Contribution of the premotor cortex to consolidation of motor sequence learning in humans during sleep.

Motor learning and memory consolidation require the contribution of different cortices. For motor sequence learning, the primary motor cortex is involved primarily in its acquisition. Premotor areas might be important for consolidation. In accordance, modulation of cortical excitability via transcranial DC stimulation (tDCS) during learning affects performance when applied to the primary motor cortex, but not premotor cortex. We aimed to explore whether premotor tDCS influences task performance during motor memory consolidation. The impact of excitability-enhancing, -diminishing, or placebo premotor tDCS during rapid eye movement (REM) sleep on recall in the serial reaction time task (SRTT) was explored in healthy humans. The motor task was learned in the evening. Recall was performed immediately after tDCS or the following morning. In two separate control experiments, excitability-enhancing premotor tDCS was performed 4 h after task learning during daytime or immediately before conduction of a simple reaction time task. Excitability-enhancing tDCS performed during REM sleep increased recall of the learned movement sequences, when tested immediately after stimulation. REM density was enhanced by excitability-increasing tDCS and reduced by inhibitory tDCS, but did not correlate with task performance. In the control experiments, tDCS did not improve performance. We conclude that the premotor cortex is involved in motor memory consolidation during REM sleep.

Concurrent occurrence of multiple sclerosis and primary CNS lymphoma: a case report.

We present the patient with the diagnosis of multiple sclerosis (MS), relapsing-remitting form with long lasting remission. Unexpectedly, this patient presented dramatical clinical deterioration and revealed clinical symptoms such as bradypsychia, cognitive symptoms, central vestibulare syndrome, spastic quadruparesis. Clinical findings suggested secondary progressive MS, but MRI called in question this diagnosis. The MRI appearance suggested, that MS had been complicated by a different brain pathological lesion, and the brain biopsy was indicated. A histological examination confirmed primary CNS lymphoma (PCNSL). This case exemplifies important aspects of clinical neurology. A re-evaluation of the diagnosis of MS should always be performed in a patient when new symptoms are presented that are unusual or could be due to other pathological processes. MRI offers the highly sensitive way to detect the coexistence of MS and other brain disease. Primary goal of imaging modalities is differential diagnosis between demyelinating diseases, such as MS and other brain lesions. Advanced focus demand contrast- enhancing and mass- effect lesions. It is important to realize, that contrast-enhancement and brain edema may be mitigated by treatment with corticosteroids. In some cases a brain biopsy is needed.