Affective picture modulation: Valence, arousal, attention allocation and motivational significance

The present study analyses the modulatory effects of affective pictures in the early posterior negativity (EPN),
the late positive potential (LPP) and the human startle response on both the peripheral (eye blink EMG) and
central neurophysiological levels (Probe P3), during passive affective pictures viewing. The affective pictures
categories were balanced in terms of valence (pleasant; unpleasant) and arousal (high; low). The data shows
that EPN may be sensitive to specific stimulus characteristics (affective relevant pictures versus neutral pictures)
associated with early stages of attentional processing. In later stages, the heightened attentional resource
allocation aswell as themotivated significance of the affective stimuliwas found to elicit enhancedamplitudes of
slow wave processes thought to be related to enhanced encoding, namely LPP,. Although pleasant low arousing
pictureswere effective in engaging the resources involved in the slowwave processes, the highly arousing affective
stimuli (pleasant and unpleasant) were found to produce the largest enhancement of the LPP, suggesting
that high arousing stimulimay are associatedwith increasedmotivational significance. Additionally the response
to high arousing stimulimay be suggestive of increasedmotivational attention, given the heightened attentional
allocation, as expressed in the P3 probe, especially for the pleasant pictures. The hedonic valencemay then serve
as amediator of the attentional inhibition to the affective priming, potentiating or inhibiting a shift towards
defensive activation, as measured by the startle reflex.
Portuguese Foundation for Science
and Technology with individual grants (SFRH/BD/41484/2007
and SFRH/BD/64355/2009) and by the Spanish Xunta de Galicia –
with FEDER funds – (DOG 233 — Resolution date: 2009 November
18th