title: Are the neural correlates of subitizing and estimation dissociable? An fNIRS investigation.
abstract: Human performance in visual enumeration tasks typically shows two distinct patterns as a function of set size. For small sets, usually up to 4 items, numerosity judgments are extremely rapid, precise and confident, a phenomenon known as subitizing. When this limit is exceeded and serial counting is precluded, exact enumeration gives way to estimation: performance becomes error-prone and more variable. Surprisingly, despite the importance of subitizing and estimation in numerical cognition, only few neuroimaging studies have examined whether the neural activity related to these two phenomena can be dissociated. In the present work, we used multi-channel near-infrared spectroscopy (fNIRS) to measure hemodynamic activity of the bilateral parieto-occipital cortex during a visual enumeration task. Participants had to judge the numerosity of dot arrays and indicate it by means of verbal response. We observed a different hemodynamic pattern in the parietal cortex, both in terms of amplitude modulation and temporal profile, for numerosities below and beyond the subitizing range. Crucially, the neural dissociation between subitizing and estimation was strongest at the level of right IPS. The present findings confirm that fNIRS can be successfully used to detect subtle temporal differences in hemodynamic activity and to produce inferences on the neural mechanisms underlying cognitive functions.
authors: Department of General Psychology, University of Padova, Italy. Electronic address: simone.cutini@unipd.it.
authors: Simone
authors: S
authors: Cutini
authors: Pietro
authors: P
authors: Scatturin
authors: Sara
authors: S
authors: Basso Moro
authors: Marco
authors: M
authors: Zorzi
mesh_terms: D000328:Adult; D001931:Brain Mapping; D002560:Cerebrovascular Circulation / Q000502:physiology; D003071:Cognition / Q000502:physiology*; D003627:Data Interpretation, Statistical; D005260:Female; D059907:Functional Neuroimaging / Q000379:methods*; D006454:Hemoglobins / Q000032:analysis / Q000378:metabolism; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007600:Judgment; D008297:Male; D008433:Mathematics; D010775:Photic Stimulation; D011597:Psychomotor Performance / Q000502:physiology*; D019265:Spectroscopy, Near-Infrared / Q000379:methods*; D055815:Young Adult
chemical_list: D006454:Hemoglobins
keywords: Estimation; Numerical cognition; Numerical magnitude processing; Subitizing; fNIRS