Separate and joint effects of alcohol and caffeine on conflict monitoring and adaptation

Alcohol and Neural Dynamics: A Meta-analysis of Acute Alcohol Effects on Event-Related Brain Potentials

BACKGROUND

An understanding of alcohol's acute neural effects could augment our knowledge of mechanisms underlying alcohol-related cognitive/motor impairment and inform interventions for addiction. Focusing on studies employing event-related brain potential methods, which offer a direct measurement of neural activity in functionally well-characterized brain networks, we present the first meta-analysis to explore acute effects of alcohol on the human brain.

METHODS

Databases were searched for randomized laboratory alcohol-administration trials assessing brain activity using event-related potentials. Hedges' g coefficients were pooled using 3-level random-effects meta-regression.

RESULTS

Sixty independent randomized controlled trials met inclusion (total N = 2149). Alcohol's effects varied significantly across neural systems, with alcohol leading to reductions in event-related potential components linked with attention (P3b), g = -0.40, 95% CI (-0.50, -0.29), automatic auditory processing (mismatch negativity), g = -0.44, 95% CI (-0.66, -0.22), and performance monitoring (error-related negativity), g = -0.56, 95% CI (-0.79, -0.33). These effects were moderated by alcohol dose, emerging as significant at doses as low as 0.026% blood alcohol concentration and increasing to moderate/large at 0.12%. In contrast, irrespective of dose, relatively small or nonsignificant alcohol effects emerged in other processing domains, including those linked to executive control (N2b responses) and stimulus classification (N2c responses).

CONCLUSIONS

Contrary to traditional conceptualizations of alcohol as a "dirty drug" with broad central nervous system depressant effects, results instead support accounts positing targeted alcohol effects in specific processing domains. By identifying alcohol effects on brain systems involved in performance monitoring and attention, results move toward the identification of mechanisms underlying alcohol-related impairment as well as factors reinforcing addiction.

Parsing the Neural Mechanisms of Short-Term and Long-Term Associations in the Flanker Tasks: An ERP Analysis

The neural mechanisms of cognitive conflicts within various flanker tasks are still unclear, which may be mixed with different effects of short-term associations and long-term associations. We applied a perceptual (color) flanker task and a symbolic (arrow) flanker task to 25 healthy young adults, while the event-related potentials (ERP) and behavioral performance were recorded. The former contains stimulus-stimulus conflict (SSC) of short-term memory (STM) associations, and the latter contains stimulus-response conflict (SRC) of long-term memory (LTM) associations. Both flanker tasks included congruent and incongruent conditions. The reaction time demonstrated the stimulus-response conflict effect in the arrow flanker task without the stimulus-stimulus conflict effect in the color flanker task. The ERP results showed SSC enhanced the frontocentral N2b without behavioral effects. SRC increased the frontocentral P2 but decreased the centroparietal P3b with prolonged reaction time. In the comparison between both tasks, the color flanker task elicited both the centroparietal N2b/N300 and the frontocentral N400, and the arrow flanker task increased the occipital N1. Our findings provide new evidence that different neural mechanisms underlie conflict effects based on different types of memory associations.

Modulation of compatibility effects in response to experience: Two tests of initial and sequential learning

Attentional control is a key component of goal-directed behavior. Modulation of this control in response to the statistics of the environment allows for flexible processing or suppression of relevant and irrelevant items in the environment. Modulation occurs robustly in compatibility-based attentional tasks, where incompatibility-related slowing is reduced when incompatible events are likely (i.e., the proportion compatibility effect; PCE). The PCE implicates dynamic changes in the measured compatibility effects that are central to fields of study such as attention, executive functions, and cognitive control. In these fields, stability in compatibility effects are generally assumed, which may be problematic if individual or group differences in measured compatibility effects may arise from differences in statistical learning speed or magnitude. Further, the sequential nature of many studies may lead the learning of certain statistics to be inadvertently applied to future behaviors. Here, we report tests of learning the PCE across conditions of task statistics and sequential blocks. We then test for the influence of feedback on the development of the PCE. We find clear evidence for the PCE, but no conclusive evidence for its slow development through experience. Initial experience with more incompatible trials selectively mitigated performance decreases in a subsequent block. Despite the lack of behavioral changes associated with patterns of learning, systematic within-task changes in compatibility effects remain an important possible source of variation in a wide range of attention research.

Temporal dynamics of reactive cognitive control as revealed by event-related brain potentials

Reactive cognitive control refers to a complementary set of cognitive operations by which individuals monitor for and detect the presence of goal-interfering conflict (i.e., conflict monitoring/evaluation) and, subsequently, initiate attention-focusing and response selection processes to bolster goal-directed action in the face of such conflict (regulative control). The purpose of the current study was to characterize the nature of conflict adaptation in both components of this dynamic process across sequences of trials and, more broadly, across time as participants complete a cognitive control task. Fifty-two young adults completed a standard arrow flanker task while behavioral and ERP data were recorded. Multilevel modeling of sequences of compatible and incompatible trials over time showed that, whereas response time data demonstrated a typical conflict adaptation effect throughout the task, N2 and frontal slow wave (FSW) indices of conflict monitoring and regulative control, respectively, demonstrated significant conflict adaptation only during the early part of the task. Moreover, although differential change in N2 and FSW over time suggested that conflict monitoring and regulative control were dissociable, a reciprocal relation between them was maintained throughout the task and was not present in a component theoretically unrelated to conflict adaptation (visual attention-related N1). Findings are discussed in terms of compensatory processes that help to maintain goal-directed performance even as control-related neural responses become fatigued.