11 research outputs found
Fast Micron-Scale 3D Printing with a Resonant-Scanning Two-Photon Microscope
3D printing allows rapid fabrication of complex objects from digital designs.
One 3D-printing process, direct laser writing, polymerises a light-sensitive
material by steering a focused laser beam through the shape of the object to be
created. The highest-resolution direct laser writing systems use a femtosecond
laser to effect two-photon polymerisation. The focal (polymerisation) point is
steered over the shape of the desired object with mechanised stages or
galvanometer-controlled mirrors. Here we report a new high-resolution direct
laser writing system that employs a resonant mirror scanner to achieve a
significant increase in printing speed over galvanometer- or piezo-based
methods while maintaining resolution on the order of a micron. This printer is
based on a software modification to a commerically available resonant-scanning
two-photon microscope. We demonstrate the complete process chain from hardware
configuration and control software to the printing of objects of approximately
m, and validate performance with objective
benchmarks. Released under an open-source license, this work makes micro-scale
3D printing available the large community of two-photon microscope users, and
paves the way toward widespread availability of precision-printed devices.Comment: Corresponding author: BWP ([email protected]). TJG and TMO contributed
equally to this work. TJG is an employee of Neuralink In
Printable microscale interfaces for long-term peripheral nerve mapping and precision control
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 advanced 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-resolution recordings of behaviorally-linked nerve activity over multi-week timescales. In addition, we show that multi-channel, current-steering-based stimulation can achieve a high degree of functionally-relevant modulatory specificity within the small scale of the device. These results highlight the potential of new microscale design and fabrication techniques for the realization of viable implantable devices for long-term peripheral interfacing.https://www.biorxiv.org/node/801468.fullFirst author draf
The Basal Ganglia Is Necessary for Learning Spectral, but Not Temporal, Features of Birdsong
SummaryExecuting a motor skill requires the brain to control which muscles to activate at what times. How these aspects of control—motor implementation and timing—are acquired, and whether the learning processes underlying them differ, is not well understood. To address this, we used a reinforcement learning paradigm to independently manipulate both spectral and temporal features of birdsong, a complex learned motor sequence, while recording and perturbing activity in underlying circuits. Our results uncovered a striking dissociation in how neural circuits underlie learning in the two domains. The basal ganglia was required for modifying spectral, but not temporal, structure. This functional dissociation extended to the descending motor pathway, where recordings from a premotor cortex analog nucleus reflected changes to temporal, but not spectral, structure. Our results reveal a strategy in which the nervous system employs different and largely independent circuits to learn distinct aspects of a motor skill
Templated self-assembly of gold nanoparticles in smectic liquid crystals confined at 3D printed curved surfaces
The fabrication of assembled structures of topological defects in liquid
crystals (LCs) has attracted much attention during the last decade, stemming
from the potential application of these defects in modern technologies. A range
of techniques can be employed to create large areas of engineered defects in
LCs, including mechanical shearing, chemical surface treatment, external
fields, or geometric confinement. The technology of 3D printing has recently
emerged as a powerful method to fabricate novel patterning topographies
inaccessible by other microfabrication techniques, especially confining
geometries with curved topographies. In this work, we show the advantages of
using 3D-printed curved surfaces and controlled anchoring properties to confine
LCs and engineer new structures of topological defects, whose structure we
elucidate by comparison with a novel application of Landau-de Gennes free
energy minimization to the smectic A-nematic phase transition. We also
demonstrate the ability of these defects to act as a scaffold for assembling
gold (Au) nanoparticles (NPs) into reconfigurable 3D structures. We discuss the
characteristics of this templated self-assembly (TSA) approach and explain the
relationship between NP concentrations and defect structures with insights
gained from numerical modeling. This work paves the way for a versatile
platform of LC defect-templated assembly of a range of functional nanomaterials
useful in the field of energy technology.Comment: Main text: 30 pages, 6 figures. Supplementary Information: 5 pages, 4
figure
Unstable neurons underlie a stable learned behavior
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. The most dramatic shifts occur over intervals of sleep. In contrast to the transient participation of excitatory neurons, ensemble measurements dominated by inhibition persist unchanged even after damage to downstream motor nerves. These observations offer a principle of motor stability: spatiotemporal patterns of inhibition can maintain a stable scaffold for motor dynamics while the population of principal neurons that directly drive behavior shift from one day to the next
Changes in the neural control of a complex motor sequence during learning
The acquisition of complex motor sequences often proceeds through trial-and-error learning, requiring the deliberate exploration of motor actions and the concomitant evaluation of the resulting performance. Songbirds learn their song in this manner, producing highly variable vocalizations as juveniles. As the song improves, vocal variability is gradually reduced until it is all but eliminated in adult birds. In the present study we examine how the motor program underlying such a complex motor behavior evolves during learning by recording from the robust nucleus of the arcopallium (RA), a motor cortex analog brain region. In young birds, neurons in RA exhibited highly variable firing patterns that throughout development became more precise, sparse, and bursty. We further explored how the developing motor program in RA is shaped by its two main inputs: LMAN, the output nucleus of a basal ganglia-forebrain circuit, and HVC, a premotor nucleus. Pharmacological inactivation of LMAN during singing made the song-aligned firing patterns of RA neurons adultlike in their stereotypy without dramatically affecting the spike statistics or the overall firing patterns. Removing the input from HVC, on the other hand, resulted in a complete loss of stereotypy of both the song and the underlying motor program. Thus our results show that a basal ganglia-forebrain circuit drives motor exploration required for trial-and-error learning by adding variability to the developing motor program. As learning proceeds and the motor circuits mature, the relative contribution of LMAN is reduced, allowing the premotor input from HVC to drive an increasingly stereotyped song
Printable microscale interfaces for long-term peripheral nerve mapping and precision control
Modulation of peripheral nervous system signalling has many applications in medicine, neurobiology and machine-man interfaces. Here the authors develop a microscale implantable device for chronic interfacing with a small diameter nerve, and show multi-week in vivo recording and control of activity