Importantly, a recency weighting, determined by the time that has passed since the end of that segment, is also applied to each segment in the summation process. Further, in the bimodal experiment the order in which the stimuli of different modalities were presented affected the way in which they were timed, a finding that none of the current models can explain. This highlights that a comprehensive model of interval timing must consider not only the modalities of to-be-timed intervals but also the order in which different modalities must be timed.

The neural correlates of emotion processing in juvenile offenders.

Individuals with severe antisocial behaviour often demonstrate abnormalities or difficulties in emotion processing. Antisocial behaviour typically onsets before adulthood and is reflected in antisocial individuals at the biological level. We therefore conducted a brain-based study of emotion processing in juvenile offenders. Male adolescent offenders and age-matched non-offenders passively viewed emotional images whilst their brain activity was recorded using electroencephalography. The early posterior negativity (EPN) and the late positive potential (LPP) components were used as indices of emotion processing. For both juvenile offenders and non-offenders, the EPN differentiated unpleasant images from other image types, suggesting that early perceptual processing was not impaired in the offender group. In line with normal emotion processing, the LPP was significantly enhanced following unpleasant images for non-offenders. However, for juvenile offenders, the LPP did not differ across image categories, indicative of deficient emotional processing. The findings indicated that this brain-based hypo-reactivity occurred during a late stage of cognitive processing and was not a consequence of atypical early visual attention or perception. This study is the first to show attenuated emotion processing in juvenile offenders at the neural level. Overall, these results have the potential to inform interventions for juvenile offending.

The Maturation of Interference Suppression and Response Inhibition: ERP Analysis of a Cued Go/Nogo Task

Inhibitory control is a core function that allows us to resist interference from our surroundings and to stop an ongoing action. To date, it is not clear whether inhibitory control is a single process or whether it is composed of different processes. Further, whether these processes are separate or clustered in childhood is under debate. In this study, we investigated the existence and development of two hypothesized component processes of inhibitory control–interference suppression and response inhibition–using a single task and event related potential components. Twenty 8-year-old children and seventeen adults performed a spatially cued Go/Nogo task while their brain activity was recorded using electroencephalography. Mean N2 amplitudes confirmed the expected pattern for response inhibition with both the children and the adults showing more negative N2 for Nogo vs. Go trials. The interference suppression N2 effect was only present in adults and appeared as a more negative N2 in response to Go trials with a congruent cue than Go trials with an incongruent cue. Contrary to previous findings, there was no evidence that the interference suppression N2 effect was later occurring than the response inhibition N2 effect. Overall, response inhibition was present in both the children and the adults whereas interference suppression was only present in the adults. These results provide evidence of distinct maturational processes for both component processes of inhibitory control, with interference suppression probably continuing to develop into late childhood.

Psychosocial Intervention Is Associated with Altered Emotion Processing: An Event-Related Potential Study in At-Risk Adolescents

Emotion processing is vital for healthy adolescent development, and impaired emotional responses are associated with a number of psychiatric disorders. However, it is unclear whether observed differences between psychiatric populations and healthy controls reflect modifiable variations in functioning (and thus could be sensitive to changes resulting from intervention) or stable, non-modifiable, individual differences. The current study therefore investigated whether the Late Positive Potential (LPP; a neural index of emotion processing) can be used as a marker of therapeutic change following psycho-social intervention. At-risk male adolescents who had received less than four months intervention (minimal-intervention, N = 32) or more than nine months intervention (extended-intervention, N = 32) passively viewed emotional images whilst neural activity was recorded using electroencephalography. Significant differences in emotion processing, indicated by the LPP, were found between the two groups: the LPP did not differ according to valence in the minimal-intervention group, whereas the extended-intervention participants showed emotion processing in line with low risk populations (enhanced LPP for unpleasant images versus other images). Further, an inverse relationship between emotional reactivity (measured via the LPP) and antisocial behaviour was observed in minimal-intervention participants only. The data therefore provide preliminary cross-sectional evidence that abnormal neural responses to emotional information may be normalised following psychosocial intervention. Importantly, this study uniquely suggests that, in future randomised control trials, the LPP may be a useful biomarker to measure development and therapeutic change.

Temporal discrimination of one’s own reaction times in dual-task performance: Context effects and methodological constraints

In this study we used the method of constant stimuli to investigate introspective reaction times in the psychological refractory period (PRP) paradigm under different temporal contexts. Previous introspective PRP studies have mostly used visual analogue scales to assess introspective reaction times and found that participants were largely unaware of the typical dual-task costs that arise in this paradigm (PRP effect). This apparent limitation of introspection has been taken as evidence for a serial processing bottleneck that encompasses response selection as well as conscious perception. In our study, in each trial participants first performed the PRP task and were then presented with a comparison interval that they had to compare with their reaction time to the second task (RT2). Across three experiments, we observed that the subjective estimates of RT2 (i.e., the points of subjective equality) did not reflect the objective pattern but were almost completely biased toward the center of the comparison intervals (asymmetry effect). In a control experiment in which participants discriminated RT2s of other participants without performing the PRP task, this bias was largely reduced. We interpret these results as indicating that in dual-task performance participants acquire only poor temporal representations of their own reaction times, and the apparent unawareness of the PRP effect may reflect disturbed timing abilities rather than a conscious perception bottleneck.

Introspection is not always blind to the costs of multitasking: The case of task switching.

Previous studies have provided evidence that introspection about dual-task performance in the psychological refractory period (PRP) paradigm is severely limited. The present study investigated introspection at the other pole of the multitasking continuum, namely task switching. In 2 experiments, participants provided estimates of their response times (i.e., introspective RTs) after each trial in modified versions of the alternating-runs and the task-cuing paradigm, which included only 2 tasks in a trial. In contrast to the previously observed unawareness of dual-task costs in the PRP paradigm, participants reported their switch costs in introspective RTs. Thus, introspection about multitasking performance appears to not always be as limited as in the PRP paradigm. Nevertheless, introspection is not without limits also in task switching. Participants only partly reported the beneficial impact of longer preparation time on their performance. The present results suggest that introspective RTs depend on multiple cues, of which some are valid and some are invalid.

Psychosocial intervention in at-risk adolescents: using event-related potentials to assess changes in decision making and feedback processing

Decision making and feedback processing are two important cognitive processes that are impacted by social context, particularly during adolescence. The current study examined whether a psychosocial intervention could improve psychological wellbeing in at-risk adolescent boys, thereby improving their decision making and feedback processing skills. Two groups of at-risk adolescents were compared: those who were relatively new to a psychosocial intervention, and those who had engaged over a longer time period. Electroencephalography was recorded while the young people participated in a modified version of the Taylor Aggression Paradigm. The late positive potential (LPP) was measured during the decision phase of the task (where participants selected punishments for their opponents). The feedback-related negativity (FRN) and P3 components were measured during the task’s outcome phase (where participants received ‘win’ or ‘lose’ feedback). Adolescents who were new to the intervention (the minimal-intervention group) were harsher in their punishment selections than those who had been engaged in the program for much longer. The minimal-intervention group also showed an enhanced LPP during the decision phase of the task, which may be indicative of immature decision making in that group. Analysis of the FRN and P3 amplitudes revealed that the minimal-intervention group was physiologically hypo-sensitive to feedback, compared with the extended-intervention group. Overall, these findings suggest that long-term community-based psychosocial intervention programs are beneficial for at-risk adolescents, and that event-related potentials can be employed as biomarkers of therapeutic change. However, because participants were not randomly allocated to treatment groups, alternative explanations cannot be excluded until further randomized controlled trials are undertaken.