Effect of methylphenidate on visual responses in the superior colliculus in the anaesthetised rat: Role of cortical activation.

The mechanism of action of psychostimulant drugs in the treatment of Attention Deficit Hyperactivity Disorder is still largely unknown, although recent evidence suggests one possibility is that the drugs affect the superior colliculus (SC). We have previously demonstrated that systemically administered d-amphetamine attenuates/abolishes visual responses to wholefield light flashes in the superficial layers of the SC in anaesthetised rats, and the present study sought to extend this work to methylphenidate (MPH). Anaesthetised rats were administered MPH at a range of doses (or saline) and subjected to monocular wholefield light flashes at two intensities, juxta-threshold and super-threshold. In contrast to d-amphetamine, systemic MPH produced an enhancement of visual activity at both intensities. Methylphenidate was also found to produce activation of the cortical EEG in anaesthetised rats. Furthermore, cortical activation induced by electrical stimulation of the pons was found to enhance visual responses in superficial layers of the SC, and when MPH was paired with pontine-induced cortical activation, the response-enhancing effects of MPH were substantially attenuated. Taken together, the results suggest that the enhancement of visual responses in the superficial layers of the SC by MPH in the anaesthetised rat is an artefact of the drug's interaction with cortical arousal.

[Cochlear reimplantation - experiences and results]. / Die Cochlea-Revisionsimplantation - Erfahrungen und Ergebnisse.

BACKGROUND: There have been remarkable developments in Cochlear Implants in the past years. Technical improvements lead to more reliable and durable devices. In cases of traumatic and atraumatic device failure a reimplantation of the Cochlear Implant is necessary. METHODS: In a retrospective study we examined 15 patients with 17 Cochlear reimplantation procedures after a traumatic or atraumatic device failure between 1996 and 2002. The reasons leading to the revision, the intraoperative findings, the perioperative complications and the postoperative audiological results as well as the personal evaluation of the revision procedure were analyzed. RESULTS: In our study there were 11 children and 4 adults. In 10 cases a traumatic and in 7 cases an atraumatic device failure lead to the reimplantation. In 13 of the 15 patients the revision surgery took place within 1 month after the date of device failure. The electrode array could be reinserted safely without any perioperative complications. The postoperative results showed a continuous development of speech perception in all patients. The personal evaluation of the reimplantation procedure was positive in all cases. CONCLUSIONS: Cochlear reimplantation in cases of traumatic or atraumatic device failure is a safe procedure without any serious perioperative complications. The timely reimplantation leads to a continuous development of speech perception.