Abstract
The striatum is an input structure of the basal ganglia implicated in several time-dependent functions including reinforcement learning, decision making, and interval timing. To determine whether striatal ensembles drive subjects' judgments of duration, we manipulated and recorded from striatal neurons in rats performing a duration categorization psychophysical task. We found that the dynamics of striatal neurons predicted duration judgments, and that simultaneously recorded ensembles could judge duration as well as the animal. Furthermore, striatal neurons were necessary for duration judgments, as muscimol infusions produced a specific impairment in animals' duration sensitivity. Lastly, we show that time as encoded by striatal populations ran faster or slower when rats judged a duration as longer or shorter, respectively. These results demonstrate that the speed with which striatal population state changes supports the fundamental ability of animals to judge the passage of time.
Highlights
Time, like space, is a fundamental dimension of the environment, yet how it is processed in the brain is poorly understood
Consistent with duration information being encoded at the population level, we found that for sessions in which greater numbers of neurons were recorded simultaneously psychometric and neurometric performances were similar and strongly correlated (r2 = 0.76, p
Attempts to understand the neural mechanisms of time estimation have begun to focus on continuously evolving population dynamics as a general mechanism for time encoding across the brain (MacDonald et al, 2011; Mauk and Buonomano, 2004; Buonomano, 2014; Buonomano and Merzenich, 1995; Gershman et al, 2013)
Summary
Like space, is a fundamental dimension of the environment, yet how it is processed in the brain is poorly understood. A number of recent studies have identified dynamics that allow for robust representation of time by populations of neurons in multiple areas including the hippocampus (Pastalkova et al, 2008; MacDonald et al, 2011), prefrontal (Kim et al, 2013; Xu et al, 2014), parietal (Leon and Shadlen, 2003; Janssen and Shadlen, 2005) and motor (Lebedev et al, 2008) cortices, cerebellum (Mauk and Buonomano, 2004), and the striatum (Matell et al, 2003; Jin et al, 2009; Adler, 2012; Mello et al, 2015). Any dynamics that result in a continuously-evolving and non-repeating population state can be used to encode time (Buonomano, 2014), and it is not known whether such temporal representations would inform subjects’ judgments of duration or merely covary with elapsing time. To determine whether striatal ensembles drive subjects’ judgments of duration, we manipulated and recorded from striatal neurons in rats performing a duration categorization psychophysical task
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