Introduction Gatev et al., 2006; Hammond et al., 2007; Uhlhaas and Singer, 2006 Brown et al., 2004; Hashimoto et al., 2003 MacKinnon et al., 2005 Ashby et al., 1999, 2001 Moro et al. (2002) Chen et al. (2007) Timmermann et al. (2004) Fogelson et al., 2005 Hammond et al., 2007 Goldberg et al., 2004; Raz et al., 1996, 2000 Giovannoni et al., 1999; Rabey et al., 2002 Chen et al., 2006a Materials and methods Patients and surgery Table 1 Chen et al., 2007 Hariz et al., 2003 n p t Protocol Table 1 Temperli et al., 2003 Task Chen et al., 2006a, 2007 Table 1 Statistics accordingly n n Chen et al., 2006a, 2007 p Results Materials and methods F [3,48] p F [3,48] p F [1,16] p F [1,16] p Fig. 1 F [1,16] p F [1.9,32.8] p F [3,48] p F [1,16] p F [1,16] p Fig. 2 F [1,16] p t p Discussion Chen et al., 2007; Fogelson et al., 2005; Moro et al., 2002 Timmermann et al., 2004 Chen et al., 2006a, 2007 Chen et al., 2007; Fogelson et al., 2005 Hammond et al., 2007 Giovannoni et al., 1999; Shimoyama et al., 1990 Hinton et al., 2007 Sheridan et al., 1987 Hausdorff et al., 2003 Timmermann et al. (2004) Liu et al., 2002a Alonso-Frech et al., 2006 Chen et al., 2006b; Liu et al., 2002b; Silberstein et al., 2003 l De Letter et al., 2006 Abel et al., 2003 Gatev et al., 2006; Uhlhaas and Singer, 2006; Hammond et al., 2007 Fogelson et al., 2006