Notations-, Aufgaben- und Strategiespezifität in der Zahlenverarbeitung : eine fMRT-Studie

Introduction: The anatomo-functional model of Dehaene and Cohen (1995) assumes a number processing network of different number representations. Most importantly, the inferior parietal lobule contains an abstract semantic magnitude representation. The model does not consider notation-, task- or strategy-specific differences. However, the SNARC effect can be observed for number words in a parity task but not in a phoneme detection task, while for Arabic numerals the effect occurs in both tasks. Fias et al. (1996) proposed a model considering this task- and notation-specificity: besides a central semantic route, they suggest an additional asemantic route for number words in a non-semantic task as the phoneme detection task. We investigated whether this notation- and task-specificity is reflected in the functional activation. Finally, we examined individual strategies in number processing. Kosslyn (1999) has claimed that the same task can be solved by different strategies resulting in different activation patterns (for number processing see also Burbaud et al., 1999). Methods: In a fMRI study we investigated 20 healthy volunteers in a phoneme detection and a parity task in five notations (positive and negative Arabic numerals, Roman numbers, number words, dot patterns). After the investigation subjects were asked about their individual solution strategy. Results: Notation-specificity: Less familiar notations (Roman numbers, dot patterns) produced stronger activation than familiar notations (Arabic numbers, number words), especially in superior parietal and frontal areas. Symbolic notations produced more activation in the occipito-temporal junction, involved in object recognition. Number words were the only notation producing activation maxima in Broca’s area in both tasks. Task-specificity: Activation in verbal as well as in number specific areas was stronger for the phoneme task. In contrast, the occipito-temporal junction was more activated in the parity task. Strategy-specificity: Participants reporting a verbal strategy produced more frontal and parietal activation, whereas subjects using a visual strategy had more occipital and temporal activation along the ventral pathway. Conclusion: Functional activation in number processing is modulated by notation, task and individual strategy. The model of Dehaene and Cohen is generally supported with respect to the postulated cortical network. However, notation-, task- and strategy-specific modulations are not considered. The model of Fias et al. is confirmed in its assumption of notation- and task-specific processing. However, the inferior parietal activation for number words in the phoneme detection task is not consistent with the model assumptions. Finally, individual strategies may lead to different activation patterns even in simple tasks questioning the conclusiveness of functional imaging studies.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2003

Author dc:creator

• Dambeck, Nina

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

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-121139%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:59344