title: Re-assessing acalculia: Distinguishing spatial and purely arithmetical deficits in right-hemisphere damaged patients.
abstract: Arithmetical deficits in right-hemisphere damaged patients have been traditionally considered secondary to visuo-spatial impairments, although the exact relationship between the two deficits has rarely been assessed. The present study implemented a voxelwise lesion analysis among 30 right-hemisphere damaged patients and a controlled, matched-sample, cross-sectional analysis with 35 cognitively normal controls regressing three composite cognitive measures on standardized numerical measures. The results showed that patients and controls significantly differ in Number comprehension, Transcoding, and Written operations, particularly subtractions and multiplications. The percentage of patients performing below the cutoffs ranged between 27% and 47% across these tasks. Spatial errors were associated with extensive lesions in fronto-temporo-parietal regions -which frequently lead to neglect- whereas pure arithmetical errors appeared related to more confined lesions in the right angular gyrus and its proximity. Stepwise regression models consistently revealed that spatial errors were primarily predicted by composite measures of visuo-spatial attention/neglect and representational abilities. Conversely, specific errors of arithmetic nature linked to representational abilities only. Crucially, the proportion of arithmetical errors (ranging from 65% to 100% across tasks) was higher than that of spatial ones. These findings thus suggest that unilateral right hemisphere lesions can directly affect core numerical/arithmetical processes, and that right-hemisphere acalculia is not only ascribable to visuo-spatial deficits as traditionally thought.
authors.affiliation: IRCCS San Camillo Hospital Foundation, Neuropsychology Unit, Lido-Venice, Italy. Electronic address: silviabenavides@gmail.com.
authors.forename: S
authors.initials: S
authors.lastname: Benavides-Varela
authors.affiliation: IRCCS San Camillo Hospital Foundation, Neuropsychology Unit, Lido-Venice, Italy.
authors.forename: D
authors.initials: D
authors.lastname: Piva
authors.affiliation: IRCCS San Camillo Hospital Foundation, Neuropsychology Unit, Lido-Venice, Italy; Neuroscience Department, University of Padova, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Burgio
authors.affiliation: IRCCS San Camillo Hospital Foundation, Neuropsychology Unit, Lido-Venice, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Passarini
authors.affiliation: Neuroscience Department, University of Padova, Italy; Padova Hospital, Neuroradiology Unit, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Rolma
authors.affiliation: IRCCS San Camillo Hospital Foundation, Neuropsychology Unit, Lido-Venice, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Meneghello
authors.affiliation: IRCCS San Camillo Hospital Foundation, Neuropsychology Unit, Lido-Venice, Italy; Neuroscience Department, University of Padova, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Semenza
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003430:Cross-Sectional Studies; D060705:Dyscalculia / Q000000981:diagnostic imaging / Q000209:etiology* / Q000503:physiopathology; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008433:Mathematics; D008875:Middle Aged; D009483:Neuropsychological Tests; D010468:Perceptual Disorders / Q000000981:diagnostic imaging / Q000209:etiology* / Q000503:physiopathology; D011340:Problem Solving / Q000502:physiology*; D013028:Space Perception / Q000502:physiology*; D020521:Stroke / Q000150:complications* / Q000000981:diagnostic imaging / Q000503:physiopathology
keywords: Acalculia; Arithmetical errors; Calculation; Right hemisphere; Spatial errors