17. The contribution of intracranial eeg to research on the empathy for pain

Abstract

In the last decade, a number of functional neuroimaging studies have identified a set of neural structures that are involved in empathy for another person’s pain. Bilateral anterior insular cortex and medial/anterior cingulate cortex seem to play a crucial role, but several other brain regions are also co-activated; this includes structures associated mostly with “Theory of Mind” or “mentalizing”, including precuneus, ventral prefrontal cortex, superior temporal cortex, and temporo-parietal junction. Electrophysiological pain-empathy responses have been analyzed to investigate the temporal dynamics of neural activity underlying this process. To the best of our knowledge, however, this has been performed with scalp recordings only; pain empathy-related brain potentials have not recorded using intracranial electrodes until now. In the present study, we investigated intracranial event-related brain potentials (ERPs) from three intractable epileptic patients who underwent preoperatively diagnostic invasive video-EEG monitoring. During the experiment, patients watched 3-second dynamic visual stimuli depicting needle injections into a left hand (N = 42), or the same left hand touched by a cue tip (N = 42). Intracranial EEGs were recorded using intracerebral and subdural electrodes, investigating in total more than 300 brain sites. The ERPs in each condition (needle and cue tip) were averaged separately off-line, and statistical differences in response amplitudes after painful vs. non-painful stimuli were detected. In all three subjects, significantly different event-related responses to painful vs. non-painful stimuli were observed in some investigated neural structures, including left-hemispheric temporo-parietal junction, right-sided temporo-occipital junction, and right-sided lateral occipital cortex. In these brain sites, painful needle stimuli evoked more prominent ERPs compared to cue-tip touch. The latency of these intracranial ERPs can be used for direct measurement of local activation with millisecond temporal resolution, and can be compared across different brain structures as well as with the scalp ERPs. Our pilot data demonstrate the ability of intracranial ERP recordings to contribute to our understanding of pain empathy. More generally, these data provide important insights into more complex social phenomena, and complement widely available functional neuroimaging data which are limited by their reliance on hemodynamic rather than direct neural measurements.