Emotions modulate pain perception, although the mechanisms underlying this phenomenon remain unclear. In this study, we show that intensity reports significantly increased when painful stimuli were concomitant to images showing human pain, whereas pictures with identical emotional values but without somatic content failed to modulate pain. Early somatosensory responses (Ͻ200 ms) remained unmodified by emotions. Conversely, late responses showed a significant enhancement associated with increased pain ratings, localized to the right prefrontal, right temporo-occipital junction, and right temporal pole. In contrast to selective attention, which enhances pain ratings by increasing sensory gain, emotions triggered by seeing other people's pain did not alter processing in SI-SII (primary and second somatosensory areas), but may have biased the transfer to, and the representation of pain in short-term memory buffers (prefrontal), as well as the affective assignment to this representation (temporal pole). Memory encoding and recall, rather than sensory processing, appear to be modulated by empathy with others' physical suffering.

Conscious perception of painful stimuli needs the contribution of an extensive cortico-subcortical network, and is completed in less than one second. While initial activities in operculo-insular and mid-cingulate cortices have been extensively assessed, the activation timing of most areas supporting conscious pain has barely been studied. Here we used intracranial EEG to investigate the dynamics of 16 brain regions (insular, parietal, prefrontal, cingulate, hippocampal and limbic) during the first second following nociceptive-specific laser pulses. Three waves of activation could be defined according to their temporal relation with conscious perception, ascertained by voluntary motor responses. Pre-conscious activities were recorded in the posterior insula, operculum, mid-cingulate and amygdala. Antero-insular, prefrontal and posterior parietal activities started later and developed during time-frames consistent with conscious voluntary reactions. Responses from hippocampus, perigenual and perisplenial cingulate developed latest and persisted well after conscious perception occurred. Nociceptive inputs reach simultaneously sensory and limbic networks, probably through parallel spino-thalamic and spino-parabrachial pathways, and the initial limbic activation precedes conscious perception of pain. Access of sensory information to consciousness develops concomitant to fronto-parietal activity, while late-occurring responses in the hippocampal region, perigenual and posterior cingulate cortices likely underlie processes linked to memory encoding, self-awareness and pain modulation. Hum Brain Mapp 37:4301-4315, 2016. © 2016 Wiley Periodicals, Inc.