A system for the determination of planar force vectors from spontaneously active chicken embryos.

Generally, a combination of kinematic, electromyographic (EMG), and force measurements are used to understand how an organism generates and controls movement. The chicken embryo has been a very useful model system for understanding the early stages of embryonic motility in vertebrates. Unfortunately, the size and delicate nature of embryos makes studies of motility during embryogenesis very challenging. Both kinematic and EMG recordings have been achieved in embryonic chickens, but two-dimensional force vector recordings have not. Here, we describe a dual-axis system for measuring force generated by the leg of embryonic chickens. The system employs two strain gauges to measure planar forces oriented with the plane of motion of the leg. This system responds to forces according to the principles of Pythagorean geometry, which allows a simple computational program to determine the force vector (magnitude and direction) generated during spontaneous motor activity. The system is able to determine force vectors for forces >0.5 mN accurately and allows for simultaneous kinematic and EMG recordings. This sensitivity is sufficient for force vector measurements encompassing most embryonic leg movements in midstage chicken embryos allowing for a more complete understanding of embryonic motility. Variations on this system are discussed to enable nonideal or alternative sensor arrangements and to allow for translation of this approach to other delicate model systems.

Esophageal reflexes modulate frontoparietal response in neonates: Novel application of concurrent NIRS and provocative esophageal manometry.

Central and peripheral neural regulation of swallowing and aerodigestive reflexes is unclear in human neonates. Functional near infrared spectroscopy (NIRS) is a noninvasive method to measure changes in oxyhemoglobin (HbO) and deoxyhemoglobin (HbD). Pharyngoesophageal manometry permits evaluation of aerodigestive reflexes. Modalities were combined to investigate feasibility and to test neonatal frontoparietal cortical changes during pharyngoesophageal (visceral) stimulation and/or swallowing. Ten neonates (45.6 ± 3.0 wk postmenstrual age, 4.1 ± 0.5 kg) underwent novel pharyngoesophageal manometry concurrent with NIRS. To examine esophagus-brain interactions, we analyzed cortical hemodynamic response (HDR) latency and durations during aerodigestive provocation and esophageal reflexes. Data are presented as means ± SE or percent. HDR rates were 8.84 times more likely with basal spontaneous deglutition compared with sham stimuli (P = 0.004). Of 182 visceral stimuli, 95% were analyzable for esophageal responses, 38% for HDR, and 36% for both. Of analyzable HDR (n = 70): 1) HbO concentration (µmol/l) baseline 1.5 ± 0.7 vs. 3.7 ± 0.7 poststimulus was significant (P = 0.02), 2) HbD concentration (µmol/l) between baseline 0.1 ± 0.4 vs. poststimulus -0.5 ± 0.4 was not significant (P = 0.73), and 3) hemispheric lateralization was 21% left only, 29% right only, and 50% bilateral. During concurrent esophageal and NIRS responses (n = 66): 1) peristaltic reflexes were present in 74% and HDR in 61% and 2) HDR was 4.75 times more likely with deglutition reflex vs. secondary peristaltic reflex (P = 0.016). Concurrent NIRS with visceral stimulation is feasible in neonates, and frontoparietal cortical activation is recognized. Deglutition contrasting with secondary peristalsis is related to cortical activation, thus implicating higher hierarchical aerodigestive protective functional neural networks.