Abstract
Human faces may signal relevant information and are therefore analysed rapidly and effectively by the brain. However, the precise mechanisms and pathways involved in rapid face processing are unclear. One view posits a role for a subcortical connection between early visual sensory regions and the amygdala, while an alternative account emphasises cortical mediation. To adjudicate between these functional architectures, we recorded magnetoencephalographic (MEG) evoked fields in human subjects to presentation of faces with varying emotional valence. Early brain activity was better explained by dynamic causal models containing a direct subcortical connection to the amygdala irrespective of emotional modulation. At longer latencies, models without a subcortical connection had comparable evidence. Hence, our results support the hypothesis that a subcortical pathway to the amygdala plays a role in rapid sensory processing of faces, in particular during early stimulus processing. This finding contributes to an understanding of the amygdala as a behavioural relevance detector.
Highlights
Rapid detection of salient stimuli in the environment is of crucial importance for the survival of an organism
To examine whether emotional faces reach the amygdala via a dualroute or via a cortical pathway only, we recorded MEG data from 12 subjects, while they performed a gender discrimination task for neutral, happy and fearful faces
We found that a subcortical connection between the pulvinar and the amygdala plays a role in early, but not late, visual processing
Summary
Rapid detection of salient stimuli in the environment is of crucial importance for the survival of an organism. One model suggests that visual information about faces or whole bodies – in a fearful or threatening context – is conveyed to the amygdala by a cortical and a subcortical processing route (de Gelder et al, 2004; Morris et al, 1998; Rudrauf et al, 2008; Vuilleumier et al, 2003). This is thought to enable rapid and automatic information processing more so than a resource-dependent cortical route (Tamietto and de Gelder, 2010). The functional importance and mechanistic contribution of a subcortical connection has been questioned (Kumar et al, 2012; Pessoa, 2005)
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