3. The numerate brain Flashcards
What is the dorsal stream?
Important for spatial localisation (WHERE)
What is the ventral stream?
Important for object identification (WHAT)
Mishkin et al (1983) DOUBLE DISSOCIATION:
Monkeys trained for:
- picking up objects that are closer in one condition (location)
VS
- Picking up a particular shape in the other condition (shape)
Monkeys split into two lesion groups:
- Dorsal where path (parietal lobe)
- Ventral what path (temporal lobe)
- Monkeys with PARIETAL lesion FAILED on LOCATION, successful with shape.
- Monkeys with TEMPORAL lesion FAILED on SHAPE, successful with location.
What separates the inferior parietal lobule and superior parietal lobule?
Intraparietal Sulcus (IPS)
Which Broadman areas (BA) lie in the Inferior Parietal Lobule (IPL)
BA39, BA40
The Inferior Parietal Lobule (IPL) is sometimes called the ____ and consists of…
Ventral parietal cortex
and consists of the ANGULAR GYRUS and the SUPRAMARGINAL GYRUS
Which areas are in the monkey Intraparietal Sulcus (IPS)?
- AIP
- L(lateral)IP
- M(medial)IP
- PIP
- V(ventral)IP
What is the Fractionation vs overarching view?
Fractionation (specialisation):
- each subregion within a region has distinct cognitive functions (no functional overlap)
Overarching (functional overlap):
- Each subregion within a region is involved in every cognitive function but to a varying extent
Maths lec: what typically happens when the parietal lobe is lesioned following a tumour or stroke?
- Visuospatial neglect: half of the world does not exist (like a broken radar)
- Impaired object grasping (anterior Intraparietal Sulcus damage)
- Acalculia (inferior Parietal Lobe damage -aka- ventral Parietal Cortex damage): problems with arithmetic
- Reading impairment
- WM deficits
- Reasoning disorders
- Impairments in intentionality & theory of mind
What is Acalculia?
Complete inability to calculate, such disturbance resulting from brain injury
What are numerical codes?
Anything providing information about amount/number
What is the Dehaene’s (2000) triple code model?
proposes that numbers are represented in three codes that serve different functions, have distinct functional neuroarchitectures, and are related to performance on specific tasks:
- Analog magnitude representation: non-symbolic representation (estimation) bilateral
- Visual Arabic (or any) Number Form: Arabic numeral reading/writing
- bilateral*
- Verbal Word Frame: Spoken/written number-words
- left hemisphere*
Eger et al (2003):
fMRI on healthy participants
- Supramodal (all modalities) number representation
- The Intraparietal Sulcus (IPS) is significantly more activated by visual & auditory NUMBERS than by letters or colours
Nieder & Miller (2004):
Representation of Numerosity in monkeys (TRAINING)
Tested monkeys with small numerosities (small numbers) of dots
TRAINED:
e. g:
1. 4 dots displayed
- then either matching or non-matching amount displayed
Objective = Monkey decides if second amount matches first amount
- If match & indicated correctly = reward
- every non-match = a matching amount is displayed for the monkey after
Nieder (2005):
Representation of Numerosity in monkeys (recording sites):
- Interparietal Sulcus
- Prefrontal areas
After being trained to match amounts of dots (non-symbolic), signal from the brain was recorded during the performance of the numerosity matching task.
- L(lateral)IP
- M(medial)IP
- V(ventral)IP
- There was a neuron that responded the most to number 1 (less to 2, then less to 3, 4, 5)
- Another neuron, responded later than the first one and responded more to 4 and 5 (then less to 3, 2, 1)
- Neurons found to respond mostly in PFC (most activity), however, earlier responses recorded in VIP (signals travel IPS -> PFC)
!!!Found some neurons that responded most to particular numbers (Number selective neurons) in IPS
Piazza et al (2004):
fMRI: Do humans have number selective neurons (dots = non-symbolic)?
Presented participants with a stream of stimuli (e.g. adapting participants to 16 dots with various sizes and configurations)
- occasionally, a deviant amount of dots will appear (e.g. 8 = far deviation / 14 = close deviation)
As you get adapted to 16 dots, there is less firing with each presentation…
- if a deviant numerosity is presented, the neurons are not adapted to that amount so activity will be larger
Harvey et al (2013)
Numerosity map?
Superior Parietal Lobule (SPL) seems to have areas that respond more to certain numerosities (numbers map onto certain parts of the lobule)
- used a method of adaptation
Number Form Area: What bone disrupts fMRI signal around putative location
petrous bone
part of the temporal bone
Grotheer, Herrmann & Kovacs (2016)
Discovering the Number Form Area (with fMRI)
presented Numbers/Letters/Objects in three different versions (Standard, False which look like some symbols, Noise which are just masks)
Found a Number Form area in BOTH hemis
- activation was higher for numbers compared to false numbers, letters and objects
There is also a Letter Form area found only in the LEFT hemi
Grotheer, Ambrus & Kovacs (2016): Disrupting the RIGHT Number Form Area (NFA) to investigate functionality
Decided to disrupt RIGHT Number Form Area, this disrupted accuracy for Numbers
BUT also,
disrupted accuracy for Letters to a lesser extent than for numbers (the previous study did not find activity for Letters in the RIGHT hemisphere, only in Left)
Grabner et al (2007):
fMRI study of calculation
- Found out each participant’s mathematical-numerical IQ
- placed them in fMRI where they done calculations
- activation in the left Angular Gyrus was sig related to numerical IQ (r = .63)
!!!! The higher numerical IQ, the higher that participant’s activation of left Angular Gyrus during calculations
Arsalidou & Taylor (2011):
Meta-analysis of arithmetic calculation
- Areas of the Triple-code model (different types of number processing) were consistent
Proposed updates of areas which are also involved along the Triple-code model areas:
- Arithmetic Neural networks = Core Neurocognitive processes (Menon, 2015)
Menon (2015):
Arithmetic Neural networks = Core Neurocognitive processes
Number Form Area + Intraparietal Sulcus (IPS) = Visuospatial representation of numerical quantity
For arithmetic tasks, you need a hierarchy of short-term representations (lasting several seconds)
Menon proposed that there are Procedural and WM systems responsible for this and involve these areas:
- IPS & SMG (Supramarginal Gyrus)
- Pre-motor cortex (PMC)
- Supplementary motor area (SMA)
- Dorsolateral prefrontal cortex (DLPFC)
- ## Basal Ganglia (BG)Areas important for Long-term memory formation and integration in calculation:
- Angular Gyrus
- Medial Temporal Lobe
- Anterior Temporal Lobe
Guidance and maintenance of attention, problem solving and decision making involves these areas:
- Anterior insula (AI)
- Ventrolateral prefrontal cortex (VLPFC)
Cantlon et al (2006):
Intraparietal Sulcus activation in 4-yr-olds through non symbolic numerates (clusters of dots)
- children show similar adaptation to numbers as adults, there is overlap in the right intraparietal sulcus
Rivera et al (2005):
Changes in activation with age (8-20) during mental arithmetic
With age, activity increases in:
- left Parietal Cortex
- Lateral Occipito-Temporal areas
- left Supramarginal Gyrus
With age, activity decreases in:
- Frontal cortex areas
- Anterior Temporal Lobes
These areas are involved in WM, as we become more proficient we require less WM due to efficiency in arithmetic tasks
Mathematical difficulties (DSM V)
Mathematical difficulties are classified as a form of a specific learning disorder:
- Neurodevelopmental disorder of biological origin
- Manifested in learning difficulty and problems in acquiring academic skills markedly below age level (manifested in early school years)
- Lasts at least 6 months
- Cannot be attributed to intellectual disabilities/developmental, neurological or motor disorders
Can be mild/moderate/severe
- If severe, it is known as dyscalculia
Isaacs et al (2001):
Brain bases of developmental dyscalculia: STRUCTURAL DIFFERENCES
- Lower grey matter density in left Intraparietal Sulcus in individuals with dyscalculia compared to healthy counterparts
Ashkenazi et al (2013):
Brain bases of developmental dyscalculia: FUNCTIONAL DIFFERENCES
Looked at differences in fMRI activation in children with developmental dyscalculia vs controls across 3 numeric tasks:
Non-symbolic comparison (dots):
- right Intraparietal Sulcus
- Fusiform Gyrus
Symbolic comparison (Arabic Nums): - right Intraparietal Sulcus
Regular Arithmetic (Addition/subtraction):
- right Intraparietal Sulcus
- Fusiform Gyrus
Depending on task, some activate more some less in dyscalculia (Not full understood why, possibly some compensation?)
