Flexibility decline contributes to similarity of past and future thinking in Alzheimer's disease

Abstract

A striking similarity has been suggested between past and future thinking in Alzheimer’s Disease (AD), a similarity attributable to abnormalities in common modular cognitive functions and neuroanatomical substrates. This study extends this literature by identifying specific executive function deficits underlying past and future thinking in AD. Twenty-four participants with a clinical diagnosis of probable (mild) AD and 26 older controls generated past and future events and underwent tests of binding and the executive functions of flexibility, inhibition, and updating. AD patients showed similar autobiographical performances in past and future event generation, and so did control participants. In each group, the similarity of past and future thinking was predicted by flexibility. Furthermore, AD patients with low flexibility showed higher similarity of past and future thinking than those with high flexibility. These findings are interpreted in terms of involvement of the hippocampus and frontal lobes in future thinking. Deficits in these brain regions in AD are likely to compromise the ability to recombine episodic information into novel and flexible configurations as scenarios for the future.

Phenomenological Reliving and Visual Imagery During Autobiographical Recall in Alzheimer’s Disease

“…Reduced autobiographical memory in AD has been the subject of considerable study (Addis & Tippett, 2004; Dalla Barba, 1997; Donix et al, 2010; El Haj et al, 2012a, 2012b, 2013; El Haj, Antoine, & Kapogiannis, 2015b, 2015c; Irish et al, 2011; Leyhe et al, 2009; Moses et al, 2004; Piolino et al, 2003; Rauchs et al, 2007). However, beyond documenting declines in general autobiographical recall and autobiographical specificity, this body of literature has provided a comprehensive rather than piecemeal attempt to investigate phenomenological reliving in individuals with AD.…”

Episodic future thinking: mechanisms and functions

“…For example, studies that have used the AI to compare healthy older adults with young adults consistently show that older adults produce fewer internal/episodic details and more external/semantic details for both remembered past events and imagined future events, suggesting a common role of episodic memory in both event types (for review of early studies, see 16, and for recent and related evidence, see 5, 17–21). Reductions in episodic detail for both past and future events using the AI and related procedures have also been documented in various patient populations, including in recent studies of patients with depression (22), post-traumatic stress disorder (23), amnesic syndrome (24–27; but see 28 for relatively preserved future imagining in amnesics), Alzheimer’s disease (29–30), unilateral temporal lobe epilepsy (31), schizophrenia (32), prefrontal lesions (33), and long-term opiate users (34). …”

Autobiographical memory decline in Alzheimer’s disease, a theoretical and clinical overview

“…In line with this assumption, studies in normal aging have showed lower production of episodic autobiographical memories (e.g., recall of locations, time, perceptions, and thoughts) than semantic autobiographical memories (e.g., general knowledge about one’s self) in healthy older adults (Levine et al, 2002; Piolino et al, 2010, 2006). This overgenerality is exaggerated in AD, since several studies have observed a substantial shift from episodic to semantic autobiographical recall in AD patients (Barnabe et al, 2012; El Haj et al, 2015a,b, 2011; Graham and Hodges, 1997; Greene et al, 1995; Hou et al, 2005; Irish et al, 2011; Ivanoiu et al, 2006; Leyhe et al, 2009; Meeter et al, 2006; Moses et al, 2004; Muller et al, 2013; Seidl et al, 2011). This shift was observed in these studies despite explicit instructions to AD participants to provide detailed descriptions of personal events that occurred at specific times and places, according to the norms for autobiographical memory assessment [see the Autobiographical Memory Test (Williams and Scott, 1988), the Autobiographical Memory Interview, the Autobiographical Interview, the Test Episodique de Mémoire du Passé autobiographique (Piolino et al, 2003)].…”