Temporal dynamics of selective attention and conflict resolution during cross-dimensional go-nogo decisions

<p>Abstract</p> <p>Background</p> <p>Decision-making is a fundamental capacity which is crucial to many higher-order psychological functions. We recorded event-related potentials (ERPs) during a visual target-identification task that required go-nogo choices. Targets were identified on the basis of cross-dimensional conjunctions of particular colors and forms. Color discriminability was manipulated in three conditions to determine the effects of color distinctiveness on component processes of decision-making.</p> <p>Results</p> <p>Target identification was accompanied by the emergence of prefrontal P2a and P3b. Selection negativity (SN) revealed that target-compatible features captured attention more than target-incompatible features, suggesting that intra-dimensional attentional capture was goal-contingent. No changes of cross-dimensional selection priorities were measurable when color discriminability was altered. Peak latencies of the color-related SN provided a chronometric measure of the duration of attention-related neural processing. ERPs recorded over the frontocentral scalp (N2c, P3a) revealed that color-overlap distractors, more than form-overlap distractors, required additional late selection. The need for additional response selection induced by color-overlap distractors was severely reduced when color discriminability decreased.</p> <p>Conclusion</p> <p>We propose a simple model of cross-dimensional perceptual decision-making. The temporal synchrony of separate color-related and form-related choices determines whether or not distractor processing includes post-perceptual stages. ERP measures contribute to a comprehensive explanation of the temporal dynamics of component processes of perceptual decision-making.</p

Time- and task-dependent non-neural effects of real and sham TMS

Transcranial magnetic stimulation (TMS) is widely used in experimental brain research to manipulate brain activity in humans. Next to the intended neural effects, every TMS pulse produces a distinct clicking sound and sensation on the head which can also influence task performance. This necessitates careful consideration of control conditions in order to ensure that behavioral effects of interest can be attributed to the neural consequences of TMS and not to non-neural effects of a TMS pulse. Surprisingly, even though these non-neural effects of TMS are largely unknown, they are often assumed to be unspecific, i.e. not dependent on TMS parameters. This assumption is inherent to many control strategies in TMS research but has recently been challenged on empirical grounds. Here, we further develop the empirical basis of control strategies in TMS research. We investigated the time-dependence and task-dependence of the non-neural effects of TMS and compared real and sham TMS over vertex. Critically, we show that non-neural TMS effects depend on a complex interplay of these factors. Although TMS had no direct neural effects, both pre- and post-stimulus TMS time windows modulated task performance on both a sensory detection task and a cognitive angle judgment task. For the most part, these effects were quantitatively similar across tasks but effect sizes were clearly different. Moreover, the effects of real and sham TMS were almost identical with interesting exceptions that shed light on the relative contribution of auditory and somato-sensory aspects of a TMS pulse. Knowledge of such effects is of critical importance for the interpretation of TMS experiments and helps deciding what constitutes an appropriate control condition. Our results broaden the empirical basis of control strategies in TMS research and point at potential pitfalls that should be avoided

Partial repetition costs persist in nonsearch compound tasks: evidence for multiple-weighting-systems hypothesis

Search performance is sequence-dependent. A specific finding observed in compound-search tasks consists of an interaction between cross-trial sequences (repetition vs. change) of the target-defining (primary) and response-defining (secondary) features: The effect of a target change is greater when the response stays the same than when the response changes. The present study tested whether this interaction arises from processes involved in target search or from later processes in compound tasks. Uncertainty about the upcoming target location—that is, the search component of compound tasks—was removed in different experiments, either by the use of exogenous spatial precues or by presenting only one, central item. Despite having removed the search component, we observed a robust interaction between target (primary) and response (secondary) feature sequences. These results suggest that this interaction originates from a processing stage concerned with discriminating the response feature of a single (selected) item, rather than from a search-related stage. Furthermore, the results support our multiple-weighting-systems hypothesis, according to which sequence effects in visual search tasks do not stem from a single, unitary mechanism; rather, multiple stages of processing on any given trial can lead to separate memory traces, which in turn have effects on different stages of processing on the subsequent trial

The scope and precision of specific temporal expectancy: Evidence from a variable foreperiod paradigm

Recent evidence from choice response time experiments with variable foreperiods (FPs) has shown that temporal expectancy can be event specific. When a certain target appears particularly frequent after one certain FP, participants tend to expect that target after that FP. This typically results in best performance for that target when it appears after that FP. In the present study, we investigated how temporally precise event-specific temporal expectancy is, and in which range of FPs it can be found. Two target stimuli were asymmetrically distributed over two “peak-FPs” and were equally distributed over 13 additional FPs. Event-specific expectancies were found for peak-FP pairs of 500/1,100 ms and 300/500 ms. Furthermore, the event expectancies generalized to a wide range of nonpeak FPs surrounding the peak FPs