Personal Identity and Cortical Midline Structure (CMS): Do Temporal Features of CMS Neural Activity Transform Into “Self-Continuity”?

It must be distinguished from the more concrete momentary cognitive contents. It remains unclear what this stability consists in, though: What exactly endures, remains context independent, and is rather abstract? Are these specific cognitive contents, that is, information? This is rather unlikely given that basically all information including psychological and physiological change over time. As has been extensively discussed in philosophy (Northoff, 2016; Northoff & Wagner, 2017), neither physiological nor psychological contents endure and remain stable. Even our own brain continuously changes its cells and activity pattern; the brain is highly plastic rather than stable and enduring. The continuous change of both psychological and physiological contents and their information makes such cognitive view of identity rather unlikely. Berkman et al. are somewhat aware of that when they associate identity with salience, value, and motivation. That shifts the focus from a cognitive concept of identity to a more rewardand affect-based motivational concept of identity. Identity can then be considered a value, a strong subjective value that is associated with positive affect, that is, a positive value, as they say. Being such positive value, identity can then impact our long-term goals as well as relate our self to externally directed processing—the self thus becomes extended (Kim & Johnson, 2012, 2014) or, as I say, relational (Northoff, 2016). What does identity as positive value consist in? Although psychologically the characterization of identity by subjective value rather than cognitive information is a major step forward, we may need to go even one step further. Specifically, we need to search for the underpinnings of the stability and enduring character of subjective values to account for identity and its underlying neuronal mechanisms. That is the aim in my commentary. Temporal Features of CMS Neuronal Activity—Transformation Into “Self-Continuity” My focus is specifically on the temporal component of identity while, for the sake of simplicity, I neglect the specific characterization of that temporal component by subjective value, motivation, and positive affect. Given that the CMS have been shown to be central in the synchronic self, one may also suppose a central role of CMS and their spontaneous activity in mediating diachronic self, that is, self-continuity as core of identity. My main and overarching aim is to demonstrate that neural activity in CM shows specific features (i.e., temporal features) that make it well suitable to mediate our diachronic self with selfcontinuity as core of our personal identity. Based on recent data from brain imaging, I suggest that the temporal features of identity are mediated by corresponding temporal features in the spontaneous activity of CMS. Specifically, I propose that the temporal features of spontaneous neuronal activity in CMS predispose the temporal expansion of the “synchronic self” in time—this results in a “diachronic self” with “self-continuity” as core of our identity. In a nutshell, I postulate that the temporal features of spontaneous CMS neuronal activity transform into corresponding temporal features on the psychological level of self, that is, “self-continuity” as core of our identity. Temporal Features of Neural Activity in CMS Temporal Features of CMS—Strong Power in Infraslow Frequencies Most of the findings on CMS have been obtained in functional magnetic resonance imaging (fMRI). To better understand the physiological and specifically temporal features of CMS, we therefore need to get into the physiological basis of the BOLD signal as measured with fMRI. The BOLD signal as obtained in fMRI is electrophysiologically best correlated with local field potentials (Khader, Schicke, R€oder, & R€osler, 2008; Logothetis, 2008; Logothetis, Pauls, Augath, Trinath, & Oeltermann, 2001; Raichle & Mintun, COMMENTARIES 123