Lecture 2 Flashcards
Tiedmann (1836)
There exists “an indisputable connection between the size of the brain and the mental energy displayed by the individual man”
Head size vs intelligence
- Vernon et al (2000) – Population correlation between head size and intelligence is 0.19.
- Nguyen and McDaniel (2000) – Population correlations from 0.17 to 0.26 (different sub categories of external head size measures).
Brain volume vs intelligence
- Vernon et al (2000) – Population correlation between brain volume and intelligence is 0.33
- Nguyen and McDaniel (2000) – Population correlations is 0.33
- Gignac, Vernon and Wickett (2003) – Mean correlation is 0.37
McDaniel (2005) Meta-analysis Findings
Significant weak positive correlation (between 0.3-0.4). Stronger correlation for females.
Pietschnig et al (2015)
Reviewed published and unpublished studies of over 8000 individuals. Significant positive correlation of 0.24 between brain volume and IQ.
Evidence of publication bias for studies that show strong positive correlations.
Grey matter definition
Consists of neuronal cell bodies
Cortical thickness definition
The thickness of the brain’s grey matter
White matter definition
The connecting network of axons (or ‘wires’) in the brain
White matter integrity definition
A measure of the health of the white matter connections
White matter hyperintensities definition
Scars in the brain connections
2019 UK Biobank Study (Cox et al, 2019) participants
29004 overall
18426 providing MRI and at least one cognitive test
Mean age 63 years
Cox et al (2019) correlations
Total brain volume - 0.276
Cortical thickness - 0.24
White matter integrity - 0.24
White matter hyperintensities – -0.2 (high IQ means fewer white matter hyperintensities)
Cox et al (2019) results
Grey and white matter amount for more than double the g variance in older participants compared to younger
No sex differences
The largest brain regions that affected intelligence were insula, frontal, anterior/superior, medial temporal, posterior and paracingulate, lateral occipital cortices, thalamic volume, the white matter microstructure of thalamic and association fibres, and of the forceps minor.
Pietschnig et al (2015) quote
“While it is tempting to interpret this association in the context of human cognitive evolution and species differences in brain size and cognitive ability, we show that it is not warranted to interpret brain size as an isomorphic proxy of human intelligence differences.”
Songthawornpong et al (2021)
50 brains from Danish males (aged 20-52 years) for whom there was documentation of premorbid IQ (mean 94, SD 14)
IQ does not correlate with the number of brain cells in the human neocortex and was only weakly correlated to brain weight.
Neurons definition
The basic working units of the brain. They transmit information via electrical impulses to other nerve cells, muscles or gland cells
Oligodendrocytes definition
Lay down myelin around some, but not all, axons. Myelin sheets accelerate the transmission of electrical signals along the neurons axon.
Astrocytes definition
Maintain an appropriate chemical environment for neuronal signalling
Microglial cells definition
Scavenger cells that remove cellular debris from sites of injury or normal cell turnover. Following brain damage, the number of microglial at the site of injury increases dramatically.
Kabadayi et al (2016) animal studies results
The Corvus species performed on a similar level to the great apes, despite vastly smaller absolute brain sizes.
A chimpanzee brain is roughly 26 times larger than a raven’s, but both species achieve 100% success.
The jackdaws were more successful than either the bonobos or gorillas, despite a brain 70-94 times smaller.
Absolute brain size is no overall predictor of motor self-regulation across a wider range of animal taxa.
Scholz et al (2009)
48 healthy adults, 24 control.
Other 24 underwent juggling sessions for 6 weeks for 20 minutes. White matter in the brain changed.
Maguire et al (2000)
Correlation of volume change with time as a taxi driver
Haier et al (1988)
Negative correlation between glucose metabolic rate and intelligence score using Raven’s matrices.
Haier et al (1992a)
After learning a complex visuo-spacial task there was decreased cerebral metabolism
Haier et al (1992b)
After learning to play tennis there were decreases in cerebral metabolism in higher IQ participants.
Ruigrok et al (2014)
On average, adult male brains have 10.8% larger total brain volume than women
(Dyliert et al, 2009; Flynn, 2012; Johnson et al, 2009)
There is an absence of sex differences when it comes to intelligence
Haier and Benbow (1995)
• 22 male and 22 female participants
Half of the males and half of the females had high SAT-Maths Scores (collect entrance; >700)
The other half had average SAT-Maths Scores (410-540)
• During the PET scan, each participant completed a new SAT-Maths test
• Male Participants: significant correlations between the math score and glucose metabolism in the temporal lobes bilaterally (middle, inferior, and posterior; analogous to Bas 20, 21, 22)
• Female participants: no correlations
Cultural differences
Gross Domestic Product (GDP) was significantly correlated with spatial-visual intelligence in a video game created by UCL to help with dementia research.
Ryman et al (2016) - White matter efficiency differences
In male participants: no correlation with IQ
In female participants: positive correlation with IQ
Ryman et al (2016) - Grey matter differences
In male participants: a significant positive relationship between fronto-parietal grey matter region volumes and intelligence.
In female participants: total grey matter volume did predict intelligence in females, but regionally specific contribution of the fronto-parietal gray matter volume was not evident.
Finn et al (2015)
fMRI obtained from 126 participants. Connectivity was stable across all conditions but are unique to individuals.
Finn et al (2015) quote.
“functional connectivity profiles act as a ‘fingerprint’ that can accurately identify subjects from a large group”
“connectivity profiles … that were most discriminating of individuals were also most predictive of cognitive behaviour”
Miranda-Dominguez et al (2014)
A given brain region can be described by the weighted sum of its functional neighbouring regions. (Brains have a different way of showing intelligence for each different person).
Miranda-Dominguez et al (2018)
Individual intelligence is genetic and most heritable systems include the fronto-parietal, dorsal attention, ventrical attention, cingulo-opercular and default systems.
