Episodic Memory

Endel Tulving’s Concept of Episodic Memory

Episodic memory refers to the conscious recollection of a personal experience that contains information on whtat has happened and also where and when it happened. Recollection from episodic memory also implies a kind of first-person subjectivity that has been termed autonoetic consciousness.

This initial definition is amenable to operationalization using a pure behaviorist approach to measure learning and memory performance (Dere et al., 2008, 2010) and has stimulated the development of what, where, and when paradigms for testing whether animals have the capacity to form episodic memories (Clayton and Dickinson, 1998; Dere et., 2005a).

In later work, Tulving widened the concept of episodic memory to include prerequisites of a fully developed episodic memory system (Tulving, 2001, 2002).

Additionally, he described phenomenological processes that are specifically associated with the retrieval of episodic Opens in new window but not semantic memories Opens in new window.

Furthermore, Tulving proposed that humans have a sense of subjective time which enables them to distinguish between mental representations Opens in new window of the self in the past, present, and future (Tulving, 2001, 2002).

Recently, the definition of episodic memory has been expanded by Klein (2013) by postulating that the core features of episodic memory in terms of a memory for what happened, where and when are also shared semantic memory Opens in new window and that episodic recollection requires the coordinated function of a number of distinct, but interacting, “enabling” systems.

As enabling systems Klein postulates the para-mnestic constructs “ownership,” “self,” “subjective temporality,” and “agency” that are necessary for episodic or autonoetic recollection in the sense of Tulving (2001, 2002).

It is further assumed that the type of subjective awareness provided by episodic or autonoetic recollection is relational rather than intrinsic in nature. Klein also assumes that the latter would imply that in some patient populations autonoetic recollection can be disturbed while core elements of episodic-like memory remain intact and are indistinguishable from the content of semantic long-term memory (Klein, 2013).

Impairments of Human Episodic Memory

Episodic memory is extremely sensitive to cerebral aging and neurodegenerative diseases.

In Alzheimer’s disease (AD) Opens in new window deficits in episodic memory function are among the first cognitive symptoms observed. Furthermore, impaired episodic memory function is also observed in a variety of other neuropsychiatric diseases including dissociative disorders, schizophrenia, and Parkinson disease.

Episodic memory deficits observed after medial temporal lobe injury (Nyberg et al., 1996) which includes important memory structures such as the hippocampus Opens in new window (Burges et al., 2002) and amygdala Opens in new window (Markowitsch and Staniloiu, 2011), but also after lesions to the frontal cortex (Kirchhoff et al., 2000) and diencephalic structures, such as the mediodorsal thalamus and the mammillary bodies (Tsivilis et al., 2008; Wolf et al., 2008).

Episodic memory impairments have also been demonstrated in the course of healthy aging (Tulving, 1983; Shing et al., 2010), the acute phase following mild traumatic brain injury (Dickerson and Eichenbaum, 2010; Tsirka et al., 2010), and in a variety of neuropsychiatric diseases (Butters et al., 1987; Dere et al., 2010).

Furthermore, it seems that episodic memory deficits usually precede more global cognitive impairments associated with neurodegenerative diseases such as AD or PD (Williams-Gray et al., 2006; Dubois et al., 2007). Therefore, one can view episodic memory functioning as a highly sensitive indicator or seismograph of incipient brain pathology which manifests well before the full dimension of the disease becomes evident at the psychological and behavioral level.