6- Biological Theories (Neuroscience theories) Flashcards
Premise(s) and does IQ correlate with brain size?
Genes to
Biology to
Brain to
Intelligence to
Intelligent Behavior
IQ and Brain Size
Need to control for body size
Wasn’t always done in intelligence studies
“Old” methods :
* Endocast
* Head circumference
Jensen (1998) : “ head
size is mostly correlated
with g because head
size is a proxy for brain
size. “
(See brain parts) in slide 7
Does IQ correlate with brain regions?
Lesions studies
EARLY INSIGHTS INTO BRAIN FUNCTIONALITIES
Localizationism and Anti-localizationism
Flourens: pigeon brains, many had no effects of the legions, concluded we only use 10% of our brain
Broca: human legions, specializations in the brain, language production (Broca’s area), Broca’s aphasia
Lashley: (anti-localizationism) Rats after legions and mazes, equipotentiality= one part of the cortex can take over if another is legioned, mass action= efficacy of learning depends on the amount of cortex available, not about localization but about the amount of brain that we affect
Gazaniga: studying epilepsy patients, split brain, right brain and left brain
Milner: specific brain regions serve different purposes, patient H.M., ‘’mother of neuropsych’’
Lesion studies
Ex: Phineas Gage
Highlight the importance of PFC in intelligence
-Brain regions
being damaged = a drop in full IQ (especially anti-localizationism, but true as well)
-Brain regions
being damaged = Drop in IQ indexes
(domain specific) (especially localizationism)
Perceptual organization affected if legion in the occipital cortex (seeing)
Verbal comprehension affected if… (read about it cuz i didn’t hear)
IQ and brain regions: Brain imaging: Structural imaging
“Modern” methods:
1. CT Scan : Computed
tomography using X-rays
2. MRI : Magnetic Resonance
Imaging
revealing the structure of soft
tissue in the body.
It uses magnetic fields and
radio waves to produce two or three-dimensional images
of brain structures.
Yes IQ scores correlate with total brain size
Positive correlation with total brain volume and IQ
Around .3 (McDaniel,
2005; Gignac et al 2005)
More recent review say .4 (Colom et al 2010)
Correlation is higher in
female (Gignac et al
2003) But not always
(Gur et al 1999; Haier et
al 2005)
Correlation is higher in adults than children (children less because of pruning and development)
Structural imaging showed highest
Correlations IQ / g / Gf & grey matter are
found in
* Prefrontal
* Parietal
* Occipital
* Cerebellum
Structural imaging (brain density):
Correlations IQ & grey matter are more
important in
* Prefrontal
* Parietal (Δ across studies)
* Cingulate gyrus - Limbic system
IQ scores and brain activity: Brain imaging: Functional imaging
IN THE EARLY 1980S, PET WAS A GAMECHANGER…
FDG PET fMRI
Reminder: Functional imaging = “activation” (use of glucose or O2) in X area
Images with consumption
of GLU or O2
Conclusion : the regions
that “light up” are
involved in the test
Jung and Haier (2007) reviewed 37 structural and functional neuroimaging studies
Discrete brain regions of the dorsolateral prefrontal
cortex and the parietal cortex could be
considered most important for human intelligence.
Based on the commonalities found in their analysis, they
proposed the Parieto-Frontal Integration Theory (PFIT)
Functional imaging: the Network
theory -
The Fronto Parietal integration theory (PFIT)
Areas consistently foun to be associated with
intelligent behavior
* Frontal lobes
* Parietal lobes
* White matter tracks connecting the regions
“distributed network
of intelligence”
Brain integrates in posterior
areas then further integration
to higher level processes
(inhibition/decision) in the
anterior areas
This network may explain
why 2 person can produce
an intelligent behavior with
activating different regions
Efficiency theory - Neural Efficiency
Brain functioning is expensive!
Represents 2% of body weight
Consumes
* 20% of total O2
* 25% of total Glucose
Brain efficiency theory (90s) : “ its not how
hard the brain works that makes you smart,
its how efficiently it works” Haier and coll.
Study: FDG PET :
glucose
metabolism
Example of 2 individual working on Raven Matrices(total n=8)
Results:
Less brain activation on one with the higher score (more efficient) (goes against the idea that more activation=working harder and better score)
FDG PET : takes approx 32 min to get an image –low time
resolution. We cant look at performance for each item :(
Other study: Haier et al 1992
Naive vs. practice
Playing Tetris game
The high IQ participants became more efficient after practice (WAIS + Raven’s Matrices used to assess intelligence) Many other studies have replicated this decreased activity after practice
(see parts of the brain slide 33)
Higher the IQ the more intense the decrease activity: The high IQ participants became more efficient after practice (WAIS + Raven’s Matrices used to assess intelligence). So higher IQ people would be better at learning
Fast-forward in the future… review from 2009
* most early studies confirmed the efficiency hypothesis
* later research revealed moderating variables : sex, task type, task complexity or brain area
* Effect found for tasks of (subjectively) low to moderate task difficulty
* Effect is mainly observable for frontal brain areas
The inefficiency hypothesis
Haier and collabs were then wondering ..
if low IQ individuals might have less efficient brains, due to a failure of neural pruning.
Neural pruning : normal developmental reduction of extra synapsis
- starts around 5 years in humans
Recruited and scanned during the CPT (an attentional task).
Individual with low IQ (50-75) (n=7)
- the research at the time suggested that it could be resulting of a failure in neural pruning) *next slide
Individual with down syndrome (n=10)
Controls (n=10)
Interpretation : better use of resources after practice
Low IQ individuals show greater consumption of Glucose (due to failure of pruning aka lack of specialization aka less efficient)
Proves the same thing as the efficiency theory
Predictions
PET scan of low IQ individual would show lower activity
because of some kind of brain damage was assumed to be responsible for the low IQ.
PET scan of low IQ individual would show lower activity in
individuals with down syndrome because it was thought to be caused by a failure of neural pruning
Findings:
The PET image showed more activities (i.e. yellow and red) through the brain in both low IQ groups compared to normal controls on the right.
They saw this as evidence for the efficiency hypothesis.
Each subject from the previous study ALSO
completed structural MRI to determine
brain volume..
Result:
“Bigger brains use less glucose” Glucose consumption rate and brain volume correlation= -0.7 (but inflated results)
Fast-forward in the future… review from 2009
* training studies suggest that the amount and quality of learning also has to be taken into account
* Effect found for easier novel tasks or after sufficient practice allowing participants to develop appropriate (efficient) strategies to deal with the task.
Also…
* When the task is very complex, higher IQ individuals invest MORE cortical resources resulting in positive correlations between brain usage and cognitive ability.
Resting and Passive States
Default mode network
network of brain regions that are active when an
individual is awake and at rest (chilling)
- Circuit of interconnected and defined brain regions
Activates when individuals focus on internal tasks
- daydreaming, envisioning the future, retrieving
memories, and gauging others’ perspectives
(IDK if this is important or not but the salmon study… In the same vein, here is one of my favorite fMRI study..The task:
* The task administered to the participant involved
completing an open-ended mentalizing task.
* The Participant was shown a series of photographs
depicting human individuals in social situations with a
specified emotional valence.
* The participant was asked to determine what emotion
the individual in the photo must have been
experiencing. Subject: dead salmon
Moral of the story: with the extreme dimensionality of fMRI data comes an extreme risk for false positives)
Passive tasks:
Results showed greater activation in specific posterior brain areas (left BA37/19) in high RAPM scorers ( P=.02, corrected for multiple comparisons). AKA (higher iq show greater activation even at rest)
Subsequent analyses revealed a high/low RAPM group difference in
functional connectivity between left BA37/19 activity and the left
anterior cingulate/medial frontal gyrus.
Passive tasks, fMRI
In short :
* Haier et al (2003) found a correlation with their Ravens
score and activation in posterior area during the
mindless task. (Haier 2003).
* Later studies also did find link between frontal
activations and passive tasks like watching TV (van den
Heuvel et al 2009; Buckner et al 2009)
* Boivin et al. (1992), did PET with 33 subjects at ‘‘rest’’
(i.e., no specific g task) and found inverse positive correlations
between frontal lobe activity and scores on the RAPM
and the WAIS. (agrees with Haier et al.)
EEG and resting state:
-Generally, N1 is assumed to reflect
selective attention to basic stimulus
characteristics, initial selection for later
pattern recognition, and intentional
discrimination processing (e.g., Vogel
& Luck, 2000).
-the P300 component is thought to reflect a higher cognitive
response to unexpected and/or cognitively salient stimuli
(??)
Look at the shape of the wave of the event-related potential (ERP)
High IQ= bigger amplitude (but these results haven’t been replicated) (contrary to efficiency theory), but it’s actually the other way (negative correlation) (more studies prove the efficiency theory)
Summary
IQ scores correlate with brain size, brain regions and brain activity
Neuromyths
We only use 10% of our brain. (False)
Some of us are “left-brained” and some are “right-brained,” and this helps explains differences in how we learn. (False)
Exercises that rehearse coordination of motor-perception skills
can improve literacy skills. (False)
Individuals learn better when they receive information in their
preferred learning style (e.g., auditory, visual, kinesthetic). (False)
Mental capacity is genetic and cannot be changed by the environment or experience. (False)
Brain development has finished by the time children reach
puberty. (False)
We use our brains 24 h a day. (True)
There are specific periods in childhood after which certain
things can no longer be learned. (False)
