Progress in neurobiology
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Progress in neurobiology · Jan 2011
ReviewModulation of cortical excitability induced by repetitive transcranial magnetic stimulation: influence of timing and geometrical parameters and underlying mechanisms.
Transcranial magnetic stimulation (TMS) is a non-invasive brain stimulation technique that activates neurons via generation of brief pulses of high-intensity magnetic field. If these pulses are applied in a repetitive fashion (rTMS), persistent modulation of neural excitability can be achieved. The technique has proved beneficial in the treatment of a number of neurological and psychiatric conditions. ⋯ The different mechanisms interact with each other and this will contribute to the variability of rTMS-induced excitability changes. This review investigates the links between rTMS and synaptic plasticity, describes their similarities and differences, and highlights a neglected contribution of the membrane potential. In summary, the principal aims of this review are (i) to discuss the different experimental and subject-related factors that contribute to the variability of excitability modulation induced by rTMS, and (ii) to discuss a generalized underlying mechanism for the excitability modulation.
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In the present article the putative role of environmental factors in schizophrenia is reviewed and synthesized. Accumulating evidence from recent studies suggests that environmental exposures may play a more significant role in the etiopathogenesis of this disorder than previously thought. This expanding knowledge base is largely a consequence of refinements in the methodology of epidemiologic studies, including birth cohort investigations, and in preclinical research that has been inspired by the evolving literature on animal models of environmental exposures. ⋯ In the final section, future studies including new, larger, and more rigorous epidemiologic investigations, and research on translational and clinical neuroscience, gene-environment interactions, epigenetics, developmental trajectories and windows of vulnerability, are elaborated upon. These studies are aimed at confirming observed risk factors, identifying new environmental exposures, elucidating developmental mechanisms, and shedding further light on genes and exposures that may not be identified in the absence of these integrated approaches. The study of environmental factors in schizophrenia may have important implications for the identification of causes and prevention of this disorder, and offers the potential to complement, and refine, existing efforts on explanatory neurodevelopmental models.