Adaptation of cortical activity to sustained pressure stimulation on the fingertip

Background Tactile adaptation is a phenomenon of the sensory system that results in temporal desensitization after an exposure to sustained or repetitive tactile stimuli. Previous studies reported psychophysical and physiological adaptation where perceived intensity and mechanoreceptive afferent signals exponentially decreased during tactile adaptation. Along with these studies, we hypothesized that somatosensory cortical activity in the human brain also exponentially decreased during tactile adaptation. The present neuroimaging study specifically investigated temporal changes in the human cortical responses to sustained pressure stimuli mediated by slow-adapting type I afferents. Methods We applied pressure stimulation for up to 15 s to the right index fingertip in 21 healthy participants and acquired functional magnetic resonance imaging (fMRI) data using a 3T MRI system. We analyzed cortical responses in terms of the degrees of cortical activation and inter-regional connectivity during sustained pressure stimulation. Results Our results revealed that the degrees of activation in the contralateral primary and secondary somatosensory cortices exponentially decreased over time and that intra- and inter-hemispheric inter-regional functional connectivity over the regions associated with tactile perception also linearly decreased or increased over time, during pressure stimulation. Conclusion These results indicate that cortical activity dynamically adapts to sustained pressure stimulation mediated by SA-I afferents, involving changes in the degrees of activation on the cortical regions for tactile perception as well as in inter-regional functional connectivity among them. We speculate that these adaptive cortical activity may represent an efficient cortical processing of tactile information.open

"The last egg in the basket?" Elderly primiparity: A review of findings

The recent trend of later childbearing among primiparous women is examined with attention to its possible motivations and how they might relate to maternal and infant outcomes. The influence of psychological factors is examined in the context of the inconsistencies in the obstetric literature regarding the risk factors associated with advancing maternal age. An interplay of psychological and biologic factors in determining the outcome of pregnancy and adaptation to motherhood in elderly primiparous women is proposed in terms of the compensatory as opposed to cumulative effect of psychological factors. The adoption of a broad perspective in the study of the experience of later motherhood is recommended as the direction for future research