New insights into neurocognition provided by brain mapping: visuospatial cognition

The last century has shown a tremendous amount of progress in neurosurgery going from blind and frequently lethal brain surgery to intraoperative electrical stimulations (IES) for a functional living (in vivo) brain mapping. IES combined with good neuropsychological assessments allows a much better mapping of brain functions, resulting in a clear definition of the borders of a brain resection. Thus, the risks of definitive postoperative neurological deficits can be significantly decreased. Nevertheless, the difficulty to assess nonlan- guage cognitive functions during the opera- tions has led to an underestimation of the func- tional importance of the right hemisphere. An overview of the historical context of brain stimulations, with a special focus on re- cent advancements in visuospatial mapping, constitutes the subject matter of this chapter. We first describe the invention of brain stimu- lation and its application to the neurosurgical practice. We then survey the importance of the right hemisphere for spatial processing. Finally, we review the new insights into visuospatial cognition provided by IES and lesion-based brain mapping. Hopefully, the ideas expressed in this chapter will encourage the practice of awake brain surgery of the right hemisphere and emphasize the importance to assess visuo- spatial functions with IES.