Timothy C. Marzullo

Open Labware: 3-D Printing Your Own Lab Equipment

The introduction of affordable, consumer-oriented 3-D printers is a milestone in the current “maker movement,” which has been heralded as the next industrial revolution. Combined with free and open sharing of detailed design blueprints and accessible development tools, rapid prototypes of complex products can now be assembled in one’s own garage—a game-changer reminiscent of the early days of personal computing. At the same time, 3-D printing has also allowed the scientific and engineering community to build the “little things” that help a lab get up and running much faster and easier than ever before.

Reduction of neurovascular damage resulting from microelectrode insertion into the cerebral cortex using in vivo two-photon mapping

Penetrating neural probe technologies allow investigators to record electrical signals in the brain. The implantation of probes causes acute tissue damage, partially due to vasculature disruption during probe implantation. This trauma can cause abnormal electrophysiological responses and temporary increases in neurotransmitter levels, and perpetuate chronic immune responses. A significant challenge for investigators is to examine neurovascular features below the surface of the brain in vivo. The objective of this study was to investigate localized bleeding resulting from inserting microscale neural probes into the cortex using two-photon microscopy (TPM) and to explore an approach to minimize blood vessel disruption through insertion methods and probe design. 3D TPM images of cortical neurovasculature were obtained from mice and used to select preferred insertion positions for probe insertion to reduce neurovasculature damage. There was an 82.8 +/- 14.3% reduction in neurovascular damage for probes inserted in regions devoid of major (>5 microm) sub-surface vessels. Also, the deviation of surface vessels from the vector normal to the surface as a function of depth and vessel diameter was measured and characterized. 68% of the major vessels were found to deviate less than 49 microm from their surface origin up to a depth of 500 microm. Inserting probes more than 49 microm from major surface vessels can reduce the chances of severing major sub-surface neurovasculature without using TPM.

The SpikerBox: a low cost, open-source bioamplifier for increasing public participation in neuroscience inquiry.

Although people are generally interested in how the brain functions, neuroscience education for the public is hampered by a lack of low cost and engaging teaching materials. To address this, we developed an open-source tool, the SpikerBox, which is appropriate for use in middle/high school educational programs and by amateurs. This device can be used in easy experiments in which students insert sewing pins into the leg of a cockroach, or other invertebrate, to amplify and listen to the electrical activity of neurons. With the cockroach leg preparation, students can hear and see (using a smartphone oscilloscope app we have developed) the dramatic changes in activity caused by touching the mechanosensitive barbs. Students can also experiment with other manipulations such as temperature, drugs, and microstimulation that affect the neural activity. We include teaching guides and other resources in the supplemental materials. These hands-on lessons with the SpikerBox have proven to be effective in teaching basic neuroscience.

Development of Closed-Loop Neural Interface Technology in a Rat Model: Combining Motor Cortex Operant Conditioning With Visual Cortex Microstimulation

Closed-loop neural interface technology that combines neural ensemble decoding with simultaneous electrical microstimulation feedback is hypothesized to improve deep brain stimulation techniques, neuromotor prosthetic applications, and epilepsy treatment. Here we describe our iterative results in a rat model of a sensory and motor neurophysiological feedback control system. Three rats were chronically implanted with microelectrode arrays in both the motor and visual cortices. The rats were subsequently trained over a period of weeks to modulate their motor cortex ensemble unit activity upon delivery of intra-cortical microstimulation (ICMS) of the visual cortex in order to receive a food reward. Rats were given continuous feedback via visual cortex ICMS during the response periods that was representative of the motor cortex ensemble dynamics. Analysis revealed that the feedback provided the animals with indicators of the behavioral trials. At the hardware level, this preparation provides a tractable test model for improving the technology of closed-loop neural devices.

Cooling enhances in vitro survival and fusion-repair of severed axons taken from the peripheral and central nervous systems of rats

Severed segments of rat peripheral (PNS; sciatic) and central nervous system (CNS; spinal) axons continue to conduct action potentials when maintained in vitro at 6-9 degrees C for up to 7 (sciatic axons) and 2 days (spinal axons), compared with only 36 h at 37-38 degrees C for sciatic axons and 6 h for spinal axons. These PNS and CNS axonal segments can be crushed and then treated with polyethylene glycol (PEG), resulting in a rapid reconnection (fusion) of the surviving axons at the crush site, as assessed by conduction of action potentials through the crush site within minutes after PEG administration. Severed PNS or CNS axons maintained in vitro at 6-9 degrees C prior to crushing can be successfully PEG-fused for up to 4 and 1.5 days, respectively, compared with only 24 (sciatic) and 3 h (spinal) at 37-38 degrees C. These data demonstrate that cooling significantly increases both the survival time of severed mammalian PNS and CNS axons and the time that severed axons can still be PEG-fused (rejoined) to rapidly re-establish axonal continuity in vitro.

Suitability of the Cingulate Cortex for Neural Control

Recent neuroprosthetic work has focused on the motor cortex as a source of voluntary control signals. However, the motor cortex can be damaged in upper motor neuron degenerative diseases such as primary lateral sclerosis and amyotrophic lateral sclerosis. The possibility exists that prefrontal areas may also be used in neuroprosthetic devices. Here, we report the use of the cingulate cortex in a neuroprosthetic model. Seven rats were able to significantly modulate spiking activity in the cingulate cortex in order to receive reward. Furthermore, experiments with single neurons provide evidence that the cingulate cortex neuronal modulation is highly flexible and thus useful for a neuroprosthetic device

In-vivo Evaluation of Chronically Implanted Neural Microelectrode Arrays Modified with Poly (3,4-ethylenedioxythiophene) Nanotubes

The interface between neural prostheses and neural tissue plays a significant role in the long term performance of these devices. Conducting polymers have been used to modify the electrical properties of neural microelectrodes. The objective of this study was to evaluate recording chronic neural activity of neural microelectrodes that were modified with nanofibers-templated of poly (3,4-ethylenedioxythiophene) (PEDOT) nanotubes over seven week periods using impedance spectroscopy and signal-to-noise ratio measurements. PEDOT nanotubes-coated sites were found to have lower impedance and higher signal-to-noise ratio than control site.

Correction: Open Labware: 3-D Printing Your Own Lab Equipment

[This corrects the article DOI: 10.1371/journal.pbio.1002086.].

Use of a Bayesian maximum-likelihood classifier to generate training data for brain-machine interfaces.

Brain-machine interface decoding algorithms need to be predicated on assumptions that are easily met outside of an experimental setting to enable a practical clinical device. Given present technological limitations, there is a need for decoding algorithms which (a) are not dependent upon a large number of neurons for control, (b) are adaptable to alternative sources of neuronal input such as local field potentials (LFPs), and (c) require only marginal training data for daily calibrations. Moreover, practical algorithms must recognize when the user is not intending to generate a control output and eliminate poor training data. In this paper, we introduce and evaluate a Bayesian maximum-likelihood estimation strategy to address the issues of isolating quality training data and self-paced control. Six animal subjects demonstrate that a multiple state classification task, loosely based on the standard center-out task, can be accomplished with fewer than five engaged neurons while requiring less than ten trials for algorithm training. In addition, untrained animals quickly obtained accurate device control, utilizing LFPs as well as neurons in cingulate cortex, two non-traditional neural inputs.

Lower layers in the motor cortex are more effective targets for penetrating microelectrodes in cortical prostheses.

Improving cortical prostheses requires the development of recording neural interfaces that are efficient in terms of providing maximal control information with minimal interface complexity. While the typical approaches have targeted neurons in the motor cortex with multiple penetrating shanks, an alternative approach is to determine an efficient distribution of electrode sites within the layers of the cortex with fewer penetrating shanks. The objective of this study was to compare unit activity in the upper and lower layers of the cortex with respect to movement and direction in order to inform the design of penetrating microelectrodes. Four rats were implanted bilaterally with multi-site single-shank silicon microelectrode arrays in the neck/shoulder region of the motor cortex. We simultaneously recorded unit activity across all layers of the motor cortex while the animal was engaged in a movement direction task. Localization of the electrode array within the different layers of the cortex was determined by histology. We denoted units from layers 2 and 3 and units as upper layer units, and units from layers 5 and 6 as lower layer units. Analysis of unit spiking activity demonstrated that both the upper and lower layers encode movement and direction information. Unit responses in either cortical layer of the cortex were not preferentially associated with contralateral or ipsilateral movement. Aggregate analysis (633 neurons) and best session analysis (75 neurons) indicated that units in the lower layers (layers 5, 6) are more likely to encode direction information when compared to units in the upper layers (layers 2, 3) (p< 0.05). These results suggest that electrode sites clustered in the lower layers provide access to more salient control information for cortical neuroprostheses.