Seminars
Psilocybin is a serotonergic psychedelic with growing interest as a psychiatric therapeutic, yet how it reshapes brain activity and perception at the circuit level remains poorly understood. I will present two complementary studies from head-fixed mouse models that combine large-scale electrophysiology with behavior to address this question. The first study characterizes how a single dose of psilocybin alters firing rates, local field potentials, EEG oscillations, and burst dynamics across cortical (prefrontal, sensory), hippocampal, and thalamic regions, comparing psilocybin to saline controls and to a ketanserin pre-treatment group that isolates effects dependent on the 5-HT2A receptor. The second study found that psilocybin collapsed performance in a visual change-detection task to chance level while leaving motor kinematics unperturbed, yet, surprisingly, without impairing visual coding itself. Instead, psilocybin biased visual cortex toward sensory surprise by aberrantly recruiting change-encoding neurons even when no change occurred, an effect linked to a prominent 4-Hz oscillation strongest in somatostatin-expressing (SST) interneurons. Together, these studies link psilocybin's receptor pharmacology to circuit-level dynamics and their behavioral/perceptual consequences.
The basal ganglia are often thought to select discrete actions. This talk presents evidence for a broader role: the basal ganglia help control continuous changes in the body and coordinate the sequence of smaller action elements that make up complex behavior. Recordings from mice show that different parts of the basal ganglia represent variables such as movement velocity, body position, and head orientation. These signals may serve as instructions for brainstem systems that maintain posture and guide movement. In this view, the basal ganglia operate within layered feedback loops, continually adjusting the body’s configuration as behavior unfolds. Experiments also show that separate basal ganglia circuits control different components of an action, including aiming, reaching, and licking. Activating one circuit can initiate or prolong a particular component while suppressing competing components, whereas another circuit can terminate the current component and help restart the sequence. These findings suggest that the basal ganglia function less like a simple “action gate” and more like a dynamic coordinator that organizes continuous movements and their transitions.
