The 2018 Lake Louise Acute Mountain Sickness Score.

Roach, Robert C., Peter H. Hackett, Oswald Oelz, Peter Bärtsch, Andrew M. Luks, Martin J. MacInnis, J. Kenneth Baillie, and The Lake Louise AMS Score Consensus Committee. The 2018 Lake Louise Acute Mountain Sickness Score. High Alt Med Biol 19:1-4, 2018.- The Lake Louise Acute Mountain Sickness (AMS) scoring system has been a useful research tool since first published in 1991. Recent studies have shown that disturbed sleep at altitude, one of the five symptoms scored for AMS, is more likely due to altitude hypoxia per se, and is not closely related to AMS. To address this issue, and also to evaluate the Lake Louise AMS score in light of decades of experience, experts in high altitude research undertook to revise the score. We here present an international consensus statement resulting from online discussions and meetings at the International Society of Mountain Medicine World Congress in Bolzano, Italy, in May 2014 and at the International Hypoxia Symposium in Lake Louise, Canada, in February 2015. The consensus group has revised the score to eliminate disturbed sleep as a questionnaire item, and has updated instructions for use of the score

The Motor Thalamus: An Invigorating Hub of Neural Activity

The motor thalamus (Mthal) is poised between subcortical and cortical motor structures and is, in the simplest terms, understood as a “relay” for neural activity. However, it is increasingly appreciated that Mthal plays a complex, integrative function. This view is emerging from clinical applications where modifying Mthal activity ameliorates the motor symptoms of several movement disorders, including Parkinson’s disease (PD). Little is understood, however, about how neural signals are integrated by Mthal and how this integration shapes ongoing behavior. Answers to these questions hold important implications for basic science and future therapies of brain disease. My studies address major questions about Mthal physiology by recording chronic, in vivo electrophysiology in behaving rats. Given the parallels between rodent and human motor circuits, rats are a useful translational model. I leveraged a two-alternative forced choice task where movement is both ballistic and lateralized. I found that Mthal single unit activity (or “spiking”) is greatly enhanced around movement initiation. Importantly I identified units that fired in a manner that was either “directionally selective” or “non-directionally selective”. Using two performance measures, reaction time (RT) and movement time (MT), I also show that Mthal activity is proportional to the speed of movement. Directionally selective units correlate with RT and MT, non-directionally selective units correlate exclusively with RT. Mthal spiking is known to be correlated with rhythmic oscillations in the extracellular local field potential (LFP). I therefore determined relationships between Mthal unit spiking, behavior and LFP. I discovered that the phase of low frequency oscillations in the delta band (1-4 Hz) predicts spike timing, especially for directionally selective units. Delta phase also predicts RT and aligns to each event, suggesting a role in task timing. The power of higher frequency oscillations, namely beta (13-30 Hz) and low-gamma (30-70 Hz), are nested within the delta phase. Taken together, these results support a model whereby delta phase regulates high-frequency interactions and neuronal excitability in Mthal, which reflects motor performance. To begin parsing behavioral causality with spatiotemporal precision, I implemented a suite of optogenetic tools to anatomically isolate Mthal circuitry. I show that an adeno-associated virus injected in upstream structures can be reliably trafficked to and expressed in Mthal. These techniques establish methods to test hypotheses concerning complex spike-LFP and LFP-LFP interactions ultimately leading to a better understanding of how movement signals are mediated by Mthal.PHDNeuroscienceUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/151630/1/mgaidica_1.pd

Data_Sheet_1_An implantable neurophysiology platform: Broadening research capabilities in free-living and non-traditional animals.docx

Animal-borne sensors that can record and transmit data (“biologgers”) are becoming smaller and more capable at a rapid pace. Biologgers have provided enormous insight into the covert lives of many free-ranging animals by characterizing behavioral motifs, estimating energy expenditure, and tracking movement over vast distances, thereby serving both scientific and conservational endpoints. However, given that biologgers are usually attached externally, access to the brain and neurophysiological data has been largely unexplored outside of the laboratory, limiting our understanding of how the brain adapts to, interacts with, or addresses challenges of the natural world. For example, there are only a handful of studies in free-living animals examining the role of sleep, resulting in a wake-centric view of behavior despite the fact that sleep often encompasses a large portion of an animal’s day and plays a vital role in maintaining homeostasis. The growing need to understand sleep from a mechanistic viewpoint and probe its function led us to design an implantable neurophysiology platform that can record brain activity and inertial data, while utilizing a wireless link to enable a suite of forward-looking capabilities. Here, we describe our design approach and demonstrate our device’s capability in a standard laboratory rat as well as a captive fox squirrel. We also discuss the methodological and ethical implications of deploying this new class of device “into the wild” to fill outstanding knowledge gaps.</p

Interactions Between Motor Thalamic Field Potentials and Single-Unit Spiking Are Correlated With Behavior in Rats

Field potential (FP) oscillations are believed to coordinate brain activity over large spatiotemporal scales, with specific features (e.g., phase and power) in discrete frequency bands correlated with motor output. Furthermore, complex correlations between oscillations in distinct frequency bands (phase-amplitude, amplitude-amplitude, and phase-phase coupling) are commonly observed. However, the mechanisms underlying FP-behavior correlations and cross-frequency coupling remain unknown. The thalamus plays a central role in generating many circuit-level neural oscillations, and single-unit activity in motor thalamus (Mthal) is correlated with behavioral output. We, therefore, hypothesized that motor thalamic spiking coordinates motor system FPs and underlies FP-behavior correlations. To investigate this possibility, we recorded wideband motor thalamic (Mthal) electrophysiology as healthy rats performed a two-alternative forced-choice task. Delta (1–4 Hz), beta (13–30 Hz), low gamma (30–70 Hz), and high gamma (70–200 Hz) power were strongly modulated by task performance. As in the cortex, the delta phase was correlated with beta/low gamma power and reaction time. Most interestingly, subpopulations of Mthal neurons defined by their relationship to the behavior exhibited distinct relationships with FP features. Specifically, neurons whose activity was correlated with action selection and movement speed were entrained to delta oscillations. Furthermore, changes in their activity anticipated power fluctuations in beta/low gamma bands. These complex relationships suggest mechanisms for commonly observed FP-FP and spike-FP correlations, as well as subcortical influences on motor output.http://deepblue.lib.umich.edu/bitstream/2027.42/177390/2/Interactions Between Motor Thalamic Field Potentials and Single-Unit Spiking Are Correlated With Behavior in Rats.pdfPublished versionDescription of Interactions Between Motor Thalamic Field Potentials and Single-Unit Spiking Are Correlated With Behavior in Rats.pdf : Published versio

Distinct populations of motor thalamic neurons encode action initiation, action selection, and movement vigor

Motor thalamus (Mthal) comprises the ventral anterior, ventral lateral, and ventral medial thalamic nuclei in rodents. This subcortical hub receives input from the basal ganglia (BG), cerebellum, and reticular thalamus in addition to connecting reciprocally with motor cortical regions. Despite the central location of Mthal, the mechanisms by which it influences movement remain unclear. To determine its role in generating ballistic, goal-directed movement, we recorded single-unit Mthal activity as male rats performed a two-alternative forced-choice task. A large population of Mthal neurons increased their firing briefly near movement initiation and could be segregated into functional groups based on their behavioral correlates. The activity of “initiation” units was more tightly locked to instructional cues than movement onset, did not predict which direction the rat would move, and was anticorrelated with reaction time (RT). Conversely, the activity of “execution” units was more tightly locked to movement onset than instructional cues, predicted which direction the rat would move, and was anticorrelated with both RT and movement time. These results suggest that Mthal influences choice RT performance in two stages: short latency, nonspecific action initiation followed by action selection/invigoration. We discuss the implications of these results for models of motor control incorporating BG and cerebellar circuits.http://deepblue.lib.umich.edu/bitstream/2027.42/177387/2/6563.full.pdfPublished versionDescription of 6563.full.pdf : Published versio

The 2018 Lake Louise Acute Mountain Sickness Score

The Lake Louise Acute Mountain Sickness (AMS) scoring system has been a useful research tool since first published in 1991. Recent studies have shown that disturbed sleep at altitude, one of the five symptoms scored for AMS, is more likely due to altitude hypoxia per se, and is not closely related to AMS. To address this issue, and also to evaluate the Lake Louise AMS score in light of decades of experience, experts in high altitude research undertook to revise the score. We here present an international consensus statement resulting from online discussions and meetings at the International Society of Mountain Medicine World Congress in Bolzano, Italy, in May 2014 and at the International Hypoxia Symposium in Lake Louise, Canada, in February 2015. The consensus group has revised the score to eliminate disturbed sleep as a questionnaire item, and has updated instructions for use of the score