Neuroimaging intelligence testing: Difference between revisions

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{{Orphan|date=March 2013}}

'''Neuroimaging intelligence testing''' concerns the use of [[neuroimaging]] techniques to evaluate human [[intelligence]]. Neuroimaging technology has advanced such that scientists hope to use neuroimaging increasingly for investigations of brain function related to [[Intelligence quotient|IQ]].

== IQ testing ==

Traditional [[Intelligence quotient|IQ tests]] observe the test-taker's performance in a standardized battery of samples of behavior. The resulting IQ standard score is the subject of much investigation as psychologists check correlations between IQ and other life outcomes. The [[Wechsler Adult Intelligence Scale|Wechsler]] IQ tests for adults and for children have long been regarded as the "gold standard" in IQ testing.<ref name="WechslerGold" />

[[File:Functional magnetic resonance imaging.jpg|thumbnail|fMRI data showing regions of activation]]

== Neural bases of intelligence ==

The varying techniques of imaging-based testing search for different signs of intelligence. The types of intelligence analyzed in this review were [[fluid intelligence]] (Gf), [[general intelligence]] (g), and [[crystallized intelligence]] (Gc). Early studies utilized information from patients with brain damage, noticing changes in intelligence scores that correlated to certain regions of the brain. As imaging technology has improved, so has the ability for deeper neuro-analysis. MRI studies have found that the volume of gray matter correlates to intelligence, providing evidence for generalizations made regarding brain/head-size and intelligence. Additionally, PET and fMRI studies have revealed more information regarding the functionality of certain regions of the brain.

By recording and interpreting the brain activity of subjects as they complete a variety of tasks, researchers are able to draw connections between the types of task (and thus, the type of intelligence) that calls on particular areas of the brain. This is interesting as knowingKnowing how parts of the brain are utilized may reveal more information about the structure and hierarchy used in neural development. It also may provide interesting information regarding the pathways of neural signals as they navigate the nervous system. Image-based testing may allow researchers to discover why certain neurons are connected, if they are indeed aligned in a purposeful manner and consequently, how to repair such pathways when they are damaged.<ref>{{cite journal | last1 = Gray | first1 = J. R. | last2 = Thompson | first2 = P. M. | year = 2004 | title = Neurobiology of intelligence: science and ethics | journal = Nature Reviews. Neuroscience | volume = 5 | issue = 6| pages = 471–82 | doi = 10.1038/nrn1405 | pmid=15152197| s2cid = 2430677 }}</ref>

In general, there have been two types of intelligence studies: psychometric and biological. Biological approaches make use of neuroimaging techniques and examine brain function. Psychometrics focuses on mental abilities. Ian Deary and associates suggest that a greater overlap of these techniques will reveal new findings.<ref name=deary1>{{cite journal|last=Deary|first=Ian J.|author2=Austin, Elizabeth J. |author3=Caryl, Peter G. |title=Testing versus understanding human intelligence.|journal=Psychology, Public Policy, and Law|date=1 January 2000|volume=6|issue=1|pages=180–190|doi=10.1037/1076-8971.6.1.180}}</ref>

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===Brain event-related potentials (ERPs)===

Brain ERPs allow for the "sequencing" of psychologically interesting processing. These [[event-related potentials]] are measured brain responses to specific stimuli, such as sensory, cognitive or motor events. ERPs, when compared to "mental speed," have shown a negative correlation with IQ. Research with ERPs suggests that high IQ individuals have a faster response time in some test conditions, have distinguishable ERP waveforms that are different than those of people with lower IQs, and may have less variability in their ERPs. The lack of variability suggests that individuals with a high IQ will have good scores in a variety of testing situations.<ref name=deary2>{{cite journal|last=Deary|first=IJ|author2=Caryl, PG|title=Neuroscience and human intelligence differences.|journal=Trends in Neurosciences|date=August 1997|volume=20|issue=8|pages=365–71|pmid=9246731|doi=10.1016/S0166-2236(97)01070-9|s2cid=13295937 }}</ref>

ERPs can be measured using electroencephalography (EEG), which uses electrodes placed on the scalp to measure the electrical activity of the brain. The ERP waveform itself is constructed from the averaged results of many trials (100 or more). The average reduces signal noise from random-brain activity, leaving just the ERP.<ref>{{cite book|last=Rugg|first=edited by Michael D.|title=Electrophysiology of mind event-related brain potentials and cognition|year=1996|publisher=Oxford University Press|___location=Oxford|isbn=9780198524168|edition=Reprinted.|author2=Coles, Michael G.H.}}</ref> An advantage of ERPs are that they measure processing between stimulus and response continuously. Having this stream of information makes it possible to see where the brain's electrical activity is being affected by specific stimuli.<ref>{{cite book|last=Luck|first=Steven J.|title=An introduction to the event-related potential technique|url=https://archive.org/details/ebusinesserptran00luck|url-access=limited|year=2005|publisher=MIT Press|___location=Cambridge, Mass.|isbn=978-0-262-62196-0|pages=[https://archive.org/details/ebusinesserptran00luck/page/n24 21]–23}}</ref>

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A 2009 study examined intracerebral volumetric relationships in twins. Making use of high resolution MRI data, they found strong genetic connections correlations between cerebral structures. Specifically, the study suggests that a strong correlation exists between the tissue type or spatial proximity and genes. By examining the differences or lack thereof between the brain size of twin children, the researchers drew conclusions that individuals that share genes (i.e. twins) will show similar physiological brain properties compared to genetically-unrelated individuals.<ref>{{cite journal|last=Schmitt|first=JE|author2=Wallace, GL |author3=Lenroot, RK |author4=Ordaz, SE |author5=Greenstein, D |author6=Clasen, L |author7=Kendler, KS |author8=Neale, MC |author9= Giedd, JN |title=A twin study of intracerebral volumetric relationships.|journal=Behavior Genetics|date=March 2010|volume=40|issue=2|pages=114–24|pmid=20112130|doi=10.1007/s10519-010-9332-6|pmc=3403699}}</ref> This study provides evidence of the genetic influence of the brain structure and size, which are believed to both influence intelligence in some way.

Another study in 2006 examined 100 postmortem brains, seeking a relationship between an individual’s Full Scale [[Wechsler Adult Intelligence Scale]] score and the volume of their brain regions. Prior to death, the subjects had completed the WAIS test, which measures verbal and visuospatial abilities. The factors considered important to the relationship between brain size and intelligence were age, sex and hemispheric functional lateralization. They found that general verbal ability was correlated with cerebral volume in women and right-handed men. It was not possible to find a relationship between ability and volume in with every group, however.<ref>{{cite journal|last=Witelson|first=S. F.|title=Intelligence and brain size in 100 postmortem brains: sex, lateralization and age factors|journal=Brain|date=26 October 2005|volume=129|issue=2|pages=386–398|doi=10.1093/brain/awh696|pmid=16339797|doi-access=free}}</ref>

===Neural conduction speed===

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A 2012 study from [[Washington University, in St. Louis]] described the global connectivity of the prefrontal cortex. Global connectivity is the mechanism by which components of the frontoparietal brain network might coordinate control of other tasks. Cole et al. wrote that:

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The [[lateral prefrontal cortex]] is a region of interest because those who have injuries to that part of the brain often have issues with common, every dayeveryday tasks such as planning their day. The LPFC is thought to be important for "cognitive control capacity," which can be used to predict future outcomes such as success in school and the workplace. It was found by van den Heuvel et al. that higher intelligence individuals employ more efficient whole-brain network organization. This had led to the thought that cognitive control capacity may be supported by these whole-brain network properties. The 2012 study used a theoretic approach to neuroimage data known as global brain connectivity (GBC) or weighted degree centrality. GBC let the researches look closely at specific regions and their range of connectivity. It was then possible to examine each region's role in human cognitive control and intelligence. The study used fMRI to acquire data and examine each region's connectivity.<ref>{{cite journal|pmid=22745498 | doi=10.1523/JNEUROSCI.0536-12.2012 | volume=32 | issue=26 | title=Global connectivity of prefrontal cortex predicts cognitive control and intelligence | pmc=3392686 |date=June 2012 | journal=J. Neurosci. | pages=8988–99| last1=Cole | first1=M. W. | last2=Yarkoni | first2=T. | last3=Repovs | first3=G. | last4=Anticevic | first4=A. | last5=Braver | first5=T. S. }}</ref>

== Ethical implications ==

[[Privacy]] and [[confidentiality]] are major concerns for neuroimaging studies. With high-resolution anatomical images, such as those generated by [[fMRI]], it is possible to identify individual subjects, putting their personal / [[medical privacy]] at risk. It is possible to create surface renderings of the brain and face from a [[volumetric]] MRI, which can be paired with photographs to identify the individual.<ref>{{cite journal|last=Kulynych|first=J|title=Legal and ethical issues in neuroimaging research: human subjects protection, medical privacy, and the public communication of research results.|journal=Brain and Cognition|date=December 2002|volume=50|issue=3|pages=345–57|pmid=12480482|doi=10.1016/S0278-2626(02)00518-3|s2cid=2559078}}</ref>

It is becoming more accepted that a neurobiological basis for intelligence exists (at least for reasoning and problem-solving). The success of these intelligence studies present ethical issues. A large concern for the general population is the issue of [[race and intelligence]]. While little variation has been found between racial groups, the public perception of intelligence studies has been negatively impacted by concerns of [[racism]]. It is important to consider the consequences of studies that investigate intelligence differences in population-groups (racial or ethnic) and if it is ethical to conduct these studies. A study suggesting that one group is biologically more intelligent than another may cause tension. This has made neuroscientists reluctant to investigate individual or group differences in intelligence, as they may be perceived as racist.<ref>{{cite journal|last=Gray|first=Jeremy R.|author2=Thompson, Paul M.|title=Neurobiology of intelligence: science and ethics|journal=Nature Reviews Neuroscience|date=1 June 2004|volume=5|issue=6|pages=471–482|doi=10.1038/nrn1405|pmid=15152197|s2cid=2430677 }}</ref>

==See also==

*[[Evolution of human intelligence]]

*[[Intelligence]]

*[[Psychometrics]]

*[[Neuroscience and intelligence]]

*[[Neuroimaging]]

==References==

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[[Category:Intelligence tests|*]]

[[Category:Neuroimaging]]