Episodic memories in humans

One of the most challenging goals of neuroscience is to understand how electrical activity in the brain forms memories of events which can be mentally reexperienced (i.e. episodic memories). The ability to form such memories is critically dependent on active neurons in a set of interconnected brain areas in the medial temporal lobe. In humans, lesions to these areas result in episodic memory deficits and the same areas show increased activity during encoding and retrieval of episodic memories.


How can we assess episodic memory functions? A large proportion of studies of memory uses animal models in which neural activity is assessed in parallel to overt behavioral read-outs of memory retrieval. Despite significantly contributing to our understanding of the neural processes underlying memory functions, this approach has inherent limitations. Reexperiencing the past is also a subjective experience hardly accessible to researchers using animal models. In contrast to animals, humans have the unique ability to describe what they are experiencing, thinking, and remembering. For this reason, if we ultimately aim to understand the relationships between neural activity and subjective reexperience of the past, analysis must be moved to humans.

How will we study the relationship between neural activity and memory processes in humans? We will use electrodes placed (for clinical reasons) in the medial temporal lobe of patients with epilepsy to record neural activity during memory formation and recall. Electrodes placed within brain tissue make it possible to measure neural activity on a single neuron level. We aim to relate the measured activity directly to the reported subjective experience of an episodic memory.

Our vision is to progress our understanding on how the human brain acquires, organizes, and retrieves episodic memories. Since the human brain is the most complex biological system we know, this is a crucial step as one of the main goals of neuroscience is to understand how the brain performs higher cognitive functions, and ultimately how these functions are disturbed in cognitive disorders. For several reasons our approach is vital to translate animal findings and insights into an enhanced description of the mechanisms underlying cognitive functions in humans. First, we will test whether the hypotheses that have emerged from animal studies can account for psychological phenomena in humans. Second, we will record neural activity in the area first affected in the progression of Alzheimer’s disease. For this reason the project can potentially contribute to the development of more appropriate animal models for human brain diseases. In the future, such knowledge may increase the likelihood of finding a treatment that can stop or prevent the development of memory disorders.