Jessica A. Clark

Effect of Growth Hormone Replacement Therapy on Cognition after Traumatic Brain Injury

Traumatic brain injury (TBI) is a major public health issue, and yet medical science has little to offer for the persistent symptoms that prevent many of these individuals from fully re-entering society. Post-traumatic hypopituitarism, and specifically growth hormone deficiency (GHD), has been found in a large percentage of individuals with chronic moderate to severe TBI. Presently, there are no published treatment studies of hormone replacement in this population. In this study, 83 subjects with chronic TBI were screened for hypopituitarism. Forty-two subjects were found to have either GHD or GH insufficiency (GHI), of which 23 agreed to be randomized to either a year of GH replacement or placebo. All subjects completed the study with no untoward side effects from treatment. A battery of neuropsychological tests and functional measures were administered before and after treatment. Improvement was seen on the following tests: Dominant Hand Finger Tapping Test, Wechsler Adult Intelligence Scale III-Information Processing Speed Index, California Verbal Learning Test II, and the Wisconsin Card Sorting Test (executive functioning). The findings of this pilot study provide preliminary evidence suggesting that some of the cognitive impairments observed in persons who are GHD/GHI after TBI may be partially reversible with appropriate GH replacement therapy.

Use of the Wechsler Adult Intelligence Scale Digit Span subtest for malingering detection: A meta-analytic review

Twenty-four studies utilizing the Wechsler Adult Intelligence Scale (WAIS) Digit Span subtest—either the Reliable Digit Span (RDS) or Age-Corrected Scaled Score (DS-ACSS) variant—for malingering detection were meta-analytically reviewed to evaluate their effectiveness in detecting malingered neurocognitive dysfunction. RDS and DS-ACSS effectively discriminated between honest responders and dissimulators, with average weighted effect sizes of 1.34 and 1.08, respectively. No significant differences were found between RDS and DS-ACSS. Similarly, no differences were found between the Digit Span subtest from the WAIS or Wechsler Memory Scale (WMS). Strong specificity and moderate sensitivity were observed, and optimal cutting scores are recommended.

Identification of Feigned Mental Retardation Using the New Generation of Malingering Detection Instruments: Preliminary Findings

A recent Supreme Court decision—Atkins v. Virginia, 536 U.S. 304 (2002)—prohibiting the execution of mentally retarded (MR) defendants may have raised the attractiveness of feigning this condition in the criminal justice system. Unfortunately, very few published studies have addressed the detection of feigned MR. The present report compared results from tests of intelligence, psychiatric feigning, and neurocognitive faking in a group of 26 mild MR participants (MR) and 25 demographically matched community volunteers asked to feign MR (CVM). Results showed that the CVM suppressed their IQ scores to approximate closely the level of MR participants. WAIS-III and psychiatric malingering measures were relatively ineffective at discriminating feigned from genuine MR. Although neurocognitive malingering tests were more accurate, their reduced specificity in MR participants was of potential concern. Revised cutting scores, set to maintain a Specificity rate of about .95 in MR clients, were identified, although they require cross-validation. Overall, these results suggest that new cutting scores will likely need to be validated to detect feigned MR using current malingering instruments.

Detection of Malingered Mental Retardation

In a cross-validation of results from L. O. Graue et al. (2007), standard psychological assessment instruments, as well as tests of neurocognitive and psychiatric feigning, were administered under standard instructions to 24 participants diagnosed with mild mental retardation (MR) and 10 demographically matched community volunteers (CVH). A 2nd group of 25 community volunteers was instructed to malinger MR (CVM) during testing. CVM participants obtained Wechsler Adult Intelligence Scale (3rd ed.; D. Wechsler, 1997) Full Scale Intelligence Quotient scores that were significantly lower than the demographically similar CVH group but comparable to the MR group, suggesting that CVM subjects feigned cognitive impairment. On the basis of standard cutting scores from test manuals or published articles, of the 11 feigning measures administered, only the Test of Memory Malingering (TOMM; T. N. Tombaugh, 1996) retention trial had a specificity rate >.90 in the MR group. However, the 2nd learning trial of the TOMM, as well as a short form of the Digit Memory Test (T. J. Guilmette, K. J. Hart, A. J. Guiliano, & B. E. Leininger, 1994), approached this level of specificity, with both at .88. These results raise concerns about the specificity rates at recommended cutting scores of commonly used feigning tests in defendants with MR.

New Measures to Detect Malingered Neurocognitive Deficit: Applying Reaction Time and Event-Related Potentials

The ability of the Test of Memory Malingering (TOMM), reaction times (RTs), and event-related potentials (ERPs) to detect malingered neurocognitive deficit (MNCD) was examined in 32 normal individuals answering under honest (HON; n = 16) or malingering (MAL; n = 16) instructions as well as in 15 patients with traumatic brain injury (TBI) who answered under honest instructions. Overall, the TOMM was the most effective at classifying groups. However, new accuracy, RT, and ERP measures reached promising hit rates in the range of 71–88%. In particular, the difference in frontal versus posterior ERP obtained during an old–new task was effective at classifying MAL versus TBI (hit rate = 87%).

Known-Groups Cross-Validation of the Letter Memory Test in a Compensation-Seeking Mixed Neurologic Sample

Compensation-seeking neuropsychological evaluees were classified into Honest (HON; n = 37) or Probable Cognitive Feigning (PCF; n = 53) groups based on results from the Victoria Symptom Validity Test, the Test of Memory Malingering, and the Digit Span subtest of the Wechsler Adult Intelligence Scale—3rd ed. The groups were generally comparable on demographic, background, and injury severity characteristics, although HON TBI participants were significantly more likely to have a documented loss of consciousness, whereas PCF participants were significantly more likely to be currently on disability. PCF participants scored significantly lower on many neuropsychological test, particularly of memory, as well as higher on most MMPI-2 clinical scales. The PCF group also had significantly higher scores on multiple indices of feigning of psychiatric symptoms. Results from the Letter Memory Test (LMT) were significantly lower for the PCF group, and using the recommended cutting score, specificity was .984, whereas sensitivity was .640, suggesting adequate performance on cross-validation.

CROSS-VALIDATION OF A MANUAL FORM OF THE LETTER MEMORY TEST USING A KNOWN-GROUPS METHODOLOGY

A manual form of the Letter Memory Test (LMT: Orey, Cragar, & Berry, 2000) was compared in neuropsychological evaluees classified as honest (HON: n = 39) or probable cognitive feigners (PCF: n = 10) using results from two well-validated motivational tests. With the exception of lower educational level and higher rate of compensation seeking in the PCF, the groups were equivalent on most important demographic and injury severity parameters. PCF participants scored significantly lower on most neuropsychological tests (median Cohens d = 1.2), as well as on the manual LMT (Cohens d = 4.2). Operating characteristics of the manual LMT in the present sample were comparable to those reported in a similar study using the computerized version of the LMT in neuropsychiatric patients (Vagnini et al., 2006).

Detection of Feigning of Head Injury Symptoms on the MMPI-2

Current epidemiological data suggest that traumatic brain injury (TBI) is among the most common neurological hospital discharge diagnoses in the United States (Kraus & Chu, 2005). These data also indicate that head injuries range considerably in severity. Although a number of alternative indices are available, the most well-accepted indicator of initial head injury severity is the Glasgow Coma Scale (GCS), which quantifies disturbance of consciousness on a scale ranging from 3 to 15 (Eisenberg & Weiner, 1987). Head injuries producing GCS scores in the moderate (9–12) to severe (3–8) range, particularly if accompanied by cerebral hemorrhage and/or skull fracture, are often associated with increased mortality and morbidity (Kraus & Chu, 2005). Head injuries resulting in GCS scores of 13–15 are classified as mild, and approximately 80% of all head injuries fall in this category (Kraus & Chu, 2005). In contrast to the outcome literature on moderate-to-severe head injury, the largest and best-controlled studies to date suggest that by 1-year postinjury, neuropsychological and psychosocial outcome for patients suffering an uncomplicated mild head injury (disturbance of consciousness lasting no more than 1 h and no other indicators of neurological disorder) is comparable to that experienced by patients suffering peripheral trauma not involving brain damage (Dikmen, Machamer, Winn, & Temken, 1995; Dikmen, Ross, Machamer, & Temkin, 1995). Of course, the general trends observed in group studies, however methodologically sound, do not preclude the possibility of poor outcome in selected individual cases.

Reduced Sensitivity of Older Adults to Affective Mismatches

The present study investigated age-related differences in emotional processing by using a paradigm of affective priming. Eighteen, right-handed, younger (mean age 22) and 15 older (mean age 68) subjects pressed buttons to indicate pleasantness of target words. The valence of each prime-target pair was congruent (e.g., win-love), incongruent (e.g., love-loss), or neutral (time-flower). Two sets of 720 prime-target pairs used either affective words or pictures as primes, and affect words as targets. We included well-matched positive and negative valence pairs in all congruent, neutral, and incongruent conditions, and controlled for possible contamination by semantic meaning, word frequency, and repetition effects. The response time (RT) results revealed that young participants responded faster to the targets in affectively congruent conditions than in incongruent conditions. In older participants, the responses to target words were indifferent to all valence congruency conditions. The age effect in affective priming largely reflects reduced sensitivity to affective mismatches among older adults. Intriguingly, emotional Stroop effect and some perceptual priming have been linked to increased interferences and mismatches in older adults. The age-related changes in affective, perceptual, and semantic processes are discussed.

Comparison of functional network integrity in TBI and orthopedic controlpatientsusing graph-theoretical analysis

The integrity of functional brain networks inpatients (n=12) diagnosed with traumatic brain injury (TBI) was compared to age-matched subjects (n=12) with orthopedic injury (OI) during a working memory task. A graph-theoretical analysis algorithm was developed and integrated into the AFNI software. Functional networks with correlations between time courses as edge-weights were automatically created and their integrity was quantified by determining the statistical significance of the following network parameters: diameter, density, clustering coefficient, average path length, two largest eigenvalues, spectral density, and minimum eccentricity. Network graphs using a spring-embedded layout (Cytoscape) and a 3D layout integrated into the anatomical space (Paraview) were created. Functional images were composed by color-coding the degree of each voxel (network node) and transformed into Talairach space. Using the AFNI Talairach atlas, degrees of distinct brain regions were quantified. Reduced averaged BOLD responses were found for the TBI group with a higher network integrity potentially as a compensatory mechanism. Regions of high functional connectivity varied in between groups with largest differences in the cerebellum, the temporal lobes and deep brain structures including the lentiform nucleus, caudate and thalamus.