“…While some findings are similar for both disorders (Haukvik et al, 2014;Mathew et al, 2014), differences are described in the overall extent and in the premorbid manifestation of hippocampal volume reductions (Ellison-Wright and Bullmore, 2010;Fornito et al, 2009;Fusar-Poli et al, 2011;Fusar-Poli et al, 2012), which may relate to different underlying biological mechanisms (Bellivier et al, 2013). At the histological and cellular level, several studies have found hippocampal neurons of compromised morphology and organization, as well as pre-synaptic and dendritic deficits, in schizophrenia (Harrison, 2004) and bipolar disorder (Konradi et al, 2011b). Amongst the neuron populations affected by these changes, GABAergic interneurons, and particularly those of the fast-spiking basket-and chandelier type, have come into the focus in schizophrenia and bipolar disorder research, mainly because of solid evidence for widespread reductions in the concentration of proteins typically expressed by fast-spiking cells such as GAD67, somatostatin, and parvalbumin (Lewis et al, 2005;Woo et al, 1997) in several cortical regions (Hashimoto et al, 2008).…”