Relative burst amplitude of muscle sympathetic nerve activity is an indicator of altered sympathetic outflow in chronic anxietyHolwerda, Seth W.; Luehrs, Rachel E.; Gremaud, Allene L.; Wooldridge, Nealy A.; Stroud, Amy K.; Fiedorowicz, Jess G.; Abboud, Francois M.; Pierce, Gary L.
doi: 10.1152/jn.00064.2018pmid: 29537916
Relative burst amplitude of muscle sympathetic nerve activity in response to acute mental and physiological stress is selectively augmented in individuals with chronic anxiety, which is a prevalent condition that predicts the development of cardiovascular disease. Augmented sympathetic burst amplitude occurs with chronic anxiety in the absence of common comorbidities. These findings provide important insight into the relation between anxiety, acute stress and sympathetic activation.
Computer-aided neurophysiology and imaging with open-source PhysImageHayes, John A.; Papagiakoumou, Eirini; Ruffault, Pierre-Louis; Emiliani, Valentina; Fortin, Gilles
doi: 10.1152/jn.00048.2017pmid: 29488837
High-throughput analyses of both concurrent electrophysiological and imaging recordings has been a major challenge in neurophysiology. We submit an open-source solution that may be able to alleviate, or at least reduce, many of these concerns by providing an institutionally proven mechanism (i.e., ImageJ) with the added benefits of open-source Python scripting of PhysImage data that eases the workmanship of 2D trace data, which includes electrophysiological data. Together, with the ability to autogenerate prototypical figures shows this technology is a noteworthy advance.
Sherlock Holmes and the curious case of the human locomotor central pattern generatorKlarner, Taryn; Zehr, E. Paul
doi: 10.1152/jn.00554.2017pmid: 29537920
Evidence first described in reduced animal models over 100 years ago led to deductions about the control of locomotion through spinal locomotor central pattern-generating (CPG) networks. These discoveries in nature were contemporaneous with another form of deductive reasoning found in popular culture, that of Arthur Conan Doyle’s detective, Sherlock Holmes. Because the invasive methods used in reduced nonhuman animal preparations are not amenable to study in humans, we are left instead with deducing from other measures and observations. Using the deductive reasoning approach of Sherlock Holmes as a metaphor for framing research into human CPGs, we speculate and weigh the evidence that should be observable in humans based on knowledge from other species. This review summarizes indirect inference to assess “observable evidence” of pattern-generating activity that leads to the logical deduction of CPG contributions to arm and leg activity during locomotion in humans. The question of where a CPG may be housed in the human nervous system remains incompletely resolved at this time. Ongoing understanding, elaboration, and application of functioning locomotor CPGs in humans is important for gait rehabilitation strategies in those with neurological injuries.
Role of the head-direction signal in spatial tasks: when and how does it guide behavior?Weiss, Shahaf; Derdikman, Dori
doi: 10.1152/jn.00560.2017pmid: 29537921
Since their discovery, mammalian head-direction (HD) cells have been extensively researched in terms of sensory origins, external cue control, and circuitry. However, the relationship of HD cells to behavior is not yet fully understood. In the current review, we examine the anatomical clues for information flow in the HD circuit and an emerging body of evidence that links neural activity of HD cells and spatial orientation. We hypothesize from results obtained in spatial orientation tasks involving HD cells that when properly aligned with available external cues, the HD signal could be used for guiding rats to a goal location. However, contradictory inputs from separate sensory systems may reduce the influence of the HD signal such that animals are able to switch between this and other systems according to their impact on behavior.
Muscle coactivation: definitions, mechanisms, and functionsLatash, Mark L.
doi: 10.1152/jn.00084.2018pmid: 29589812
The phenomenon of agonist-antagonist muscle coactivation is discussed with respect to its consequences for movement mechanics (such as increasing joint apparent stiffness, facilitating faster movements, and effects on action stability), implication for movement optimization, and involvement of different neurophysiological structures. Effects of coactivation on movement stability are ambiguous and depend on the effector representing a kinematic chain with a fixed origin or free origin. Furthermore, coactivation is discussed within the framework of the equilibrium-point hypothesis and the idea of hierarchical control with spatial referent coordinates. Relations of muscle coactivation to changes in one of the basic commands, the c-command, are discussed and illustrated. A hypothesis is suggested that agonist-antagonist coactivation reflects a deliberate neural control strategy to preserve effector-level control and avoid making it degenerate and facing the necessity to control at the level of signals to individual muscles. This strategy, in particular, allows stabilizing motor actions by covaried adjustments in spaces of control variables. This hypothesis is able to account for higher levels of coactivation in young healthy persons performing challenging tasks and across various populations with movement impairments.