LETTER TO THE EDITOR Reply: Morality: incomplete without the cerebellum?

Sir, We thank Demirtas-Tatlidede and Schmahmann (2013) for their interest in our paper and for their comments that witness the growing attention to the neurology of moral behaviour. Although, as they suggest, we could have discussed the potential cerebellar role in morality, our review aimed to outline only the major research findings and we deliberately included proved experimental and clinical data (Fumagalli and Priori, 2012). For this reason we were unable to mention the studies referenced by Demirtas-Tatlidede and Schmahmann (2013). Equally important, none of these studies or the previous reviews in this field (Cooper et al., 1976; Heath, 1977; Moll et al., 2005; Raine and Yang, 2006; Young and Koenigs, 2007; Eslinger et al., 2009; Funk and Gazzaniga, 2009; Harada et al., 2009; Huebner et al., 2009; Moll and Schulkin, 2009; Demirtas-Tatlidede et al., 2010; Harenski et al., 2010; Shenhav and Greene, 2010) specifically discuss the cerebellum as a major brain structure for moral behaviour. Also, to explain the cerebellar role in morality and violence DemirtasTatlidede and Schmahmann (2013) proposed the ‘dysmetria of thought theory’. Although interesting, the scarce data available imposes caution in concluding that the cerebellum acts as a specific and determinant ‘moral regulator’. For several years our research group has been conducting research work on the human cerebellum’s cognitive/affective role (Ferrucci et al., 2008, 2012, 2013) and we are well aware of non-motor cerebellar functions. We conjecture that the cerebellum might indirectly and non-specifically influence moral behaviour, by exerting control on high-order cognitive and affective processes. This influence could travel through cerebellar connections directed to cortical and subcortical structures found to be involved in morality and in other high-order cognitive and behavioural processes for which the cerebellum now appears to be a general regulator. For instance, our finding that cerebellar stimulation influences the recognition of negative emotions such as anger (Ferrucci et al., 2012) could provide another clue to the multifaceted puzzle involving the physiology of aggressive behaviour and, ultimately, of moral behaviour. Finally, in the last paragraph in their letter, referring to the ‘ethics of stimulation’, Demirtas-Tatlidede and Schmahmann (2013) underline the ethical caveats that apply especially to the possible future use of brain stimulation techniques for shaping morality. We fully agree that even though immoral behaviours violate ethical rules we must guard against proposing treatment that could violate them until we have developed impeccable guidelines; we concluded our review by stating