Copyright 2012 Aileen M. Echiverri-Cohen - University of Washington

studies show a correspondence between decreased cognitive activation in the prefrontal region
(e.g., decreased P3 amplitude, decreased regional cerebral blood flow) and decreased reaction
time or decreased accuracy on response tasks in individuals with PTSD compared to those
without psychopathology (e.g., Boudarene & Timsit-Berthier, 1997; McFarlane, et al., 1993;
Galletly et al., 2001; Clark et al., 2003; Shaw et al., 2002; Semple et al.; 1996; Vasterling et al.,
1998, 2002; Koso & Hansen, 2006; Navalta et al., 2006; Beers et al., 2002). However, many of
these studies suffer from low sample sizes, lack of comparison groups to control for trauma
exposure, or failure to control for such things as history of psychotropic treatment and substance
use. Nevertheless, the initial pattern of results suggests that deficient inhibitory processes
underlie, at least in part, the poor cognitive performance in tasks using trauma-neutral stimuli
and the decreased activity in the prefrontal brain regions observed in individuals with PTSD.
Two relevant measures of inhibition are attentional blink (AB; Raymond, Shapiro, &
Arnell, 1992), a behavioral measure assessing reduced ability to direct attention to multiple
stimuli in a visual stream, and prepulse inhibition of startle (PPI; Braff & Geyer, 1990), a
psychophysiological measure evaluating the strength of inhibition in gating irrelevant
information. The AB is a cognitive paradigm that is thought to be linked to inhibitory processes
by directing attentional resources to one target thereby affecting the processing of the subsequent
target (Raymond et al., 1992). Using a rapid serial visual presentation sequence (RSVP) in which
target (T) stimuli (e.g., letters) are embedded in a stream of distractor (D) stimuli (e.g., numbers;
Raymond, et al., 1992), participants are instructed to identify the first and second targets from a
set of possible targets that are separated by intervening distractors also referred to as a lag (L).
Individuals typically show high rates of correct identification of both targets under a Lag 1
condition (e.g., no intervening distractors between targets); however, individuals typically show
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