The role of mediodorsal thalamus in temporal differentiation of reward-guided actions

Abstract

The mediodorsal thalamus (MD) is a crucial component of the neural network involved in the learning and generation of goal-directed actions. A series of experiments reported here examined the contributions of MD to the temporal differentiation of reward-guided actions. In Experiment 1, we trained rats on a discrete-trial, fixed-criterion temporal differentiation task, in which only lever presses exceeding a threshold duration value were rewarded. Pre-training MD lesions impaired temporal differentiation of action duration, by increasing the dispersion of the duration distribution. Post-training MD lesions also impaired differentiation, but by reducing the average emitted press durations, thus shifting the distribution without increasing the dispersion. In Experiment 2, we trained rats to space their lever pressing above criterion inter-press-intervals in order to earn rewards. Both pre-training and post-training MD lesions impaired the differentiation of inter-press-intervals. These results show that MD plays an important role in the acquisition and expression of action differentiation.

Mechanisms of Action Selection and Timing in Substantia Nigra Neurons

“…A two-way ANOVA revealed no interaction between criterion duration and session (F (2, 8) ϭ 1.97, p Ͼ 0.05), a main effect of duration (F (1,8) , p Ͻ 0.001), and a main effect of session (F (1,8) , p Ͻ 0.001). As shown in Figure 1 D, in accord with previous work (Platt et al, 1973;Yin, 2009;Yu et al, 2010), the median duration approached the criterion duration with training. As the duration requirement increased, the mice also failed more often, producing more prematurely released lever presses (percentage of correct trials: Ͼ400 ms, 52 Ϯ 4%; Ͼ800 ms, 39 Ϯ 4%; Ͼ1600 ms, 28 Ϯ 3%).…”

“…Animals can modify action timing through experience with feedback (Platt et al, 1973;Yin, 2009;Yu et al, 2010), but the neural mechanisms underlying such learning remain poorly understood (Mita et al, 2009).…”

Action, time and the basal ganglia

“…On each trial, to earn a piece of food reward, the mouse must produce an action of a minimum duration [32,33]. The lever is transiently retracted after release, and a reward is delivered if the press duration exceeded the criterion duration.…”

“…Muscle tension is sensed by the Golgi tendon organs, which send Ib afferents representing the negative feedback for the force control system. In this connection, it is worth noting that increased stiffness in skeletal muscles is also observed in Parkinson's patients, as a result [33,35]. Mice must press a lever and hold it down for a minimum amount of time in order to earn a food pellet.…”

Cortico-Basal Ganglia Networks and the Neural Substrates of Actions

“…The limbic and associative networks overlap, especially in regions such as the medial prefrontal cortex, nucleus accumbens core, and mediodorsal thalamus (Haber, 2003;Joel & Weiner, 1994;Yin et al, 2008;Yu, Fan, Lopez, & Yin, 2012;Yu, Gupta, & Yin, 2010).…”