Neuroscience
-
It is well established that the primary motor cortex (M1) plays a significant role in motor learning in healthy humans. It is unclear, however, whether mechanisms of motor learning include M1 oscillatory activity. In this study, we aimed to test whether M1 oscillations, entrained by transcranial Alternating Current Stimulation (tACS) at motor resonant frequencies, have any effect on motor acquisition and retention during a rapid learning task, as assessed by kinematic analysis. ⋯ At the end of training, corticospinal excitability had similarly increased in the three sessions. The results are compatible with the hypothesis that entrainment of the two major motor resonant rhythms through tACS over M1 has different effects on motor learning in healthy humans. The effects, however, were unrelated to corticospinal excitability changes.
-
Perceptual selection can be guided by the contents of working memory (WM). Neuroimaging and neuropsychological data point to a role of a fronto-parietal and fronto-thalamic networks in WM guidance. Here we assessed the effect of transcranial direct current stimulation of the left dorsal frontal cortex (lDFC) in a combined WM/attention paradigm. ⋯ Notably, across two experiments we found that lDFC-tDCS modulated WM guidance of visual selection in the context of high processing loads in WM. No effects of tDCS were observed in WM accuracy. These findings suggest that the role of the left dorsal frontal cortex in WM guidance is associated with selective attentional control rather than mnemonic processing.
-
Acetylcholine (ACh) is an abundant neurotransmitter and neuromodulator in many species. In Drosophila melanogaster ACh is the neurotransmitter used in peripheral sensory neurons and is a primary excitatory neurotransmitter and neuromodulator within the central nervous system (CNS). The receptors that facilitate cholinergic transmission are divided into two broad subtypes: the ionotropic nicotinic acetylcholine receptors (nAChRs) and the metabotropic muscarinic acetylcholine receptors (mAChRs). ⋯ We combined this with targeted AChR RNAi-mediated knockdown to identify specific receptor subtypes facilitating ACh modulation of circuit efficacy. We identify a contribution by both mAChRs and nAChRs in regulation of locomotor behavior and reveal they play a role in modulation of the excitability of a sensory-CNS-motor circuit. We further reveal a conspicuous role for mAChR-A and mAChR-C in motor neurons in modulation of their input-output efficacy.
-
Neural substrates for estrogen regulation of glucose homeostasis remain unclear. Female rat dorsal vagal complex (DVC) A2 noradrenergic neurons are estrogen- and metabolic-sensitive. The ventromedial hypothalamic nucleus (VMN) is a key component of the brain network that governs counter-regulatory responses to insulin-induced hypoglycemia (IIH). ⋯ Both ERs oppose hypoglycemic hyperglucagonemia, while ERβ contributes to reduced corticosterone output. Outcomes reveal that input from the female hindbrain to the VMN is critical for energy reserve mobilization, metabolic transmitter signaling, and counter-regulatory hormone secretion during hypoglycemia, and that ERs control those cues. Evidence that VMN NE content is not controlled by hindbrain ERα or -β implies that these receptors may regulate VMN function via NE-independent mechanisms, or alternatively, that other neurotransmitter signals to the VMN may control local substrate receptivity to NE.
-
Physical exercise is now generally considered as a strategy to maintain cognitive abilities and to prevent age-related cognitive decline. In the present study, Wistar rats were subjected to moderate intensity treadmill exercise for 6 months prior to sacrifice at 12-, 24- and 32-month of age. This chronic physical intervention was tested on motility in the Open field (OF). ⋯ Massive ChAT fiber aberrations in all investigated areas which developed in senescence were clearly attenuated by exercise. The results suggest that moderate intensity chronic exercise in the rat is especially beneficial in advanced age. In conclusion, chronic exercise attenuates the age-related decline in cognitive and motor behaviors as well as age-related cholinergic fiber reduction, reduces malformations of cholinergic forebrain innervation.