## 2 Decoding Processing Preferences by Means of EEG Methodology  
Methodologically, non-invasive electroencephalography (EEG) and the analysis of event-related brain potentials (ERPs) from the electroencephalogram (EEG) are ideally suited neurophysiological techniques to unravel the processing biases of cognitive vulnerability and determine how these biases unfold over the time course of information processing. EEG methodology allows precise insights into the time course of stimulus- and information processing and their task- and mood-related changes. The latency, as well as the amplitude modulation of early and late ERPs in response to the averaged stimulus response recorded in different task contexts allow differentiated conclusions about the different stimulus and information processing stages from stimulus perception to more in-depth processing [14]. In contrast to behavioral methods, EEG methodology allows the investigation of stimulus processing and its time course even in designs in which no behavioral responses are required and no tasks are given other than to, e.g., read, watch, or listen to the stimulus presentation. EEG methods therefore might be ideally suited to study bottom-up processing without the confounding influence of task-related factors, while at the same time allowing for comparisons between spontaneous (no task) and task-related stimulus processing. Moreover, in event-related stimulus designs, a number of event-related brain potentials can be elicited that, depending on the stimulus and processing specificities, have been shown to be reliable markers of, e.g., perceptual, cognitive, semantic, sensorimotor, or affective processing [14]. Regarding emotional processing, as exemplified in Figure 2, the processing of emotional and neutral stimuli can elicit the modulation of early and late event-related brain potentials (ERPs). For example, in an EEG-ERP experiment with emotional and neutral stimuli, the amplitude amplification of early event-related potentials such as the EPN (early posterior negativity) has often been observed, irrespective of the type of stimuli presented, whether it is words or pictures of emotionally evocative scenes [15; 16; 17]. Due to its almost obligatory elicitation across many study designs (passive viewing tasks, fast stimulus presentations, or selective attentive stimulus processing), the EPN has been suggested to be a prominent neural marker of early stimulus-driven processing of high-arousing stimulus content of motivational salience [15; 16; 17]. Therefore, in the EEG, a larger EPN amplitude modulation during the processing of stimuli of negative content, compared to stimuli of positive or neutral content, would argue for a rapid, spontaneous, and bottom-up driven allocation of visual attention to negative stimulus information that, according to the two-process models mentioned above, occurs at fast--and probably still associative--levels of information processing. Figure 1: Information processing according to cognitive vulnerability models of depression. For further details, please see text and e.g., [10]. In addition, the amplitude modulation of temporally later ERP components such as the N400 ERP component, typically elicited by lexical stimuli (but also found to be elicited by non-lexical stimuli such as faces), can indicate semantic processing due to facilitated lexical access [18], facilitated activation of long-term memory representation [19], or contextual integration of the stimuli [20]. Contextual integration can be established either experimentally by a sentence context [20], a specific task context, or an internal context such as the current mood and affective state of the participant [21; 22; 23].