In particular, the robust paired-pulse facilitation characteristic of adult neurons is almost entirely lacking in newborns. To examine developmental changes in processes controlling [Ca2+]res, we measured the timecourse of [Ca2+]res decay in presynaptic terminals of Schaffer collateral to CA1 synapses in acute hippocampal slices following single and paired orthodromic stimuli in the stratum radiatum. PLX4032 in vivo Developmental changes were observed
in both the rise time and slow exponential decay components of the response to single stimuli such that this decay was larger and faster in the adult. Furthermore, we observed a greater caffeine-sensitive basal Ca2+ store, which was differentially affected when active uptake into the endoplasmic reticulum was blocked, in the presynaptic fields of the Schaffer collateral to CA1 terminals of P6 and younger mice when compared to adults. These transitions in [Ca2+]res dynamics occurred gradually over the first weeks of postnatal life and correlated with changes in short-term plasticity. “
“Several transcranial magnetic stimulation (TMS) studies have reported facilitation of the primary motor cortex (M1) during the mere observation of actions. This facilitation was shown to be highly congruent, in terms of somatotopy, with the observed action, even at the level of single muscles. With
the present study, we investigated whether this muscle-specific facilitation of the observer’s motor system reflects the degree of muscular force that is Olaparib concentration exerted in an observed action. Two separate TMS experiments are reported in which corticospinal excitability was measured in the hand area of M1 while subjects observed the lifting of objects of different weights. The type of action ‘grasping-and-lifting-the-object’ was always identical, but the grip force varied according to the object’s weight. In accordance Lck to previous findings, excitability of M1 was shown to modulate in a muscle-specific way, such that
only the cortical representation areas in M1 that control the specific muscles used in the observed lifting action became increasingly facilitated. Moreover, muscle-specific M1 facilitation was shown to modulate to the force requirements of the observed actions, such that M1 excitability was considerably higher when observing heavy object lifting compared with light object lifting. Overall, these results indicate that different levels of observed grip force are mirrored onto the observer’s motor system in a highly muscle-specific manner. The measured force-dependent modulations of corticospinal excitability in M1 are hypothesized to be functionally relevant for scaling the observed grip force in the observer’s own motor system. In turn, this mechanism may contribute, at least partly, to the observer’s ability to infer the weight of the lifted object.