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Neuropsychologia 2021 Apr 12:107849. Epub 2021 Apr 12.

Educational Neuroscience, Institute of Psychology, University of Graz, Austria.

Single-digit multiplications are thought to be associated with different levels of interference because they show different degrees of feature overlap (i.e., digits) with previously learnt problems. Recent behavioral and neuroimaging studies provided evidence for this interference effect and showed that individual differences in arithmetic fact retrieval are related to differences in sensitivity to interference (STI). The present study investigated whether and to what extent competence-related differences in STI and its neurophysiological correlates can be modulated by a multiplication facts training. Participants were 23 adults with high and 23 adults with low arithmetic competencies who underwent a five-day multiplication facts training in which they intensively practiced sets of low- and high-interfering multiplication problems. In a functional magnetic resonance imaging (fMRI) test session after the training, participants worked on a multiplication verification task that comprised trained and untrained problems. Analyses of the behavioral data revealed an interference effect only in the low competence group, which could be reduced but not resolved by training. On the neural level, competence-related differences in the interference effect were observed in the left supramarginal gyrus (SMG), showing activation differences between low- and high-interfering problems only in the low competent group. These findings support the idea that individuals' low arithmetic skills are related to the development of insufficient memory representations because of STI. Further, our results indicate that a short training by drill (i.e., learning associations between operands and solutions) was not fully effective to resolve existing interference effects in arithmetic fact knowledge.

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http://dx.doi.org/10.1016/j.neuropsychologia.2021.107849 | DOI Listing |

April 2021

J Intell 2021 Feb 17;9(1). Epub 2021 Feb 17.

Educational Neuroscience, University of Graz, Universitätsplatz 2, 8010 Graz, Austria.

Mathematical creativity is perceived as an increasingly important aspect of everyday life and, consequently, research has increased over the past decade. However, mathematical creativity has mainly been investigated in children and adolescents so far. Therefore, the first goal of the current study was to develop a mathematical creativity measure for adults (MathCrea) and to evaluate its reliability and construct validity in a sample of 100 adults. The second goal was to investigate how mathematical creativity is related to intelligence, mathematical competence, and general creativity. The MathCrea showed good reliability, and confirmatory factor analysis confirmed that the data fitted the assumed theoretical model, in which fluency, flexibility, and originality constitute first order factors and mathematical creativity a second order factor. Even though intelligence, mathematical competence, and general creativity were positively related to mathematical creativity, only numerical intelligence and general creativity predicted unique variance of mathematical creativity. Additional analyses separating quantitative and qualitative aspects of mathematical creativity revealed differential relationships to intelligence components and general creativity. This exploratory study provides first evidence that intelligence and general creativity are important predictors for mathematical creativity in adults, whereas mathematical competence seems to be not as important for mathematical creativity in adults as in children.

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http://dx.doi.org/10.3390/jintelligence9010010 | DOI Listing |

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8006241 | PMC |

February 2021

J Exp Psychol Learn Mem Cogn 2021 Feb 4. Epub 2021 Feb 4.

Parenting and Special Education Research Unit.

There is broad consensus on the assumption that adults solve single-digit multiplication problems almost exclusively by fact retrieval from memory. In contrast, there has been a long-standing debate on the cognitive processes involved in solving single-digit addition problems. This debate has evolved around two theoretical accounts. Proponents of a fact-retrieval account postulate that these are also solved through fact retrieval, whereas proponents of a compacted-counting account propose that solving very small additions (with operands between 1 and 4) involves highly automatized and unconscious compacted counting. In the present electroencephalography (EEG) study, we put these two accounts to the test by comparing neurophysiological correlates of solving very small additions and multiplications. Forty adults worked on an arithmetic production task involving all (nontie) single-digit additions and multiplications. Afterward, participants completed trial-by-trial strategy self-reports. In our EEG analyses, we focused on induced activity (event-related synchronization/desynchronization, ERS/ERD) in three frequency bands (theta, lower alpha, upper alpha). Across all frequency bands, we found higher evidential strength for similar rather than different neurophysiological processes accompanying the solution of very small addition and multiplication problems. In the alpha bands, evidence for similarity was even stronger when operand-1-problems were excluded. In two additional analyses, we showed that ERS/ERD can differentiate between self-reported problem-solving strategies (retrieval vs. procedure) and between very small × 1 and + 1 problems, demonstrating its high sensitivity to cognitive processes in arithmetic. The present findings support a fact-retrieval account, suggesting that both very small additions and multiplications are solved through fact retrieval. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

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http://dx.doi.org/10.1037/xlm0000982 | DOI Listing |

February 2021

Front Hum Neurosci 2020 27;14:116. Epub 2020 Mar 27.

Educational Neuroscience, Institute of Psychology, University of Graz, Graz, Austria.

Previously conducted structural magnetic resonance imaging (MRI) studies on the neuroanatomical correlates of mathematical abilities and competencies have several methodological limitations. Besides small sample sizes, the majority of these studies have employed voxel-based morphometry (VBM)-a method that, although it is easy to implement, has some major drawbacks. Taking this into account, the current study is the first to investigate in a large sample of typically developed adults the associations between mathematical abilities and variations in brain surface structure by using surface-based morphometry (SBM). SBM is a method that also allows the investigation of brain morphometry by avoiding the pitfalls of VBM. Eighty-nine young adults were tested with a large battery of psychometric tests to measure mathematical competencies in four different areas: (1) simple arithmetic; (2) complex arithmetic; (3) higher-order mathematics; and (4) numerical intelligence. Also, we asked participants for their mathematics grades for their final school exams. Inside the MRI scanner, we collected high-resolution T1-weighted anatomical images from each subject. SBM analyses were performed with the computational anatomy toolbox (CAT12) and indices for cortical thickness, for cortical surface complexity, for gyrification, and sulcal depth were calculated. Further analyses revealed associations between: (1) the cortical surface complexity of the right superior temporal gyrus and numerical intelligence; (2) the depth of the right central sulcus and adults' ability to solve complex arithmetic problems; and (3) the depth of the left parieto-occipital sulcus and adults' higher-order mathematics competence. Interestingly, no relationships with previously reported brain regions were observed, thus, suggesting the importance of similar research to confirm the role of the brain regions found in this study.

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http://dx.doi.org/10.3389/fnhum.2020.00116 | DOI Listing |

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7118203 | PMC |

March 2020

Neuropsychologia 2020 04 19;141:107405. Epub 2020 Feb 19.

Section of Educational Neuroscience, Institute of Psychology, University of Graz, Austria. Electronic address:

Behavioural and neuroimaging studies have recently demonstrated that symbolic numerical order processing (i.e., deciding whether numbers are in an increasing/decreasing sequence or not) and symbolic numerical magnitude processing (e.g., deciding which of two numerals is larger) engage different cognitive mechanisms and brain regions. Because of this dissociation, growing interest has emerged to better understand the neurocognitive mechanisms of symbolic numerical order processing and their relationship to individual differences in arithmetic performance. In the present functional imaging work, we further investigated this link in a group of thirty children (7.2-10.25 years) from elementary school, who completed a symbolic numerical order verification (are the numbers going up? e.g., 1-2-3) and a symbolic numerical magnitude comparison task (which is the larger number? e.g., 5-7) inside the scanner, as well as an arithmetic fluency test outside the scanner. Behavioural results demonstrated the unique role of numerical order to predict children's arithmetic skills and confirmed its mediating power to explain the association between numerical magnitude and arithmetic performance. Imaging results showed a significant association between numerical order and arithmetic in the intersection of the right inferior frontal gyrus and insula, as well as the posterior middle temporal gyrus. An age-dependent change in brain activity was found in the left intraparietal sulcus. These findings solidify the developmental importance of symbolic numerical order processing in children and provide new evidence that the semantic control network mediates the relationship with arithmetic performance.

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http://dx.doi.org/10.1016/j.neuropsychologia.2020.107405 | DOI Listing |

April 2020

Hum Brain Mapp 2020 04 18;41(6):1591-1610. Epub 2019 Dec 18.

Numerical Cognition Laboratory, Department of Psychology and Brain and Mind Institute, The University of Western Ontario, London, Ontario, Canada.

How are number symbols (e.g., Arabic digits) represented in the brain? Functional resonance imaging adaptation (fMRI-A) research has indicated that the intraparietal sulcus (IPS) exhibits a decrease in activation with the repeated presentation of the same number, that is followed by a rebound effect with the presentation of a new number. This rebound effect is modulated by the numerical ratio or difference between presented numbers. It has been suggested that this ratio-dependent rebound effect is reflective of a link between the symbolic numerical representation system and an approximate magnitude system. Experiment 1 used fMRI-A to investigate an alternative hypothesis: that the rebound effect observed in the IPS is related to the ordinal relationships between symbols (e.g., 3 comes before 4; C after B). In Experiment 1, adult participants exhibited the predicted distance-dependent parametric rebound effect bilaterally in the IPS for number symbols during a number adaptation task, however, the same effect was not found anywhere in the brain in response to letters. When numbers were contrasted with letters (numbers > letters), the left intraparietal lobule remained significant. Experiment 2 demonstrated that letter stimuli used in Experiment 1 generated a behavioral distance effect during an active ordinality task, despite the lack of a neural distance effect using fMRI-A. The current study does not support the hypothesis that general ordinal mechanisms underpin the neural parametric recovery effect in the IPS in response to number symbols. Additional research is needed to further our understanding of mechanisms underlying symbolic numerical representation in the brain.

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http://dx.doi.org/10.1002/hbm.24897 | DOI Listing |

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7268023 | PMC |

April 2020

Cortex 2019 11 19;120:375-393. Epub 2019 Jul 19.

Educational Neuroscience, Institute of Psychology, University of Graz, Austria. Electronic address:

Single-digit multiplications are mainly solved by memory retrieval. However, these problems are also prone to errors due to systematic interference (i.e., co-activation of interconnected but incorrect solutions). Semantic control processes are crucial to overcome this type of interference and to retrieve the correct information. Previous research suggests the importance of several brain regions such as the left inferior frontal cortex and the intraparietal sulcus (IPS) for semantic control. But, this evidence is mainly based on tasks measuring interference during the processing of lexico-semantic information (e.g., pictures or words). Here, we investigated whether semantic control during arithmetic problem solving (i.e., multiplication fact retrieval) draws upon similar or different brain mechanisms as in other semantic domains (i.e., lexico-semantic). The brain activity of 46 students was measured with fMRI while participants performed an operand-related-lure (OR) and a picture-word (PW) task. In the OR task participants had to verify the correctness of a given solution to a single-digit multiplication. Similarly, in the PW task, participants had to judge whether a presented word matches the concept displayed in a picture or not. Analyses showed that resolving interference in these two tasks modulates the activation of a widespread fronto-parietal network (e.g., left/right IFG, left insula lobe, left IPS). Importantly, conjunction analysis revealed a neural overlap in the left inferior frontal gyrus (IFG) pars triangularis and left IPS. Additional Bayesian analyses showed that regions that are thought to store lexico-semantic information (e.g., left middle temporal gyrus) did not show evidence for an arithmetic interference effect. Overall, our findings not only indicate that semantic control plays an important role in arithmetic problem solving but also that it is supported by common brain regions across semantic domains. Additionally, by conducting Bayesian analysis we confirmed the hypothesis that the semantic control network contributes differently to semantic tasks of various domains.

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http://dx.doi.org/10.1016/j.cortex.2019.06.007 | DOI Listing |

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6853793 | PMC |

November 2019

Brain Res 2019 07 2;1714:147-157. Epub 2019 Mar 2.

Parenting and Special Education Research Unit, KU Leuven, Leopold Vanderkelenstraat 32, Box 3765, 3000 Leuven, Belgium.

Within children's multiplication fact retrieval, performance can be influenced by various effects, such as the well-known problem size effect (i.e., smaller problems are solved faster and more accurately) and the more recent interference effect (i.e., the quality of memory representations of problems depends on previously learned problems; the more similar a problem is to a previously learned one, the more proactive interference impacts on storing in long-term-memory). This interference effect has been observed in behavioral studies, and determines a substantial part of performance beyond problem size. Unlike the problem size effect, the neural basis of the interference effect in children has not been studied. To better understand the underpinning mechanisms behind children's arithmetic fact retrieval, we aimed to investigate the neural basis of both effects in typically developing children. Twenty-four healthy 9- to 10-year-olds took part in a behavioral and fMRI scanning session, during which multiplication items had to be solved. Data were analyzed by manipulating problem size and interference level in a 2 × 2 factorial design. Concurring with previous studies, our results reveal clear behavioral effects of problem size and interference, with larger and high interfering items being solved significantly slower. On the neural level, a clear problem size effect was observed in a fronto-parietal and temporal network. The interference effect, however, was not detected; no clear neural distinctions were observed between low and high interfering items.

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http://dx.doi.org/10.1016/j.brainres.2019.03.002 | DOI Listing |

July 2019

Acta Psychol (Amst) 2019 Feb 22;193:30-41. Epub 2018 Dec 22.

Educational Neuroscience, Institute of Psychology, University of Graz, Austria.

Recent findings have demonstrated that numerical order processing (i.e., the application of knowledge that numbers are organized in a sequence) constitutes a unique and reliable predictor of arithmetic performance. The present work investigated two central questions to further our understanding of numerical order processing and its relationship to arithmetic. First, are numerical order sequences processed without conscious monitoring (i.e., automatically)? Second, are automatic and intentional ordinal processing differentially related to arithmetic performance? In the first experiment, adults completed a novel ordinal congruity task. Participants had to evaluate whether number triplets were arranged in a correct (e.g., ) physical order or not (e.g., ). Results of this experiment showed that participants were faster to decide that the physical size of ascending numbers was in-order when the physical and numerical values were congruent compared to when they were incongruent (i.e., congruency effect). In the second experiment, a new group of participants was asked to complete an ordinal congruity task, an ordinal verification task (i.e., are the number triplets in a correct order or not) and an arithmetic fluency test. Results of this experiment revealed that the automatic processing of ascending numerical order is influenced by the numerical distance of the numbers. Correlation analysis further showed that only reaction time measures of the intentional ordinal verification task were associated with arithmetic performance. While the findings of the present work suggest that ascending numerical order is processed automatically, the relationship between numerical order processing and arithmetic appears to be limited to the intentional manipulation of numbers. The present findings show that the mental engagement of verifying the order of numbers is a crucial factor for explaining the link between numerical order processing and arithmetic performance.

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http://dx.doi.org/10.1016/j.actpsy.2018.12.001 | DOI Listing |

February 2019

Neuroimage 2018 05 11;172:718-727. Epub 2018 Feb 11.

Educational Neuroscience, Institute of Psychology, University of Graz, Austria.

In the development of math ability, a large variability of performance in solving simple arithmetic problems is observed and has not found a compelling explanation yet. One robust effect in simple multiplication facts is the problem size effect, indicating better performance for small problems compared to large ones. Recently, behavioral studies brought to light another effect in multiplication facts, the interference effect. That is, high interfering problems (receiving more proactive interference from previously learned problems) are more difficult to retrieve than low interfering problems (in terms of physical feature overlap, namely the digits, De Visscher and Noël, 2014). At the behavioral level, the sensitivity to the interference effect is shown to explain individual differences in the performance of solving multiplications in children as well as in adults. The aim of the present study was to investigate the individual differences in multiplication ability in relation to the neural interference effect and the neural problem size effect. To that end, we used a paradigm developed by De Visscher, Berens, et al. (2015) that contrasts the interference effect and the problem size effect in a multiplication verification task, during functional magnetic resonance imaging (fMRI) acquisition. Forty-two healthy adults, who showed high variability in an arithmetic fluency test, participated in our fMRI study. In order to control for the general reasoning level, the IQ was taken into account in the individual differences analyses. Our findings revealed a neural interference effect linked to individual differences in multiplication in the left inferior frontal gyrus, while controlling for the IQ. This interference effect in the left inferior frontal gyrus showed a negative relation with individual differences in arithmetic fluency, indicating a higher interference effect for low performers compared to high performers. This region is suggested in the literature to be involved in resolution of proactive interference. Besides, no correlation between the neural problem size effect and multiplication performance was found. This study supports the idea that the interference due to similarities/overlap of physical traits (the digits) is crucial in memorizing arithmetic facts and in determining individual differences in arithmetic.

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http://dx.doi.org/10.1016/j.neuroimage.2018.01.060 | DOI Listing |

May 2018

Neuroimage 2017 10 8;159:430-442. Epub 2017 Aug 8.

Department of Psychology & Human Development, Peabody College, Vanderbilt University, 230 Appleton Place, Nashville, TN, 37203, USA. Electronic address:

Nonsymbolic numerical comparison task performance (whereby a participant judges which of two groups of objects is numerically larger) is thought to index the efficiency of neural systems supporting numerical magnitude perception, and performance on such tasks has been related to individual differences in math competency. However, a growing body of research suggests task performance is heavily influenced by visual parameters of the stimuli (e.g. surface area and dot size of object sets) such that the correlation with math is driven by performance on trials in which number is incongruent with visual cues. Almost nothing is currently known about whether the neural correlates of nonsymbolic magnitude comparison are also affected by visual congruency. To investigate this issue, we used functional magnetic resonance imaging (fMRI) to analyze neural activity during a nonsymbolic comparison task as a function of visual congruency in a sample of typically developing high school students (n = 36). Further, we investigated the relation to math competency as measured by the preliminary scholastic aptitude test (PSAT) in 10th grade. Our results indicate that neural activity was modulated by the ratio of the dot sets being compared in brain regions previously shown to exhibit an effect of ratio (i.e. left anterior cingulate, left precentral gyrus, left intraparietal sulcus, and right superior parietal lobe) when calculated from the average of congruent and incongruent trials, as it is in most studies, and that the effect of ratio within those regions did not differ as a function of congruency condition. However, there were significant differences in other regions in overall task-related activation, as opposed to the neural ratio effect, when congruent and incongruent conditions were contrasted at the whole-brain level. Math competency negatively correlated with ratio-dependent neural response in the left insula across congruency conditions and showed distinct correlations when split across conditions. There was a positive correlation between math competency in the right supramarginal gyrus during congruent trials and a negative correlation in the left angular gyrus during incongruent trials. Together, these findings support the idea that performance on the nonsymbolic comparison task relates to math competency and ratio-dependent neural activity does not differ by congruency condition. With regards to math competency, congruent and incongruent trials showed distinct relations between math competency and individual differences in ratio-dependent neural activity.

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http://dx.doi.org/10.1016/j.neuroimage.2017.08.023 | DOI Listing |

October 2017

Neuroimage 2017 06 22;153:16-27. Epub 2017 Mar 22.

Numerical Cognition Laboratory, Department of Psychology & Brain and Mind Institute, The University of Western Ontario, Canada.

A growing body of evidence from functional Magnetic Resonance Imaging adaptation (fMRIa) has implicated the left intraparietal sulcus (IPS) as a crucial brain region representing the semantic of number symbols. However, it is currently unknown to what extent the left IPS brain activity can be generalized across modalities (e.g., Arabic digits and spoken number words) and how robust and reproducible numerical adaptation effects are. In two separate fMRIa experiments we habituated the brain response of 20 native English-speaking (Experiment 1) and 34 native German-speaking (Experiment 2) adults to Arabic digits or spoken number words. Consistent with previous findings, experiment 1 revealed numerical ratio dependent adaptation to Arabic numerals in the left IPS using both conventional and cortex-based alignment techniques. Experiment 2 revealed numerical ratio dependent signal recovery in the left IPS following adaptation to both Arabic numerals and spoken number words using both conventional and cortex-based alignment techniques. Together, these findings suggest that the left IPS is involved in symbolic number processing across modalities.

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http://dx.doi.org/10.1016/j.neuroimage.2017.03.048 | DOI Listing |

June 2017

Neuropsychologia 2017 03 16;97:163. Epub 2017 Feb 16.

Numerical Cognition Laboratory, Department of Psychology & Brain and Mind Institute, The University of Western Ontario, Westminster Hall, Room 325, London, Ontario, Canada N6A 3K7. Electronic address:

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http://dx.doi.org/10.1016/j.neuropsychologia.2017.02.003 | DOI Listing |

March 2017

Neuropsychologia 2017 01 21;94:139. Epub 2016 Aug 21.

Numerical Cognition Laboratory, Department of Psychology & Brain and Mind Institute, The University of Western Ontario, Westminster Hall, Room 325, London, Ont., Canada N6A3K7. Electronic address:

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http://dx.doi.org/10.1016/j.neuropsychologia.2016.08.010 | DOI Listing |

January 2017

J Cogn Neurosci 2016 Jan 6;28(1):166-76. Epub 2015 Oct 6.

The University of Western Ontario.

It is well established that, when comparing nonsymbolic magnitudes (e.g., dot arrays), adults can use both numerical (i.e., the number of items) and nonnumerical (density, total surface areas, etc.) magnitudes. It is less clear which of these magnitudes is more salient or processed more automatically. In this fMRI study, we used a nonsymbolic comparison task to ask if different brain areas are responsible for the automatic processing of numerical and nonnumerical magnitudes, when participants were instructed to attend to either the numerical or the nonnumerical magnitudes of the same stimuli. An interaction of task (numerical vs. nonnumerical) and congruity (congruent vs. incongruent) was found in the right TPJ. Specifically, this brain region was more strongly activated during numerical processing when the nonnumerical magnitudes were negatively correlated with numerosity (incongruent trials). In contrast, such an interference effect was not evident during nonnumerical processing when the task-irrelevant numerical magnitude was incongruent. In view of the role of the right TPJ in the control of stimulus-driven attention, we argue that these data demonstrate that the processing of nonnumerical magnitudes is more automatic than that of numerical magnitudes and that, therefore, the influence of numerical and nonnumerical variables on each other is asymmetrical.

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http://dx.doi.org/10.1162/jocn_a_00887 | DOI Listing |

January 2016

Dev Cogn Neurosci 2015 Apr 10;12:61-73. Epub 2014 Dec 10.

Numerical Cognition Laboratory, Department of Psychology, The University of Western Ontario, London, ON, Canada. Electronic address:

The way the human brain constructs representations of numerical symbols is poorly understood. While increasing evidence from neuroimaging studies has indicated that the intraparietal sulcus (IPS) becomes increasingly specialized for symbolic numerical magnitude representation over developmental time, the extent to which these changes are associated with age-related differences in symbolic numerical magnitude representation or with developmental changes in non-numerical processes, such as response selection, remains to be uncovered. To address these outstanding questions we investigated developmental changes in the cortical representation of symbolic numerical magnitude in 6- to 14-year-old children using a passive functional magnetic resonance imaging adaptation design, thereby mitigating the influence of response selection. A single-digit Arabic numeral was repeatedly presented on a computer screen and interspersed with the presentation of novel digits deviating as a function of numerical ratio (smaller/larger number). Results demonstrated a correlation between age and numerical ratio in the left IPS, suggesting an age-related increase in the extent to which numerical symbols are represented in the left IPS. Brain activation of the right IPS was modulated by numerical ratio but did not correlate with age, indicating hemispheric differences in IPS engagement during the development of symbolic numerical representation.

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http://dx.doi.org/10.1016/j.dcn.2014.12.001 | DOI Listing |

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6989778 | PMC |

April 2015

J Exp Child Psychol 2015 Jan 19;129:26-39. Epub 2014 Sep 19.

Numerical Cognition Laboratory, Department of Psychology, University of Western Ontario, London, Ontario N6G 2K3, Canada. Electronic address:

A growing body of evidence has indicated a link between individual differences in children's symbolic numerical magnitude discrimination (e.g., judging which of two numbers is numerically larger) and their arithmetic achievement. In contrast, relatively little is known about the processing of numerical order (e.g., deciding whether two numbers are in ascending or descending numerical order) and whether individual differences in judging numerical order are related to the processing of numerical magnitude and arithmetic achievement. In view of this, we investigated the relationships among symbolic numerical magnitude comparison, symbolic order judgments, and mathematical achievement. Data were collected from a group of 61 first-grade children who completed a magnitude comparison task, an order judgment task, and two standardized tests of arithmetic achievement. Results indicated a numerical distance effect (NDE) in both the symbolic numerical magnitude discrimination and the numerical order judgment condition. However, correlation analyses demonstrated that although individual differences in magnitude comparison correlated significantly with arithmetic achievement, performance on the order judgment task did not. Moreover, the NDE of the magnitude and order comparison performance was also found to be uncorrelated. These findings suggest that order and numerical magnitude processing may be underpinned by different processes and relate differentially to arithmetic achievement in young children.

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http://dx.doi.org/10.1016/j.jecp.2014.07.010 | DOI Listing |

January 2015

Neuropsychologia 2013 Apr 13;51(5):979-89. Epub 2013 Feb 13.

Numerical Cognition Laboratory, Department of Psychology & Brain and Mind Institute, The University of Western Ontario, Westminster Hall, Room 325, London, Ont. N6A 3K7, Canada.

How are numerical and non-numerical magnitudes processed in the brain? Brain imaging research, primarily using comparison paradigms (i.e. judging which of two magnitudes is larger), has provided strong evidence demonstrating that the intraparietal sulcus (IPS) is a key region for processing both numerical (e.g. Arabic numerals, arrays of dots) and non-numerical magnitudes (e.g. height, brightness). These studies have suggested that there is both activation overlap and segregation in the brain regions involved in processing different dimensions of magnitude. In the present functional Magnetic Resonance Imaging (fMRI) study, we extended this line of investigation by probing the brain mechanisms underlying the mapping of numerical (Arabic numerals) and non-numerical magnitudes (brightness levels) onto a number line. Consistent with previous studies the present results revealed that number and brightness estimation was associated with overlapping activation within right lateralized areas of the posterior IPS. In addition, the contrast between number and brightness estimation revealed that bilateral anterior regions of the IPS are specifically involved in the process of estimating the position of symbolic numbers onto a number line. Furthermore, we found a significant influence of landmark reference points (0, 50 and 100) on brain activation in the right IPS for number estimation only. No regions were found to be specifically associated with brightness estimation. The results of this study reveal that the estimation of both numerical and non-numerical magnitude are associated with the engagement of a right lateralized magnitude system, but that symbolic number estimation is associated with additional engagement of bilateral regions of the anterior IPS.

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http://dx.doi.org/10.1016/j.neuropsychologia.2013.02.001 | DOI Listing |

April 2013

J Cogn Neurosci 2013 Mar 19;25(3):388-400. Epub 2012 Nov 19.

Department of Psychology, Westminster Hall, The University of Western Ontario, London, ON N6A 3K7, Canada.

The ability to process the numerical magnitude of sets of items has been characterized in many animal species. Neuroimaging data have associated this ability to represent nonsymbolic numerical magnitudes (e.g., arrays of dots) with activity in the bilateral parietal lobes. Yet the quantitative abilities of humans are not limited to processing the numerical magnitude of nonsymbolic sets. Humans have used this quantitative sense as the foundation for symbolic systems for the representation of numerical magnitude. Although numerical symbol use is widespread in human cultures, the brain regions involved in processing of numerical symbols are just beginning to be understood. Here, we investigated the brain regions underlying the semantic and perceptual processing of numerical symbols. Specifically, we used an fMRI adaptation paradigm to examine the neural response to Hindu-Arabic numerals and Chinese numerical ideographs in a group of Chinese readers who could read both symbol types and a control group who could read only the numerals. Across groups, the Hindu-Arabic numerals exhibited ratio-dependent modulation in the left IPS. In contrast, numerical ideographs were associated with activation in the right IPS, exclusively in the Chinese readers. Furthermore, processing of the visual similarity of both digits and ideographs was associated with activation of the left fusiform gyrus. Using culture as an independent variable, we provide clear evidence for differences in the brain regions associated with the semantic and perceptual processing of numerical symbols. Additionally, we reveal a striking difference in the laterality of parietal activation between the semantic processing of the two symbols types.

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http://dx.doi.org/10.1162/jocn_a_00323 | DOI Listing |

March 2013

Behav Brain Funct 2009 Aug 5;5:35. Epub 2009 Aug 5.

Department of Psychology, University of Salzburg, Salzburg, Austria.

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http://dx.doi.org/10.1186/1744-9081-5-35 | DOI Listing |

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2731029 | PMC |

August 2009

Cortex 2008 Oct 20;44(9):1248-55. Epub 2008 Jan 20.

Innsbruck Medical University, Clinical Department of Paediatrics IV, Division of Neuropediatrics, Innsbruck, Austria.

Aim of this functional magnetic resonance imaging (fMRI) study was to dissociate normal aging and minimal cognitive impairment (MCI) concerning magnitude processing and interference control. We examined the neural correlates of a numerical Stroop task in elderly individuals with and without MCI. Fifteen elderly participants (six patients with MCI and nine controls) were subjected to a numerical Stroop task requiring numerical/physical magnitude classifications while inhibiting task-irrelevant stimulus dimensions. Effects of distance and congruity were examined. Behaviourally, robust distance and congruity effects were observed in both groups and tasks. Imaging baseline conditions revealed stronger and more distributed activations in MCI patients relative to controls which could not be explained by the higher error rates committed by patients. Across tasks, conjunction analysis revealed highly significant activations in intra-parietal and prefrontal regions suggesting that both groups recruit comparable brain regions upon processing magnitude and interference, respectively. MCI patients exhibited stronger pre-/postcentral and thalamic activations, possibly reflecting more effortful response-selection processes or alternatively, deficient inhibitory control. Moreover, MCI patients exhibited additional activations in fronto-parietal (magnitude) and occipital/cerebellar (congruity) regions. To summarize, though MCI patients needed to recruit more distributed activation patterns conjunction analysis revealed common activation sites in response to magnitude processing and interference control.

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http://dx.doi.org/10.1016/j.cortex.2007.11.009 | DOI Listing |

October 2008

Cortex 2008 Apr 23;44(4):376-85. Epub 2007 Dec 23.

Innsbruck Medical University, Clinical Department of Pediatrics IV, Division of Neuropediatrics, Innsbruck, Austria.

This functional magnetic resonance imaging (fMRI) study systematically investigates whether there is a neurofunctional overlap of nonsymbolic numerical and spatial cognition in (intra)parietal regions in children and adults. The study also explores the association between finger use and (nonsymbolic) number processing across development. Twenty-four healthy individuals (12 children, 12 adults) were asked to make nonsymbolic numerical and spatial (experimental tasks) as well as color discriminations (control task). Using identical stimulus material across the three tasks disentangled nonsymbolic number representations from general attentional mechanisms, visual-spatial processing and response selection requirements. In both age groups, behavioral distance effects were obtained upon processing numerical (but not spatial and/or color) stimuli. Baseline imaging effects revealed age-dependent, partly overlapping activations of nonsymbolic numerical and spatial processing in the right posterior superior parietal lobe (PSPL) in adults only. Interestingly, regions more activated in children relative to adults were centred on bilateral supramarginal gyrus (SMG) and lateral portions of the anterior intraparietal sulcus (IPS), further extending to adjacent right post- and precentral gyrus, the latter of which has been reported to support grasping previously (Simon et al., 2002). Overall, our results are first evidence for an age-dependent neurofunctional link between areas supporting finger use and nonsymbolic number processing and furthermore, might be suggestive of a special role of fingers for the development of number magnitude representations and early arithmetic.

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http://dx.doi.org/10.1016/j.cortex.2007.08.003 | DOI Listing |

April 2008