Trait impulsivity and increased pre-attentional sensitivity to intense stimuli in bipolar disorder and controls

• Amplitude–intensity slopes are a physiological measure of responses to stimuli.
• Slope of the pre-attentional N1 potential correlated with impulsivity in bipolar disorder.
• This relationship appeared independent of clinical state or treatment.
• Impulsivity was not related to later attentional responses.
• Impulsivity may be related to exaggerated pre-attentional responses to stimuli.

Impulsivity and sensation seeking are stimulus-oriented traits. Because they differ in degree of intention and planning, they may have distinct neurophysiological mechanisms. Impulsivity is prominent in bipolar disorder, and may be related to pre-attentional information filtering and stimulus-orientation. We investigated specificity of relationships between impulsivity and sensitivity to stimulus intensity in bipolar disorder and controls, using intensity–sensitivity of auditory evoked potentials. Seventy-six subjects (37 healthy controls, 39 with bipolar disorder) were administered an intensity–sensitivity paradigm. Additional measures included Barratt Impulsiveness Scale (BIS-11) and Eysenck Impulsivity and Venturesomeness scores. State-dependent rapid-response impulsivity was measured using the Immediate Memory Task. Intensity-sensitivities of the auditory evoked P1N1, N1P2, P1, N1, and P2 potentials were assessed as the slope of amplitude relative to loudness. Analyses used general linear models (GLM) with impulsivity-related measures as dependent variables and age, gender, education, and diagnosis as dependent variables. BIS-11 total, motor, and attentional impulsivity scores correlated positively with pre-attentional N1 and P1N1 intensity–sensitivity slopes in bipolar disorder, but not in controls. BIS-11 nonplanning and Eysenck Venturesomeness scores did not correlate with intensity–sensitivity. Intensity–sensitivity slopes did not correlate with rapid-response impulsivity. Correlations between N1 or P1N1 slopes and BIS-11 scores in bipolar disorder were not affected by age, education, WAIS, treatment, symptoms, or gender. Trait impulsivity in bipolar disorder may be related to poorly modulated stimulus-driven late pre-attentional responses to stimuli, potentially resulting in exaggerated responses to intense stimuli even before conscious awareness. Components of trait impulsivity are physiologically heterogenous relative to intensity–sensitivity.