Limits...
Quantity without numbers and numbers without quantity in the parietal cortex.

Cappelletti M, Muggleton N, Walsh V - Neuroimage (2009)

Bottom Line: Our results showed that IPS involvement in numerical cognition is neither stimulus-specific nor specific for conceptual tasks.However, IPS-TMS showed no impairment for perceptual decisions on numbers without any conceptual processing (i.e. colour judgment), nor for conceptual decisions that did not involve quantity or number stimuli (e.g. summer object: 'bikini' or 'coat'?).Rather, our results show that the IPS is only necessary when conceptual operations need to be explicitly oriented to numerical concepts.

View Article: PubMed Central - PubMed

Affiliation: Institute of Cognitive Neuroscience and Dept of Psychology, University College London, 17 Queen Square, London WC1N 3AR, UK. m.cappelletti@ucl.ac.uk

ABSTRACT
A dominant view in numerical cognition is that processing the quantity indicated by numbers (e.g. deciding the larger between two numbers such as '12.07' or '15.02') relies on the intraparietal regions (IPS) of the cerebral cortex. However, it remains unclear whether the IPS could play a more general role in numerical cognition, for example in (1) quantity processing even with non-numerical stimuli (e.g. choosing the larger of 'bikini' and 'coat'); and/or (2) conceptual tasks involving numbers beyond those requiring quantity processing (e.g. attributing a summer date to either '12.07' or '15.02'). In this study we applied fMRI-guided TMS to the left and right IPS, while independently manipulating stimulus and task. Our results showed that IPS involvement in numerical cognition is neither stimulus-specific nor specific for conceptual tasks. Thus, quantity judgments with numerical and non-numerical stimuli were equally affected by IPS-TMS, as well as a number conceptual task not requiring quantity comparisons. However, IPS-TMS showed no impairment for perceptual decisions on numbers without any conceptual processing (i.e. colour judgment), nor for conceptual decisions that did not involve quantity or number stimuli (e.g. summer object: 'bikini' or 'coat'?). These results are consistent with proposals that the parietal areas are engaged in the conceptual representation of numbers but they challenge the most common view that number processing is so automatic that the simple presentation of numbers activates the IPS and a sense of magnitude. Rather, our results show that the IPS is only necessary when conceptual operations need to be explicitly oriented to numerical concepts.

Show MeSH

Related in: MedlinePlus

Performance impairments following TMS. Bars indicate the mean difference in response time in ms in the left (black bars) and right IPS (grey bars) after TMS relative to sham stimulation to the same areas, for quantity, non-quantity categorical and colour decisions with numbers and object names respectively. TMS conditions in which response times significantly differed from sham stimulation or between conditions are indicated by an asterisk above the bars. Numbers below bars indicate the mean differences in error rates between TMS and Sham in each experimental condition.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2683244&req=5

fig3: Performance impairments following TMS. Bars indicate the mean difference in response time in ms in the left (black bars) and right IPS (grey bars) after TMS relative to sham stimulation to the same areas, for quantity, non-quantity categorical and colour decisions with numbers and object names respectively. TMS conditions in which response times significantly differed from sham stimulation or between conditions are indicated by an asterisk above the bars. Numbers below bars indicate the mean differences in error rates between TMS and Sham in each experimental condition.

Mentions: A two-way ANOVA revealed a significant interaction of condition (left and right TMS and sham) and stimulus-type (numbers and object names), [F(2,10) = 9.31, p < 0.006]. Specifically, performance in quantity tasks with numbers (e.g. which is larger: 12.07 or 15.02?) was significantly impaired (slower performance) by stimulation over the IPS relative to sham stimulation of the same areas, with longer RTs following rTMS to either left [871.63 ms, 34.5 ms difference with sham, t(5) = 9.56, p < 0.001] or right IPS [855.56 ms, 17.8 ms difference with sham, t(5) = 4.91, p = 0.004]. Left and right IPS stimulation differed significantly, left IPS-TMS inducing a larger impairment than right IPS-TMS [t(5) = 3.25, p < 0.02] (See Fig. 3). Moreover, left and right IPS-TMS impairment was greater for comparisons of close numbers relative to numbers far apart, i.e. distance effect [left IPS: t(5) = 2.593, p < 0.04 right IPS t(5) = 11.14, p < 0.001]. A distance effect was also observed in both the sham [t(5) = 2.76, p < 0.03] and the non-TMS conditions [t(5) = 10.99, p < 0.001].


Quantity without numbers and numbers without quantity in the parietal cortex.

Cappelletti M, Muggleton N, Walsh V - Neuroimage (2009)

Performance impairments following TMS. Bars indicate the mean difference in response time in ms in the left (black bars) and right IPS (grey bars) after TMS relative to sham stimulation to the same areas, for quantity, non-quantity categorical and colour decisions with numbers and object names respectively. TMS conditions in which response times significantly differed from sham stimulation or between conditions are indicated by an asterisk above the bars. Numbers below bars indicate the mean differences in error rates between TMS and Sham in each experimental condition.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2683244&req=5

fig3: Performance impairments following TMS. Bars indicate the mean difference in response time in ms in the left (black bars) and right IPS (grey bars) after TMS relative to sham stimulation to the same areas, for quantity, non-quantity categorical and colour decisions with numbers and object names respectively. TMS conditions in which response times significantly differed from sham stimulation or between conditions are indicated by an asterisk above the bars. Numbers below bars indicate the mean differences in error rates between TMS and Sham in each experimental condition.
Mentions: A two-way ANOVA revealed a significant interaction of condition (left and right TMS and sham) and stimulus-type (numbers and object names), [F(2,10) = 9.31, p < 0.006]. Specifically, performance in quantity tasks with numbers (e.g. which is larger: 12.07 or 15.02?) was significantly impaired (slower performance) by stimulation over the IPS relative to sham stimulation of the same areas, with longer RTs following rTMS to either left [871.63 ms, 34.5 ms difference with sham, t(5) = 9.56, p < 0.001] or right IPS [855.56 ms, 17.8 ms difference with sham, t(5) = 4.91, p = 0.004]. Left and right IPS stimulation differed significantly, left IPS-TMS inducing a larger impairment than right IPS-TMS [t(5) = 3.25, p < 0.02] (See Fig. 3). Moreover, left and right IPS-TMS impairment was greater for comparisons of close numbers relative to numbers far apart, i.e. distance effect [left IPS: t(5) = 2.593, p < 0.04 right IPS t(5) = 11.14, p < 0.001]. A distance effect was also observed in both the sham [t(5) = 2.76, p < 0.03] and the non-TMS conditions [t(5) = 10.99, p < 0.001].

Bottom Line: Our results showed that IPS involvement in numerical cognition is neither stimulus-specific nor specific for conceptual tasks.However, IPS-TMS showed no impairment for perceptual decisions on numbers without any conceptual processing (i.e. colour judgment), nor for conceptual decisions that did not involve quantity or number stimuli (e.g. summer object: 'bikini' or 'coat'?).Rather, our results show that the IPS is only necessary when conceptual operations need to be explicitly oriented to numerical concepts.

View Article: PubMed Central - PubMed

Affiliation: Institute of Cognitive Neuroscience and Dept of Psychology, University College London, 17 Queen Square, London WC1N 3AR, UK. m.cappelletti@ucl.ac.uk

ABSTRACT
A dominant view in numerical cognition is that processing the quantity indicated by numbers (e.g. deciding the larger between two numbers such as '12.07' or '15.02') relies on the intraparietal regions (IPS) of the cerebral cortex. However, it remains unclear whether the IPS could play a more general role in numerical cognition, for example in (1) quantity processing even with non-numerical stimuli (e.g. choosing the larger of 'bikini' and 'coat'); and/or (2) conceptual tasks involving numbers beyond those requiring quantity processing (e.g. attributing a summer date to either '12.07' or '15.02'). In this study we applied fMRI-guided TMS to the left and right IPS, while independently manipulating stimulus and task. Our results showed that IPS involvement in numerical cognition is neither stimulus-specific nor specific for conceptual tasks. Thus, quantity judgments with numerical and non-numerical stimuli were equally affected by IPS-TMS, as well as a number conceptual task not requiring quantity comparisons. However, IPS-TMS showed no impairment for perceptual decisions on numbers without any conceptual processing (i.e. colour judgment), nor for conceptual decisions that did not involve quantity or number stimuli (e.g. summer object: 'bikini' or 'coat'?). These results are consistent with proposals that the parietal areas are engaged in the conceptual representation of numbers but they challenge the most common view that number processing is so automatic that the simple presentation of numbers activates the IPS and a sense of magnitude. Rather, our results show that the IPS is only necessary when conceptual operations need to be explicitly oriented to numerical concepts.

Show MeSH
Related in: MedlinePlus