Showing papers by "Margaret M. Bradley published in 2013"

Appetitive and Defensive Motivation: Goal-Directed or Goal-Determined?

Abstract: Our view is that fundamental appetitive and defensive motivation systems evolved to mediate a complex array of adaptive behaviors that support the organism’s drive to survive—defending against threat and securing resources. Activation of these motive systems engages processes that facilitate attention allocation, information intake, sympathetic arousal, and, depending on context, will prompt tactical actions that can be directed either toward or away from the strategic goal, whether defensively or appetitively determined. Research from our laboratory that measures autonomic, central, and somatic reactions when processing emotional scenes is described which indicates that motivationally relevant cues, whether appetitive or defensive, capture attention preferentially, prompt enhanced perceptual processing and information gathering, and occasion metabolic arousal that mobilizes the organism for coping actions.

Repetition and brain potentials when recognizing natural scenes: Task and emotion differences

Abstract: Repetition has long been known to facilitate memory performance, but its effects on event-related potentials (ERPs), measured as an index of recognition memory, are less well characterized. In Experiment 1, effects of both massed and distributed repetition on old-new ERPs were assessed during an immediate recognition test that followed incidental encoding of natural scenes that also varied in emotionality. Distributed repetition at encoding enhanced both memory performance and the amplitude of an old-new ERP difference over centro-parietal sensors. To assess whether these repetition effects reflect encoding or retrieval differences, the recognition task was replaced with passive viewing of old and new pictures in Experiment 2. In the absence of an explicit recognition task, ERPs were completely unaffected by repetition at encoding, and only emotional pictures prompted a modestly enhanced old-new difference. Taken together, the data suggest that repetition facilitates retrieval processes and that, in the absence of an explicit recognition task, differences in old-new ERPs are only apparent for affective cues.

Perceptual processing of natural scenes at rapid rates: Effects of complexity, content, and emotional arousal

Abstract: During rapid serial visual presentation (RSVP), the perceptual system is confronted with a rapidly changing array of sensory information demanding resolution. At rapid rates of presentation, previous studies have found an early (e.g., 150–280 ms) negativity over occipital sensors that is enhanced when emotional, as compared with neutral, pictures are viewed, suggesting facilitated perception. In the present study, we explored how picture composition and the presence of people in the image affect perceptual processing of pictures of natural scenes. Using RSVP, pictures that differed in perceptual composition (figure–ground or scenes), content (presence of people or not), and emotional content (emotionally arousing or neutral) were presented in a continuous stream for 330 ms each with no intertrial interval. In both subject and picture analyses, all three variables affected the amplitude of occipital negativity, with the greatest enhancement for figure–ground compositions (as compared with scenes), irrespective of content and emotional arousal, supporting an interpretation that ease of perceptual processing is associated with enhanced occipital negativity. Viewing emotional pictures prompted enhanced negativity only for pictures that depicted people, suggesting that specific features of emotionally arousing images are associated with facilitated perceptual processing, rather than all emotional content.

Explicit and spontaneous retrieval of emotional scenes: electrophysiological correlates.

Abstract: There is abundant evidence from memory research using event-related potentials (ERPs) that items that have been experienced before elicit a larger late (500–800 ms) centro-parietal positive potential than new items when presented in the context of a recognition test (for reviews see Friedman & Johnson, 2000; Rugg & Curran, 2007) Whether stimuli are emotionally arousing or neutral, differences in ERP positivity between old and new items has been reliably found during explicit recognition for words (Windmann & Kutas, 2001), faces (Johansson et al, 2004), and scenes (Koenig and Mecklinger, 2008; Versace et al, 2010; Weymar et al, 2010) The amplitude of the difference, however, is often affected by whether the post-encoding task explicitly probes episodic memory or not (eg, Rugg & Wilding, 2000) For instance, old-new ERP differences are attenuated when old and new words are presented in the context of a semantic categorization task (Duzel et al, 1999; Rugg & Wilding, 2000) Using natural scenes, a robust old/new ERP difference was found during explicit recognition, but when old and new exemplars were simply viewed with no task, a significant old-new ERP difference was found only for emotional scenes (Ferrari et al, 2012) Assuming the late old-new ERP difference reflects retrieval from episodic memory (Rugg & Curran, 2007), these data suggest that not all post-encoding tasks prompt episodic retrieval, and that emotional stimuli may be more likely to be spontaneously retrieved in the absence of explicit recognition In two experiments, we further investigated the brain dynamics of implicit and explicit retrieval In Experiment 1, old and new pictures were presented in different instructional contexts following encoding: One group performed a semantic categorization task, in which the participant decided whether each picture included one person or more than one person and pressed a button indicating their decision This task, like explicit recognition (and unlike free viewing) requires both an active decision and a motor response Old-new ERPs measured during semantic categorization were compared to ERPs elicited in a group of participants who either made an explicit recognition decision (ie old/new) or simply viewed old and new pictures; both of these conditions are identical to those used by Ferrari et al (2012) Differences in ERP timing and topography have previously been suggested to index different mnemonic processes (Rugg and Curran, 2007) An early (300–500 ms) difference that is maximal over frontal sensors is often attributed to decisions that are based on familiarity (Rugg & Curran, 2007), while a later (>500 ms) difference that is maximal over central sensors has been attributed to explicit recollection, as it is enhanced by depth of processing, correct source judgments (eg, Curran, Tepe, & Piatt, 2006; Rugg & Curran, 2007) and confidence ratings (Weymar et al, 2009) Previous ERP studies have reported similar old/new differences in the late ERP for both emotional and neutral pictures on an immediate recognition test (Koenig & Mecklinger, 2008; Ferrari et al, 2012; Versace et al, 2006, 2010), whereas a larger old/new difference for emotional, compared to neutral, pictures has been reported after longer retention intervals (eg, Schaefer et al, 2010; Weymar et al, 2009) In Experiment 1, we assessed effects of task context on both early and late components of the ERP Of critical interest are ERP old/new differences for emotional and neutral pictures presented in the context of a semantic categorization (one or more people?) task, which does not explicitly probe episodic memory Because a number of studies have reported old-new differences in implicit (or indirect) tasks (eg, Guillem et al, 2000; Kazmerski & Friedman, 1997), one hypothesis is that an old-new ERP difference will be found for both emotional and neutral pictures during categorization If so, the previous null effect for neutral pictures during free viewing may simply reflect the lack of a requirement to process the picture On the other hand, if spontaneous retrieval is more likely for affectively arousing cues when memory retrieval is not explicitly required, enhanced ERP positivity for old, compared to new, pictures will again be found for emotional, but not neutral, pictures in the semantic categorization task, paralleling the effects reported by Ferrari et al (2012) during free viewing