Cerebellar Transcranial Direct Current Stimulation Does Not Alter Somatosensory Temporal Discrimination Threshold.

This study aimed to explore the role of the cerebellum on the somatosensory temporal discrimination (STD) process. Twenty healthy volunteers were enrolled in the study. Each participant was included in three different transcranial direct current stimulation (tDCS) sessions as anodal, cathodal, and sham sessions in randomised order. Anodal and cathodal cerebellar tDCS (cTDCS) were given for 20 min at an intensity of 2 mA. The results of the study indicate no effect of cTDCS on STD. Although the study results show that cTDCS does not affect STD, because of the restricted sample size of the study, it is useful and necessary to investigate this relationship more in depth in a larger healthy subject population using different cTDCS methodologies.

Voluntary movement reverses the effect of cathodal transcranial direct current stimulation (tDCS) on corticomotor excitability.

Motor cortex activity level is a critical part of the effect of transcranial direct current stimulation (tDCS) on corticomotor excitability. Based on homeostatic plasticity, the state of the stimulated cortical area influences the direction of neuroplastic changes induced by stimuli. Owing to homeostatic plasticity, cathodal tDCS (c-tDCS) would likely have a pronounced inhibitory effect on corticomotor excitability during a motor task, compared with the resting state. To test this hypothesis, we detected motor evoked potential (MEP) amplitude changes before and during c-tDCS with voluntary movement. Twelve healthy right-handed volunteers (9 males, 27-48 years) were enrolled in the study. Subjects performed little finger abduction motor task. Passive (APB) and active (ADM) muscles were studied. MEP amplitudes were measured during resting (baseline) and movement stages, and subsequently with the contralateral M1 modulated by c-tDCS. c-tDCS caused reduced baseline MEP amplitude in the ADM (p < 0.05) and APB (p < 0.001) muscles. Sham stimulation had no effect on the baseline MEP amplitudes. MEP amplitude ratio (MEP amplitude triggered by movement/baseline MEP amplitude) was higher during c-tDCS than before c-tDCS (p < 0.01). Our results suggested that during voluntary contraction, c-tDCS has an opposite effect on corticospinal excitability compared with resting state modulation effect. This contrast effect could be related to modulation of movement preparation and execution.

An evaluation of lateralizing signs in patients with temporal lobe epilepsy.

Resective epilepsy surgery has been accepted as an effective treatment for patients with medically intractable temporal lobe epilepsy (TLE) to control the seizures and to limit cognitive dysfunction. Complete resection of the epileptic zone, and therefore the success of the surgery, depends on the identification of the seizure focus. Reliable lateralizing semiologic signs, together with other presurgical assessments, are of great importance for an accurate identification of the seizure focus. In this respect, this study evaluated the frequency of semiologic signs in medically intractable temporal lobe epilepsy (TLE) together with the lateralizing values and variations according to the age and gender groups. Two hundred seventy-three seizures of 55 patients of the Adult Epilepsy Monitoring Unit of Gazi University Faculty of Medicine with the diagnosis of medically intractable TLE, whose epileptic foci were detected through noninvasive presurgical procedures and seizures were controlled successfully after anterior temporal lobectomy (ATL), were analyzed retrospectively. Seizure semiologies of the patients were evaluated in terms of lateralizing values, and it was inquired whether age/gender causes any variation. Versive head rotation, unilateral dystonic limb posturing, asymmetric tonic limb posturing, and the combination of unilateral hand automatisms and dystonic posturing were determined as the semiologic signs with the highest lateralizing values (90-100%). While hand automatisms were observed frequently in the group with early seizure-onset age (onset age ≤ 2), asymmetric tonic limb posturing was detected as more frequent in the group with later seizure-onset age (onset age > 2; p < .005). In addition to this, semiologic signs were noted to be different between male and female groups; psychic and autonomic auras and ictal emotional signs were associated with women (p < .005).