Attentional control of the creation and retrieval of stimulus–response bindings

Two experiments studied the degree to which the creation and retrieval of episodic feature bindings is modulated by attentional control. Experiment 1 showed that the impact of bindings between stimulus and response features varies as a function of the current attentional set: only bindings involving stimulus features that match the current set affect behavior. Experiment 2 varied the time point at which new attentional sets were implemented—either before or after the processing of the to-be-integrated stimuli and responses. The time point did not matter, suggesting that the attentional set has no impact on feature integration proper but controls which features get access to and can thus trigger the retrieval of bindings.     

Temporal dynamics of unimodal and multimodal feature binding

In two experiments, we studied the temporal dynamics of feature integration with auditory (Experiment 1) and audiovisual (Experiment 2) stimuli and manual responses. Consistent with previous observations, performance was better when the second of two consecutive stimuli shared all or none of the features of the first, rather than when only one of the features overlapped. Comparable partial-overlap costs were obtained for combinations of stimulus features and responses. These effects decreased systematically with increasing time between the two stimulus-and-response events, and the decreased rate was comparable for unimodal and multimodal bindings. General effect size reflected the degree of task relevance of the dimension or modality of the respective feature, but the effects of relevance and of temporal delay did not interact. This suggests that the processing of stimuli on task-relevant sensory modalities and feature dimensions is facilitated by task-specific attentional sets, whereas the temporal dynamics might reflect that bindings “decay” or become more difficult to access over time.     

Auditory event files: Integrating auditory perception and action planning

The features of perceived objects are processed in distinct neural pathways, which call for mechanisms that integrate the distributed information into coherent representations (the binding problem). Recent studies of sequential effects have demonstrated feature binding not only in perception, but also across (visual) perception and action planning. We investigated whether comparable effects can be obtained in and across auditory perception and action. The results from two experiments revealed effects indicative of spontaneous integration of auditory features (pitch and loudness, pitch and location), as well as evidence for audio—manual stimulus—response integration. Even though integration takes place spontaneously, features related to task-relevant stimulus or response dimensions are more likely to be integrated. Moreover, integration seems to follow a temporal overlap principle, with features coded close in time being more likely to be bound together. Taken altogether, the findings are consistent with the idea of episodic event files integrating perception and action plans.     

The relationship between feature binding and consciousness: evidence from asynchronous multi-modal stimuli

Processing the various features from different feature maps and modalities in coherent ways requires a dedicated integration mechanism (“the binding problem”). Many authors have related feature binding to conscious awareness but little is known about how tight this relationship really is. We presented subjects with asynchronous audiovisual stimuli and tested whether the two features were integrated. The results show that binding took place up to 350 ms feature-onset asynchronies, suggesting that integration covers a relatively wide temporal window. We also asked subjects to explicitly judge whether the two features would belong to the same or to the different events. Unsurprisingly, synchrony judgments decreased with increasing asynchrony. Most importantly, feature binding was entirely unaffected by conscious experience: features were bound whether they were experienced as occurring together or as belonging to a separate events, suggesting that the conscious experience of unity is not a prerequisite for, or a direct consequence of binding.     

Stimulating Creativity: Modulation of Convergent and Divergent Thinking by Transcranial Direct Current Stimulation (tDCS)

Creativity has been conceptualized as involving 2 distinct components; divergent thinking, the search for multiple solutions to a single problem, and convergent thinking, the quest for a single solution either through an analytical process or the experience of insight. Studies have demonstrated that these abilities can be improved by cognitive stimulation, mood, and meditation. This investigation examined whether convergent and divergent thinking can be enhanced by noninvasive transcranial direct current stimulation (tDCS). In different sessions, participants received bilateral stimulation over the dorsolateral prefrontal cortex—DLPFC (Experiment1) and over the posterior parietal cortex–PPC (Experiment2), while performing the Compound Remote Associative task (CRA) assessing convergent thinking and the Alternative Uses Task (AUT) assessing divergent thinking. In Experiment1, anodal-left cathodal-right stimulation over the DLPFC significantly enhanced CRA performance. In Experiment2, stimulations over the PPC significantly increased insight solutions and decreased analytical solutions compared to the no stimulation condition. These findings provide direct evidence for the role of the left DLPFC in convergent and divergent thinking and a mediating role of the PPC in problem-solving behavior, presumably through attentional processes. From a methodological perspective, brain stimulation can be used as a tool to modulate and to explore components of creativity.     

Intermodal event files: integrating features across vision,audition, taction,and action

Understanding how the human brain integrates features of perceived events calls for the examination of binding processes within and across different modalities and domains. Recent studies of feature-repetition effects have demonstrated interactions between shape, color, and location in the visual modality and between pitch, loudness, and location in the auditory modality: repeating one feature is beneficial if other features are also repeated, but detrimental if not. These partial-repetition costs suggest that co-occurring features are spontaneously bound into temporary event files. Here, we investigated whether these observations can be extended to features from different sensory modalities, combining visual and auditory features in Experiment 1 and auditory and tactile features in Experiment 2. The same types of interactions, as for unimodal feature combinations, were obtained including interactions between stimulus and response features. However, the size of the interactions varied with the particular combination of features, suggesting that the salience of features and the temporal overlap between feature-code activations plays a mediating role.