Abstract
As a test of the idea of a common brain system responsible for representing all prothetic dimensions, schizophrenic patients and healthy participants took part in a line bisection task and two visual temporal bisection tasks, one using durations from 1 to 4 s and another using 30 s long specially designed stimuli (aging faces). Against expectations, schizophrenics showed better precision (smaller variable error) both in line bisection and the aging faces temporal task than healthy controls. Moreover, patients also showed less bias (smaller constant error) than controls in the aging faces task. This increased precision correlated with degree of severity of schizophrenia. Although no group differences were found in the temporal task with shorter intervals, both variable and constant error measures correlated marginally with severity of schizophrenia, also in the direction of smaller error in more severe cases. Thus, overall, spatial and temporal tasks behaved similarly across groups. However, bias and precision indexes did not covary across the three tasks when correlations where computed over the whole set of participants in the present study. The results thus provide mixed support for a common system behind spatial and temporal processing and point toward the need of developing a more nuanced view of magnitude representation in the mind/brain.
Highlights
How are abstract magnitudes, such as space, time, and numerosity, represented and processed? Do we use the same neuronal substrate for all dimensions? According to the highly influential A Theory of Magnitude (ATOM) proposed by Walsh (2003), prothetic dimensions, such as space, time, and numerosity, are processed by a common brain system located in the inferior parietal cortex
As in Experiment 1, we found no pseudoneglect in Line Bisection, neither in the control nor schizophrenic groups
To Experiment 1, we found a bias toward the “end” side of the time interval in the Aging Faces task, but this time only in controls: Schizophrenic patients showed no bias
Summary
How are abstract magnitudes, such as space, time, and numerosity, represented and processed? Do we use the same neuronal substrate for all dimensions? According to the highly influential A Theory of Magnitude (ATOM) proposed by Walsh (2003), prothetic dimensions (those which can be experienced as “more than” or “less than”), such as space, time, and numerosity, are processed by a common brain system located in the inferior parietal cortex. Recent years have seen an increase in the interest on dimensional concepts (magnitudes such as space, time, pitch, evaluation, or social power; for reviews see Bueti and Walsh, 2009; Landau et al, 2010; Santiago et al, 2011; Bonato et al, 2012). Discriminating past from future times is faster if the “past” response is given with the left hand and the “future” response with the right hand than if the opposite mapping is used (Santiago et al, 2007) This pattern of interaction has most often been interpreted as revealing the use of a “mental time line,” a spatial representation underlying the processing of time. Analogous evidence have been used to support a spatial basis for understanding numerical magnitude (Dehaene et al, 1993), pitch (Rusconi et al, 2006), or social power (Schubert, 2005)
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