Memory, Emotion, and Age: The Work of Kinugawa et al. (2013)

Memory is the key to our life. Already in 1870, the famous physiologist Hering (1) stated in a booklet that memory “connects innumerable single phenomena into a whole, and just as the body would be scattered like dust in countless atoms if the attraction of matter did not hold it together so consciousness – without the connecting power of memory – would fall apart in as many fragments as it contains moments” (p. 12; my translation). With this statement, he emphasized that healthy human beings are able to mentally travel in time and that in their presence they can learn from their past to find optimal solutions for their future. It is known that this capacity needs time, brain maturation, and the establishment of an autonomous self (including theory of mind abilities and the ability to show empathy) in order to develop and persist (2). Adults consequently cannot consciously remember events that had occurred prior to the age of 3–4 years (3– 6). On the other hand, in dementia the ability to travel back in time deteriorates and then gets lost totally (7). The deterioration of episodic–autobiographical memory [cf. the Figure in Ref. (8), or Figure 3 in Ref. (9)] is accompanied by a reduction in emotional colorization of retrieved events – the descriptions become more fact-like, are less detailed, and are reproduced without corresponding affect (10) (Figure 1). The reduced emotional FIGURE 1 | Production of semantic and episodic–autobiographical details in patients with mild cognitive impairment (MCI), mild to moderate Alzheimer’s disease (AD mild/moderate), and severe Alzheimer’s disease (AD severe). Data from Seidl et al. (10).