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7 Entopeduncular Nucleus (EP)

The entopeduncular nucleus’, also called the GPi in primates, actions are strongly regulated by expected reward outcomes and it is an important output centre of the basal ganglia (Rajakumar et al., 1993).

7.1 Efferents

Different parts of the EP appear to perform different tasks.

The caudal part of the EP has efferents to the (vm-)thalamus and brainstem nuclei and therefore controls motor activity (Rajakumar et al., 1993) (Wallace et al., 2017).
The rostral part of the EP has strong projections to the lateral subnuclei of the LHb (including the oval nucleus)LHb (Hong and Hikosaka, 2008; Rajakumar et al., 1993) which are glutamatergic and excitatory (Shabel et al., 2012; Wallace et al., 2017). The LHb then projects primarily to the rostral medial tegmental area (rMTg) which is a GABAergic nucleus that innervates the VTA.

7.2 Function

The reward prediction error is considered to be instigated from the LHb and Barrot et al, 2012 theorised that the EP could play a major role in this activity as it has such an important input to the LHb (Barrot et al., 2012) and in turn to the VTA as mentioned above. This relates to the rostral part of the EP.