Vol.:(0123456789) 1 3 Brain Topogr DOI 10.1007/s10548-017-0574-y ORIGINAL PAPER Left Spatial Neglect Evoked by Electrostimulation of the Right Inferior Fronto-occipital Fasciculus Guillaume Herbet 1,2,3  · Yordanka N. Yordanova 2,4  · Hugues Dufau 1,2,3   Received: 26 February 2017 / Accepted: 17 June 2017 © Springer Science+Business Media, LLC 2017 anatomical landmark to identify the IFOF. Disconnection analyses confrmed the high probability of IFOF discon- nection during neglect-related stimulations. Taken together, our fndings provide support for a role of the right IFOF in spatial cognition. We discuss these results in the light of the newly discovered fronto-parietal connections of the IFOF and suggest that some subcomponents of this tract might be involved in between-system integration within the attention network. Keywords Spatial neglect · Spatial cognition · Spatial attention · White matter tracts · Inferior fronto-occipital fasciculus Introduction Unilateral spatial neglect (i.e. an inability to pay attention to events on the contralateral side) is a debilitating neuro- logical condition that may occur after lesion of many cor- tical territories of the brain, especially in the right hemi- sphere (see Molenberghs et al. 2012 for a meta-analysis). Decades of neuropsychological studies have indeed pin- pointed a plethora of cortical areas associated with spatial neglect, including mainly parietal (angular gyrus, supra- marginal gyrus, superior parietal lobule and temporo-pari- etal junction) (Heilman et al. 1983; Vallar and Perani 1986; Mort et al. 2003; Chechlacz et al. 2010; Karnath et al. 2011; Thiebaut de Schotten et al. 2014; Vallar et al. 2014) temporal (superior and middle temporal gyri) (Samuelsson et al. 1997; Karnath et al. 2001, 2004; Roux et al. 2011) and posterior frontal areas (inferior and middle frontal gyri, premotor cortex) (Binder et al. 1992; Husain and Kennard 1996; Committeri et al. 2007; Verdon et al. 2010; Ren- gachary et al. 2011). As spatial neglect is widely viewed Abstract Left spatial neglect is a debilitating condition that may occur after lesion of many cortical territories in the right hemisphere. At the subcortical level, the sec- ond and third branches of the right superior longitudinal fasciculus has emerged as strong candidates in convey- ing information exchanges within the attention networks as their damage has been repeatedly associated to spa- tial neglect in neuromodulation and neuropsychological studies. Yet, a few cases of spatial neglect have also been observed after damage to the right inferior fronto-occipital fasciculus (IFOF), suggesting an involvement of this asso- ciative connectivity in spatial attention. Here we report three rare cases of patients having undergone a wide-awake craniotomy with direct electrostimulation for right tempo- ral glioma. An intraoperative monitoring of spatial cogni- tion was performed using a standard line bisection task. Responsive cortical sites were observed in the supramar- ginal gyrus and the posterior part of both the middle and superior temporal gyri. Critically, in all patients, signifcant rightward deviations were observed by the stimulation of the white matter deep in the temporal lobe, along the roof of the inferior horn of the lateral ventricle—a well-known * Guillaume Herbet Guillaume.herbet@gmail.com 1 Department of Neurosurgery, Gui de Chauliac Hospital, Montpellier University Medical Center, 80, Avenue Augustin Fliche, 34295 Montpellier, France 2 Institute for Neuroscience of Montpellier, INSERM 1051, Team “Plasticity of Central Nervous System, Human Stem Cells and Glial Tumors”, Saint Eloi Hospital, Montpellier University Medical Center, 34091 Montpellier, France 3 University of Montpellier, 34967 Montpellier, France 4 Department of Neurosurgery, ‘Percy’ Military Hospital, 92140 Clamart, France