Combining NIBS with EEG: What Can It Tell Us About Normal Cognition?

Cause or consequence? Alpha oscillations in visuospatial attention

A well-established finding in the literature of human studies is that alpha activity (rhythmical brain activity around 10 Hz) shows retinotopic amplitude modulation during shifts in visual attention. Thus, it has long been argued that alpha amplitude modulation might play a crucial role in attention-driven alterations in visual information processing. Recently, there has been a revival of the topic, driven in part by new studies directly investigating the possible causal relationship between alpha activity and responses to visual input, both neuronally and perceptually. Here, we discuss evidence for and against a causal role of alpha activity in visual attentional processing. We conclude with hypotheses regarding the mechanisms by which top-down-modulated alpha activity in the parietal cortex might select visual information for attentive processing.

Transcranial Magnetic Stimulation and the Understanding of Behavior

The development of the use of transcranial magnetic stimulation (TMS) in the study of psychological functions has entered a new phase of sophistication. This is largely due to an increasing physiological knowledge of its effects and to its being used in combination with other experimental techniques. This review presents the current state of our understanding of the mechanisms of TMS in the context of designing and interpreting psychological experiments. We discuss the major conceptual advances in behavioral studies using TMS. There are meaningful physiological and technical achievements to review, as well as a wealth of new perceptual and cognitive experiments. In doing so we summarize the different uses and challenges of TMS in mental chronometry, perception, awareness, learning, and memory.

Non-invasive stimulation in the social brain: the methodological challenges

Use of non-invasive brain stimulation methods (NIBS) has become a common approach to study social processing in addition to behavioural, imaging and lesion studies. However, research using NIBS to investigate social processing faces challenges. Overcoming these is important to allow valid and reliable interpretation of findings in neurotypical cohorts, but also to allow us to tailor NIBS protocols to atypical groups with social difficulties. In this review, we consider the utility of brain stimulation as a technique to study and modulate social processing. We also discuss challenges that face researchers using NIBS to study social processing in neurotypical adults with a view to highlighting potential solutions. Finally, we discuss additional challenges that face researchers using NIBS to study and modulate social processing in atypical groups. These are important to consider given that NIBS protocols are rarely tailored to atypical groups before use. Instead, many rely on protocols designed for neurotypical adults despite differences in brain function that are likely to impact response to NIBS.

Right hemisphere occipital rTMS impairs working memory in visualizers but not in verbalizers

Distinguishing between verbal and visual working memory processes is complicated by the fact that the strategy used is hard to control or even assess. Many stimuli used in working memory tasks can be processed via verbal or visual coding, such as the digits in the digit span backwards task (DSB). The present study used repetitive transcranial magnetic stimulation (rTMS) to examine the use of visual processing strategies in the DSB. A total of 47 German university students took part in the study, 23 spontaneously using a verbal processing strategy and 24 using a visual strategy. After rTMS to the right occipital cortex, visualizers showed a significantly stronger mean performance decrease compared to verbalizers. The results indicate that the visual cortex is more critical for visualizers compared to verbalizers in the DSB task. Furthermore, the favored processing modality seems to be determined by the preference for a cognitive strategy rather than the presentation modality, and people are aware of the applied strategy. These findings provide insight into inter-individual differences in working memory processing and yield important implications for laboratory studies as well as clinical practice: the stimulus does not necessarily determine the processing and the participant can be aware of that.