Showing papers by "Margaret M. Bradley published in 2003"

Activation of the visual cortex in motivated attention.

Abstract: Functional activation (measured with fMRI) in occipital cortex was more extensive when participants view pictures strongly related to primary motive states (i.e., victims of violent death, viewer-directed threat, and erotica). This functional activity was greater than that observed for less intense emotional (i.e., happy families or angry faces) or neutral images (i.e., household objects, neutral faces). Both the extent and strength of functional activity were related to the judged affective arousal of the different picture contents, and the same pattern of functional activation was present whether pictures were presented in color or in grayscale. It is suggested that more extensive visual system activation reflects "motivated attention," in which appetitive or defensive motivational engagement directs attention and facilitates perceptual processing of survival-relevant stimuli.

The psychophysiology of anxiety disorder: Fear memory imagery

Abstract: Psychophysiological response to fear memory imagery was assessed in specific phobia, social anxiety disorder, panic disorder with agoraphobia, post-traumatic stress disorder (PTSD), and healthy controls. Heart rate, skin conductance, and corrugator muscle were recorded as participants responded to tone cues signaling previously memorized descriptor sentences. Image contents included personal fears, social fears, fears of physical danger, and neutral (low arousal) scenes. Reactions to acoustic startle probes (eyeblink) were assessed during recall imagery and nonsignal periods. Participants were significantly more reactive (in physiology and report of affect) to fear than neutral cues. Panic and PTSD patients were, however, less physiologically responsive than specific phobics and the socially anxious. Panic and PTSD patients also reported the most anxiety and mood symptoms, and were most frequently comorbidly depressed. Overall, physiological reactivity to sentence memory cues was greatest in patients with focal fear of specific objects or events, and reduced in patients characterized by generalized, high negative affect.

Early modulation of visual perception by emotional arousal: evidence from steady-state visual evoked brain potentials.

Abstract: Allocation of processing resources to emotional picture stimuli was examined using steady-state visual evoked brain potentials (ssVEPs). Participants viewed a set of 60 colored affective pictures from the International Affective Picture System, presented in a flickering mode at 10 Hz in order to elicit ssVEPs. Phase and amplitude of the 10-Hz ssVEP were examined for six picture categories: threat and mutilation (unpleasant), families and erotica (pleasant), and household objects and persons (neutral). Self-reported affective arousal and hedonic valence of the picture stimuli were assessed by means of subjective ratings. Viewing affectively arousing (unpleasant and pleasant) pictures was associated with enhanced ssVEP amplitude at parieto-occipital recording sites, as compared with neutral stimuli. Phase information suggested increased coactivation of right occipitotemporal and frontotemporal sources during processing of affectively arousing stimuli. These findings are consistent with reentrant modulation of early visual processing by distributed networks including subcortical and neocortical structures according to a stimulus's motivational relevance.

Startle Reflex Modulation: Perception, Attention, and Emotion

Abstract: In this chapter, we discuss a new method for assessing attention and affect that relies on the measurement of a simple reflex that occurs in all mammalian species — the startle reflex. The abrupt presentation of a sensory stimulus— for example, a burst of noise or a flash of light — elicits a reflexive startle response. The gross features of startle in humans include a forward thrusting of the head and a descending flexor wave reaction that extends through the trunk to the knees. The first, fastest, and most stable element in the startle sequence is the reflexive eyeblink, occurring within 30–80 ms after stimulus onset, which is a reliable motor response that is easy both to measure and to quantify.