Preparatory process hypothesis

The anticipation of a threat or an unpleasant situation serves an adaptive function (Baumeister, Vohs, DeWall, & Zhang, 2007; Lorini, Piunti, Castelfranchi, Falcone, & Miceli, 2008). The Ps-Dm effect has been explained regarding preparatory processes at work which facilitate memory encoding (Galli et al., 2011; Park & Rugg, 2010). However, it remains largely unknown when and how the preparatory processes benefit memory. One reason may be that these studies have largely ignored the electrophysiological literature regarding cortical measures related to anticipation. Namely, that orienting responses to warning cues are separate from the subsequent anticipated stimulus-preceding emotional event. In this project, an attempt has been made to elucidate the mechanism behind the Ps-Dm effect, as well as the preparatory process, by incorporating a theoretical framework from the electrophysiological literature. Therefore, the focus of the current study is on the examination of the neural initiation of different temporal stages of anticipation. This anticipatory model consists of two stages: (1) instant responses to warning cues displayed before negative or neutral pictures and (2) sustained anticipatory responses leading up to the onset of that picture (Birbaumer et al., 1990; Bocker et al., 2001; Grupe et al. 2013). Thus, a theoretical framework based on electrophysiological and cortical measures of

103 anticipation has been adopted, to refine the methodological issues that have been largely ignored in previous Ps-Dm effect ERP studies.

In the first ERP study on Ps-Dm effect, cues remained on the screen for the whole duration of anticipation that was 1400ms and disappeared only a 100ms before the picture was presented (Galli, et al., 2011). It appears that the Ps-Dm effect is confined to that time interval for which the cue remained on the screen. Since the analysis fot the 100ms when the cue disappeared has not been provided in this particular study. Hence, It is still unknown, if Ps-Dm effect sustains during the same anticipatory phase as well when the cue disappears after for a short display of cue while in the rest of the time participants wait for the anticipated stimuli. One possibility might be that Ps-Dm effect is more related to the immediate responses to the cues than to the perception of sustained anticipation activity. Out of 3000ms cue epoch, the current experiment has the cue remain on the screen only for a short duration, i.e., 1000ms. Rest of the 2000ms time participants waited for the stimuli to appear.

The anticipation of emotional stimuli is a non-motor ERP component. From an experimental psychology perspective, preparatory processes involve the activation of the motor system for the execution of a movement (van Boxtel & Böcker, 2004). On a perception-action- continuum, anticipation represents the perception while preparation represents the action domain (van Boxtel & Böcker, 2004). The intermediate processes on this continuum may be activated if a quick action is required in response to the upcoming stimuli. However, if the upcoming stimulus is emotional, these intermediate processes tend to get activated in advance because of the motivational significance of the emotions. ERP literature on anticipation has documented that, slow cortical brain waves are elicited just 200ms before the onset of emotional stimuli. These slow negative wave forms reflects an index of anticipation of emotional stimuli and referred to as Stimulus Preceding Negativity (SPN) (Chwilla & Brunia, 1991; Hillman, Apparies, & Hatfield, 2000). The slow waves are not associated with motor responses; that is why they are identified as the non-motor ERP component specific to emotional anticipation. In those studies, where participants are given explicit instructions to respond quickly to emotional stimuli, the motor response becomes a confound (Galli et al., 2011). It is important to determine whether the Ps-Dm effect is the result of general action-oriented preparation towards upcoming stimuli, or emotional preparation that does not require a motor action. In the current experiment, the picture-rating (SAM valence rating) task is self-paced, and no quick reaction is required. It is done with the consideration that SPN is a non-motor EPR component, and assumes that the

104 emotional anticipation is itself motivationally significant and occurs without a quick reaction to the experimental task.

Anticipatory preparation is an endogenous cognitive process, according to Bozinovski and Bozinovska (2004) and contrasts with expectation/ prediction, which is initiated by some expected external event. That is, anticipation is a more instinctively mediated process, which does not necessarily follow higher-order cognitive functions like expectation or prediction processes. Therefore, higher or lesser brain activation in response to anticipation depends on the expectation of the impending aversive event. For instance, one study found that low pain cues modulate anticipation and dampen brain activation compared to high pain cues (Koyama, McHaffie, Laurienti, & Coghill, 2005). Similarly, the Mackiewicz, Sarinopoulos, Cleven, & Nitschke (2006) study showed greater activation in the amygdala and hippocampus during anticipation of high-arousal negative pictures. Findings from these studies suggest that the perception of high-intensity aversive stimuli led to the Ps-Dm effect. In contrast, a Magnetoencephalography (MEG) study showed that activity in visual evoked magnetic fields (VEF) was reduced in response to emotionally negative cues (Onoda et al., 2007). Together these studies suggest that preparation is a type of adaptive behaviour, which can either depress or enhance brain potentials to deal with the situation. Preparation increases the efficiency of cognitive processes by eliciting advanced activation of the neural substrates involved in those processes (Bollinger et al., 2010; Irwin, Knott, McAdam, & Rebert, 1966; B. K. Schmidt, Vogel, Woodman, & Luck, 2002). That is, being prepared primes the brain to certain stimuli and responses. In line with this finding, shorter reactions times have been observed in anticipatory trials (Park & Rugg, 2010). Additionally, affective stimuli are deemed motivationally significant and are processed in a prioritized manner. Therefore, in the current experiment, quicker reaction times for rating negative pictures presented with informative cues are expected. In the previous ERP study (Galli et al., 2011), no information on reaction time measures was provided. Therefore, this study was interested in measuring participants’ reaction times without them first being given explicit instructions to respond quickly to stimuli (due to the possible confounding effect of a speeded response on the SPN).