Research Techniques

Operant and classical conditioning tasks are a cornerstone of our lab. We use them to assess animals' cognitive abilities and how neural circuit manipulations, drug abuse, or environmental factors such as stress can affect these abilities. The operant tasks we use include probability and delay discounting tasks, reversal learning, go / no-go, and others. These complement our chemogenetic, photometry, and electrophysiological approaches (see below), and are often used concurrently with these other methods.

Drug abuse in humans is typically voluntary. Therefore, to effectively model the neurobiological effects of human drug use, we often allow our animals to consume drugs voluntarily. Drugs can be provided in drinking water, via "jello shots", or in the subject's food, and can even be self-administered in an operant chamber during behavioral testing (rat bar).

Direct electrical stimulation of the reward circuitry, called brain stimulation reward, has been used since the 1950s to study reward processing. Our lab uses this method in 2 ways: to determine how drugs influence reward sensitivity, and as a more precise reinforcer in operant tasks. As a reinforcer, brain stimulation is free of many of the confounds associated with food and drug reward, and is highly motivating.

This approach allows us to record the activity of individual neurons,  groups of neurons, or entire regions while animals are awake and performing various behavioral tasks. We can then relate their behavior with their neural activity, to infer how neurons and brain regions control behavior. Additionally, by combining with other systems-level approaches, we can determine how the computations within a region change as its inputs and outputs are modified.

Using viral methods, we can target the expression of a novel receptor system to specific populations of neurons based on their anatomical projections or molecular identity. We can then activate or deactivate these neurons with their selective pharmaceutical ligand, clozapine-n-oxide. This method give us unprecedented control of specific neural circuits. It is also called "Designer Receptors Exclusively Activated by Designer Drugs", and it pairs well with our electrophysiological  and behavioral studies.

Recently developed viruses that express reactive fluorescent "dyes" have provided us with this new method to observe neural activity in awake and behaving animals. These  "dyes" include indicators of general neural activity (e.g. GCaMP), but also indicators of neurotransmitter-specific activity (e.g. dLight). Virus transfection is combined with fiber optic cable implantation, allowing us to examine patterns of activity in specific neural circuits, while animals perform behavioral tasks. This tool pairs well with our operant and pavlovian training paradigms, but also with drug self-administration, allowing us to relate specific patterns of neural activity with the behaviors they cause.

Fiber tracing allows us to determine the anatomical connectivity patterns within various circuits of the brain. When combined with immuno-histochemical methods, we can determine not only if brain regions are connected, but also if those connections are inhibitory or excitatory, informing us of their function. This information is critical to our understanding of how regions work together to coordinate behavior.

By labeling the location of specific proteins and enzymes in the brain, we can learn about how changes in an animal's experience alter its neuroanatomy. For example, we can determine how drug abuse changes the adolescent brain, or how differences in maternal care can change the brain systems that control social behavior. Additionally, we can learn how neural systems change and grow during normal development and aging. This approach relies on the Center for Advanced Microscopy at Miami.

We use a variety of molecular biology tools to identify the genes that underlie specific behavioral patterns, by studying level of RNA and protein expression. These methods include qPCR, autoradiography, Targeted RNA Expression analysis (T-Rex), and next-generation gene sequencing technologies. These methods rely on the Center for Bioinformatics and Functional Genomics at Miami.