Unstable neurons underlie a stable learned behavior

William A Liberti III*, Jeffrey E Markowitz*, L Nathan Perkins, Derek C Liberti, Daniel P Leman, Grigori Guitchounts, Tarciso Velho, Darrell N Kotton, Carlos Lois, Timothy J Gardner

Nature Neuroscience. 2016. Download PDF

Motor skills can be maintained for decades, but the biological basis of this memory persistence remains largely unknown. The zebra finch, for example, sings a highly stereotyped song that is stable for years, but it is not known whether the precise neural patterns underlying song are stable or shift from day to day. Here we demonstrate that the population of projection neurons coding for song in the premotor nucleus, HVC, change from day to day.


Mesoscopic patterns of neural activity support songbird cortical sequences

Jeffrey E Markowitz*, William A Liberti III*, Grigori Guitchounts, Tarciso Velho, Carlos Lois, Timothy J Gardner

PLoS Biology. 2015. Download PDF.

Time-locked sequences of neural activity can be found throughout the vertebrate forebrain in various species and behavioral contexts. From “time cells” in the hippocampus of rodents to cortical activity controlling movement, temporal sequence generation is integral to many forms of learned behavior. However, the mechanisms underlying sequence generation are not well known. Here, we describe a spatial and temporal organization of the songbird premotor cortical microcircuit that supports sparse sequences of neural activity.



A carbon-fiber electrode array for long-term neural recording

Grigori Guitchounts*, Jeffrey E Markowitz*, William A Liberti*, Timothy J Gardner

Journal of Neural Engineering. 2013. Download PDF.

Chronic neural recording in behaving animals is an essential method for studies of neural circuit function. However, stable recordings from small, densely packed neurons remains challenging, particularly over time-scales relevant for learning. We describe an assembly method for a 16 channel electrode array consisting of carbon fibers (<5 μm diameter) individually insulated with Parylene-C and fire-sharpened. The diameter of the array is approximately 26 microns, along the full extent of the implant. Carbon fiber arrays were tested in HVC (used as a proper name), a song motor nucleus, of singing zebra finches where individual neurons discharge with temporally precise patterns. Previous reports of activity in this population of neurons has required the use of high impedance electrodes on movable microdrives. Here, the carbon fiber electrodes provided stable multi-unit recordings over time-scales of months.



Grigori Guitchounts, Deirdre S Stewart, Stuart A Forman

Anesthesiology. 2012. Download PDF.

Etomidate is a potent hypnotic agent that acts via γ-aminobutyric acid type A (GABAA) receptors. Evidence supports the presence of two etomidate sites per GABAA receptor, and current models assume that each site contributes equally and non-cooperatively to drug effects. These assumptions remain untested. We used concatenated dimer (β2-α1) and trimer (γ2-β2-α1) GABAA subunit assemblies that form functional α1β2γ2 channels, and inserted α1M236W etomidate site mutations into both dimers (β2-α1M236W) and trimers (γ2-β2-α1M236W)...