No abstract

A repetition paradigm was used to assess the nature of affective modulation of early and late components of the event-related potential (ERP) during picture viewing. High-density ERPs were measured while participants passively viewed affective or neutral pictures that were repeated up to 90 times each. Both ERP components were modulated by emotional arousal, with ERPs elicited when viewing pleasant and unpleasant pictures different than when viewing neutral pictures. On the other hand, repetition had different effects on these two components. The early occipitotemporal component (150-300 msec) primarily showed a decrease in amplitude within a block of repetitions that did not differ as a function of picture content. The late centroparietal component (300-600 msec) showed a decrease both between and within blocks of repetitions, with neutral pictures eliciting no late positive potential in the final block of the study. The data suggest that the early ERP primarily reflects obligatory perceptual processing that is facilitated by active short-term memory representations, whereas the late ERP reflects increased resource allocation due to the motivational relevance of affective cues.

Visual attention can be voluntarily oriented to detect target stimuli in order to facilitate goal-directed behaviors. Other visual stimuli capture attention because of motivational significance. The aim of the present study was to investigate the relationship between directed and motivated attention using event-related potentials. Affectively engaging pictures were presented either as target stimuli or as nontargets in a categorization task. Results indicated that both task relevance and emotional significance modulated the late positive potential (LPP) over centro-parietal sensors. Effects of directed and motivated attention on the LPP were additive, with the largest centro-parietal positivity found for emotional pictures that were targets of directed attention, and the least for neutral pictures that were nontargets. Taken together, the data provide new information regarding the relationship between motivated and directed attention, and suggest that the LPP reflects the operation of attentional neural circuits that are utilized by both top-down and bottom-up processes.

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 viewing 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.Affect reliably modulates the magnitude of a late positive potential (LPP) measured over centro-parietal sensors, with the largest LPPs elicited when viewing either pleasant or unpleasant, compared to neutral, pictures (e.g., Cacioppo, Crites, & Gardner, 1996;Codispoti, Mazzetti, & Bradley, 2009;Cuthbert, Schupp, Bradley, Birbaumer, & Lang, 2000;Johnston, Miller, & Burleson, 1986;Palomba, Angrilli, & Mini, 1997). Several recent studies have found that, despite a decrease in overall amplitude of the LPP with repeated presentation of the same picture, emotional pictures continue to elicit a larger late positive potential than neutral pictures (Codispoti, Ferrari & Bradley, 2006. One interpretation is that the LPP reflects, in part, motivational significance, defined as activation of corticolimbic appetitive and defensive systems that mediate the sensory and motor processes that support perception and action (Bradley, 2009).In our previous studies, however, repeated pictures were always presented intermixed among other (repeated) pictures. Thus, although the pictures were highly familiar, initial encoding and attention allocation processes were still necessary for picture identification on each presentation and it may be these processes that underlie continued modulation of the LPP. We tested this hypothesis in two experiments by repeatedly presenting the same picture over and over with no intervening stimuli between repetitions. If it is motivational significance that mediates the persistent modulation found for emotionally engaging picture despite repetition, we expected to continue to find differences in LPP amplitude between emotional and neutral pictures; to the extent that the LPP primarily indexes heightened initial attention allocation, we expected the differences to disappear. We employed two other reliable measures of attention and emotion in picture viewing to aid in interpreting changes in the late positive potential with massed repetition. Presentation of an acoustic startle probe during affective picture viewing modulates both the reflexive eyeblink and the amplitude of the P3 component o...

The present study examined cortical indicators of selective attention underlying categorization based on target features in natural scenes. The primary focus was to determine the neural sources associated with the processing of target stimuli containing animals compared to non-target control stimuli. Neural source estimation techniques [current source density (CSD) and L2-minimum norm estimate (L2-MNE)] were used to determine the sources of the potential fields measured from 58 sensor sites. Assuring an excellent signal-to-noise ratio, the categorization task consisted of 2400 trials. Replicating previous findings, target and non-target ERP activity diverged sharply around 150 ms after stimulus onset and the early differential ERP activity appeared as positive deflection over fronto-central sensor sites and as negative deflection over temporo-occipital regions. Both source estimation techniques (CSD and L2-MNE) suggested primary sources of the early differential ERP activity in posterior, visual-associative brain regions and, although less pronounced, revealed the contribution of additional anterior sources. These findings suggest that selective attention to category-relevant features reflects the interactions between prefrontal and inferior temporal cortex during visual processing of natural scenes.