This study sought to determine whether prepulse
inhibition and valence modulation of startle are independent,
both within and across individuals. Acoustic probes (105
dB) were delivered as 68 undergraduates viewed
pleasant, neutral, and unpleasant pictures. Weak acoustic
stimuli (8 dB above background) preceded half of the probes
by 120 ms. As expected, startles were larger during unpleasant
than during pleasant pictures, and smaller on prepulse
than no-prepulse trials. In general, valence modulation
and prepulse inhibition of startle were unrelated. That
is, prepulse inhibition was consistent across affective
states, valence modulation did not differ between no-prepulse
and prepulse trials, and valence modulation and prepulse
inhibition effects were uncorrelated across individuals.
Analysis of raw and percent modification scores generally
led to similar conclusions. It is concluded that valence
modulation and prepulse inhibition are independent startle
modulatory phenomena, although this conclusion is tempered
by a finding of poor internal consistency reliability for
valence modulation.