GRIFFITH LAB @ BRANDEIS
LEARNING AND MEMORY
Using experience to guide behavior is adaptive, and basic learning rules and mechanisms are conserved across phylla. Drosophila exhibit robust long-term and short-term memory after training, making this genetically malleable organism ideal for understanding the cellular and molecular processes that allow learning.
Our lab uses genetics, imaging, electrophysiology to investigate how animals make, store and use memory. Areas of focus are explored below.
Sleep and memory formation
Previous work in the lab (Haynes et al., 2015) demonstrated that DPM neurons, which mediate memory consolidation, are sleep promoting. The role of sleep in memory is, however, complicated. We have found that the structure of sleep, not just the total amount, is critical for learning (Liu et al., 2019). More recently, in a collaboration with the Sehgal lab (Chouhan et al., 2020) it was determined that the requirement for sleep is modulated by food availability.
An in vitro model for associative learning
We have developed a paired stimulation paradigm in the dissected brain that can generate potentiation of calcium responses to antennal lobe stimulation in the mushroom body. Unlike previous paradigms, this model has a strict pairing requirement and is input-specific. We are interested in understanding the dynamics of information flow in the mushroom body and in the cellular mechanisms of plasticity.
Memory formation and the circadian clock
Cognitive function has been known to be subject to circadian regulation for many years. Little, however was known about the roles specific clock outputs. We have recently shown (Flyer-Adams et al., 2020) that both PDF, a clock-specific peptide, and its receptor, PDFR, are critical for memory formation and act to allow effective memory formation to occur at all times of day.
We have developed an appetitively-reinforced operant learning paradigm in which flies learn to turn left or right in a Y maze for a food reward. In this self-paced assay, rest during training is required for learning. Flies rewarded independently of their behavior do not form a learned association but have the same amount of rest as trained flies, showing that rest is not a consequence of learning. We also find that optogenetically-induced rest does not promote learning, indicating that rest is not sufficient for learning the operant task. This new operant task will provide a novel platform for understanding the relationship between sleep and learning.