Does emotion modulate the blink reflex in human conditioning? Startle potentiation during pleasant and unpleasant cues in the picture–picture paradigm KIMBERLEY M. MALLAN and OTTMAR V. LIPP School of Psychology, University of Queensland, Queensland, Australia Abstract Emotional processes modulate the size of the eyeblink startle reflex in a picture-viewing paradigm, but it is unclear whether emotional processes are responsible for blink modulation in human conditioning. Experiment 1 involved an aversive differential conditioning phase followed by an extinction phase in which acoustic startle probes were presented during CS1, CS À , and intertrial intervals. Valence ratings and affective priming showed the CS1 was unpleasant postacquisition. Blink startle magnitude was larger during CS1 than during CS À . Experiment 2 used the same design in two groups trained with pleasant or unpleasant pictorial USs. Ratings and affective priming indicated that the CS1 had become pleasant or unpleasant in the respective group. Regardless of CS valence, blink startle was larger during CS1 than CS À in both groups. Thus, startle was not modulated by CS valence. Descriptors: Affective learning, Eyeblink startle, Conditioning, Emotion The eyeblink startle reflex is a simple brain stem reflex that can be elicited by a brief intense stimulus presented in the acoustic, visual, or tactile modality. In human research, startle eyeblink modulation is the difference between the magnitude of reflexes elicited during foreground stimuli and reflexes elicited during baseline periods or the difference in magnitude between reflexes elicited during different foreground stimuli. The extent of blink modulation varies with the lead interval, the time between the onset of the foreground and startle eliciting stimulus. At short lead intervals (60 to 500 ms), startle magnitude is attenuated, whereas at lead intervals greater than 2000 ms, startle is facil- itated. These blink modulation phenomena are of interest as they are modified by psychological processes such as emotion (Lang, Bradley, & Cuthbert, 1990) or attention (e.g., Lipp, Neumann, Pretorius, & McHugh, 2003). Sensitivity to both attentional and emotional processes can, however, be problematic, as these two processes are not independent. As noted by Lang, Bradley, and Cuthbert (1997), whenever attention is allocated to salient stim- uli, emotional processes are likely to be involved, and emotional processes cannot occur in the absence of simultaneous attentio- nal processes. Emotional modulation of blink startle at long lead intervals has been investigated predominately in the picture-viewing par- adigm (Lang et al., 1990). In this paradigm, blink startle is elici- ted while participants view pleasant, neutral, and unpleasant pictures, and startle magnitude covaries in a linear fashion with the valence of the picture. During viewing of pleasant pictures, the startle eyeblink response magnitude is inhibited relative to startles elicited during neutral pictures, whereas it is facilitated when viewing unpleasant pictures. Emotional modulation of startle has also been found when perceiving other affective fore- ground stimuli such as films, sounds, and smells (Bradley, Cuth- bert, & Lang, 1999). An exception to this pattern of affective modulation at long lead intervals is that startle responses elicited during affective imagery are potentiated during both pleasant and unpleasant scenes compared to during neutral scenes (Miller, Patrick, & Levenston, 2002). The motivational priming hypothesis has been suggested to account for affective modulation of startle during perception of affective stimuli (Bradley, 2000). According to the motivational theory of emotion, stimulus valence and arousal determine the direction of motivational activation (appetitive or defensive) and the degree of activation of either system, respectively (Bradley, Codispoti, Cuthbert, & Lang, 2001). When the defensive moti- vational system is dominant, then other defensive responses, such as the startle reflex, are primed. Thus, in a perception paradigm with affective stimuli, the startle reflex will be potentiated during unpleasant stimuli and inhibited during pleasant stimuli. In the context of aversive conditioning, the fear-potentiated startle reflex has been well established in animal subjects (Davis, Falls, Campeau, & Kim, 1993). In this paradigm, startle mod- ulation is assessed during neutral cues that either predict the occurrence (CS1) or absence (CS À ) of a shock US. The pattern of startle modulation conforms to an emotional modulation account: Startle is facilitated during the neutral cue (CS1) that was paired with the aversive shock. Aversive conditioning Address reprint requests to: Kimberley M. Mallan or Ottmar V. Lipp, School of Psychology, The University of Queensland, QLD, 4072, Australia. E-mail: mallan@psy.uq.edu.au or o.lipp@psy.uq.edu.au Psychophysiology, 44 (2007), **–**. Blackwell Publishing Inc. Printed in the USA. Copyright r 2007 Society for Psychophysiological Research DOI: 10.1111/j.1469-8986.2007.00541.x 1