Table 1.

Systematic review components in PICOS format (population, intervention, comparators, outcomes, and study designs).

Population	Healthy participants (no psychiatric or neurologic conditions), all age ranges. (nb. Participants may be from a healthy control group or a placebo group in a study including a separate clinical group).
Intervention	All studies using an empathy task An empathy task is defined as one in which the instructions required participants: - to observe the emotional or sensory state of others (with or without an explicit instruction to do so), - to share the emotional or sensory state of another person and make a subsequent judgement or evaluation, or - to imagine what another person is feeling
Comparators	Neural correlates of: - empathy in general - empathy for pain vs. empathy for non-pain negative affective states - empathy for pain using different stimuli (facial pain expressions vs. acute pain inflictions) - empathy using different paradigms (cognitive/evaluative vs. affective/perceptual empathy) - empathy for pain using different paradigms (cognitive/evaluative vs. affective/perceptual empathy)
Outcomes	Neural activation foci (coordinates of relevant contrasts in MNI space) and sample size
Study Designs	Original research (reviews or abstracts not included) Functional imaging (fMRI or PET) Whole brain analysis of activation patterns (region of interest analysis only or functional connectivity analyses not included) Coordinates presented between empathy condition and baseline or neutral condition (group analyses, correlation analyses, comparison of two empathy conditions not included*) No manipulation that may bias results (e.g., pharmacological challenge or priming)

MNI, Montreal Neurologic Institute;

^*As our definition of an empathy task included tasks without explicit instructions (i.e., passive watching/distraction tasks), paradigms using high-order baselines were excluded (e.g., making a gender judgement of facial pain expressions).