Numerosity impairment in corticobasal syndrome.
OBJECTIVE
We assessed the representation of numerosity in corticobasal syndrome (CBS), a neurodegenerative condition affecting the parietal lobe.


METHODS
Patients judged whether a target numerosity (e.g., "3") falls between two bounding numerosities (e.g., "1" and "5"). We manipulated the format for representing numerosity (Arabic numerals or dot arrays), the size of the gap between the two bounding numerosities, the absolute magnitude of the numerosities, and the order for presenting the bounding numerosities. In a subset of patients with available imaging, we related performance to cortical atrophy using voxel-based morphometry.


RESULTS
CBS patients were significantly impaired overall (65.7% +/- 16.2 correct) compared to healthy seniors (96.6% +/- 2.4 correct), and required three times longer than controls to judge correct stimuli. This deficit was equally evident for Arabic numeral and dot array formats. Controls were significantly slower with smaller gaps than larger gaps, consistent with the greater challenge distinguishing between numerosities that are more similar to each other than very different numerosities. However, CBS patients were equally slow and inaccurate for all gap sizes. Controls also were significantly slower with larger numerosities than smaller numerosities, but CBS patients were equally slow and inaccurate with all numerosity magnitudes. Voxel-based morphometry revealed significant cortical atrophy in parietal and frontal regions in CBS compared to controls, including the intraparietal sulcus.


CONCLUSIONS
These observations are consistent with the claim that the representation of numerosity is degraded in CBS.
Koss
Shira
S
Department of Neurology, University of Pennsylvania, PA, USA.
Clark
Robin
R
Vesely
Luisa
L
Weinstein
Jessica
J
Powers
Chivon
C
Richmond
Lauren
L
Farag
Christine
C
Gross
Rachel
R
Liang
Tsao-Wei
TW
Grossman
Murray
M
D000368:Aged; D001479:Basal Ganglia / Q000503:physiopathology*; D001930:Brain Injuries / Q000150:complications* / Q000473:pathology*; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000503:physiopathology*; D003072:Cognition Disorders / Q000209:etiology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008433:Mathematics; D008875:Middle Aged; D009483:Neuropsychological Tests; D010364:Pattern Recognition, Visual / Q000502:physiology; D010775:Photic Stimulation / Q000379:methods; D011930:Reaction Time / Q000502:physiology; D013028:Space Perception / Q000502:physiology; D018709:Statistics, Nonparametric