Time estimation is a fundamental cognitive skill, linked to our ability to perceive regularity, involving processes like attention and memory. A leading hypothesis suggests it is a form of immediate memory, where time itself is the stimulus. To investigate this, we created a unique paradigm using hungry Drosophila that perform a Proboscis Extension Response (PER) to receive a timed, uncued sugar water reward. This approach allows us to study a-purely temporal behavior. Our research tests two main hypotheses. The behavioral one suggests that flies trained with fixed intervals will learn to anticipate the reward, while those trained with variable intervals will not. The mechanistic hypothesis predicts that fixed and variable intervals training protocols will trigger distinct neuronal activity patterns in the flies' mushroom bodies (MBs). Our experimental plan is twofold. First, we will compare the behavioral performance of flies trained on fixed vs. variable schedules to measure their ability to anticipate the reward. Second, we will use transgenic flies expressing CRTC::GFP to visualize and analyze the neuronal activity in their mushroom bodies after training. Ultimately, this work will provide a direct correlation between the flies' anticipatory behavior and the underlying neural activity, thus implicating the mushroom bodies in the processing of interval estimation.