Transcranial Magnetic Stimulation Intensities in Cognitive Paradigms

BACKGROUND: Transcranial magnetic stimulation (TMS) has become an important experimental tool for exploring the brain's functional anatomy. As TMS interferes with neural activity, the hypothetical function of the stimulated area can thus be tested. One unresolved methodological issue in TMS experiments is the question of how to adequately calibrate stimulation intensities. The motor threshold (MT) is often taken as a reference for individually adapted stimulation intensities in TMS experiments, even if they do not involve the motor system. The aim of the present study was to evaluate whether it is reasonable to adjust stimulation intensities in each subject to the individual MT if prefrontal regions are stimulated prior to the performance of a cognitive paradigm. METHODS AND FINDINGS: Repetitive TMS (rTMS) was applied prior to a working memory task, either at the 'fixed' intensity of 40% maximum stimulator output (MSO), or individually adapted at 90% of the subject's MT. Stimulation was applied to a target region in the left posterior middle frontal gyrus (pMFG), as indicated by a functional magnetic resonance imaging (fMRI) localizer acquired beforehand, or to a control site (vertex). Results show that MT predicted the effect size after stimulating subjects with the fixed intensity (i.e., subjects with a low MT showed a greater behavioral effect). Nevertheless, the individual adaptation of intensities did not lead to stable effects. CONCLUSION: Therefore, we suggest assessing MT and account for it as a measure for general cortical TMS susceptibility, even if TMS is applied outside the motor domain

Is there a difference? Comparison of golden retrievers and dogs affected by breed-specific legislation regarding aggressive behavior

Abstract Between 2000 and 2002, legislation in Lower Saxony insinuated a special dangerousness of certain dog breeds, and controls were imposed on them. Exemption was only possible if the dogs passed a standardized temperament test. In a previous study, test results of 415 dogs belonging to breeds affected by the legislation were analyzed. Ninety-five percent of the dogs showed no indication of disturbed aggressive communication or aggressive behavior in inappropriate situations. Because a control group was not available at that time, these results referred to a comparison between the affected breeds. In this study, golden retrievers were tested and used as control group. Seventy golden retrievers were tested in the temperament test. The order of testing was: veterinary examination, learning test, situations of dog-human-, dog-environment-, and dog-dog-contact, and obedience. Levels of escalation in aggressive behavior were scored using a scale of 1-7. A total of 58.57% of the dogs did not show aggressive behavior (Scale 1). Forty percent displayed aggressive behavior referring to Scale 2, and 1.43% showed aggressive behavior referring to Scale 5. A total of 98.57% of the dogs reacted appropriately, and 1.43% displayed aggressive behavior in inappropriate situations. In the previous study, 95% of the animals reacted appropriately, whereas 5% displayed excessive aggressive communication or aggressive behavior in inappropriate situations. Comparing the results of golden retrievers and breeds affected by the legislation, no significant difference was found. A scientific basis for breed specific lists does not exist. Therefore, legislation in Lower Saxony was changed, and breed lists were withdrawn