A role for anterior thalamic nuclei in contextual fear memory.

Understanding the neural processes that govern the attribution of a predictive value to environmental stimuli is a major issue in behavioural neuroscience. The main strategy to explore this question has been the use of Pavlovian fear conditioning paradigms. While a majority of studies have focussed on the specific role of the hippocampus and amygdala in contextual versus cued fear, very few studies examined the potential role of subcortical limbic areas. Among those, the anterior thalamic nuclei (ATN) connect to both the hippocampus and the amygdala and also to the cingulate region which is known to support fear-related activity. Here, we show that rats sustaining ATN lesions exhibit a specific impairment following context but not tone conditioning. ATN lesions slowed down acquisition without preventing normal freezing behaviour when rats were reexposed to the conditioning context 24 h later. However, ATN rats exhibited poor retrieval of contextual but not cued fear when assessed 3 weeks after conditioning. In addition, extinction was faster in ATN rats and spontaneous recovery of contextual fear was impaired by the lesions. These deficits indicate that contextual fear memories established in the absence of the ATN are not robust. Collectively, these findings support an involvement of the ATN in the circuits underlying contextual fear memory.