No abstract

Over the last years, individualization of repetitive Transcranial Magnetic Stimulation (rTMS) parameters has been a focus of attention in the field of non-invasive stimulation. It has been proposed that in stress-related disorders personality characteristics may influence the clinical outcome of rTMS. However, the underlying physiological mechanisms as to how personality may affect the rTMS response to stress remains to be clarified. In this sham-controlled crossover study, after being stressed by the Trier Social Stress Test, 38 healthy females received two sessions of intermittent theta burst stimulation (iTBS) applied to the left dorsolateral prefrontal cortex. To take possible personality influences into account, they also completed the Temperament and Character Inventory. Mood and salivary cortisol were assessed throughout the experimental protocol. Overall, two iTBS sessions did not significantly alter mood or influenced cortisol secretion. When taking into account personality features, higher scores on the character dimension Cooperativeness was related to decreased cortisol output, only when active iTBS was administered after the social stressor. In line with other studies, personality features such as the character dimension Cooperativeness may be of particular interest to explain individual neurobiological responses to neurostimulation.

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1. "Unmasking" of weak synaptic connections has been suggested as a mechanism for the early changes in cortical topographic maps that follow alterations of sensory activity. For such a mechanism to operate, convergent sensory inputs must already exist in the normal cortex. 2. We tested for topographic and cross-modality convergence in primary somatosensory cortex of raccoon. The representation of glabrous skin of forepaw digits was chosen because, even though it is dominated by inputs from the glabrous skin of a single digit, it nevertheless comes to respond to stimulation of other digits when, e.g., a digit is removed. 3. Intracellular recordings were made from 109 neurons in the representation of glabrous skin of digit 4. Neurons were tested for somatosensory inputs with electrical and natural stimulation of digits. 4. Excitatory postsynaptic potentials (EPSPs) were evoked in 100% of the neurons (109/109) by electrical stimulation of glabrous skin of digit 4, and in 79% (31 of 39) by vibrotactile stimulation. 5. Glabrous skin of digit 4 was not the sole source of somatosensory inputs. A minority of neurons generated EPSPs after electrical stimulation of hairy skin of digit 4 (10 of 98 neurons, 10%). Electrical stimulation of digits 3 or 5 evoked EPSPs in 22 of 103 neurons (21%). Natural stimulation (vibrotactile or hair bending) was also effective in most of these latter cases (digit 3, 6/7; digit 5, 9/10). 6. Intracortical microstimulation of the "heterogeneous zone" was used to test for corticocortical connections to neurons in the glabrous zone.(ABSTRACT TRUNCATED AT 250 WORDS)