Mental number representation as assessed by the number bisection task : a combined reaction time and fMRI study

In this combined reaction time (RT) and functional Magnetic Resonance Imaging (fMRI) study, the number bisection task as a verification paradigm was used to examine whether this task only relies on a quantitative representation of number magnitude as postulated by Dehaene and Cohen (1997) or perhaps also on other number representations and processes. Furthermore, the localisation of the different activation areas found in this study was compared with the specifications made in the triple-code model by Dehaene and Cohen (1995, 1997; Dehaene, 1992) and other findings from the literature on brain activation in number processing and calculation tasks. The reaction time results clearly showed that not only effects related to number magnitude, but also multiplication tables and parity play a role in the number bisection task as a verification paradigm. Number triplets that belong to a multiplication table like 3_6_9 and 63_72_81 were responded to faster than 2_5_8 and 62_71_80. It was more difficult to reject bisectable triplets like 6_9_14 (where a numerical middle exists, namely 10) than 6_9_13 (where the numerical middle is 9.5). This effect is assumed to be related to congruent parity of the two outer numbers. The fMRI results were not as easy to interpret as the behavioural data. For triplets linked to quantity representation, strong activation of the whole number processing network, in particular in the region of the intraparietal sulcus, could be found. This effect remained stable for masked and non-masked conditions. However, both for multiplicativity and parity, there was a discrepancy between the unequivocal behavioural data and fMRI results. The expected activation of verbal areas e.g. in the perisylvian language areas was not found in this study. Only the assumption of a left-hemispheric multiplication fact storage could be supported. Also for parity there were few systematic differences, in contrast to the reaction time results. However, the suggestion of parity decisions linked to visual identification area can tentatively be supported. Further research is necessary to clarify the last two points, in particular.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2005

Author dc:creator

• Geppert, Barbara Elisabeth

Contributors dc:contributor

• Willmes-von Hinckeldey, Klaus

• info:eu-repo/classification/ddc/610
• Medizin
• Zahlenverarbeitung
• fMRT
• Neuropsychologie

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

eng

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123500%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:61886