Fortalecer la red de monitoreo y sus herramientas

The Late Positive Potential (LPP) elicited between 400 and 800ms post stimulus onset reflects a broadly distributed positivity (Friedman & Johnson, 2000) that is maximal at central and parietal sites (Krug et al., 2000). In terms of the neural source of the LPP, the characteristic scalp distribution of the LPP suggests that it may reflect neural activity generated in the posterior parietal cortex (Keil, Bradley, Hauk, Rockstroh, Elbert, & Lang, 2002;

Sabatinelli, Lang, Keil, & Bradley, 2007; Rugg & Curran, 2007). The LPP has been researched within a number of paradigms including attention and both short and long term memory paradigms, and has been found to be particularly relevant for emotion processing (Olofsson et al., 2008). As the LPP is evoked when perceptual demands are high, the LPP is assumed to provide an index of further processing that is beyond the capacity reflected by the P3 component (Rugg & Curran, 2007). Discussed further below, the LPP is thought to index the intrinsic motivational significance of emotional stimuli and provide an indication of the timing and level at which evaluation of a stimulus influences

further stimuli processing and response appraisal (Cacioppo, Crites, & Gardner, 1996; Leite et al., 2012; Purves et al., 2008).

Previous emotional ERP research has consistently found LPP to be highly sensitive towards emotionally salient stimuli (pleasant and unpleasant) compared to neutral stimuli (e.g., Balconi et al., 2012; Cuthbert et al., 2000; Flaisch, Junghöfer, Bradley, Schupp, & Lang, 2008; Foti & Hajcak, 2008; Hajcak & Nieuwenhuis, 2006; Hajcak, Dunning, & Foti, 2007; Hajcak & Olvet, 2008; Hajcak et al., 2010; Hilgard, Weinberg, Hajcak, & Barthlow, 2014; Hot et al., 2006; MacNamara & Hajcak, 2009, 2010; Olofsson et al., 2008; Pastor, Bradley, Low, Versace, Molto, & Lang, 2008; Sand & Derntl, 2011; Schupp et al., 2000; 2003, 2006; 2012; Weinberg & Hajcak, 2010; Wiens, Sand, Norberg, & Andersson, 2011). Such findings provide evidence that attention is more deeply engaged by motivationally relevant stimuli (i.e., stimuli that activate the appetitive and aversive systems) as compared to neutral information (e.g., Amrhein et al., 2004; Cuthbert et al., 2000; Keil et al., 2002; Schupp et al., 2003, 2004, 2004, 2012). However, a number of studies have demonstrated that unpleasant stimuli elicit larger LPPs than pleasant or neutral stimuli (e.g., Cano et al., 2009; Carretié, Hinojosa, Martín- Loeches, Mercardo, & Tapia, 2004; Carretié, Mercardo, Tapia, & Hinojosa, 2001; Cuthbert et al., 2000; Delplanque et al., 2004, 2005, 2006; Feng et al., 2014; Foti et al., 2009; Hajcak & Olvet, 2008; Huang & Luo, 2006; Ito et al., 1998; Kaestner & Polich, 2011; Smith et al., 2003; Stewart et al., 2010; Yuan et al., 2007), even when the unpleasant and pleasant stimuli are equally arousing (e.g., Ito et al.).

In addition to stimuli valence, LPP to emotional relative to neutral pictures has been shown to be larger for more intense stimuli (i.e., stimuli with higher arousal ratings and eliciting the greatest SCR; Cuthbert et al., 2000), and is thus greater for highly arousing pleasant (e.g., erotica) and unpleasant (e.g., threat) stimuli (Schupp, Junghöfer et al., 2004; Schupp, Ohman et al., 2004; Cuthbert et al., 2004). Additionally, enhanced LPP for emotional compared to neutral stimuli does not show habituation over repeated

presentations of stimuli (Codispoti, Ferrari, & Bradley, 2006, 2007; Olofsson & Polich, 2007; Syrjanan & Wiens, 2013). Further, in the studies by Yuan et al. (2007), Yuan et al. (2008), and Meng et al. (2009) where participants were required to view highly unpleasant, moderately unpleasant, and neutral stimuli while competing a standard/deviation categorisation task, LPP amplitude was found to be greater to the highly unpleasant relative to moderately unpleasant and neutral stimuli, with moderately unpleasant stimuli also eliciting larger LPP amplitudes than neutral stimuli. These findings highlight the sensitivity of the brain to different valence levels in emotionally unpleasant stimuli during stimuli evaluation processes which are reflected by the LPP.

As indicated above, the LPP response to emotionally salient stimuli (high arousing pleasant or unpleasant relative to neutral stimuli) has been consistently reported across a range of paradigms. For example, Hilgard et al. (2014) investigated whether task paradigm and stimuli content influenced the occurrence of a negativity bias by presenting participants with pleasant

affiliative, pleasant thrilling, unpleasant threatening, and neutral images in the context of oddball, blocked, and random viewing paradigms. They

did neutral stimuli across all task paradigms. They also found a negativity bias in the oddball paradigm when thrilling rather than affiliative stimuli were used. Overall, current evidence suggests that emotional modulation of the LPP is a robust and stable effect and that the LPP indexes motivational significance and emotional salience, and thus the degree to which attention is allocated to emotional stimuli (Bradley, 2009; Olofsson et al., 2008).

Further research has demonstrated that the LPP is consistently

modulated by emotion regulation instruction whereby LPP activation has been shown to be higher when emotional reactivity is increased and lower when one’s emotional response is decreased. For example, Moser et al. (2006) examined the LPP during an emotion regulation task in which participants were instructed to maintain, decrease (suppress), or increase their emotional responses to unpleasant images and found reduced LPP during the decrease instruction. Hajcak and Nieuwenhuis (2006) replicated these findings by recording ERPs during an emotion regulation task which involved participants attending to, or reappraising, unpleasant images to demonstrate reduced LPP following reappraisal. Similarly, Moser et al. (2009) and Gardener et al. (2013) measured ERPs during an emotion regulation task that required participants to maintain, decrease (reappraise), or increase their emotional response to

unpleasant images. Moser et al. and Gardener et al. found increased LPP amplitude following the increase emotional response instruction, with Moser et al. also finding reduced LPP following the decrease instruction. Hence, the LPP provides a robust and objective electrophysiological marker of later, conscious, response-related emotion regulation (Dennis & Hajcak, 2009;

Gardener et al., 2013; Moser et al., 2006; Moser et al., 2009; Moser et al., 2010; Oloffson et al. 2008).

Experimental paradigms demonstrating LPP evidence for the motivational model have been reported, with previous ERP studies demonstrating that the LPP is greater to emotional (both pleasant and

unpleasant) relative to neutral stimuli (e.g., Balconi et al., 2012; Cuthbert et al., 2000; Flaisch et al., 2008; Foti & Hajcak, 2008; Hajcak & Nieuwenhuis, 2006; Hajcak et al., 2007, 2010; Hajcak & Olvet, 2008; Hilgard et al., 2014; Hot et al., 2006; MacNamara & Hajcak, 2009, 2010; Olofsson et al., 2008; Pastor et al., 2008; Sand & Derntl, 2011; Schupp et al., 2000; 2003, 2006; 2012; Weinberg & Hajcak, 2010; Wiens et al., 2011). Such findings provide evidence that attention is more deeply engaged by motivationally relevant stimuli (i.e., stimuli that activate the appetitive and aversive systems) as compared to neutral information (e.g., Amrhein et al., 2004; Cuthbert et al., 2000; Keil et al., 2002; Schupp et al., 2003, 2004, 2004, 2012). However other studies report enhanced LPP to unpleasant relative to pleasant and neutral stimuli (e.g., Cano et al., 2009; Carretié et al., 2001, 2004; Cuthbert et al., 2000; Delplanque et al., 2004, 2005, 2006; Feng et al., 2014; Foti et al., 2009; Hajcak & Olvet, 2008; Huang & Luo, 2006; Ito et al., 1998; Kaestner & Polich, 2011; Meng et al., 2009; Smith et al., 2003; Stewart et al., 2010; Yuan et al., 2007, 2008), even when the unpleasant and pleasant stimuli are equally arousing (e.g., Ito et al.).

A positivity bias where pleasant stimuli can elicit comparable or even more pronounced LPP responses compared with unpleasant stimuli has also been reported (e.g., Brown, van Steenbergen, Band, de Rover, & Nieuwenhuis,

2012), with a recent meta-analysis revealing a modest attentional bias for pleasant compared with neutral stimuli in both early and late processing (Pool, Brosch, Delplanque, & Sander, 2016). Further, other studies have found no valence differences in LPP response (e.g., Glaser, Mendrek, Germain, Lakis, & Lavoie, 2012; Rozenkrants & Polich, 2008; Weinberg et al., 2012). Research such as the study by Hilgard et al. (2014) noted above suggests that task paradigm and the semantic content of emotional stimuli influences whether the negativity bias effect is observed in the LPP.

In summary, the LPP has been observed in emotion processing and emotion regulation tasks. LPP amplitude has been associated with the emotional intensity of stimuli which indicates that LPP modulation is

influenced by the motivational importance and/or emotional salience of stimuli (Bradley, 2009; Friedman & Johnson, 2000; Krug et al., 2000; Moser et al., 2009; Oloffson et al., 2008). The LPP has consistently been found to be a non- habituating regulative response which is sensitive to highly arousing emotional (pleasant or unpleasant) relative to neutral stimuli, and is consequently seen to reflect a robust index of emotion processing and emotion regulation (Dennis & Hajcak, 2009; Moser et al., 2006, 2009, 2010). However studies showing motivational model support are tempered by other studies which have reported evidence in line with the negativity bias hypothesis (Foti et al., 2009; Hajcak & Olvet, 2008; Yuan et al., 2007, 2008).