Associate Professor, Knight Campus
Ph.D. Rockefeller University
B.S. Princeton University
Tim Gardner’s research focuses on the development of 3D printing and microfabrication methods for implantable neural interfaces. In the Gardner lab, new tools are applied to study sensory-motor learning in songbirds. Specific interests include the neural basis of motor sequences, motor exploration, and reinforcement learning that shapes motor learning.
For Gardner, the goal of improving neural interfaces involves close collaboration with industry – both in industry sponsored work as well as direct support of startup companies seeking to enhance the therapeutic potential of human brain implants. Most recently, he worked as a founding member of Neuralink, a company building a fully implanted bidirectional interface to the human brain. Gardner holds a bachelor’s degree in physics from Princeton University and earned his doctorate in biology and physics from Rockefeller University. He completed his post-doctoral fellowships at Rockefeller University and the Massachusetts Institute of Technology.
Hidden neural states underlie canary song syntax.
Nature. 2020 06;582(7813):539-544
Authors: Cohen Y, Shen J, Semu D, Leman DP, Liberti WA, Perkins LN, Liberti DC, Kotton DN, Gardner TJ
Coordinated skills such as speech or dance involve sequences of actions that follow syntactic rules in which transitions between elements depend on the identities and order of past actions. Canary songs consist of repeated syllables called phrases, and the ordering of these phrases follows long-range rules1 in which the choice of what to sing depends on the song structure many seconds prior. The neural substrates that support these long-range correlations are unknown. Here, using miniature head-mounted microscopes and cell-type-specific genetic tools, we observed neural activity in the premotor nucleus HVC2-4 as canaries explored various phrase sequences in their repertoire. We identified neurons that encode past transitions, extending over four phrases and spanning up to four seconds and forty syllables. These neurons preferentially encode past actions rather than future actions, can reflect more than one song history, and are active mostly during the rare phrases that involve history-dependent transitions in song. These findings demonstrate that the dynamics of HVC include 'hidden states' that are not reflected in ongoing behaviour but rather carry information about prior actions. These states provide a possible substrate for the control of syntax transitions governed by long-range rules.
PMID: 32555461 [PubMed - indexed for MEDLINE]
Effect of oxidation on intrinsic residual stress in amorphous silicon carbide films.
J Biomed Mater Res B Appl Biomater. 2019 07;107(5):1654-1661
Authors: Deku F, Mohammed S, Joshi-Imre A, Maeng J, Danda V, Gardner TJ, Cogan SF
The change in residual stress in plasma enhanced chemical vapor deposition amorphous silicon carbide (a-SiC:H) films exposed to air and wet ambient environments is investigated. A close relationship between stress change and deposition condition is identified from mechanical and chemical characterization of a-SiC:H films. Evidence of amorphous silicon carbide films reacting with oxygen and water vapor in the ambient environment are presented. The effect of deposition parameters on oxidation and stress variation in a-SiC:H film is studied. It is found that the films deposited at low temperature or power are susceptible to oxidation and undergo a notable increase in compressive stress over time. Furthermore, the films deposited at sufficiently high temperature (≥325 C) and power density (≥0.2 W cm-2 ) do not exhibit pronounced oxidation or temporal stress variation. These results serve as the basis for developing amorphous silicon carbide based dielectric encapsulation for implantable medical devices. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1654-1661, 2019.
PMID: 30321479 [PubMed - indexed for MEDLINE]
Printable microscale interfaces for long-term peripheral nerve mapping and precision control.
Nat Commun. 2020 Aug 21;11(1):4191
Authors: Otchy TM, Michas C, Lee B, Gopalan K, Nerurkar V, Gleick J, Semu D, Darkwa L, Holinski BJ, Chew DJ, White AE, Gardner TJ
The nascent field of bioelectronic medicine seeks to decode and modulate peripheral nervous system signals to obtain therapeutic control of targeted end organs and effectors. Current approaches rely heavily on electrode-based devices, but size scalability, material and microfabrication challenges, limited surgical accessibility, and the biomechanically dynamic implantation environment are significant impediments to developing and deploying peripheral interfacing technologies. Here, we present a microscale implantable device - the nanoclip - for chronic interfacing with fine peripheral nerves in small animal models that begins to meet these constraints. We demonstrate the capability to make stable, high signal-to-noise ratio recordings of behaviorally-linked nerve activity over multi-week timescales. In addition, we show that multi-channel, current-steering-based stimulation within the confines of the small device can achieve multi-dimensional control of a small nerve. These results highlight the potential of new microscale design and fabrication techniques for realizing viable devices for long-term peripheral interfacing.
PMID: 32826892 [PubMed - as supplied by publisher]