EMEGS (electromagnetic encephalography software) is a MATLAB toolbox designed to provide novice as well as expert users in the field of neuroscience with a variety of functions to perform analysis of EEG and MEG data. The software consists of a set of graphical interfaces devoted to preprocessing, analysis, and visualization of electromagnetic data. Moreover, it can be extended using a plug-in interface. Here, an overview of the capabilities of the toolbox is provided, together with a simple tutorial for both a standard ERP analysis and a time-frequency analysis. Latest features and future directions of the software development are presented in the final section.

Motivationally relevant stimuli have been shown to receive prioritized processing compared to neutral stimuli at distinct processing stages. This effect has been related to the evolutionary importance of rapidly detecting dangers and potential rewards and has been shown to be modulated by the distance between an organism and a faced stimulus. Similarly, recent studies showed degrees of emotional modulation of autonomic responses and subjective arousal ratings depending on stimulus size. In the present study, affective modulation of pictures presented in different sizes was investigated by measuring event-related potentials during a two-choice categorization task. Results showed significant emotional modulation across all sizes at both earlier and later stages of processing. Moreover, affective modulation of earlier processes was reduced in smaller compared to larger sizes, whereas no changes in affective modulation were observed at later stages.

Brain responses to engaging stimuli may be reflected both in event-related potentials (ERPs) and in electroencephalogram (EEG) oscillations. Previous studies investigating the effects of top-down factors on stimulus encoding revealed similar modulation of late ERPs and alpha-band desynchronization (α-ERD) by relevant target stimuli. Focusing on the bottom-up effects of emotional content and picture size, the present study aimed to investigate the relationship of the late positive potential (LPP) and α-ERD during the viewing of emotional pictures. Results showed similar affective modulation by picture arousal of the LPP and α-ERD. Moreover, picture size reduction diminished overall magnitude of both responses, but did not dampen affective modulation of either response. These results suggest that, during affective picture viewing, these two brain responses similarly reflect the engagement of motivational systems in order to facilitate perception.

Building on the assumption that the motivational relevance of an emotional scene depends on contextual factors such as proximity or stimulus size, the present study examined the effects of picture size on emotional perception using autonomic, facial, and subjective reactions. Affective changes were measured while participants viewed pictures presented in small, medium, and large sizes and varying in affective picture content. Whereas affective modulation of heart rate and Corrugator Supercilii muscle activity were not modulated by picture size, emotional modulation of skin conductance was absent for the smallest stimuli and increased linearly for the medium and largest stimulus sizes. Stimulus size modulated sympathetic changes possibly related to activation of the strategic motivational systems and action preparation. In contrast, responses related to orienting, categorization, and communicative functions did not covary with picture size.

The interference produced by the viewing of emotional distractors has been interpreted as evidence that emotional cues are processed in a fairly mandatory fashion, and that they divert attention from the primary ongoing task. However, few studies have examined how behavioral emotional interference varies with repeated presentation of the same emotional distractors. In two experiments, while participants were engaged in a parity judgment task, we investigated the effects of repetition of task-irrelevant emotional pictures, as reflected in both behavioral interference (Experiments 1 and 2) and neural activity (Experiment 2). Both experiments showed that the slowing of reaction times that was observed when viewing emotional, compared to neutral, scenes disappeared after only a few repetitions, suggesting diminished attention allocation to repeated emotional pictures. Conversely, in Experiment 2, neural correlates of picture processing revealed that the late positive potential (LPP) amplitude continued to be enhanced for emotional, compared to neutral, distractors despite picture repetition and the presence of a concurrent task. Altogether, these findings suggest that while evaluative processes are mandatory, and continue to engage cortico-limbic appetitive and defensive systems even after massive repetition, as suggested by the affective modulation of the LPP, attentional processes are not necessary after several repetitions of the same stimulus, as indicated by the rapid decline of behavioral emotional interference.