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Daniel Ansari

Publications and source records attributed to Daniel Ansari.

13 recordsLinked to original sources
PubMed2007

Does the parietal cortex distinguish between "10," "ten," and ten dots?

It is well established that the intraparietal sulcus (IPS) plays an important role in the processing and representation of numerical magnitude. Two recent studies by Piazza et al. and Cohen Kadosh et al. published in this issue of Neuron used fMRI adaptation to explore the extent to which parietal number processing is dependent upon or independent of a numbers' surface format. Their results, while slightly different, converge to suggest that the answer may be neither, but rather that it depends on the hemisphere.

Humans↗
PubMed2006

Dissociating response conflict from numerical magnitude processing in the brain: an event-related fMRI study.

Functional neuroimaging studies of numerical cognition have repeatedly associated activation of the intraparietal sulcus (IPS) with number processing. During number comparison, the IPS has been found to be modulated by the numerical distance. This has lead to the contention that the IPS houses the internal representation of numerical magnitude. However, this theory has been challenged by the argument that IPS activation may reflect domain-general response selection. In the present study, we used the numerical size congruity paradigm to further elucidate the role played by the IPS in number comparison. In an event-related, functional magnetic resonance imaging (fMRI) study, participants judged which of two number words was numerically larger. In addition to the numerical distance, physical stimulus size was varied such that physical size and numerical magnitude were either (a) congruent (e.g., numerically smaller number printed in smaller font) or (b) incongruent (e.g., numerically larger number printed in smaller font). This allowed for the study of both the main effects and the interaction of numerical distance and stimulus congruency. A main effect of numerical distance was found in bilateral regions of the IPS. However, these parietal areas were not significantly modulated by congruency or the interaction of distance and congruency. Instead, the main effect of congruency and an interaction of distance and congruency were observed in anterior cingulate and prefrontal cortices. These findings suggest some degree of independence between the processing of numerical distance and size congruity, lending support for the hypothesis that distance effects in IPS reflect the underlying representation of numerical magnitude.

Adolescent↗
PubMed2006

Bridges over troubled waters: education and cognitive neuroscience.

Recently there has been growing interest in and debate about the relation between cognitive neuroscience and education. Our goal is to advance the debate beyond both recitation of potentially education-related cognitive neuroscience findings and the claim that a bridge between fields is chimerical. In an attempt to begin a dialogue about mechanisms among students, educators, researchers and practitioner-scientists, we propose that multiple bridges can be built to make connections between education and cognitive neuroscience, including teacher training, researcher training and collaboration. These bridges--concrete mechanisms that can advance the study of mind, brain and education--will benefit both educators and cognitive neuroscientists, who will gain new perspectives for posing and answering crucial questions about the learning brain.

Brain↗
PubMed2006

Effect of language switching on arithmetic: a bilingual FMRI study.

The role of language in performing numerical computations has been a topic of special interest in cognition. The "Triple Code Model" proposes the existence of a language-dependent verbal code involved in retrieving arithmetic facts related to addition and multiplication, and a language-independent analog magnitude code subserving tasks such as number comparison and estimation. Neuroimaging studies have shown dissociation between dependence of arithmetic computations involving exact and approximate processing on language-related circuits. However, a direct manipulation of language using different arithmetic tasks is necessary to assess the role of language in forming arithmetic representations and in solving problems in different languages. In the present study, 20 English-Chinese bilinguals were trained in two unfamiliar arithmetic tasks in one language and scanned using fMRI on the same problems in both languages (English and Chinese). For the exact "base-7 addition" task, language switching effects were found in the left inferior frontal gyrus (LIFG) and left inferior parietal lobule extending to the angular gyrus. In the approximate "percentage estimation" task, language switching effects were found predominantly in the bilateral posterior intraparietal sulcus and LIFG, slightly dorsal to the LIFG activation seen for the base-7 addition task. These results considerably strengthen the notion that exact processing relies on verbal and language-related networks, whereas approximate processing engages parietal circuits typically involved in magnitude-related processing.

Attention↗
PubMed2006

Age-related changes in the activation of the intraparietal sulcus during nonsymbolic magnitude processing: an event-related functional magnetic resonance imaging study.

Numerical magnitude processing is an essential everyday skill. Functional brain imaging studies with human adults have repeatedly revealed that bilateral regions of the intraparietal sulcus are correlated with various numerical and mathematical skills. Surprisingly little, however, is known about the development of these brain representations. In the present study, we used functional neuroimaging to compare the neural correlates of nonsymbolic magnitude judgments between children and adults. Although behavioral performance was similar across groups, in comparison to the group of children the adult participants exhibited greater effects of numerical distance on the left intraparietal sulcus. Our findings are the first to reveal that even the most basic aspects of numerical cognition are subject to age-related changes in functional neuroanatomy. We propose that developmental impairments of number may be associated with atypical specialization of cortical regions underlying magnitude processing.

Adolescent↗
PubMed2005

Parametric effects of numerical distance on the intraparietal sulcus during passive viewing of rapid numerosity changes.

A number of functional neuroimaging studies have revealed that regions in and around the intraparietal sulcus (IPS) are parametrically modulated by numerical distance, whereby there is an inverse relationship between distance and levels of activation. These areas are thus thought to contain the internal representation of numerical magnitude. Nevertheless, it has also been suggested that the IPS is involved in response selection during number comparison tasks rather than the representation of numerical magnitude per se. In order to test the independence of the effect of distance on cortical regions, we employed a passive viewing paradigm. Sixteen right-handed male participants viewed rapidly changing slides containing arrays of squares. By varying the distance between the numerosity presented in separate blocks (8 vs. 8, 8 vs. 12, and 8 vs. 16), we examined which regions exhibit a parametric effect of numerical distance. This analysis revealed such effects in the superior part of the IPS bilaterally as well as the superior parietal lobule and the supramarginal gyrus. In contrast, slides rapidly changing in area but not number (Area constant, Area x 1, and Area x 2) did not yield a parametric effect of distance in these regions. Instead, a reverse effect of area was found in a region of the calcarine sulcus. These findings suggest that areas in and around the IPS are involved in numerical magnitude discrimination in the absence of an explicit task and response requirements.

Adult↗
PubMed2005

Neural correlates of symbolic number processing in children and adults.

Using functional magnetic resonance imaging, we examined developmental differences in the functional neuroanatomy underlying symbolic number processing. Twelve adults and 12 children had to judge the relative magnitude of two single-digit Arabic numerals. We investigated which brain areas were significantly (P<0.005, uncorrected) more activated during processing of number pairs with small relative to large numerical distances. In the adult group, symbolic distance modulated bilateral parietal regions. In contrast, the group of children primarily engaged frontal regions. We conclude that the functional neuroanatomy underlying symbolic numerical magnitude processing undergoes an ontogenetic shift towards greater parietal engagement. This change may reflect maturation of underlying representations and increasing automaticity in mapping between numerical symbols and the magnitudes they represent.

Adult↗
PubMed2005

Neural correlates of symbolic and non-symbolic arithmetic.

Recent evidence suggests that areas in and around the intraparietal sulcus (IPS) represent magnitude in a stimulus-independent format. However, it has not been established whether the same is true for mental arithmetic or whether activation for higher level numerical processing diverges as a function of stimulus format. We addressed this question in a functional imaging study by presenting participants with simple addition problems using both symbolic (Arabic numerals) and non-symbolic (arrays of dots) stimuli. Conjunction analysis revealed common neural substrates for symbolic and non-symbolic addition in the anterior IPS bilaterally, left posterior IPS, medial frontal gyrus and left precentral gyrus. Right parietal and frontal cortex showed greater activation for non-symbolic addition. Our results demonstrate that mental arithmetic, studied using addition problems, is processed within the IPS independent of stimulus form. Additionally we examined whether exact and approximate addition conditions activated different neural substrates as a function of stimulus format. We did not find any differences between exact and approximate addition using symbolic and non-symbolic stimuli. This could be due to the inability of the participants to suppress exact calculation for single-digit addition problems. In contrast to recent findings, we found no significant activation for exact addition condition in left, language-related areas.

Adult↗
PubMed2003

What makes counting count? Verbal and visuo-spatial contributions to typical and atypical number development.

Williams Syndrome (WS) is marked by a relative strength in verbal cognition coupled with a serious impairment in non-verbal cognition. A strong deficit in numerical cognition has been anecdotally reported in this disorder; however, its nature has not been systematically investigated. Here, we tested 14 children with WS (mean age=7 years 2 months), 14 typically developing controls individually matched on visuo-spatial ability (mean age=3 years 5 months) as well as a larger group of typically developing controls (mean age=3 years 4 months) on two tasks to assess their understanding that counting determines the exact quantity of sets (cardinality principle). The understanding of the cardinality principle in children with WS is extremely delayed and only at the level predicted by their visuo-spatial MA. In this clinical group, only language accounted for a significant amount of the variance in cardinality understanding, whereas in the normal comparison group only visuo-spatial competence predicted the variance. The present findings suggest that visuo-spatial ability plays a greater role than language ability in the actual development of cardinality understanding in typically developing children, whereas the opposite obtains for the clinical group.

Child↗
PubMed2002

Atypical trajectories of number development: a neuroconstructivist perspective.

Despite the fact that number deficits are as prevalent as literacy deficits, research on basic numerical skills lags seriously behind the successful studies identifying low-level deficits in dyslexia. We review current debates on number, discussing how the competing theories pertain to mathematical disabilities in normal children and numeracy deficits in genetic disorders. We stress the need to consider these issues within the framework of a developing system rather than from the neuropsychological perspective of focal damage. The earlier the exploration of atypical trajectories in very basic numerical skills, the better we will be able to chart their developmental impact on subsequent, higher-level arithmetic abilities.

Journal Article↗