Decisions Made with Less Evidence Involve Higher Levels of Corticosubthalamic Nucleus Theta Band Synchrony

The switch between automatic action selection and more controlled forms of decision-making is a dynamic process thought to involve both cortical and subcortical structures. During sensory conflict, medial pFC oscillations in the theta band (<8 Hz) drive those of the subthalamic nucleus (STN), and this is thought to increase the threshold of evidence needed for one competing response to be selected over another. Here, we were interested in testing whether STN activity is also altered by the rate at which evidence is presented during a congruent dot motion task absent of any explicit sensory conflict. By having a series of randomly moving dots gradually transform to congruent motion at three different rates (slow, medium, fast), we were able to show that a slower rate increased the time it took participants to make a response but did not alter the total amount of evidence that was integrated before the response. Notably, this resulted in a decision being made with a lower amount of instantaneous evidence during the slow and medium trials. Consistent with the idea that medial pFC–STN activity is involved in executing cognitive control, the higher levels of ambiguity during these trials were associated with increased theta band synchrony between the cortex and the STN, with the cortical oscillations Granger-causal to those of the STN. These results further confirm the involvement of the STN in decision-making and suggest that the disruption of this network may underlie some of the unwanted cognitive deficits associated with STN deep brain stimulation.

Can Children With SLI Detect Cognitive Conflict? Behavioral and Electrophysiological Evidence

Purpose This study examined whether children with specific language impairment (SLI) are deficient in detecting cognitive conflict between competing response tendencies in a GO/No-GO task. Method Twelve children with SLI (ages 10–12), 22 children with typical language development matched group-wise on age (TLD-A), and 16 younger children with TLD (ages 8–9) matched group-wise on language skills (TLD-L) were tested using a behavioral GO/No-GO paradigm with simultaneous collection of event-related potentials. The N2 component was used as a neural index of the ability to detect conflict between GO and No-GO response tendencies. Results Hit rates did not differentiate the 3 groups. The TLD-L children demonstrated the highest false-alarm rates. The N2 component was attenuated and showed delayed divergence of GO and No-GO amplitudes in SLI relative to TLD-A children in response to stimuli presented at various probability levels. The N2 effect in children with SLI resembled that of children with TLD who were approximately 3 years younger. Conclusions School-age children with SLI exhibit a maturational lag in detecting conflict between competing response alternatives. Deficient conflict detection may in turn hinder these children's ability to resolve conflict among semantic representations that are activated during language processing.

Impaired Conflict Adaptation in an Emotional Task Context following Rostral Anterior Cingulate Cortex Lesions in Humans

Recent brain imaging studies have implicated the rostral ACC (rACC) in the resolution of conflict between competing response tendencies in emotional task contexts, but not in neutral task contexts. This study tested the hypothesis that the rACC is necessary for such context-specific conflict adaptation. To this end, a group of patients with lesions of the rACC, a group of brain-damaged controls, and a group of normal controls classified the emotional expression (emotional task context) or the gender (neutral task context) of faces while ignoring congruent and incongruent words written across the faces. In all three groups, performance was worse with incongruent as compared with congruent stimuli in both task contexts. In the two control groups, this congruency effect was reduced following incongruent trials in both task contexts. By contrast, the rACC group displayed such conflict adaptation only in the neutral, but not in the emotional, task context. These results show that the rACC is necessary for conflict adaptation in emotional but not in neutral task contexts and suggest that the regulation of behavior is context specific.

Parametric Manipulation of the Conflict Signal and Control-state Adaptation

Mechanisms by which the brain monitors and modulates performance are an important focus of recent research. The conflict-monitoring hypothesis posits that the ACC detects conflict between competing response pathways which, in turn, signals for enhanced control. The N2, an ERP component that has been localized to ACC, has been observed after high conflict stimuli. As a candidate index of the conflict signal, the N2 would be expected to be sensitive to the degree of response conflict present, a factor that depends on both the features of external stimuli and the internal control state. In the present study, we sought to explore the relationship between N2 amplitude and these variables through use of a modified Eriksen flankers task in which target–distracter compatibility was parametrically varied. We hypothesized that greater target–distracter incompatibility would result in higher levels of response conflict, as indexed by both behavior and the N2 component. Consistent with this prediction, there were parametric degradations in behavioral performance and increases in N2 amplitudes with increasing incompatibility. Further, increasingly incompatible stimuli led to the predicted parametric increases in control on subsequent incompatible trials as evidenced by enhanced performance and reduced N2 amplitudes. These findings suggest that the N2 component and associated behavioral performance are finely sensitive to the degree of response conflict present and to the control adjustments that result from modulations in conflict.

On the Understanding of Non-Stationary VIV of Slender Beams

VIV of slender beams at high mode order will appear as a non-stationary response process. Amplitudes, dominating frequency and mode composition are seen to vary in time, but so far we do not have a complete understanding of this process. One approach is to attempt to understand and model the physical mechanism behind the observed behaviour, but an alterative is to establish a simplified model that can be used for fatigue calculations. The purpose of the present paper is to compare the dominant response frequencies that have been observed in large scale tests of a flexible beam to the discrete response frequencies that are predicted by an empirical model for prediction of VIV. Use of wavelet and modal analyses on experimental data makes it possible to describe the time variation of the peak frequency, and hence also the relative period of time this frequency falls into discrete frequency bins. An empirical model is also proposed for calculation of relative duration of competing response frequencies. The observed frequencies can hence be compared to the results from the proposed model. The conclusion is that the model identifies the domination response frequencies with satisfactory accuracy. The range of calculated discrete response frequencies is larger than for the discrete peak frequencies identified from the experiments. But the observed response process has a broader frequency band than the variation of the peaks. Hence, the results from the analysis seem to agree well with observations. Further analyses are, however, still needed in order to verify the proposed model.

Emergent Attributes in Person Perception

In person perception, emergent attributes are attributes that people ascribe to members of a rare or novel category combination, although they would not ascribe the same attributes to members of either of the constituent categories. The present paper first describes the processing mechanisms suggested by three theoretical models of attribute emergence. Then, competing response time predictions are derived from the models’ respective mechanisms. An empirical test of these predictions in a laboratory experiment with university students (N = 45) is reported. Results support Hastie, Schroeder, and Weber’s (1990 ) two-stage model, but not Kunda, Miller, and Claire’s (1990 ) impression-formation model or Smith and DeCoster’s (1998 ) connectionist account.