Neuroscience
-
Childhood bullying or social stress in adolescent humans is generally considered to increase the risk of developing behavioral disorders like depression in adulthood. Juveniles are hypothesized to be particularly sensitive to stressors in their environment due to the relatively late maturation of brain areas that are targeted by stress such as the prefrontal cortex and hippocampus. In our study male adolescent rats were subjected to repeated social defeat on postnatal day (PND) 28, 31 and 34 (experiment 1) or to daily social defeats between PND 35 and 42 (experiment 2). ⋯ A few acute but minor changes in brain plasticity markers and behavior were observed but these were transient and no behavioral or physiological effects persisted into adulthood. The results from both experiments support the theory developed in the so-called "match-mismatch hypothesis" which claims that the final consequence of childhood adversity depends on how well the early life environment matches the challenges in later life. Socially stressed adolescents are rather resilient to the lasting behavioral and physiological effects of the stress exposure if they are socially housed afterward and have the ability to recover.
-
In the last decade, early-onset of affective illness has been recognized as a major public health problem. However, clinical studies indicate that although children experience the symptoms of anxiety and depression in much the same way as adults, they display and react to those symptoms differently (Bostic et al., 2005). Recently, we have demonstrated that similar differences in symptoms are found also between adult and juvenile rats (Jacobson-Pick and Richter-Levin, 2010). ⋯ Exposure to forced swim stress resulted in significant alterations of dentate gyrus activity and plasticity in male rats with differences between adult and pre-pubertal animals. Stress had far less impact on females' dentate electrophysiology. The results are in agreement with the differences in behavioral response to stress between pre-pubertal and adult rats, and with reported differences for the sensitivity of male and female rats in performing hippocampus-dependent tasks under stress, such as the active avoidance task.
-
Pretend play, emerging at about 18 months, and explicit false belief (FB) understanding, arising around 4 years, constitute two pivotal milestones in the development of a Theory of Mind since both involve the ability to separate real from non-real content. The developmental lag has evoked vivid discussion with respect to whether or not pretense (PT) involves a metarepresentational understanding similar to FB. However, in children PT and FB have not yet been contrasted on a neural level to reveal whether they are subserved by the same neurocognitive mechanism. ⋯ Given the differences in latency, polarity, and topography, PT and FB seem to rely on distinct neural substrates in children. The early negative frontal slow wave indicates that for PT reasoning children may use simple mentalizing processes such as intention processing, whereas the late positive slow-wave shows that for FB children may engage in metarepresentational processing. Therefore, the present findings seem to substantiate theoretical accounts postulating simple mentalistic reasoning for PT in children.
-
Numerous clinical conditions can be treated by neuromodulation of the peripheral nervous system (PNS). Typical electrical PNS therapies activate large diameter axons at lower electrical stimulus thresholds than small diameter axons. However, recent animal experiments with peripheral optogenetic neural stimulation (PONS) of myelinated axons expressing channelrhodopsin-2 (ChR2) have shown that this technique activates small diameter axons at lower irradiances than large diameter axons. ⋯ The light-axon models enabled direct calculation of threshold irradiance for different diameter axons. Our simulations demonstrate that illumination of multiple nodal sections reduces the threshold irradiance and enhances the small-to-large diameter recruitment order. In addition to addressing biophysical questions, our light-axon model system could also be useful in guiding the engineering design of optical stimulation technology that could maximize the efficiency and selectivity of PONS.