5 ms. Electric shocks were administered by a Grass Instruments S-88 dual-channel square-pulse stimulator with an Isolation Unit SIU7 (all by Grass Instrument Division, Astro-Med Inc., West Warwick, RI, USA). The electrodes were placed on the radial side of the most distal phalanges of the left and right index fingers. Individual shock strength threshold determination was performed before conditioning and, to account for habituation effects, after half
of the total number of 80 shock presentations, separately for shocks administered to the left and right hands. Participants RG7204 price were asked to rate their sensation of shock intensity on a six-point scale ranging from one (‘not perceptible at all’) to six (‘painful’). Current levels started off at 1 mA and were gradually increased until a subjective rating of five was reached; this corresponded to an ‘unpleasant but
not painful’ sensation from the shock. The mean UCS intensity level was 5.02 ± 3.52 mA. Differential emotional significance was assigned to the click-like tones by means of MultiCS conditioning (Bröckelmann et al., 2011; Steinberg et al., 2012b). Affective conditioning BAY 80-6946 molecular weight paradigms typically involve one neutral stimulus (CS) that becomes associated with a UCS after repeated contingent CS–UCS pairings and acquires the power to elicit the CR previously evoked by UCS presentation alone (e.g., Quirk et al., 1995; Dolan et al., 2006; Stolarova et al., 2006; Keil et al., 2007; Moses et al., 2010; Kluge et al., 2011). MultiCS conditioning extends this classical approach by assigning behavioural Astemizole relevance to multiple CS per affective category and with only few contingent CS–UCS pairings. This procedure therefore challenges the brain’s capacity to process emotional stimuli in terms of speed and resolving power. In addition, for investigations
with time-sensitive neurophysiological measures such as MEG or EEG, the procedure provides a sufficiently high number of trials within each experimental condition assuring good signal-to-noise ratio for data analysis while every single stimulus is repeated only a few times, reducing extinction of the acquired emotional meaning due to repeated non-reinforced CS presentations after conditioning (Rogan et al., 1997). Upon arrival in the laboratory, participants were informed about the experimental procedure and the electric shock administration, and gave written informed consent to the protocol. The affective associative learning procedure in the MEG comprised one pre-conditioning MEG measurement, two interspersed conditioning sessions and one post-conditioning MEG measurement (Fig. 1), as well as three behavioural tasks administered after MEG data acquisition.