Compromised validity of test data due to exaggeration or fabrication of cognitive deficits inhibits the capacity to establish appropriate conclusions and recommendations in neuropsychological examinations. Detection of feigned neurocognitive impairment presents a formidable challenge, particularly for evaluations involving possibilities of significant secondary gain. Among specific populations examined in this domain, litigating mild traumatic brain injury (mTBI) samples are among the most researched. One subpopulation with potential to contribute significantly to this body of literature is that of retired athletes undergoing fixed-battery neuropsychological evaluations within an assessment program. Given the considerable prevalence of concussions sustained by athletes in this sport and the substantial monetary incentives within this program, a unique opportunity exists to establish rates of feigning within this population to be compared to similar forensic mTBI samples. Further, a fixed battery with multiple validity tests (VT) offers a chance to evaluate the classification accuracy of an aggregated VT failure paradigm, as uncertainty abounds regarding the optimal approach to the recommended use of multiple VTs for effort assessment. The current study seeks to examine rates of feigned neurocognitive impairment in this population, demonstrate prediction accuracy equivalence between models based on aggregated VT failures and logistic regression, and compare classification performance of various individual VTs.

Psychological trauma may affect higher-order executive functions, which include selective attention, inhibition, and task-switching processes. Difficulty in these executive processes can in turn influence individuals' daily functioning and may also negatively affect the psychological treatment of post-trauma symptoms. Women may be most at risk for developing problems with executive functioning following trauma, consistent with their overall greater risk of developing post-trauma symptoms. Yet, little is understood about the influence of psychological variables, premorbid functioning, and specific trauma factors in determining post-trauma cognitive functioning in women. Additionally, individual variability in susceptibility to psychological distress and neuropsychological deficits following trauma remains an open area of study. The present study investigated the relationship between psychological and trauma factors with neuropsychological outcomes in women with trauma histories as well as individual variability in risk for poor neuropsychological outcomes. In total, 60 participants' data (age M = 29.73, SD = 10.91) were included in analyses. The final sample consisted of 33 community members recruited from the UNT Psychology Clinic and the UNT student body and 27 veterans recruited from the Veterans Affairs North Texas Healthcare System (VANTHCS). Regression and path analysis identified premorbid intellectual functioning as a predictor of better neuropsychological outcomes and anxiety and depression symptoms as risk factors for worse neuropsychological functioning. Person-centered cluster analyses focused on individual differences in outcomes identified three groups differing in psychological distress and neuropsychological functioning. Additional analyses identified differences in trauma exposure, psychological functioning, and neuropsychological performance between subgroups of civilians and veterans and those with and without a history of PTSD.

This thesis investigates the effect of normal ageing on the strategies adopted during episodic memory retrieval, using a combination of neuropsychological profiling and neuroimaging data measured during performance on a source memory exclusion task. The exclusion task is a type of source memory task where participants distinguish between targets (studied items from one source e.g. female voice), non-targets (studied items from another source e.g. male voice) and new items. Unlike a source memory task where three separate buttons are pressed for each item at test, in the exclusion task one button is pressed for targets and a second for non-target and new items. As this task is more complex than a normal source memory paradigm and also allows participants to perform the task in more than one way, it places high emphasis on the use of strategies to facilitate retrieval and is therefore ideal for investigating strategic retrieval. Previous source memory studies have shown that while older adults are reasonably good at recognising whether items are old or new, they show marked impairments at remembering the source in which items were presented at study. Dual process theories propose that the age-related decline in source memory occurs because recollection becomes impaired with ageing whereas familiarity remains relatively spared. The results reported in this thesis support dual process theory. Experiment 2a showed that, behaviourally, as expected, the young outperformed the elderly. Event-related potentials (ERPs), recorded while a source memory exclusion test was performed, revealed that both young and older adults showed bilateral frontal and left parietal old/new effects, thought to index familiarity and recollection respectively. Importantly, the magnitude of the left parietal effect was significantly reduced in the older adults. The ERP findings also suggested that dual process theories represent an oversimplification of episodic memory decline with age. In Experiment 1a, three temporally and topographically distinct late frontal old/new effects were present in the younger adults: a bilateral anterior frontal effect (450-900ms post stimulus), a right prefrontal effect (900-1300ms) and a right frontal effect (1300-2000ms). Significant positive correlations between the magnitude of these effects and performance on neuropsychological tests of executive functioning in Experiment 1b, revealed that the bilateral anterior frontal effect was related to working memory, strategy use and planning; the right prefrontal effect was related to working memory and planning while the right frontal effect was related to planning. By contrast, the older adults in Experiment 2a only produced the right frontal effect, which correlated with planning across all three time windows in Experiment 2c. Post-retrieval monitoring in older adults therefore appeared to be qualitatively different than their younger counterparts. Performance on the neuropsychological tests in Experiment 2b, revealed that the older adults’ working memory and strategy use was impaired compared to the young, whereas planning was relatively intact, suggesting that age-related differences in post retrieval processing may be due to reduced executive functioning in older adults. Identifying distinct late frontal effects and demonstrating a relationship between these effects and specific executive functions is a novel finding. The presence of a left parietal target greater than non-target difference in the young adults from Experiment 1a and 2a was interpreted as the young reducing recollection of irrelevant non-target information. The modulation did not differ in magnitude for targets and non-targets in the elderly adults from Experiment 2a, suggesting they were less able to reduce activation of goal irrelevant non-target information. The results in the young adults from Experiment 1a also highlight the importance of considering the context of source information on the processes engaged at retrieval. The bilateral frontal effect was significant for the retrieval of the intrinsic context (source information inherent to the studied item), but not the extrinsic context (source information not inherent to the studied item). This finding was interpreted within a unitisation framework, where the intrinsic context became unitised with the item and enhanced familiarity based remembering. The findings also highlight that in order to fully understand post retrieval processing in both young and old adults, focus should move away from examining quantitative differences in the right frontal effect over long time periods and instead identify qualitatively distinct late frontal effects that may reflect the engagement of various executive functions over time.

Thesis (Doctoral)--Ludwig-Maximilians-Universität.

Text in Afrikaans / Hierdie studie ondersoek die moontlikheid dat aandagtekort versteuring met hiperaktiwiteit(ATHV/H) verband hou met probleme met voortgesette aandag, terwyl aandagtekort versteuring sander hiperaktiwiteit(ATHV/SO) verband hou met probleme met gefokusde aandag. Neurosielkundige toetse waarmee voortgesette- en gefokusde aandag gemeet word, word gebruik om drie groepe, naamlik ATHV/H(n=24), ATHV/SO(n=l5) en 'n kontrole groep(n=21), met mekaar te vergelyk. Resul tate dui daarop dat die groep ATHV/SO beduidend swakker presteer as die ander twee groepe op sommige van die toetse van gefokusde aandag, en ook neig om swakker te presteer op die toets van voortgesette aandag. Die groep ATHV/SO se probleme blyk gekoppel te wees aan 'n stadiger spoed van kognitiewe prosessering en 'n toestand van hipoopwekking. Die groep ATHV/H presteer nie beduidend swakker as die ander twee groepe op die toets van voortgesette aandag nie, maar presteer wel swakker as die kontrole groep op die Stroop Colour-Word Test waar inhibisie van ontoepaslike response vereis word. Die groep ATHV /H se probleme blyk verband te hou met frontale disfunksie wat manifesteer as 'n neighing tot impulsiwiteit en gebrekkige gedragsregulering. / This study examined the possibility that attention deficit disorder with hyperactivity(ADHD/H) is related to problems with sustained attention, while attention deficit disorder without hyperactivity (ADHD/WO) is related to problems with focussed attention. The performance of three groups: ADHD/H (n=24), ADHD/WO(n=15) and a control group(n=21) were compared. Results indicated that the ADHD/WO group performed significantly poorer than the other two groups on some of the tests of focussed attention and also tended to perform poorer on the test assessing sustained attention. This groups' symtoms appear to be related to a slowed speed of processing and a state of hypo-arousal. The ADHD/H group did not perform poorer than the other two groups on the test assessing sustained attention. The ADHD/H groups' symptoms appear to be related to frontal dysfunction resulting in impulsivity and poor behavioural control. / Psychology / M.A. (Sielkunde)

Objective: The long-term cognitive effects of mild traumatic brain injury (MTBI) and sport-related concussion (SRC) are not always clear. Higher-level longer-term cognitive difficulties can indicate enduring neurological damage, as part of a post-concussion syndrome (PCS). This study aimed to investigate whether cognitive performance and self-reported PCS symptoms of athletes (rugby players) relate to SRC and whether gender moderates these effects. Method: Eighty-six participants completed a questionnaire detailing SRC history (frequency and severity) and rated long-term symptoms using the Sport Concussion Assessment Tool 3 (SCAT3) symptom evaluation scales, before completing the CogState Brief Battery and STOP-IT (stop-signal response inhibition task). Results: No significant relationships between SRC dosage (frequency/severity), self-reported PCS symptoms, and cognitive test performance were identified. A greater proportion of males reported SRC compared to females, but no effect of gender was found on any of the cognitive outcome measures or self-reports of PCS symptoms. Conclusions: The results show that SRC has no observable long-term effects on cognitive test performance or PCS symptom self-reports. The analysis may have lacked power to detect effects. Analysis of individual performance over time against baseline scores may be more relevant for accurate diagnosis than relying on normative test scores. Recommendations for future research were made.

Text in Afrikaans / Hierdie studie ondersoek die moontlikheid dat aandagtekort versteuring met hiperaktiwiteit(ATHV/H) verband hou met probleme met voortgesette aandag, terwyl aandagtekort versteuring sander hiperaktiwiteit(ATHV/SO) verband hou met probleme met gefokusde aandag. Neurosielkundige toetse waarmee voortgesette- en gefokusde aandag gemeet word, word gebruik om drie groepe, naamlik ATHV/H(n=24), ATHV/SO(n=l5) en 'n kontrole groep(n=21), met mekaar te vergelyk. Resul tate dui daarop dat die groep ATHV/SO beduidend swakker presteer as die ander twee groepe op sommige van die toetse van gefokusde aandag, en ook neig om swakker te presteer op die toets van voortgesette aandag. Die groep ATHV/SO se probleme blyk gekoppel te wees aan 'n stadiger spoed van kognitiewe prosessering en 'n toestand van hipoopwekking. Die groep ATHV/H presteer nie beduidend swakker as die ander twee groepe op die toets van voortgesette aandag nie, maar presteer wel swakker as die kontrole groep op die Stroop Colour-Word Test waar inhibisie van ontoepaslike response vereis word. Die groep ATHV /H se probleme blyk verband te hou met frontale disfunksie wat manifesteer as 'n neighing tot impulsiwiteit en gebrekkige gedragsregulering. / This study examined the possibility that attention deficit disorder with hyperactivity(ADHD/H) is related to problems with sustained attention, while attention deficit disorder without hyperactivity (ADHD/WO) is related to problems with focussed attention. The performance of three groups: ADHD/H (n=24), ADHD/WO(n=15) and a control group(n=21) were compared. Results indicated that the ADHD/WO group performed significantly poorer than the other two groups on some of the tests of focussed attention and also tended to perform poorer on the test assessing sustained attention. This groups' symtoms appear to be related to a slowed speed of processing and a state of hypo-arousal. The ADHD/H group did not perform poorer than the other two groups on the test assessing sustained attention. The ADHD/H groups' symptoms appear to be related to frontal dysfunction resulting in impulsivity and poor behavioural control. / Psychology / M.A. (Sielkunde)

One of the consequences of traumatic brain injury is the postconcussion syndrome. The symptoms in this syndrome include headache, dizziness, poor memory, poor concentration, easy fatigue, drowsiness, irritability, sensitivity to light, sensitivity to noise, low alcohol tolerance, visual problems, auditory problems, nausea, vomiting, anxiety, and depression. Several factor analytic studies have shown that these symptoms load onto cognitive and noncognitive factors (Bohnen, Twijnstra, & Jolles, 1992). The aim of this study was to determine whether patients who report different symptoms also evidence differences in cognitive deficits, as indexed by reaction time. For this purpose 106 subjects (mean age 25.92 years; SD=6.05) of both sexes were tested on 8 reaction time tasks adapted from Shum, McFarland, Bain, and Humphreys (1990). There were 54 traumatic brain injury patients (mean age 26.40 years; SD=6.23) drawn from three Pretoria hospitals. They were heterogeneous with respect to diagnosis and severity of injury. For the controls (N=52), the mean age was 25.43 years (SD=5.88). The eight reaction time tasks constituted 4 task variables, each with 21evels. From these tasks, 36 reaction time indexes were derived. The indexes were classified into 4 groups, viz., reaction time (RT), movement time (MT), total reaction time (TT), and subtraction scores (SB, the difference between the 2 levels for each task variable). RT reflects the decision component and MT reflects the response execution component of reaction time. Partial correlation coefficients for all symptoms (p0,01) showed that some symptoms were most frequently associated with RT whilst others were most frequently associated with MT. On factor analysis with varimax rotation, symptoms loaded predominantly with SB scores. Symptoms also loaded with different task variablseuiggesting that they correlated with deficits on different stages of information processing. Taking into account possible methodological constraints that were discussed, these results confirm that different symptoms within the postconcussion syndrome correlate with different cognitive deficits. The correlations between symptoms and indices of reaction time are moderated by the characteristics of the symptoms (frequency & intensity), and the duration since injury. These findings have significance for understanding the aetiology of the postconcussion symptoms and for planning treatment. / Psychology / Ph. D. (Psychology)

The present study aimed at investigating the neuropsychological sequelae of transient ischaemic attacks. Transient ischaemic attacks are defined as those neurological disorders in which there is complete resolution of neurological symptoms within twenty·four hours. Transient ischaemic attacks may or may not reveal evidence of brain infarcts on imaging studies. In the present study, the neuropsychological sequelae of transient ischaemic attacks in the carotid circulation were investigated since, within the perspective of cognitive neuropsychology, it was assumed that localized changes in cognitive functions could be demonstrated.Since several psychological, medical and neurological factors are known to influence scores·on neuropsychological tests, regression analyses were performed to determine which factors contributed significantly to the variance of scores on neuropsychological tests in the transient ischaemic attack and control groups. Two transient ischaemic attack groups, each comprising forty left and forty right hemisphere involvement patients, were then compared with each other and with a control group of forty general medical patients. Stenosis of the carotid artery formed a significant predictor of test scores in the combined transient ischaemic attack group. When the groups were·analyzed independently, in the left transient ischaemic attack group stenosis predicted performance on the same tests reaching significance for the combined group, and for the Wisconsin Card Sorting Test (Perseverative Score). In the right transient ischaemic attack group, stenosis significantly predicted performance on Digits Forward, Backward and Total, the PASAT (2.4 seconds) and Trails B. On the other hand, education formed a significant predictor of performance on Digits Forward, Digits Backward and Digits Total and the PASAT (all levels) in the control group. Multivariate comparisons revealed that the left and right transient ischaemic attack groups performed worse than the controls on tests of attention, concentration and conceptual flexibi1ity. The left transient ischaemic attack group performed worse than the right transient ischaemic attack group on all tests of attention and concentration, but there was a significantly better performance of the former group on the Rey Auditory Verbal Learning Test (Trial 1), Block Designs and Verbal Fluency. The findings on the PASAT that left transient ischaemic attack patients performed significantly worse than the right hemisphere group ·were considered to be relatively unreported previously in the literature on transient ischaemic attacks. The findings obtained are discussed from a neurocognitive perspective of neuropsychological functioning in transient ischaemic attacks. / Psychology / Ph. D. (Psychology)

Pain is a personal subjective experience with physiological and psychological components and involves many complex processes. In 1965 Melzack and Wall proposed the influential gate control theory (GCT) of pain and, in general, this has been supported by subsequent research. This theory postulates that cells in the substantia gelatinosa, located within the spinal cord, act like a gate mechanism that modulates the flow of information through the spinal cord to the brain and thus impacts on the pain experience. The abundance of literature and experimental data that is available from pain research supports the development and testing of computational models for the simulation and exploration of the pain process. Despite the fact that pain is an ideal candidate for modeling, it is an area that has received little attention. One of the few published models (Britton and Skevington, 1989; Britton et al., 1996) translated the explicitness of the GCT and its well-defined architecture into a basic mathematical model. The aim of this research is to develop a biologically appropriate computational model of pain, capable of modelling both acute and chronic pain states, and describe applications and simulations appropriate to such a model. Therefore this research firstly replicates a mathematical model of pain (Britton and Skevington, 1989; Britton et al., 1996) to explore its adequacy and to assess its potential for further development. The original model is then developed and extended to produce a more biologically plausible representation of the pain processes involved in the Gate Control mechanism. The improvements in the computational model have enabled a clinically plausible simulation of a pain modulatory technique, transcutaneous electrical nerve stimulation (TENS), which validates the model’s representation of the GCT and provides insight into how pain modulation can occur. Other developments to this model show its unique ability to represent symptoms of chronic pain, such as allodynia and hyperalgesia, which are associated with pathological pain states developed through the loss of inhibition and glial cell activation