title: The role of the right hemisphere in semantic control: A case-series comparison of right and left hemisphere stroke.
abstract: Semantic control processes guide conceptual retrieval so that we are able to focus on non-dominant associations and features when these are required for the task or context, yet the neural basis of semantic control is not fully understood. Neuroimaging studies have emphasised the role of left inferior frontal gyrus (IFG) in controlled retrieval, while neuropsychological investigations of semantic control deficits have almost exclusively focussed on patients with left-sided damage (e.g., patients with semantic aphasia, SA). Nevertheless, activation in fMRI during demanding semantic tasks typically extends to right IFG. To investigate the role of the right hemisphere (RH) in semantic control, we compared nine RH stroke patients with 21 left-hemisphere SA patients, 11 mild SA cases and 12 healthy, aged-matched controls on semantic and executive tasks, plus experimental tasks that manipulated semantic control in paradigms particularly sensitive to RH damage. RH patients had executive deficits to parallel SA patients but they performed well on standard semantic tests. Nevertheless, multimodal semantic control deficits were found in experimental tasks involving facial emotions and the 'summation' of meaning across multiple items. On these tasks, RH patients showed effects similar to those in SA cases - multimodal deficits that were sensitive to distractor strength and cues and miscues, plus increasingly poor performance in cyclical matching tasks which repeatedly probed the same set of concepts. Thus, despite striking differences in single-item comprehension, evidence presented here suggests semantic control is bilateral, and disruption of this component of semantic cognition can be seen following damage to either hemisphere.
authors.affiliation: Department of Psychology and York Neuroimaging Centre, University of York, UK. Electronic address: hannah.thompson@york.ac.uk.
authors.forename: Hannah E
authors.initials: HE
authors.lastname: Thompson
authors.affiliation: Department of Psychology and York Neuroimaging Centre, University of York, UK.
authors.forename: Lauren
authors.initials: L
authors.lastname: Henshall
authors.affiliation: Department of Psychology and York Neuroimaging Centre, University of York, UK.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Jefferies
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001921:Brain / Q000000981:diagnostic imaging; D016022:Case-Control Studies; D056344:Executive Function; D005260:Female; D007839:Functional Laterality / Q000502:physiology*; D006801:Humans; D007806:Language Disorders / Q000209:etiology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests; D012660:Semantics; D020521:Stroke / Q000150:complications* / Q000000981:diagnostic imaging / Q000473:pathology; D015898:Tomography Scanners, X-Ray Computed; D014786:Vision Disorders / Q000175:diagnosis / Q000209:etiology
keywords: Control; Right hemisphere; Semantic; Summation