Papers for the month of August 2019

J. W. Reddy, I. Kimukin, Z. Ahmed, Luke T. Stewart, A. L. Barth, E. Towe, M. Chamanzar

"High density, double-sided, flexible optoelectrical neural probes with embedded micro-LEDs"
Frontiers in Neuroscience, 13:000

Mouse over here for a brief summary or click to open article in a new tab.Optical stimulation and imaging of neurons deep in the brain require implantable optical neural probes. External optical access to deeper regions of the brain is limited by scattering and absorption of light as it propagates through tissue. Implantable optoelectronic probes capable of high-resolution light delivery and high-density neural recording are needed for closed-loop manipulation of neural circuits. Micro-light-emitting diodes (μLEDs) have been used for optical stimulation, but predominantly on rigid silicon or sapphire substrates. Flexible polymer neural probes would be preferable for chronic applications since they cause less damage to brain tissue. Flexible μLED neural probes have been recently implemented by flip-chip bonding of commercially available μLED chips onto flexible substrates. Here, we demonstrate a monolithic design for flexible optoelectronic neural interfaces with embedded gallium nitride μLEDs that can be microfabricated at wafer-scale. Parylene C is used as the substrate and insulator due to its biocompatibility, compliance, and optical transparency. We demonstrate one-dimensional and two-dimensional individually-addressable μLED arrays. Our μLEDs have sizes as small as 22 × 22 μm in arrays of up to 32 μLEDs per probe shank. These devices emit blue light at a wavelength of 445 nm, suitable for stimulation of channelrhodopsin-2, with output powers greater than 200 μW at 2 mA. Our flexible optoelectronic probes are double-sided and can illuminate brain tissue from both sides. Recording electrodes are co-fabricated with μLEDs on the front- and backside of the optoelectronic probes for electrophysiology recording of neuronal activity from the volumes of tissue on the front- and backside simultaneously with bi-directional optical stimulation.

Ruff, Douglas

"Simultaneous multi-area recordings suggest that attention improves performance by reshaping stimulus representations"
Nature Neuroscience, 0: 0

Mouse over here for a brief summary or click to open article in a new tab.Ruff and Cohen find that the prominent hypotheses about how attention improves perception do not account for behavioral improvements. Instead, their results suggest that attention reshapes sensory representations so the relevant information guides behavior.

Kraynak, T., Marsland, A., Gianaros, P.

"Retrospectively reported childhood physical abuse, systemic inflammation, and resting corticolimbic connectivity in midlife adults"
Brain, Behavior, and Immunity, 202:191-199

Mouse over here for a brief summary or click to open article in a new tab.Childhood abuse confers risk for psychopathology and pathophysiology in midlife through intermediate pathways that remain unclear. Systemic inflammation was tested in the present study as one pathway that may link physical abuse in childhood to the adult functioning of corticolimbic brain circuits broadly implicated in risk for poor mental and physical health.

Ghuman, H., Hitchens, K.

"A systematic optimization of 19F MR image acquisition to detect macrophage invasion into an ECM hydrogel implanted in the stroke-damaged brain."
NeuroImage, 202:116090

Mouse over here for a brief summary or click to open article in a new tab.19F-MR imaging of perfluorocarbon (PFC)-labeled macrophages can provide a unique insight into their participation and spatio-temporal dynamics of inflammatory events, such as the biodegradation of an extracellular matrix (ECM) hydrogel implanted into a stroke cavity. To determine the most efficient acquisition strategy for 19F-MR imaging, five commonly used sequences were optimized using a design of experiment (DoE) approach and compared based on their signal-to-noise ratio (SNR). The fast imaging with steady-state precession (FISP) sequence produced the most efficient detection of a 19F signal followed by the rapid acquisition with relaxation enhancement (RARE) sequence. The multi-slice multi-echo (MSME), fast low angle shot (FLASH), and zero echo time (ZTE) sequences were significantly less efficient. Imaging parameters (matrix/voxel size; slice thickness, number of averages) determined the accuracy (i.e. trueness and precision) of object identification by reducing partial volume effects, as determined by analysis of the point spread function (PSF). A 96 × 96 matrix size (0.35 mm3) produced the lowest limit of detection (LOD) for RARE (2.85 mM PFPE; 119 mM 19F) and FISP (0.43 mM PFPE; 18.1 mM 19F), with an SNR of 2 as the detection threshold. Imaging of a brain phantom with PFC-labeled macrophages invading an ECM hydrogel further illustrated the impact of these parameter changes. The systematic optimization of sequence and imaging parameters provides the framework for an accurate visualization of 19F-labeled macrophage distribution and density in the brain. This will enhance our understanding of the contribution of periphery-derived macrophages in bioscaffold degradation and its role in brain tissue regeneration.

Dorph, R., Cannady, M.

"What Drives Visitor Engagement in Exhibits? The Interaction Between Visitor Activation Profiles and Exhibit Features"
Curator the Museum Journal, 0:0

Mouse over here for a brief summary or click to open article in a new tab.This paper explores the use of science learning activation to understand how various types of visitors engage with different exhibits. In particular, we examined how learners engaged in two very different resource‐rich exhibits using two distinct analytic techniques. Regression analyses revealed that learners’ prior science learning activation can be used to predict learners’ engagement at each of the exhibits.

Martin, K.

"The grammatical class effect is separable from the concreteness effect in language learning"
Bilingualism: Language & Cognition, 0:0

Mouse over here for a brief summary or click to open article in a new tab.Typically concrete words are learned better than abstract words (Kaushanskaya & Rechtzigel, 2012), and nouns are learned better than verbs (Kauschke & Stenneken, 2008). However, most studies on concreteness have not manipulated grammatical class (and vice versa), leaving the relationship between the two unclear.

Krawchuk M, Ruff CF, Yang X, Ross SE

"Optogenetic assessment of VIP, PV, SOM and NOS inhibitory neuron activity and cerebral blood flow regulation in mouse somato-sensory cortex"
Journal of Cerebral Blood Flow and Metabolism, AOP:1

Mouse over here for a brief summary or click to open article in a new tab.Awake head-fixed mice expressing cre recombinase were used to optogenetically stimulate sub-populations of inhibitory neurons to determine their local vasoregulatory capacity. Optogenetic stimulation of somatostatin (SOM) or nitric oxide synthase (NOS) inhibitory neurons mice produced significant increases in cerebral blood flow (CBF) that were similar to whisker responses. In SOM-cre mice, CBF increases were followed by decreases. Optogenetic stimulation of parvalbumin (PV) inhibitory neurons produced slower increases in CBF that peaked 14–18 s after stimulation onset. Optogenetic stimulation of vasointestinal peptide (VIP) inhibitory neurons did not produce consistent changes in CBF.

Conroy S.S., Krebs H.I., Zhan M., Bever C.T., Whitall J.

"Robot-Assisted Arm Training in Chronic Stroke: Addition of Transition-to-Task Practice"
Neurorehabilitation and Neural Repair, 33:751

Mouse over here for a brief summary or click to open article in a new tab.In this study, chronic upper extremity motor deficits were addressed with 36 hour-long sessions of robot-assisted arm movement practice. The replacement of part of the robotic training with nonrobotic tasks did not reduce treatment effect and may benefit stroke-affected hand use and motor task performance.


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