Improving the translation of memory research from animals to humans

In the study, carried out by Dr Kamar Ameen-Ali during her NC3Rs-funded PhD studentship, paradigms typically used to measure memory in rodents and humans have been brought together to improve translation between the two. Promoting better translation means that, in some instances, memory tasks that would have been traditionally performed in animals can take place in humans.

In human tests of episodic memory (i.e. memory of specific events in one’s life), participants are able to express and categorise their memory experience – for example, “I remember seeing that object before” (requires recollection which is episodic), or “I have a feeling that I have seen that object before” (requires familiarity which is non-episodic). With animals, however, it is more difficult to provide definitive evidence of episodic memories because such memories require conscious recollection, which animals are unable to verbally communicate.

To overcome this limitation, ‘episodic-like’ memory studies in rodents rely on the natural exploratory behaviour of these animals. As context is an important part of the recollection process underlying episodic memory, the animals are presented with objects in specific combinations of location and background contexts (consisting of particular visual and tactile features) during the sample phases of a trial. On the subsequent test phase, animals that spend more time exploring the novel configuration of the object, location and context (the what, where, which occasion descriptor used to test episodic-like memory) successfully demonstrate episodic-like memory.

The aim of the published study was to apply the same principles used in the rodent studies to a standard task of memory for humans. Establishing a single methodology that does not rely on personal introspection and that can be applied to both humans and animals means researchers can be confident that such tasks rely on the same mechanisms across species.

The Durham team used a simple computer-based object recognition task and varied the location of the test object and the background context in which it was presented, to mimic the episodic-like memory paradigm used with animals (see photo). The results showed that recollection, but not familiarity, for an object was significantly higher when that object was seen in the same location and background context as when it was first encountered. Therefore, by designing a standard human recognition task to feature information thought to be important in studies of animal episodic memory, Dr Ameen-Ali and colleagues have demonstrated a direct link between the two approaches, and can vary the degree of recollection (episodic memory) occurring in the task merely by manipulating the background information. Being able to assess recollection across species in a single experimental paradigm will allow researchers to better understand the cognitive and biological mechanisms involved in these complex forms of memory.

This study is an example of how behavioural approaches used with animal models of memory can inform human studies and ultimately promote better translation across species.