W4L2 - Brain imaging and electrophysiological studies of humans with normal and abnormal number capacity

Question 1

What are the brian areas implicated in number processing in humans.

Is humans found first or animals?

Answer 1

• Parietal and Frontal Areas
• Maybe ITG
• Humans predated Animals. Human studies before animal studies

Question 2

What brain areas does symbolic stimuli activate.

What do symbols include

Answer 2

Brain Area:

• IPS

Symbols

• Culturally learned symbolic notations such as Arabic numerals or spelled-out or spoken number words
  
  • Modality does not matter
• Parietal activation occurs for an abstract, amodal representation of numbers

Question 3

What brain areas does non-symbolic stimuli activate. What do symbols include. What are some conditions for activation.

Answer 3

• Brain Area
  
  • IPS
• Non-symbolic stimuli
  
  • Dots and Tones
• Conditions
  
  • Attending to dot stimuli: Obligatory processing
  • Passively viewing: IPS adaptation to number

Question 4

What brain areas does both symbolic and non-symbolic stimuli activate?

Answer 4

Combined symbolic and non-symbolic presentations

IPS and PFC suggest common representation

Question 5

Adaptation to Number Symbols: Study Overview and Results

Answer 5

Naache et al. (2001) fMRI adaptation study

• Rapid presentation of repeated/numerically distant numbers after adapting to a number

Results

• IPS of both hemsiphere
  
  • Repeated number
    
    • Lesser distance effect, BOLD Response reduced
  • Distant number
    
    • Greater distance effect, BOLD Response increased

[Symbols = Number Distance Effect]

Question 6

Adaptation to Dot Numeriosity: Study Overview and Result.

Answer 6

Piazza et al. (2004) fMRI adaptation of dots

• Rapid presentation of repeated/distant dot after adapting to a dot
• Brief tests at a range of ratios relative to the adaptation numerosity

Results

• Symmetric Gaussian tuning on ratio scale - just like single cells in monkey studies
• Precision of coding consistent with Weber Fraction
  
  • [Dots = Weber]

Question 7

Cross-notation adaptation: Study overview and result

Answer 7

Piazza et al. (2007): fMRI adaption of dots and numbers:

• Adaptation: 17,18,19 dots with arabic numerial 20 or 50

Results

• Distance effect
  
  • fMRI recovery if 19 vs 50
  • no fMRI recovery if 19 vs 20
• Both IPS and PFC

Question 8

How early does the IPS become specialised for number?

1st Studies Overview and results

Answer 8

Cantlon et al. (2006) fMRI adaptation study on 4 yo

• Changed
  
  • object numeriosity or object identity

Results

• Numeriosity
  
  • Right Parietal Cortex
• Identity
  
  • Occipito-Temporal Cortex

Question 9

How early does the IPS become specialised for number ? 2nd study overview

Answer 9

IIzard et al. (2008) Event-related potentials (EEG) from 3 mo

• Presented with a continuous stream of sets of objects

Results

• Numeriosity
  
  • Right Parietal Cortex
• Identity
  
  • Left Occipito-Temporal Cortex

Question 10

Adapation to Proportions (Line). Study overview and results

Answer 10

Jacob and Nieder (2009)

• Habituated to a given line length proportion
• BOLD response larger the more different the ratio
• Both IPS and PFC

Question 11

Adapation to Proportions (Fractions). Study overview and results

Answer 11

Jacob and Nieder (2009)

• Habituated to a given fraction

Results

• BOLD response larger to more different the fraction
• Fractions are the symbolic version of ratio
  
  • Symbolic Number Distance Effect
• IPS

Question 12

What is the role of the frontal lobes in numbers from childhood to adulthood?

Answer 12

• Frontal to parietal shift from childhood to adulthood as symbolic processing becomes automatic
• Prefrontal regions
  
  • Essential for nuumbers calculation
  • Related to task difficulty (Formal operations leverages on frontal areas)
  • Superior frontal gyrus involved in complex calculations

Question 13

What did ECOG study revealed in number. Another area? What is the implication

Answer 13

Inferior Temporal Gyrus

ECoG high frequency band (65-150Hz):

• Revelead neurons in ITG with a preferential response to visual numerals (not lines, curves, angles)
  
  • Additional area for symbols
  • We might have developed a special region for symbols
• Not evident in BOLD fMRI due to signal dropout
• Functional link with lateral parietal cortex (LPC) while doing arithmetic

Question 14

What is Dyscalculia. What are some properties. Prevalence. Consequence. Co-morbaility. Persistence. Heritability

Answer 14

• What:
  
  • Specific and Severe disability in learning arithmetic
  • Normal intelligence
  • Normal working memory
• Prevalence
  
  • 5-7% (developmental dyscalculia = developmental dyslexia)
• Consequence
  
  • More severe than dyslexia
• Co-morbility
  
  • Occurs with other developmental disorders like ADHD and Reading
• Persistence:
  
  • Persists into adulthood (Unclear whether it’s a delay in ability or deficit)
• Heritability
  
  • Mathematical abilities have high specific heritability

Question 15

What difficulties do dyscalculics have?

Answer 15

• Simple arithmetic
• Deficit for even the most basic representation of numerosities
  
  • Enumeration and Number Comparison

Question 16

What is the neural activation behind dyscalculias

Answer 16

• Reduced grey matter in left IPS adoloscent
• Reduced grey matter in right IPS 9yo
• Reduced probability of connections from right fusiform gyrus to other parts of the brain, including the parietal lobes
  
  • Evidence is inconsistent

Question 17

fMRI behind developmental dyscalculia

Answer 17

• Huge individual differences
  
  • Could be over/under activation
• Unclear

Question 18

Dyscalculia treatment:Does neuroplasticity/teaching allow brain changes that improve maths?

Answer 18

Teaching

• 1:1 cognitive tutoring improved performance for children with mathematical learning disabilities
• Tutoring reduced overactivation in areas, normalising brain activity

Neuroplasticity

• Recent studies via. direct stimulaton suggest usefulness