Modality-specific attentional startle modulation during continuous performance tasks: A brief time is sufficient SAKINAH S.J. ALHADAD, OTTMAR V. LIPP and HELENA M. PURKIS School of Psychology, University of Queensland, Queensland, 4072, Australia Abstract Attentional startle modulation has been found to be modality specific in continuous performance tasks (CPTs) and modality nonspecific in trial-structured tasks. Experiment 1 investigated whether attentional blink modulation in a CPT would change if a trial structure was imposed. Participants performed a visual CPT either continuously (CONT), or during brief periods of time signaled by a change in screen color with stimuli either presented all the time (MIXED) or only during the trial segments (DISC). Contrary to expectation, evidence for modality-specific attentional startle modulationFsmaller acoustic startle during targets than during nontargetsFwas strongest in Groups MIXED and DISC. Experiment 2 confirmed that this pattern of results was present during the first stimulus of the task period in group DISC. This suggests that the continuous nature of a task is not critical in determining the attentional mech- anisms engaged. Descriptors: Startle, Attention, Continuous performance task, EMG The startle eyeblink response is an early component of the startle reflex (Hoffman, 1997) and is the most reliable element of the startle reflex in humans (Berg & Balaban, 1999). It is elicited by a stimulus of a sudden or abrupt onset, such as a flash of light, a loud noise, or a quick movement near the face (Hoffman & Ison, 1992). Over the last two decades, the modulation of the startle eyeblink response has become an increasingly popular tool in psychology to index background processes such as emotion (Lang, Bradley, & Cuthbert, 1990) or attention (Graham, 1992). Modulation of startle is useful as an index of attention, as its short latency permits a good temporal resolution for the mon- itoring of attentional processes. This short latency and the mul- ticomponent nature of the response allow the observation of the independent effects of those processes thought to underlie stim- ulus encoding and response selection (Hackley & Boelhouwer, 1997). Startle may be modulated when a nonstartling, innocuous lead stimulus precedes a startle-eliciting stimulus. The specific modulation effects of the lead stimulus on startle, facilitation or inhibition, are largely dependent on the lead interval, that is, the interval between the onset of the lead and startle-eliciting stimuli, and the sensory modality in which both the lead and startle- eliciting stimuli are presented (for a review, see Filion, Dawson, & Schell, 1998). The startle eyeblink response is inhibited if the lead interval is short (i.e., between 100 ms and 300 ms following the onset of the innocuous lead stimulus; Graham, 1992). This short lead interval inhibition, or prepulse inhibition, is thought to reflect a sensory gating process that protects initial processing of the lead stimulus from interference by irrelevant stimuli (Blu- menthal, 1999). Attention to the lead stimulus enhances prepulse inhibition, regardless of the sensory modalities of the lead and startle-eliciting stimuli (Bradley, Cuthbert, & Lang, 1993; Filion, Dawson, & Schell, 1993). At lead intervals longer than 500 ms, startle prepulse facil- itation is usually observed (Filion et al., 1998). This is thought to reflect an orienting response, a response that accompanies the enhancement of information intake after presentation of a me- dium- to low-intensity stimulus (Graham, 1992). Unlike the unidirectional attentional startle modulation effects at short lead intervals, the direction of startle modulation at long lead intervals has been varied (see Filion et al., 1998). Early evidence of startle modulation at long lead intervals suggests that attention to the lead stimulus facilitates startle magnitude when directed toward the sensory modality in which the reflex eliciting stimulus is pre- sented, and inhibits startle magnitude when directed away (An- thony & Graham, 1985; Putnam, 1990). This indicates a modality-specific modulation of the startle eyeblink response. More recent research, however, queries the modality speci- ficity of attentional startle modulation. Evidence from simple discrimination and counting tasks (Bo¨ hmelt, Schell & Dawson, 1999; Lipp, Neumann, Pretorius, & McHugh, 2003; Neumann Lipp, & McHugh, 2004), reaction time tasks (Lipp & Hardwick, 2003; Lipp, Siddle, & Dall, 2000a), and passive orienting tasks (Lipp, Siddle, & Dall, 2000b) suggests that startle is enhanced during to-be-attended stimuli compared to nonattended stimuli, regardless of the sensory modality in which stimuli are presented. This suggests that attentional startle modulation at long lead intervals may be modality nonspecific. Grant DP0450465 from the Australian Research Council supported this work. Address reprint requests to: Sakinah S.J. Alhadad or Ottmar V. Lipp, School of Psychology, The University of Queensland, QLD, 4072, Aus- tralia. E-mail: s.alhadad@psy.uq.edu.au or o.lipp@psy.uq.edu.au Psychophysiology, 45 (2008), 1068–1078. Wiley Periodicals, Inc. Printed in the USA. Copyright r 2008 Society for Psychophysiological Research DOI: 10.1111/j.1469-8986.2008.00705.x 1068