Mind and behavior in psychology and neuroscience

Mind and Behaviour

Episodic memory, a type of explicit memory, includes memory for specific times, places and events that can be clearly and explicitly described. Impairment to episodic memory is one of the most common presenting clinical symptoms of Alzheimer's in its early stages. How does episodic memory function and what mechanisms are involved and affected by its dysfunction in Alzheimer's disease? Sperling et al. (2010) describe how a default network comprised of the medial temporal lobe and cortical regions are most prominently involved in memory function, in which the posteromedial cortices play a key role in the encoding and retrieval of memories. These regions are particularly susceptible to early amyloid deposition involved in the development of Alzheimer's disease (Sperling et al., 2010). Functional abnormalities in these regions have been detected through magnetic resonance imaging studies of individuals with clinical presentations of Alzheimer's disease, as well as individuals at risk of developing Alzheimer's disease, such as people with a genetic predisposition as well as elderly people that exhibit mild cognitive impairment (Sperling et al., 2010).

Research on memory dysfunction associated with Alzheimer's disease has demonstrated that processes involved in the development of the disease are characterized by negative changes in the posteromedial cortices, and alterations to these memory networks can be detected before clinical symptoms are exhibited (Sperling et al., 2010). It is noted by Sperling et al. (2010) that MRI imaging revealed that the changes to these regions manifest as increases rather decreases in measured activity, which they have interpreted as demonstrated excitotoxicity leading to imminent functional failure of the neuronal networks. Furthermore, these findings may lead in the future to potential effective predictive models and treatments for Alzheimer's disease (Sperling et al., 2010).

Explicit memory is most significantly implicated in the development of Alzheimer's disease, but what about implicit memory? Contrary to explicit memory, implicit memory involves task performance outside of the realm of conscious awareness, which includes memory for how to perform everyday tasks without conscious recollection and thought regarding how to do so. Research has determined that implicit memory may also become dysfunctional in relation to Alzheimer's disease (Fleischman et al., 2005). There are observed patterns in preservation and impairment of implicit memory associated with Alzheimer's disease, which may be related to the degree of neuropathology in the brain regions affected (Fleischman et al., 2005). Implicit memory involves perceptual and conceptual processes, and higher levels of neuropathology associated with the development of Alzheimer's disease have been found to be linked only to conceptual processes in implicit memory (Fleischman et al., 2005).