Identifying simulators of cognitive deficit through combined use of neuropsychological test performance and event-related potentials

On the Use of Eye Movements in Symptom Validity Assessment of Feigned Schizophrenia

Assessing the credibility of reported mental health problems is critical in a variety of assessment situations, particularly in forensic contexts. Previous research has examined how the assessment of performance validity can be improved through the use of bio-behavioral measures (e.g., eye movements). To date, however, there is a paucity of literature on the use of eye tracking technology in assessing the validity of presented symptoms of schizophrenia, a disorder that is known to be associated with oculomotor abnormalities. Thus, we collected eye tracking data from 83 healthy individuals during the completion of the Inventory of Problems – 29 and investigated whether the oculomotor behavior of participants instructed to feign schizophrenia would differ from those of control participants asked to respond honestly. Results showed that feigners had a longer dwell time and a greater number of fixations in the feigning-keyed response options, regardless of whether they eventually endorsed those options (d > 0.80). Implications on how eye tracking technology can deepen comprehension on simulation strategies are discussed, as well as the potential of investigating eye movements to advance the field of symptom validity assessment.

Distinguishing Between Genuine and Feigned Dementia Using Event-related Potentials

BACKGROUND

Individuals with probable Alzheimer disease (AD) may perform below cutoffs on traditional, memory-based performance validity tests. Previous studies have found success using event-related potentials (ERPs) to detect feigned neurocognitive impairment in younger populations.

OBJECTIVE

To evaluate the utility of an auditory oddball task in conjunction with the P3b peak amplitude to distinguish probable AD from simulated dementia.

METHOD

Twenty individuals with probable AD and 20 older healthy controls (HC) underwent an ERP auditory oddball protocol and the Test of Memory Malingering (TOMM). The HC were asked to perform honestly for one condition and to simulate dementia for the other. The individuals with probable AD were asked to perform honestly. The P3b peak amplitude and button press accuracy were collected from each participant and were analyzed to determine their effectiveness in detecting performance validity.

RESULTS

The P3b peak amplitude remained stable regardless of behavioral condition in the HC group. When combined with the TOMM Trial 2 score, the P3b peak amplitude further improved the ability to correctly differentiate individuals with probable AD from HC simulating dementia with 100% sensitivity and 90% specificity.

CONCLUSION

The P3b peak amplitude was found to be an effective physiologic measure of cognitive impairment in individuals with probable AD compared with HC simulating dementia. When combined with the TOMM Trial 2 score, the P3b peak amplitude served as a promising performance validity measure for differentiating individuals with probable AD from HC simulating dementia.

Feigning memory impairment in a forced-choice task: Evidence from event-related potentials

Strategies of malingering detection have brought about a wealth of neuropsychological studies in the last decades. However, the investigation of physiological measures to reliably differentiate between authentic and manipulated symptom presentations is still in its infancy. The present study examined event-related potentials (ERP) to identify feigned memory impairment. We tested instructed malingerers (n = 25) and control participants (n = 22) with a recognition task similar to the Test of Memory Malingering. No differences between groups were found for P1 (70-110 ms) but for N1 (120-170 ms) and P300 components, with lower amplitudes for instructed malingerers. Behavioral data showed a typical pattern of unrealistically high errors in a forced-choice recognition task and less overall recalled stimuli in instructed malingerers. We also found study-phase repetition and old/new effects in the P300, but no interactions with groups (control vs. malingering). Post-hoc analyses revealed that the P300 effect is greater when participants reported an attention-based faking strategy, as opposed to response-based malingerers and controls. The employment of physiological measures can yield additional information on the validity of test data without the need to perform additional tests.

ERP correlates of malingered executive dysfunction

Assessment of malingering has become an integral part of many neuropsychological evaluations, particularly in forensic settings. However, traditional malingering measures are known to be vulnerable to both manipulation and coaching. Consequently, recent research has attempted to identify physiological indices of cognitive functioning that are less susceptible to overt manipulation. While prior studies have explored the validity of physiological assessment of memory deficits, this study evaluates the effectiveness of a physiological measure of executive functioning. This study used EEG recording in conjunction with a three-stimulus oddball design to compare neural responses in simulated malingerers feigning cognitive deficits associated with traumatic brain injury (TBI) and controls. Specifically, the study explored the efficacy of an event-related potential (ERP) known as P3a, which is believed to be an index of frontal lobe executive processes, specifically the attentional orienting response. The results of this study demonstrated that simulated malingerers did not produce a P3a response that was significantly different from control participants. Furthermore, the P3a in simulated malingerers did not demonstrate any of the properties reported in prior studies with TBI patients. Not only were malingerers unable to produce a significant change in their basic orienting response, but the very process of attempting to employ additional strategies to appear impaired produced other physiological markers of deception. Therefore, the P3a component appeared to be unaffected by an individual's motivation or overt performance, which suggests that it may have potential for development as a physiological measure for differentiating between malingerers and those with genuine TBI.

Impact of stimulus similarity between the probe and the irrelevant items during a card-playing deception detection task: the "irrelevants" are not irrelevant

Event-related brain potential paradigms for the detection of concealed information commonly involve presenting probes embedded within a series of irrelevant items. This study investigated the impact of similarity of the irrelevant items with the probe. For the task, a card was shown followed by the sequential presentation of six "test" cards, one of which was the same as the initial card (the probe) along with five "irrelevant" cards that varied in terms of similarity with the probe. Participants either identified or denied recognition of the probe. The results show that P300 amplitude is modulated by stimulus similarity and highlight the importance of the irrelevant items on deception detection rates.

Die differentielle Validität neuropsychologischer Testverfahren zum Nachweis nicht-authentischer Störungen

Ziel dieser Studie ist es, die Eignung unterschiedlicher neuropsychologischer Verfahren zur Diagnostik von nicht-authentischen Störungen zu ermitteln. Darüber hinaus soll untersucht werden, ob Beschwerdenvalidierungstests (BVT) eine höhere Validität gegenüber anderen neuropsychologischen Verfahren zum Nachweis von nicht authentischen Störungen aufweisen. Dazu wurden 59 Probanden untersucht, die zwischen 2003 bis 2013 forensisch-neuropsychologisch begutachtet wurden. Sie wurden hinsichtlich ihrer Authentizität ihrer neuropsychologischen Beschwerden beurteilt. Neben neuropsychologischen Tests wurden auch BVT eingesetzt. Es zeigte sich, dass die BVT hoch signifikant mit der gutachterlichen Gesamtbeurteilung korrelieren. Zwischen den neuropsychologischen Standardverfahren und der gutachterlichen Gesamtbeurteilung konnten keine signifikanten Zusammenhänge nachgewiesen werden. Es sind demnach nur diejenigen Verfahren, die speziell für den Nachweis von nicht-authentischen Störungen entwickelt worden, dazu geeignet, die Authentizität der Beschwerdenschilderung zu messen.

Normal sensory and absent cognitive electrophysiological responses in functional visual loss following chemical eye burn

OBJECTIVE

To present a unique case of a 34-year-old patient with unilateral functional visual loss after chemical burn with normal visual evoked potentials (VEPs) and absent cognitive response (P300 wave).

METHODS

Visual functions, complete ophthalmic and neurologic examinations including computed tomography of the brain, electrophysiological testing of the visual pathway up to the cognitive brain cortex were evaluated. Data were collected prospectively during 1-year follow-up and compared with data from published case series and a literature review.

RESULTS

No abnormalities were found that could account for such a rapid monocular loss of vision with exception of absence of the P300 wave in the affected eye during cognitive tasks. Vision slowly improved during 1 year without any treatment.

CONCLUSIONS

Functional vision loss is a diagnosis of exclusion. In the event of reduced vision in the context of a normal ocular health examination, all other pathology must be ruled out before the diagnosis of functional visual loss is established. Complex visual electrophysiological testing is the preferred tool for objective examination of such disorders.

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%).

The Booklet Category Test and Malingering in Traumatic Brain Injury: Classification Accuracy in Known Groups

A known-groups design was used to determine the classification accuracy of 12 Booklet Category Test variables in the detection of malingered neurocognitive dysfunction (MND) in traumatic brain injury (TBI). Participants were 206 TBI and 60 general clinical patients seen for neuropsychological evaluation. Slick, Sherman, and Iverson's (1999) criteria were used to classify the TBI patients into non-malingering, suspect, and MND groups. Classification accuracy of the BCT depended on the specific variable and injury severity examined, with some scores detecting more than 40% of malingerers with false positive error rates of 10% or less. However, the BCT variables are often influenced by cognitive ability as well as malingering, so caution is indicated in applying the BCT to the diagnosis of malingering. Application of these data in clinical practice is discussed.

Response-Specific Scalp Distributions in Deception Detection and ERP Correlates of Psychopathic Personality Traits

Abstract University students were screened using items from the Psychopathic Personality Inventory and divided into high (n = 13) and low (n = 11) Psychopathic Personality Trait (PPT) groups. The P300 component of the event-related potential (ERP) was recorded as each group completed a two-block autobiographical oddball task, responding honestly during the first (Phone) block, in which oddball items were participants' home phone numbers, and then feigning amnesia in response to approximately 50% of items in the second (Birthday) block in which oddball items were participants' birthdates. Bootstrapping of peak-to-peak amplitudes correctly identified 100% of low PPT and 92% of high PPT participants as having intact recognition. Both groups demonstrated malingering-related P300 amplitude reduction. For the first time, P300 amplitude and topography differences were observed between honest and deceptive responses to Birthday items. No main between-group P300 effects resulted. Post-hoc analysis revealed between-group differences in a frontally located post-P300 component. Honest responses were associated with late frontal amplitudes larger than deceptive responses at frontal sites in the low PPT group only.

Event-related potentials reveal processing differences in honest vs malingered memory performance

Twenty-two undergraduate students completed a recognition memory test while event-related potentials (ERPs) were recorded. During the testing phase, subjects distinguished old from new words in a forced-choice format. There were two counterbalanced within-subject conditions, one in which subjects performed to the best of their abilities, and another with instructions to feign memory impairment. Test scores and response latencies differed significantly between the two conditions. Analysis of PCA-defined epochs revealed that old words were more positive than new in the control condition, with this difference confined to frontal regions and interpreted as reflecting familiarity-based recognition judgements. In the malingering task, this old/new word difference emerged earlier and was broadly distributed across the scalp. A discriminant function analysis using reaction time and ERP measures resulted in 82% correct classification of honest and simulated performance, with 79% correct on cross-validation.

P300 Amplitude and Topography in an Autobiographical Oddball Paradigm Involving Simulated Amnesia

Abstract The P300 component of the event-related potential was recorded during two blocks of an autobiographical oddball task. All participants performed honestly during the first block (Phone), i.e., the oddball stimuli were phone numbers. During the second block (Birthday), in which the oddball stimuli were participants' birthdays, a Truth group (N = 13) performed honestly and a Malinger group (N = 14) simulated amnesia. Amnesia simulation significantly reduced P300 amplitudes, both between groups and within the Malinger group (Phone vs. Birthday), possibly because of an increase in task difficulty in the Malinger condition. Analysis of scaled amplitudes also indicated a trend for a feigning-related alteration in P300 topography. Bootstrapping of peak-to-peak amplitudes detected significantly more (93%) Malinger individuals than bootstrapping of baseline-to-peak amplitudes (64%). Bootstrapping also provided evidence of a feigning-related amplitude difference between oddball stimuli (i.e., Phone > Birthday) in 71% of Malinger group individuals. In this comparison, the peak-to-peak measure also performed significantly better in intraindividual diagnostics.