Tag: Learning

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Memory Enhancement and Deep-Brain Stimulation of the Entorhinal Area

N Eng J Med, Vol 366(6), 9 February 2012, p 502–509. DOI: 10.1056/NEJMcibr1113400

The medial temporal structures, including the hippocampus and the entorhinal cortex, are critical for the ability to transform daily experience into lasting memories. We tested the hypothesis that deep-brain stimulation of the hippocampus or entorhinal cortex alters memory performance.

METHODS: We implanted intracranial depth electrodes in seven subjects to identify seizure-onset zones for subsequent epilepsy surgery. The subjects completed a spatial learning task during which they learned destinations within virtual environments. During half the learning trials, focal electrical stimulation was given below the threshold that elicits an afterdischarge (i.e., a neuronal discharge that occurs after termination of the stimulus).

RESULTS: Entorhinal stimulation applied while the subjects learned locations of landmarks enhanced their subsequent memory of these locations: the subjects reached these landmarks more quickly and by shorter routes, as compared with locations learned without stimulation. Entorhinal stimulation also resulted in a resetting of the phase of the theta rhythm, as shown on the hippocampal electroencephalogram. Direct hippocampal stimulation was not effective. In this small series, no adverse events associated with the procedure were observed.

CONCLUSIONS: Stimulation of the entorhinal region enhanced memory of spatial information when applied during learning.

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Lessons learned by personal failures in aneurysm surgery: what went wrong, and why?

Knut Wester

Acta Neurochir (2009) 151:1013–1024


Purpose To analyse the intraoperative complications of a single neurosurgeon, with emphasis on devastating intraoperative incidents, and how they possibly could have been avoided.
Methods All the patients operated upon by the author between 1986 and 2002, i.e. 252 patients with 270 craniotomies for 294 aneurysms, were included. All intraoperative events that possibly could have influenced the clinical outcome were recorded prospectively.
Results A total of 16 cases (6.3% of all the patients) with serious intraoperative incidents were identified. In 11 cases (3.6% of all aneurysms), an intraoperative rupture occurred that was judged to have had mild to severe consequences for the patient. In another four patients (1.6% of all patients), all with unruptured, large aneurysms (>15 mm) of the carotid or middle cerebral arteries, a major vessel occlusion occurred inadvertently. In one patient with a large, unruptured MCA aneurysm, a clip slipped after the closure of the wound, causing a fatal intracerebral haemorrhage. These events had a severe impact on the clinical outcome. In retrospect, most of these incidents could, and should have, been avoided.

Conclusions It is recommended to start the training of new aneurysm surgeons on patients with small, supratentorial, unruptured aneurysms, followed by ruptured aneurysms in all other supratentorial locations than the anterior communicating artery (ACOM), which is the supratentorial location that should be the last step in the training of independent aneurysm surgeons.

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