Fig. 4

Problematic cases of PPI results that may be confounded by basal startle reactivity. Two representative cases of PPI results in two groups of mice with different levels of basal startle reactivity are shown for 74–110 dB (a) and 78–120 dB (b) stimuli. Lines indicate regression curves of the acoustic startle response and PPI for each trial type. Blue and red circles indicate clusters of PPI data in different groups of mice with lower or higher levels of ASR (Groups A and B). The two cases may impose limitations on the interpretation of PPI results: as expected from the results of the correlation analysis of ASR and PPI, differences in PPI levels between two groups of mice may result from a low startle reactivity (a) or a high startle reactivity (b) in either group