W4L2 - Brain imaging and electrophysiological studies of humans with normal and abnormal number capacity Flashcards
1.) Human imaging and animal physiology 2.) Brain areas for numbers vs language 3.) IPS activation for number tasks 4.) Dyscalculia
What are the brian areas implicated in number processing in humans. Is humans found first or animals?
Parietal and Frontal Areas (Billaterally)
Match regions found in animals (Humans predated Animals)
What brain areas does symbolic stimuli activate. What do symbols include
Parietal regions for culturally abstract, amodal representation of numbers
Symbols: Culturally learned symbolic notations such as Arabic numerals and spelled-out or spoken number words
What brain areas does non-symbolic stimuli activate. What do symbols include. What are some conditions for activation.
Parietal Regions.
Symbols: Dots and Tones
- ) Attending to dot stimuli is sufficient for IPS activation (obligatory processing)
- ) Passively looking/ sustained viewing causes IPS adaptation to number
- ) Responses to combined symbolic and non-symbolic presentations (Common responses in IPS and pfc suggest common representation of symbolic and non symbolic)
Adaptation to Number Symbols: Study Overview
Naache et al. (2001) fMRI adaptation study
Rapid presentation of repeated/distant numbers after adapting to a number
Adaptation to Number Symbols: Study Result
BOLD changes in the IPS of both hemispheres:
Repeated number: Lesser distance effect, Response reduced.
Distant number: Greater distance effect, Response increased.
Adaptation to Dot Numeriosity: Study Overview and Result.
Piazza et al. (2004)
Rapid presentation of repeated/distant dots after adapting to a dot
Symmetric Gaussian tuning on ratio scale. Precision of coding consistent with Weber Fraction
Repeated dots: Lesser distance effect, Response reduced.
Distant dots: Greater distance effect, Response increased.
Cross notation adaptation: Study overview and result
Piazza et al. (2007)
Adaptation of 17,18,19 dots and present 20 or 50 number
50: fMRI recover/activate
20: No activation
> Adaptation effect. Response to far greater than near independent of format presentation.
How early does the IPS become specialised for number ? 1st Studies Overview
Cantlon et al. (2006)
fMRI adaptation study on 4 yo
Test changed numeriosity/object identity
How early does the IPS become specialised for number ? 1st study result
4 YO:
Representation of numerosity in right parietal cortex
Representation of identity in occipito-temporal cortex
How early does the IPS become specialised for number ? 2nd study overview
IIzard et al. (2008)
Event-related potentials (EEG) from 3 mo
Presented with a continuous stream of sets of objects
How early does the IPS become specialised for number ? 2nd study result
3 MO;
Right parietal cortex responded to numerical novelty
Left occipito-temporal cortex responded to object novelty
Where are proportions coded. What is the study
Jacob & Nieder (2009)
Habituated to a given line length PROPORTION
BOLD response larger the more different the ratio
Where are fractions coded. What is the study
Jacob & Nieder (2009)
Habituated to a given fraction
BOLD response larger to more different the fraction
(btw fractions are the symbolic version of ratio)
What is the role of the frontal lobes in numbers?
May be frontal to parietal shift from childhood to adulthood (Children process number symbols automatically)
Prefrontal regions are essential for calculation, related to task difficult (formal operations)
Superior frontal gyrus involved in complex calculations
What is the role of the inferior temporal gyrus in numbers?
ECoG high frequency band (65-150Hz)
- Neurons with a preferential response to visual numerals (not lines, curves, angles) , especially in right inferior temporal gyrus
(NOT evident in BOLD fMRI because of signal dropout)
