Neuroscience
-
Human standing balance control requires the integration of sensory feedback to produce anticipatory, stabilizing ankle torques. However, the ability of human triceps surae muscle spindles to provide reliable sensory feedback regarding the small, slow ankle movements that occur during upright standing has recently come under question. We performed microneurography to directly record axon potentials from single muscle spindle afferents in the human triceps surae during servo-controlled movement of the ankle joint. ⋯ Concatenating within muscles, coherence was significantly greater for soleus spindles at all stimulus frequencies. Voluntary contraction of the parent muscle reduced spindle sensitivity, but only significantly near the mean power frequency of the stimulus (∼0.3Hz). In conclusion, these results provide direct evidence that triceps surae muscle spindles are potentially capable of providing important sensory feedback for the control of human standing balance.
-
Midbrain dopamine neurons play critical roles in reward- and aversion-driven associative learning. However, it is not clear whether they do this by a common mechanism or by separate mechanisms that can be dissociated. In the present study we addressed this question by testing whether a partial lesion of the dopamine neurons of the rat SNc has comparable effects on conditioned place preference (CPP) learning and conditioned place aversion (CPA) learning. ⋯ In addition, the CPA scores of the 6-OHDA rats positively correlated with the tissue content of striatal dopamine. Insomuch as reward-driven learning depends on an increase in dopamine release by nigral neurons, these findings show that this mechanism is functional even in rats with a partial lesion of the SNc. On the other hand, if aversion-driven learning depends on a reduction of extracellular dopamine in the striatum, the present study suggests that this mechanism is no longer functional after the partial SNc lesion.
-
Awareness generation and modulation may depend on a balanced information integration and differentiation across default mode network (DMN) and external awareness networks (EAN). Neuromodulation approaches, capable of shaping information processing, may highlight residual network activities supporting awareness, which are not detectable through active paradigms, thus allowing to differentiate chronic disorders of consciousness (DoC). We studied aftereffects of repetitive transcranial magnetic stimulation (rTMS) by applying graph theory within canonical frequency bands to compare the markers of these networks in the electroencephalographic data from 20 patients with DoC. ⋯ There was a correlation between metrics and the behavioral awareness. Interestingly, two persons with UWS showed a residual rTMS-induced modulation of the functional correlations between the DMN and the EAN, as observed in patients with MCS. Hence, we may hypothesize that the patients with UWS who demonstrate evidence of residual DMN-EAN functional correlation may be misdiagnosed, given that such residual network correlations could support covert consciousness.
-
Embryonic stem cells (ESCs) have enormous potential as novel cell-based therapies, but their effectiveness depends on stem cell differentiation and specific signaling regulators, which remain poorly understood. In this study, a kisspeptin peptide (KP-10) was used at different dosages to determine whether rhesus macaque-derived tau GFP-Lyon ES cells underwent kisspeptin-specific neuronal differentiation. ⋯ There has been a previously observed connection between kisspeptin signaling, GnRH neurons and their dysfunction found in congenital disorders like idiopathic hypogonadotropic hypogonadism (IHH). Although therapeutics are a still a far-off goal, the formation and development of GnRH-positive neuronal-like cells following the application of KP-10 to Lyon NSC cells opens the door for future NSC-based therapies to treat specific reproductive disorders.
-
The aim of the present study was to determine whether thoracic spinal manipulation (SM) decreases temporal summation of back pain. The study comprised two controlled experiments including 16 and 15 healthy participants, respectively. Each study included six sessions during which painful or non-painful electrical stimulations were delivered in three conditions: (1) control (2) light mechanical stimulus (MS) or (3) SM. ⋯ Changes were not significant for the MS sessions (all p's>0.05) and no effect was observed for the tactile sensation (all p's>0.1). These results indicate that SM produces specific inhibitory effects on temporal summation of back pain, consistent with the involvement of a spinal anti-nociceptive mechanism in clinical pain relief by SM. This provides the first mechanistic evidence of back pain relief by spinal manipulation.