Methods: Combination of intra-cerebral drug microinfusions (to selectively manipulate nucleus accumbens neural activity) with behavioural testing (locomotor activity, PPI, watermaze test of rapid place learning) and electrophysiological techniques in rats
The role of the hippocampus in important types of rapid everyday learning, such as place learning, is well established (Eichenbaum, Stewart, & Morris, 1990; O'Keefe, 1979). However, the mechanisms via which rapidly-acquired place memory from the hippocampus may be translated into behaviour are yet to be determined. The intermediate hippocampus combines neural substrates of accurate place encoding with links to prefrontal and subcortical behavioural control sites. It has been suggested that these sites, including the nucleus accumbens (NAc), are critical for this translation (Bast et al., 2009; Bast, 2011). Recent research from our group suggests that the prefrontal cortex is not required for this process, although prefrontal activity can modulate behaviour based on hippocampus-dependent rapidly-acquired place memory (McGarrity et al, 2015).
Our aim is to determine what brain structure(s) are involved in the translation of rapidly-acquired place information into behaviour. The nucleus accumbens is a candidate due to the presence of strong hippocampo-NAc projections that have been implicated in behaviour based on place memory (Whishaw et al, 1995). To accomplish this, we use a combination of behavioural tests, such as locomotor activity testing and the delayed-matching-to-place (DMTP) watermaze task, and electrophysiological recording techniques. Through combination of these approaches, we aim to determine whether functional inhibition of neural activity in the nucleus accumbens (via microinfusion of the GABA agonist muscimol) specifically impairs performance in the DMTP task, indicating its involvement in the translation of rapidly-acquired place memory into behaviour.