Comparison of Threshold and Tolerance Nociceptive Withdrawal Reflexes in Horses

The nociceptive withdrawal reflex (NWR) is used to investigate nociception in horses. The NWR threshold is a classical model endpoint. The aims of this study were to determine NWR tolerance and to compare threshold and tolerance reflexes in horses. In 12 horses, the NWR was evoked through electrical stimulation of the digital nerve and recorded via electromyography from the deltoid. Behavioral reactions were scored from 0 to 5 (tolerance). First, the individual NWR threshold was defined, then stimulation intensity was increased to tolerance. The median NWR threshold was 7.0 mA, whereas NWR tolerance was 10.7 mA. Upon visual inspection of the records, two main reflex components R1 (median latency 44 ms) and R2 (median latency 81 ms) were identified at threshold. Increasing stimulation intensity to tolerance led to a significant increase in the amplitude and duration of R1 and R2, whereas their latency decreased. At tolerance, a single burst of early, high-amplitude reflex activity, with a median latency of 39 ms, was detected in 15 out of 23 stimulations (65%). The results of this study suggest that (1) it is feasible to determine NWR tolerance in horses and (2) high-intensity stimuli initiate ultrafast bursts of reflex activity, which is well known in practice and has now been quantified using the NWR model.

Assessment of the condition of conditioned reflex activity in the process of liquid respiration

Introduction. Liquid respiration is the ability of mammalian lungs to receive oxygen dissolved in a liquid for respiration and release carbon dioxide into it. A promising field of application is the provision of marine operations. For the use of liquid respiration during deep-sea operations, the technology must ensure the normal functioning of all organs and systems of the body, prevent decompression sickness, and allow conscious activity. The study aims to assess the safety of conditioned reflex activity during independent liquid respiration in laboratory animals in normobaric conditions. Materials and methods. We performed the study on male Syrian hamsters aged four months, weighing 120-140 g. Researchers have developed a stand with an eight-level maze with a lock. We immersed the labyrinth in an aquarium. The scientists carried out the study in two stages. At the first stage, we have developed in animals a conditioned reflex of actively avoiding drowning in conditions of breathing air. The researchers placed the animal on the lower level, then immersed the maze in an aquarium filled with water at a speed that only the animal's head was above the water level. The threat of drowning prompted the animal to search for a passage to a higher level. The training was three times a day for ten days. At the second stage, scientists studied the influence of various conditions of liquid respiration on the state of the conditioned reflex activity of animals. We used two respiratory fluids - perfluorohexane (PFH) and perfluorodecalin (PFD) in three temperature regimes: 22.0, 27.0, and 32.0°C. The researchers filled the aquarium with two oxygenated respiratory fluids of the required temperature instead of water. We have entirely immersed the maze with the animal fixed at the lower level in the aquarium. After switching to liquid respiration, scientists removed the animal from fixation. From the moment of removal from fixation, the countdown of the passage of the maze began. First, we assessed the condition of conditioned reflex activity by the number of animals in the group that successfully passed the maze and the average time of its passage. Results. Animals on liquid respiration in perfluorohexane successfully passed the labyrinth in all temperature conditions. The average transit time at 22.0°C was 323±94 s; 27.0°C - 45±12 s; 32.0°C - 147±101 s. Animals on liquid respiration in perfluorodecalin successfully passed the labyrinth at a temperature of 27.0°C; the average passage time is 131±79 s; at a temperature of 32.0°C, 20% of animals successfully passed the labyrinth, the average time is 32.5 s; at a temperature of 22.0°C, none of the animals passed the maze. Conclusions. Conditioned reflex activity during independent liquid respiration in small laboratory animals in normobaric conditions persists and depends on the physico-chemical properties and temperature of the respiratory fluid.

Primitive Reflex Activity in Relation to Motor Skills in Healthy Preschool Children

Psychomotor development in the first year of life is possible due to activity and then integration of primitive (neonatal) reflexes. The presence of active primitive reflexes (APRs) in preschool and school-aged children indicates neuromotor immaturity. Studies show dependencies between the preserved activity of primary reflexes and developmental problems such as learning difficulties (problems with reading, writing, reduced mathematics skills, and dyslexia), difficulties with coordination, and attention deficit. The primary purpose of this study is to present the activity of three tonic reflexes in a sample of 112 Polish children aged 4–6 in relation to their motor skills. The children were examined for the presence of the asymmetric tonic neck reflex (ATNR), symmetric tonic neck reflex (STNR), and tonic labyrinthine reflex (TLR). Motor performance was examined with the MOT 4–6. Statistical analysis shows an inverse correlation between the score in the test of reflexes and motor efficiency (MOT 4–6) at p < 0.05 (−0.33). Children with increased reflex activity presented a lower level of motor efficiency. The multiple regression model showed that with the older age of the child and the decrease in the level of reflex activity, the motor skills of children improve. Thus, there is a need for early screening of primitive reflexes in children. Properly selected exercises and therapeutic activities aimed at integrating APRs in children with developmental difficulties can improve their motor skills, perceptual abilities, and emotional behavior.

Concussion and the Brain Injury

Concussion is normally produced by acceleration/deceleration of head and is often characterized by a sudden brief impairment of consciousness, memory loss, and paralysis of reflex activity.

Motorische Neurografie und Reflexstudien: Wegweiser der klinischen Elektrophysiologie

Würdigung der Publikation: Electrophysiological studies of nerve and reflex activity in normal man I. Identification of certain reflexes in the electromyogram and the conduction velocity of peripheral nerve fibers

Primitive Reflex Activity in Relation to the Sensory Profile in Healthy Preschool Children

The presence of active primitive reflexes (APRs) in healthy preschool children can be an expression of immaturity in the functioning of the nervous system. Their trace presence may not significantly affect the quality of child functioning. They may also undergo spontaneous and complete integration within the stages of child development. However, a higher level of active reflexes and their significant number can disturb sensory-motor development and lead to additional problems in a child’s motor activities, social life, and education. The main purpose of this study was to examine the types of sensory disorders noticed by parents of children, if any, that accompany the presence of active primitive reflexes. The study was conducted in a group of 44 preschool children (aged 4–6 years). The sensory profile of children was determined using Child Sensory Profile Cards, and Sally Goddard-Blythe tests were used to measure their primitive reflexes. The coefficient of determination (R-squared) indicated that the level of reflex activity was most strongly associated with sensory disorders such as dyspraxia, sensory-vestibular disorders, and postural disorders, at a level of p < 0.005. The obtained research results show that the examination of non-integrated reflexes might be a screening tool for children of preschool age. Knowledge of the subject of reflexes and their impact on sensory-motor functions may contribute to more accurate diagnoses of the causes of problems and higher effectiveness of possible therapy.

Movement history influences pendulum test kinematics in children with spastic cerebral palsy

The pendulum test assesses quadriceps spasticity by dropping the lower leg of a relaxed patient from the horizontal position and observing limb movement. The first swing excursion decreases with increasing spasticity severity. Our recent simulation study suggests that the reduced initial swing results from muscle short-range stiffness and its interaction with reflex hyper-excitability. Short-range stiffness emerges from the thixotropic behavior of muscles where fiber stiffness upon stretch increases when the muscle is held isometric. Fiber stiffness might thus be higher during the first swing of the pendulum test than during consecutive swings. In addition, it has recently been suggested that muscle spindle firing reflects fiber force rather than velocity and therefore, reflex activity might depend on fiber stiffness. If this hypothesized mechanism is true, we expect to observe larger first swing excursions and reduced reflex muscle activity when the leg is moved rather than kept isometric before release, especially in patients with increased reflex activity. We performed the pendulum test in 15 children with cerebral palsy (CP) and 15 age-matched typically developing (TD) children in two conditions. In the hold condition, the leg was kept isometric in the extended position before release. In the movement condition, the leg was moved up and down before release to reduce the contribution of short-range stiffness. Knee kinematics and muscle activity were recorded. Moving the leg before release increased first swing excursion (p < 0.001) and this increase was larger in children with CP (21°) than in TD children (8°) (p < 0.005). In addition, pre-movement delayed reflex onset by 87 ms (p < 0.05) and reduced reflex activity as assessed through the area under the curve of rectus femoris electromyography (p < 0.05) in children with CP. The movement history dependence of pendulum kinematics and reflex activity supports our hypothesis that muscle short-range stiffness and its interaction with reflex hyper-excitability contribute to joint hyper-resistance in spastic CP. Our results have implications for standardizing movement history in clinical tests of spasticity and for understanding the role of spasticity in functional movements, where movement history differs from movement history in clinical tests.