Showing papers by "Margaret M. Bradley published in 2011"

Repetitive exposure: brain and reflex measures of emotion and attention.

Abstract: Effects of massed repetition on the modulation of the late positive potential elicited during affective picture viewing were investigated in two experiments. Despite a difference in the number of repetitions across studies (from 5 to 30), results were quite similar: The late positive potential continued to be enhanced when participants viewed emotional, compared to neutral, pictures. On the other hand, massed repetition did prompt a reduction in the late positive potential that was most pronounced for emotional pictures. Startle probe P3 amplitude generally increased with repetition, suggesting diminished attention allocation to repeated pictures. The blink reflex, however, continued to be modulated by hedonic valence, despite massive massed repetition. Taken together, the data suggest that the amplitude of the late positive potential during picture viewing reflects both motivational significance and attention allocation.

Scan patterns when viewing natural scenes: Emotion, complexity, and repetition

Abstract: Eye movements were monitored during picture viewing, and effects of hedonic content, perceptual composition, and repetition on scanning assessed. In Experiment 1, emotional and neutral pictures that were figure-ground compositions or more complex scenes were presented for a 6-s free viewing period. Viewing emotional pictures or complex scenes prompted more fixations and broader scanning of the visual array, compared to neutral pictures or simple figure-ground compositions. Effects of emotion and composition were independent, supporting the hypothesis that these oculomotor indices reflect enhanced information seeking. Experiment 2 tested an orienting hypothesis by repeatedly presenting the same pictures. Although repetition altered specific scan patterns, emotional, compared to neutral, picture viewing continued to prompt oculomotor differences, suggesting that motivationally relevant cues enhance information seeking in appetitive and defensive contexts.

The impact of anxiety on the neural processing of respiratory sensations

Abstract: Previous studies demonstrated that anxiety considerably impacts the reported perceptions of respiratory sensations. A novel feature of the current study is exploring the impact of anxiety on the neural processing of respiratory sensations elicited by short inspiratory occlusions during different affective contexts. Using high-density EEG, respiratory-related evoked potentials (RREP) were recorded in 23 low and 23 matched higher anxious individuals when viewing unpleasant or neutral picture series. Low anxious individuals showed the expected pattern of reduced magnitudes of later RREP components P2 and P3 during the unpleasant compared to the neutral affective context (p<0.05 and p<0.01). In contrast, higher anxious individuals showed greater magnitudes of P2 and P3 during the unpleasant compared to the neutral affective context (p's<0.05). Moreover, higher anxiety levels were correlated with greater magnitudes for P2 (r=0.44, p<0.01) and P3 (r=0.54, p<0.001) during the unpleasant relative to the neutral affective context. Earlier components of the RREP (Nf, P1, N1) were not affected by anxiety. This study demonstrates that anxiety affects the later, higher-order neural processing of respiratory sensations, but not its earlier, first-order sensory processing. These findings might represent a neural mechanism that underlies the increased perception of respiratory sensations in anxious individuals.

Threat of suffocation and defensive reflex activation.

Abstract: The current study examined emotional reflex reactions of participants threatened with respiratory distress caused by imposing a resistive load at inspiration. Cues signaling threat (breathing MAY be difficult) and safe periods were intermixed while startle reflexes, heart rate, skin conductance, and facial EMG activity were measured. Compared to safe cues, threat cues elicited significant startle potentiation, enhanced skin conductance, heightened corrugator EMG changes, and pronounced "fear bradycardia" consistent with defensive activation in the context of threatened respiratory dysfunction. These data indicate that anticipating respiratory resistance activates defensive responding, which may mediate symptomatology in patients with panic and other anxiety disorders.

Aversive picture processing: effects of a concurrent task on sustained defensive system engagement.

Abstract: Viewing a series of aversive pictures prompts emotional reactivity reflecting sustained defensive engagement. The present study examined the effects of a concurrent visual task on autonomic, somatic, electrocortical, and facial components of this defensive state. Results indicated that emotional activation was largely preserved despite continuous visual distraction, although evidence of attenuation was observed in startle reflex and electrocortical measures. Concurrent task-specific reactivity was also apparent, suggesting that motivational circuits can be simultaneously activated by stimuli with intrinsic survival significance and instructed task significance and that these processes interact differently across the separate components of defensive engagement.

Habituation in neural processing and subjective perception of respiratory sensations.

Abstract: Reduced perception of respiratory sensations is associated with negative treatment outcome in asthma. We examined whether habituation in the neural processing of repeatedly experienced respiratory sensations may underlie subjective reports of reduced respiratory perception. Respiratory-related evoked potentials (RREP) elicited by inspiratory occlusions and reports of respiratory perception were compared between early and late experimental periods in healthy subjects. Reports of respiratory perception were reduced during late, compared to early, experimental periods. This was paralleled by reduced magnitudes in RREP components N1, P2, and P3 in late, compared to early, experimental periods. Habituation in the neural processing of respiratory sensations is a potential mechanism that underlies subjective reports of reduced respiratory perception and might represent a risk factor for reduced perception of respiratory sensations in asthma.

Nucleus Accumbens and Medial Prefrontal Cortex Pleasure Rather Than Salience Activates Human

Abstract: 98: 1374–1379, 2007. Firstpublished June 27, 2007; doi:10.1152/jn.00230.2007. Recent humanfunctional imaging studies have linked the processing of pleasantvisual stimuli to activity in mesolimbic reward structures. However,whether the activation is driven specifically by the pleasantness of thestimulus, or by its salience, is unresolved. Here we find in two studiesthat free viewing of pleasant images of erotic and romantic couplesprompts clear, reliable increases in nucleus accumbens (NAc) andmedial prefrontal cortex (mPFC) activity, whereas equally arousing(salient) unpleasant images, and neutral pictures, do not. These datasuggest that in visual perception, the human NAc and mPFC arespecifically reactive to pleasant, rewarding stimuli and are not en-gaged by unpleasant stimuli, despite high stimulus salience.