MIRROR NEURONS Mirrors, Mirrors, Everywhere? the Discussion About a Possible Role Actions and Facial Expressions

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MIRROR NEURONS Mirrors, mirrors, everywhere? The discussion about a possible role actions and facial expressions. They establish whether they also contain of mirror neurons in learning and recorded from neurons in the medial mirror neurons in humans. The social cognition has been hampered frontal cortex (supplementary motor perhaps surprising finding of mirror- by the lack of direct evidence that area and anterior cingulate cortex) like neurons in the medial temporal such neurons exist in humans. Fried and the medial temporal cortex lobe led the authors to suggest that and colleagues have now recorded (entorhinal cortex, hippocampus, activity in these cells might represent single-cell activity from neurons in parahippocampal gyrus and amyg- the reactivation of a memory trace several brain areas in humans and dala). In the hippocampus, the para- for the observed or executed action. report that some of these neurons hippocampal gyrus, the entorhinal They also speculated that the neu- show mirror-like activity. cortex and the supplementary motor rons showing opposite responses to The authors recorded neuronal area, a higher percentage of the action observation and execution activity in patients with implanted recorded neurons than expected by might have a role in suppressing the electrodes while the patients chance changed their activity when execution of observed actions to observed or executed grasping hand the participant observed a particular ensure that we do not imitate every action and when he or she executed action we see. that action. Arguably, neurons that decrease Of the 68 ‘matching cells’ their firing rate during action obser- detected, 33 showed increased firing vation cannot be considered ‘classical’ during both the observation and mirror neurons, and these findings execution of a particular action will no doubt fuel the debate about and 21 cells showed decreased firing the definition and functional impor- in both conditions. Interestingly, in tance of mirror neurons. the remaining 14 neurons, the firing Leonie Welberg rate increased in one condition but decreased in the other. ORIGINAL RESEARCH PAPER Mukamel, R. et al. In monkeys, mirror neurons have Single-neuron responses in humans during execution and observation of actions. Curr. Biol. been recorded in the lateral aspects of 20, 750–756 (2010) the frontal and parietal cortex. As the FURtHER REAdING Rizzolatti, G. & Sinigaglia, C. electrodes in the present study were The functional role of the parieto-frontal mirror circuit: interpretations and misinterpretations. not placed in the regions homologous Nature Rev. Neurosci. 11, 264–274 (2010) PHOTODISC to these areas, this study could not