Brian Imber, Ph.D.(c), from Brain Health Northest in Seattle, WA summarizes some salient research about the Wechsler Adult Intelligence Scale (WAIS-IV) and brain area function mapping. All the indices and quotients of the WAIS-IV were considered when mapping to specific areas of the brain for processing while taking the test. Mapping was done using PET, MRI, SPECT, fMRI, EEG, and QEEG technologies. For the most part, there is evidence to suggest that using EEG and WAIS-IV together would result in performing better assessments than each by themselves and provide more information on the source of psychological dysfunction for the development of treatment plans.
A neuroscientist at California Institute of Technology (Caltech) conducted a comprehensive brain mapping study on cognitive abilities measured by the Wechsler Adult Intelligence Scale (WAIS-IV) to explore insights into various factors that comprise the intelligence quotient that depends on particular regions of the brain. The project was led by Jan Glascher and Ralph Adolphs and a team of neuroscientists and neuropsychologists to map WAIS-IV verbal comprehension (VCI), perceptual organization (POI), working memory (WMI), and processing speed (PSI) indices with voxel-based lesion and symptoms technology of 241 patients with focal brain damage (Gläscher et al., 2009). They found significant relationships among the inferior frontal cortex and VCI, left frontal and parietal cortex and WMI, right parietal cortex and POI. There was no specific brain localization for PSI.
The WAIS-IV was used in this study because of its excellent psychometric properties and high test-retest validity among health and clinical populations along with the extensive database for providing comparatives and standards. This blog discusses the results of this study and other related studies that have progressed the body of knowledge and insights that started with brain-cognition relationships studies of Broca’s area on language, Phineas Gage on social behavior, and H.M. on memory.
Wechsler Intelligence Scales
The Wechsler Intelligence Scales (WAIS-IV) is an individually administered battery of tests to assess areas of intellectual abilities. The test results in a full-scale IQ (FISQ) and scores on specific indices calculated over a combination of subtests. The subtests show an index of verbal comprehension (VCI), perceptual reasoning/Organization (POI), working memory (WMI), and processing speed (PSI). There are core subject subtests for each of these areas. Verbal comprehension subtests for similarities, vocabulary, and information. Perceptual reasoning subtests for block design, matrix reasoning, and visual puzzles. Working memory subtests for digit span and arithmetic. Processing speed subtests for symbol search and coding. Also, there are supplemental subtests for comprehension, figure weights picture completion, letter-number sequencing, and cancellation. Norms are based on 2,200 persons between the ages of 16 and 90 and stratified according to sex, education, ethnicity, and geographical region (Groth-Marnat & Wright, 2016).
The test was further developed for people with mild cognitive impairments, borderline intellectual functioning, traumatic brain injury, Alzheimer’s disease, autism, Asperger’s syndrome, and depression (Groth-Marnat & Wright, 2016). Classifications of scores range from 69 and below to 130 and above and classified as extremely low to very superior respectively. Scores are based on the number of standard deviations from the norm. For example, if someone is classified as very superior, they are 2 or more standard deviations from 50% of the population (Groth-Marnat & Wright, 2016).
Recent studies conducted by Groth-Marnat (2008) and Lezak, Howieson, Bigler, & Tranel (2012) show the WAIS-IV is a good predictor of neurological dysfunction and show true neurological deficits that are further supported by the brain lesion mapping project done at Caltech (Gläscher et al., 2009). The WAIS-IV also provides excellent information about a person’s cognitive strengths and weaknesses as compared to their age-related peers, and it is useful to see an individual’s pattern of strengths and weaknesses. Another major asset of the test is its use in comparing degrees of change in cognition, which is useful to clinicians and neuroscience researchers. In practice, and will be discussed later, a clinician will use the WAIS-IV during treatment with psychotherapy and neurofeedback to indicate if therapy is working and in what direction it is working.
(Gläscher et al., 2009, p. 686)
(Gläscher et al., 2009, p. 686)
Brain Lesion Mapping
Gläscher et al. (2009) conducted an extensive study of mapping brain lesions to cognitive function at Caltech and published the study in 2009. They used data from 241 neurological patients with various types of brain lesions and were psychiatrically healthy. Mapping of each patient’s lesion using CT and MR scans was referenced onto a single brain with significant lesion-deficit relationships and correlated with performance on the WAIS-IV. The etiologies of lesions were cerebrovascular disease, anterior temporal lobectomy, surgical intervention, herpes simplex encephalitis, and traumatic brain injury.
The mapping of WAIS-IV verbal indices for FSIQ, VIQ, and PIQ corresponded to left inferior frontal cortex (an area of the brain involved in speech production), insular cortex, fronto-polar cortex, and the parietal cortex, as well as underlying white matter. The cognitive indices PSI and POI corresponded to right brain hemisphere of the medial cerebral artery and the temporal-occipitoparietal regions.
A specific POI relationship was found in the supramarginal gyrus, the posterior part of the superior temporal sulcus, posterior inferior frontal gyrus, and the dorsal bank of the middle superior temporal sulcus. Lesion relationships with the VCI and WMI indices overlapped with the anterior parts of the medial cerebral artery in the left hemisphere and extending to the posterior of the parietal lobe. VCI has specific correlations with the opercular and pars trianguaris of the left inferior frontal cortex, which is Broca’s area, and all the underlying white matter.
The maximum correlation for WMI was found in the anterior and posterior bank of the central sulcus and its underlying white matter. There were specific correlations of PSI with the frontal and parietal regions of both hemispheres: left anterior precentral gyrus, posterior postcentral sulcus, inferior parietal gyrus, lingual gyrus, right middle frontal, and posterior gyrus. Further correlations of the VCI and WMI indicated a strong shared use of the neural substrate of the inferior frontal cortex.
Specificity and sensitivity analysis on the correlations further showed that POI is sensitive and specific for right hemisphere parietal-occipital and superior temporal cortex function, and VCI and WMI are sensitive and specific for left hemisphere frontoparietal cortex function. Gender and age were also examined following the research done by Haier, Jung, Yeo, Head, & Alkire (2005) that concluded after looking at the relationship between structural brain variations and general intelligence, woman have more white matter and less gray matter areas related to intelligence than men. Men had strong intelligence and gray matter correlations in frontal and parietal lobes, wherein woman the most robust associations are in the frontal lobe along Broca’s area. This study suggested that men and woman achieve similar IQ results with different parts of the brain and there is no one neuroanatomical structure for general intelligence that produces equal intellectual performance between woman and men.
Jung et al. (2005) concluded and found similar findings by looking at differences using CT, MRI, PET, and fMRI analysis with relationships to intellectual functioning among men and woman, and that woman and men use different regions of the brain controlled with similar WAIS-IV results between the two sexes.
Concerning age, Haier, Jung, Yeo, Head, & Alkire (2004) indicated that brain volume accounts for about a 16% difference in general intelligence scores and more gray matter associated with higher scores; individually corresponding to brain development over time. In the Gläscher et al. (2009) lesion study, they found similar correlations among sex and age where a woman had robust left hemisphere distributions with POI and PSI indices scores and men had robust right hemisphere distributions with POI, PSI, VCI, and WMI indices.
The figure below nicely summarizes the findings from the brain mapping and WAIS-IV study showing brain areas relating to cognitive intelligence processing; this is important and suggests clinicians can significantly benefit from using neurofeedback in combination with psychotherapy intervention planning based on cognitive tests.
Clinician Application Using EEG
Korbian Brodmann, a German neurologist, is famous for dividing up the brain into 52 distinct regions based on their characteristics. He created a map that shows regions of the brain that are relatively stable across all species of mammals. Some regions also map nicely to cognitive function, which is consistent with the brain mapping study above (note: Brodmann’s mapping occurred well before Glascher, et al. study). Concerning intelligence test like the WAIS-IV, specific Brodmann areas were associated with a cognitive function such as B10, 11, 46 associated with cognitive, emotional valence, and B45, 47, 46 associated with working memory. Furthermore, another mapping system called, the 10-20 system is projections of brain areas on the surface of the skull to do electroencephalograms assessments (Quantitative EEG – QEEG) and neuromodulation training (Soutar & Longo, 2011). For example, if the WAIS-IV WMI index indicated a problem, the clinician would focus on B45, 47, 46 (located in the prefrontal cortex) and projected to 10-20 site Fp1 on the skull; this is the location where an EEG sensor would be attached for further assessment of brain dysregulation or training for neurotherapy.
Another specific use of the WAIS-IV is a study by Polunina & Davydov (2006) who looked at brain function of heroin addicts and performance on the WAIS-IV along with resting EEG spectrographs. They found high associations of all WAIS-IV quotients with slower EEG spectrograph frequencies in the frontal and temporal regions and predicted a heroin addict would present these unique patterns on their performance of WAIS-IV and EEG assessments.
In another study performed by Marosi et al. (1999), they looked at the relationship of WAIS-IV scores and EEG broadband spectral parameters and found strong correlate of specific brain activity associated with taking the WAIS-IV. Performance correlated with right temporal brain areas with the increased power of theta frequencies. Arithmetic was correlated with left temporal brain areas with the increased power of the beta frequencies. Digit span was correlated with central dorsal brain areas with the increased power of the beta frequencies. Coding associated with the central dorsal brain areas with the increased power of theta frequencies. Picture completion correlated with the central occipital brain areas with increased power in theta frequencies. The conclusion suggested that EEG assessments and WAIS-IV together can provide a more meaningful and more fruitful set of clinical information than either could alone.
Traumatic brain injury affects intellectual functioning as seen on WAIS-IV test results and used in the assessment and rehabilitation of these patients. However, many of these patients are expected to perform poorly on the WAIS-IV. This is a known deficiency of the WAIS-IV because it only indicates a problem, not where the problem is or what brain function is causing it. It is also well known that the WAIS-IV is not a good test of intelligence in brain injury cases (Drozdick et al., 2012). Connolly, Major, Allen, & D’Arcy (1999) conducted a study using the WAIS-IV vocabulary subtest in combination with a form of EEG recording called, “Event-related Potentials” (ERP); this is specific brain wave activity called, “P300” that occurs around 300ms after an infrequent or target task stimulus and associated with memory updating. The study looked at 22 normal healthy people and brain activity recordings from 9 sites on the skull while they took the vocabulary portion of the WAIS-IV. The results of this study showed significant P300 activity when selecting the correct response on the vocabulary portion of the test. The conclusion of this study suggested there is potential use of a combination of EEG and the WAIS-IV for assessment and prediction of some brain injury pathologies that would not be possible with either one by itself.
More advanced research is focused on the relationship between brain regions and how they might work together as a network. One study used the concept of distributed neural processing theory applied to brain function interactions correlated with intelligence as measured by the WAIS-IV (da Rocha, Rocha, & Massad, 2011). These researchers found using QEEG brain mapping, a correlation of distributed intelligence processing occurring while taking the WAIS-IV, and particular high associations of multiple brain areas in visual and verbal processing.
Robert Thatcher (2012), one of the foremost scientific researchers and clinical experts on QEEG and EEG conducted a recent study looking at the network mechanisms associated with intelligence quotients. He observed a phase lock and shift relationship among theta and beta band EEG frequencies showing a high correlation of high intelligence scores and short phase lock-in theta frequencies and long phase lock-in beta frequencies. These relationships occur in short distance brain area connections, and most of this activity takes place in the left hemisphere.
The WAIS-IV and similar other intelligence tests that have strong validation measures are demonstrated to be effective and useful tools for psychological and neurological assessments. Recently, technology for performing bio-medical assessments such as PET, CT, MRI, fMRI, and QEEG are being applied in the fields of clinical psychology and neuroscience. In particular, the QEEG and EEG studies are showing how these neuro-assessment and training technologies can be used in combination with the WAIS-IV to provide more information to both the clinician and client for deciding on how to develop a treatment plan best and execute on it. It is exciting and informative to see how brain functions map to specific WAIS-IV indices and the possible applications they have together when working with clients who have brain injuries to clients wanting to optimize their performance.
If there is further interest in having this assessment for yourself or someone you know that may have symptoms discussed in this blog, Brain Health Northwest in Seattle has the technology and highly skilled and trained clinicians.
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