In 2013, a study on mice explored the relationship between motivation and sleep, focusing on the nucleus accumbens (NAc), a brain region involved in motivation, emotion, and pleasure. The NAc contains neurons with adenosine receptors that, when activated, induce sleep and increase slow-wave sleep (SWS). Conversely, inhibiting these neurons reduces SWS. The study introduced motivational stimuli like chocolate, opposite-sex mice, and toys, which led to decreased sleep duration and suppressed NAc neuron activity. This suggests that NAc neurons are influenced by motivational stimuli and regulate sleep-wake cycles. Although it's uncertain if this applies to humans, the findings indicate that emotions can affect sleep behavior in mice. The NAc is linked to the dopamine system, crucial for motivation and reward, with the dorsal striatum enhancing wakefulness and the ventral striatum promoting sleep. Additionally, social contexts impact sleep behavior, as mice exhibit synchronized sleep patterns and neurophysiological features when co-sleeping, highlighting the complex interplay between positive and negative stimuli on sleep. Understanding the NAc and dopamine system's interaction is central to how motivation and emotional valence modulate sleep-wake behavior, necessitating further research in humans and other contexts.