Comment on G. Mazzoni et al. ‘Taking the middle stance in the debate on the nature of traumatic memories’

Mazzoni et al. (2023) adhere—as already the title of their paper indicates – to a ‘middle stance in the debate on the nature of traumatic memories’—neither fish nor fowl. In general, they stress the role of traumatic memories and also use the terms ‘amnesia’ and ‘dissociation’, but never mention ‘dissociative amnesia’. At one occasion, they write, however, that ‘these memories [= traumatic memories] are characterised by … psychogenic amnesia’. Insofar, they seem to limit their view to the processing of traumatic memories as such. Initially, they introduce the trauma definition of the DSM-5 (APA, 2013), but later in their text, they broaden the term widely (see also Pettus, 2023). With respect to the stress hormone thesis of the authors, this not only follows an inverted U-shape during memory consolidation, as the authors state but also can be interpreted differently, as we have done in several publications. Stress hormone receptors are highest in the amygdala and hippocampal region, where they can suppress a synchronised emotion–memory-related action of these regions during memory retrieval. Consequently, a stress hormone-related suppressed action of these regions in the right temporo-frontal hemisphere can result in a suppression or blockade of episodic-autobiographical memory retrieval (Brand et al., 2009; Staniloiu et al., 2011; Staniloiu & Markowitsch, 2010). In our eyes, it is especially important to divide memory into episodic-autobiographical and semantic (or fact-like) memory (e.g. Markowitsch et al., 2023; Staniloiu et al., 2018; Staniloiu et al., 2020a; Staniloiu et al., 2020b; Staniloiu & Markowitsch, 2020), and not to speak of declarative memory, as Mazzoni et al. do. This, because usually only the episodic-autobiographical memory system is (retrogradely) impaired, while the semantic memory system still works normally (e.g. see figure 2 in Staniloiu & Markowitsch, 2014, or figure 1 in Markowitsch et al., 2023, or in Markowitsch & Staniloiu, 2022). Moreover, the episodic-autobiographical memory system is dependent on a well-functioning, integrated amygdalar-hippocampal system (in the right hemisphere), which is hypometabolic in patients with dissociative amnesia (see figure 5 in Staniloiu & Markowitsch, 2014; Brand et al., 2009). Consequently, in severe forms of functional memory impairments with a stress- or trauma-related background, the whole personal past is unavailable to conscious recall (‘mnestic block syndrome’; cf. Markowitsch, 2002). This blockade of autobiographical events can be interpreted as a generalisation from single traumatic events to emotion-coupled memories in general and therefore indicates, that at least in dissociative amnesias, there is a quite general amnesic condition prevalent. Of interest is the authors' idea of an epigenetic background of traumatic memories—an idea on which one of us wrote several years ago (Markowitsch, 2015). Though up to now data are very sparse, it indeed might be that there are personalities with special features such as a reduced tolerance to stress, poorly developed coping strategies etc. (cf. figure 5 of Markowitsch & Staniloiu, 2022), which can be traced back to similar vulnerabilities of their ancestors (Almli et al., 2015; Bersani et al., 2016; Blaze et al., 2015; Daskalakis & Yehuda, 2014; Dolinoy et al., 2007; Kubota et al., 2012; Lutz & Turecki, 2014; McGowan, 2013; Oberlander et al., 2008; Yehuda et al., 1996). Here, it is of special relevance to notice that the environment has a much stronger impact on personality development in the early years of life, compared with later on (Davis et al., 2009; Murgatroyd & Spengler, 2011).