Anxiety and prepulse inhibition of acoustic startle in a normative sample: The importance of signal-to-noise ratio

Previous studies have used prepulse inhibition of the startle response (PPI) to investigate the anxiety spectrum, primarily in patient samples, with mixed results. The inconsistency in findings may be due, in part, to the use of non-optimal signal-to-noise ratios (SnRs: the difference between background noise intensity and prepulse intensity) in some studies. We proposed that, as SnR approaches +15 dB, anxiety spectrum variables will be negatively correlated with PPI, even in a normative sample. Thus, we used the MCMI-III to measure levels of trait anxiety, posttraumatic stress disorder (PTSD), and the three Cluster C personality disorders in a sample of 53 undergraduate females, and then correlated their scores with their PPI levels at SnRs of +5, +10, and +15 dB. All of the anxiety constructs except obsessive-compulsive personality disorder (OCPD) were correlated with PPI, but only in the +15 dB condition. Although OCPD symptomatology was not correlated with PPI, it was negatively correlated with PTSD and may have been indicative of adaptive functioning in this normative sample. The present study demonstrates that PPI is a sensitive index of anxiety symptomatology even in the normative range, and that a SnR near +15 dB may be necessary to reliably detect associations between PPI and these psychological variables.