Effects of approach-avoidance related motor behaviour on the startle response during emotional picture processing

Motivational states may be induced by affective foreground stimulation or via proprioceptive feedback by certain postures or body movements. In the present study, we addressed the question of an interaction between basic motor actions and the valence of visual stimuli in an affective modulation of startle paradigm: is the potentiation for aversive and the attenuation for pleasant stimuli more pronounced when the muscles for a congruent approach or avoidance action are activated? Thirty-four volunteers (20 female) watched emotional pictures on a computer screen while simultaneously contracting the flexor vs. extensor muscles of the upper arm. After 3-4 s, an acoustic startle stimulus (105 dB, binaural, instantaneous rise time) was presented via headphones. Arm movement interacted with picture valence: flexion, compared to extension, increased affective startle modulation (F = 4.32, p < 0.05). This result suggests integration and not simple summation of postural and body movement effects on startle reflexivity.