This thesis examined the effects of higher cognitive mechanisms on the automatic and elaborate elicitation of motivational behaviours by visual material presented in absence (i.e. subliminal stimuli) and presence of visual awareness (i.e. optimal stimuli), respectively.
With the aim of teasing apart automatic and elaborate approach and withdrawal behaviours, the first study measured self-pain tolerance, intensity and unpleasantness during the Cold Pressor Test (within-subjects) in healthy participants (N=155) before and after passive viewing of negative or vicarious pain images at subliminal or optimal exposure (between-subjects). As a further step, the second study examined the neural and behavioural effects of right dorsolateral prefrontal cortex (rDLPFC) inhibition on automatic and elaborate negative processing pathways.
For this purpose, encephalographic (EEG) neural responses (within-subjects) were recorded while healthy participants (N=38) passively viewed negative and neutral images presented at subliminal and optimal exposure (within-subjects) before and after right dorsolateral prefrontal cortex (rDLPFC) inhibition or sham via repetitive transcranial magnetic stimulation (rTMS) (between-subjects). EEG event-related potentials were analysed for early (80-120ms), mid (120-300ms) and late time-windows (300-600ms). Participants completed behavioural attention and affective tasks after the trial presentation (N=48). Findings showed that both subliminal and optimal negative images as well as optimal vicarious pain elicited increased self-pain sensitivity, reflecting automatic and elaborate withdrawal behaviours, respectively. Conversely, subliminal vicarious pain decreased self-pain sensitivity, reflecting automatic approach responses (Study 1).
Furthermore, two networks of automatic negative processing emerged: temporal pathways showing increased early and mid-latency activity specific to subliminal negative images, which remained unaffected by rDLPFC inhibition; and occipito-parietal pathways, showing increased mid- and late latency activity for negative images after rDLPFC inhibition, independent from visual awareness. Moreover, rDLPFC inhibition increased late frontal activity for optimal negative images at elaborate processing stages. This was associated with decreased withdrawal behaviours; specifically, attenuated negative priming and faster attention disengagement (Study 2).
These results indicate that in absence of visual awareness, automatic motivational behaviours may be modulated according to whether visual material reflects self-oriented (i.e. negative) or other-oriented threat (i.e. vicarious pain), thereby requiring withdrawal or approach and empathic understanding that enhance individual or group survival, respectively. Automatic negative processing may follow multiple neural pathways, which underpin automatic attention orienting (temporal network) and stimulus encoding (occipito-temporal network). The occipito-temporal network, in particular, may integrate bottom-up and top-down input, thereby permitting disinhibited higher cognitive processes involved in top-down regulation to exert early influence on automatic activation of approach and withdrawal behaviours. In presence of visual awareness, disinhibition of the frontal control network reduced withdrawal responses, confirming its role in the regulation of elaborate motivational behaviours. It seems likely that vicarious pain processing occurs along similar pathways, albeit with different behavioural consequences; however, such speculation requires future investigation.
The distinct networks facilitating healthy automatic and elaborate stimulus processing represent a platform for further exploration, including the detection of aberrant neural activity in clinical disorders characterized by dysfunctional approach-withdrawal behaviours. Given the modulatory effects of top-down regulation on both automatic and elaborate processing, it is tentatively suggested that cognitive management strategies that enhance affective and attentional control may decrease excessive withdrawal responses. Future research may use integrative behavioural-neuroimaging methods to determine relevant boundary conditions of automatic and elaborate processing in healthy and clinical populations.