Source code for the experimental paradigm from How non-veridical perception drives actions in healthy humans: evidence from synaesthesia

We continually perform actions that are driven by our perception and it is a commonly held view that only objectively perceived changes within the ‘real’ world affect behaviour. Exceptions are generally only made for mental health disorders associated with delusions and hallucinations where behaviour may be triggered by the experience of objectively non-existent percepts. Here, we demonstrate, using synaesthesia as a model condition (in N = 19 grapheme–colour synaesthetes), how objectively non-existent (i.e. non-veridical) but still non-pathological perceptions affect actions in healthy humans. Using electroencephalography, we determine whether early-stage perceptual processes (reflected by P1 and N1 event-related potential (ERP) components), or late stage-integration processes (reflected by N2 component), underlie the effects of non-veridical perceptions on action control. ERP analysis suggests that even though the examined peculiarities and experimental variations are perceptual in nature, it is not early-stage perceptual processes, but rather higher-order executive control processes linking perceptions to the appropriate motor response underlying this effect. Source localization analysis implicates activation within medial frontal cortices in the effect of how irrelevant non-veridical perceptions modulate behaviour. Our results challenge common conceptions about the determinants of human behaviour but can be explained by well-established theoretical frameworks detailing the link between perception and action.This article is part of the discussion meeting issue ‘Bridging senses: new developments in synaesthesia’.

人类的行为始终由感知所驱动，学界普遍认为，唯有“现实”世界中被客观感知到的变化，才会对行为产生影响。而与此相悖的情况，通常仅见于与妄想、幻觉相关的精神障碍——此类患者的行为可能由客观上并不存在的感知体验所触发。本研究以联觉（synaesthesia）为模型范式，招募19名字形-颜色联觉者开展实验，以此证实：即便客观上不存在（即非真实的，non-veridical）但仍属非病理状态的感知，也会对健康人群的行为产生影响。本研究采用脑电图（electroencephalography, EEG）技术，旨在探明非真实感知对行为控制的影响，究竟源于早期感知加工过程（以P1、N1事件相关电位（event-related potential, ERP）成分为表征），还是晚期整合加工过程（以N2成分为表征）。事件相关电位分析结果显示：尽管本次实验所考察的特殊效应与实验变量均属于感知范畴，但上述效应并非源于早期感知加工过程，而是由将感知与恰当运动反应相联结的高阶执行控制过程所介导。源定位分析表明，无关非真实感知对行为的调控效应，与内侧前额叶皮层的激活存在关联。本研究结果挑战了学界关于人类行为决定因素的普遍认知，但可通过已被广泛验证的感知-行动联结理论框架加以解释。本文隶属于专题讨论会议专辑“联结感知：联觉研究的新进展”。