Morphological derivation overflow as a result of disruption of the left frontal aslant white matter tract Joanna Sierpowska a,b , Andreu Gabarrós c , Alejandro Fernandez-Coello c , Àngels Camins e , Sara Castañer e , Montserrat Juncadella d , Ruth de Diego-Balaguer a,b,f , Antoni Rodríguez-Fornells a,b,f,⇑ a Cognition and Brain Plasticity Group [Bellvitge Biomedical Research Institute – IDIBELL], 08097 L’Hospitalet de Llobregat, Barcelona, Spain b Dept. of Basic Psychology, Campus Bellvitge, University of Barcelona, 08097 L’Hospitalet de Llobregat, Barcelona, Spain c Hospital Universitari de Bellvitge (HUB), Neurosurgery Section, Campus Bellvitge, University of Barcelona – IDIBELL, 08097 L’Hospitalet de Llobregat, Barcelona, Spain d Hospital Universitari de Bellvitge (HUB), Neurology Section, Campus Bellvitge, University of Barcelona – IDIBELL, 08097 L’Hospitalet de Llobregat, Barcelona, Spain e Institut de Diagnòstic per la Imatge, Centre Bellvitge, Hospital Universitari de Bellvitge, 08907 L’Hospitalet de Llobregat, Barcelona, Spain f Catalan Institution for Research and Advanced Studies, ICREA, 08010 Barcelona, Spain article info Article history: Accepted 2 January 2015 Keywords: Frontal aslant tract Electrical Stimulation Mapping Diffusion tensor imaging Morphological derivation abstract The frontal aslant tract (FAT) is a recently described major connection between the preSMA and Broca’s area, whose functional role remains undefined. In this study we examined a patient presenting a morpho- logical overregularization strategy in a verb generation task during awake surgery. This specific language deficit coincided with brain tumor resection at the level of the left FAT. During the task execution the patient formed the non-existent verbs by applying a morphological derivation rule to the given nouns, instead of retrieving the appropriate verbs. DTI results confirmed left FAT damage. Neuropsychological follow-up showed that this morphological derivation impairment partially persisted after surgery, whereas the results on a wide spectrum of other language-related tasks remained satisfactory. Addition- ally, we compared the pre- and the post-operational fMRI activation maps for the same verb generation task. We discuss the potential role of the left FAT in the morphological derivation process and in lexical retrieval. Ó 2015 Elsevier Inc. All rights reserved. 1. Introduction The frontal aslant white-matter tract (FAT) has recently been described in detail using diffusion tensor imaging (DTI) in humans (Catani et al., 2012; Ford, McGregor, Case, Crosson, & White, 2010; Lawes et al., 2008; Oishi et al., 2008) and monkeys (Thiebaut de Schotten, Dell’Acqua, Valabregue, & Catani, 2012) but is one of the fasciculi whose functional role continues to be unresolved. The FAT is formed by the white-matter fiber bundles descending from the anterior cingulate cortex and the pre-supplementary motor area (preSMA) to Broca’s area (pars opercularis of the infe- rior frontal gyrus, BA 44). Considering its anatomical relation to these gray matter areas, it was hypothesized that this tract could be part of an extended network involved in initiating and coordi- nating complex eye, head and arm movements in reaching actions (Catani et al., 2012). In line with this proposal that the FAT is involved in specific motor functions, a recent ESM-case study by Martino and colleagues (Martino, de Lucas, Ibáñez-Plágaro, Valle- Folgueral, & Vázquez-Barquero, 2012) revealed that electrical stim- ulation of the right FAT caused Foix-Chavany-Marie syndrome, a rare type of suprabulbar palsy affecting the orofacial musculature. When we consider the possible functional role of the FAT in lan- guage processing it is the left hemisphere that should draw our focus. The main reason that suggests an important role of this white-matter pathway in language processing is the anatomical connectivity with regions involved in controlled lexical retrieval, syntactic processing, language production and monitoring. Broca’s area is known to be crucial for word production (Grodzinsky & Santi, 2008), controlled lexical retrieval (Novick, Trueswell, & Thompson-Schill, 2005; Schnur et al., 2009; http://dx.doi.org/10.1016/j.bandl.2015.01.005 0093-934X/Ó 2015 Elsevier Inc. All rights reserved. Abbreviations: FAT, frontal aslant tract; DTI, diffusion tensor imaging; ESM, Electrical Stimulation Mapping; fMRI, Functional Magnetic Resonance Imaging; TMS, Transcraneal Magnetic Stimulation; SMA, supplementary motor area; AF, arcuate fasciculus; CST, cortical spinal tract; ILF, inferior longitudinal fasciculus; IFOF, inferior fronto-occipital fasciculus; UF, uncinate fasciculus; ROI, region of interest. ⇑ Corresponding author at: Cognition and Brain Plasticity Unit, IDIBELL, Univer- sity of Barcelona (Basic Psychology Dept.), Campus Bellvitge, University of Barcelona, 08097 L’Hospitalet de Llobregat, Barcelona, Spain. Fax: +34 934024268. E-mail address: antoni.rodriguez@icrea.cat (A. Rodríguez-Fornells). Brain & Language 142 (2015) 54–64 Contents lists available at ScienceDirect Brain & Language journal homepage: www.elsevier.com/locate/b&l