“…Another issue left unaddressed in the present study is the potential functional difference in distinct VTA-DA subpopulations. There is increased appreciation that VTA-DA neurons have heterogeneous and non-canonical signals during certain tasks (Bromberg-Martin et al, 2010;Cai et al, 2020;Coddington and Dudman, 2018;Engelhard et al, 2019;Howe and Dombeck, 2016;Howe et al, 2013;Lee et al, 2019;Lerner et al, 2015;Menegas et al, 2018;Parker et al, 2016;da Silva et al, 2018). For example, there might be a population of neurons with elevated activity during the delay period, and it is specifically those neurons that are contributing causally to short-term memory performance, but not the population as a whole.…”