Midbrain dopamine neurons control judgment of time
Time is a subjective experience Time, like space, is one of the fundamental dimensions of all our experiences. However, organisms do not work like clocks, and our judgment about the passage of time is variable, depending on circumstances. Soares et al. systematically investigated midbrain dopaminergic neurons during timing behavior in mice (see the Perspective by Simen and Matell) When measuring and manipulating mouse activity, the authors observed that dopaminergic neurons controlled temporal judgments on a time scale of seconds. Science, this issue p. 1273; see also p. 1231 Mouse studies suggest that higher dopaminergic brain activity is associated with a subjective slowing down of time. Our sense of time is far from constant. For instance, time flies when we are having fun, and it slows to a trickle when we are bored. Midbrain dopamine neurons have been implicated in variable time estimation. However, a direct link between signals carried by dopamine neurons and temporal judgments is lacking. We measured and manipulated the activity of dopamine neurons as mice judged the duration of time intervals. We found that pharmacogenetic suppression of dopamine neurons decreased behavioral sensitivity to time and that dopamine neurons encoded information about trial to trial variability in time estimates. Last, we found that transient activation or inhibition of dopamine neurons was sufficient to slow down or speed up time estimation, respectively. Dopamine neuron activity thus reflects and can directly control the judgment of time.
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