Biomedical subjects

C W Mathias

Publications and source records attributed to C W Mathias.

7 recordsLinked to original sources

PubMed2001

A double-blind placebo-controlled crossover study of phenytoin in individuals with impulsive aggression.

The present study examines the behavioral and psychophysiological effects of phenytoin (PHT) in individuals who display impulsive-aggressive outbursts. In a double-blind placebo-controlled crossover design, individuals meeting previously established criteria for impulsive aggression were administered PHT and placebo during separate 6-week conditions. The efficacy measures used were the Overt Aggression Scale (OAS) and the Profile of Mood States (POMS). Psychophysiological measures (evoked potentials) were taken at baseline and at the end of each 6-week condition. Photic stimulation was used to evoke the mid-latency P1-N1-P2 waveform complex. Analysis indicated a significant decrease in the frequency of impulsive-aggressive outbursts during PHT administration compared to baseline and placebo. Analysis of the psychophysiological data showed significantly increased P1 amplitude and significantly longer N1 latency during PHT administration. In addition, a reduction in N1 amplitude during PHT administration was also suggested. These findings indicate reparation of physiological abnormalities previously observed in impulsive-aggressive individuals and imply more efficient sensory processing and effective orienting of attention. Taken together, these results provide insight as to the physiological mechanisms by which PHT serves to ameliorate impulsive-aggressive behavior.

Adult↗

PubMed2001

Impact of threat relevance on P3 event-related potentials in combat-related post-traumatic stress disorder.

The purpose of this study was to examine electrophysiological response to trauma-relevant stimuli in combat-related post-traumatic stress disorder (PTSD). Study design incorporated comparison of 10 Vietnam War veterans with PTSD diagnosis to 10 Vietnam War veterans with no mental disorder diagnosis on P3 components in a series of two oddball tasks (trauma-relevant threat, trauma-irrelevant threat) counterbalanced for order. Each task included high probability emotionally neutral distractor words and low probability neutral target words, but differed in the content of low probability threat words. Whereas threat words in the trauma-relevant oddball task pertained directly to combat trauma, threat words in the trauma-irrelevant oddball task were socially threatening words. Results revealed that, in comparison to healthy combat veterans, those diagnosed with PTSD demonstrated: (a) attenuated P3 response to neutral target items at selected electrode sites across both oddball tasks; and (b) increased responsivity to trauma-relevant combat stimuli but not to trauma-irrelevant social-threat stimuli at frontal electrode sites (F3, F4). Results are consistent with resource allocation models of PTSD, which suggest that PTSD is characterized by attentional bias to threat stimuli at the expense of attention to emotionally neutral information.

Affect↗

PubMed2001

Symptom validity testing: a critical review.

This paper provides a comprehensive review of the published literature on symptom validity tests (SVT) and, with the accompanying tables, serves as a reference to assist in their selection, interpretation, and defense. Because malingering is inherently an applied problem that frequently arises in a medico-legal context, the use of SVTs must meet certain standards. Thus, a number of methodological and theoretical weaknesses of SVT research which limit the use of SVTs as clinical tools and sources of evidence are highlighted. These criticisms incorporate recommendations which must be addressed if conclusions based on SVT data are to meet the increasingly rigorous standards for the admissibility of scientific evidence.

Brain Injury, Chronic↗

PubMed2001

Classification accuracy of the portland digit recognition test in traumatic brain injury.

This study examined the classification accuracy of the Portland Digit Recognition Test (PDRT) in traumatic brain injury (TBI). It differs from past studies in assigning patients to malingering and control groups on the basis of compensation-seeking status and the presence of external markers for malingering. Sensitivity and Specificity were.77 and 1.00, respectively. Past research comparing compensation-seekers to noncompensation-seekers reported Sensitivities of.33 or lower (Specificity is always high). This study demonstrates that past research has seriously underestimated the Sensitivity of the PDRT and raises questions about the true Sensitivity of other malingering techniques as well.

Adult↗

PubMed1999

P300 under standard and surprise conditions in self-reported impulsive aggression.

1. The purpose of the present study was to determine the cognitive psychophysiological correlates of impulsive aggression in a "high" functioning sample: college students. 2. Visual P300 was measured during a standard oddball task and a surprise task that included unexpected low probability stimuli. 3. Results indicated significantly reduced P300 amplitude and prolonged latency for impulsive aggressive subjects to target stimuli on the standard task. Target amplitude differences where further augmented under conditions involving unexpected stimuli although no significant latency differences were observed. The topography of P300 amplitude to unexpected stimuli differed from that of the target. 4. Topographic group differences found for unexpected stimuli are suggestive of cognitive processing deficits previously demonstrated using neuropsychological techniques in impulsive aggressive individuals.

Adolescent↗

PubMed1998

Auditory P300 and self-reported impulsive aggression.

1. The purpose of the present study was to determine the cognitive psychophysiological correlates of impulsive aggression in a population considered "normal" by societal standards: college students. 2. Auditory event-related potentials were acquired on all subjects during a standard oddball task. The stimuli consisted of a random sequence of two tones, a frequent 1,000 Hz tone and a rare 2,000 Hz tone. Tones were presented in a ratio of 80/20. 3. Results of the study demonstrated that impulsive aggressive subjects show significantly lower P300 amplitude at frontal electrode sites when compared to nonaggressive controls. 4. These findings are consistent with the psychophysiological findings in impulsive aggressive incarcerated criminals and support the notion of a specific behavioral syndrome associated with spontaneous aggressive outbursts.

Adolescent↗

PubMedDate not supplied

Clinical and neuropsychological correlates of impaired awareness of deficits in Alzheimer disease and Parkinson disease: a comparative study.

OBJECTIVE: To compare patients with Alzheimer disease (AD) and Parkinson disease (PD) with regard to their awareness of cognitive, emotional/social interaction, self-care, and motor-related neurologic deficits. BACKGROUND: Unawareness of deficits, a clinically important symptom, is found in AD. It has been hypothesized to be associated with disruption of frontal-subcortical circuits but has been little studied in other neurodegenerative disorders. Because PD has a different anatomic-pathologic substrate, a comparison of impairment of awareness in AD and PD may shed light on the neural basis of this phenomenon. METHOD: Impairment of awareness was measured as the difference between patient self-report and caregiver ratings of patient abilities on questionnaires tapping cognitive, emotional/social interaction, self-care, and motor function. These "discrepancy scores" were then compared between the two diagnostic groups and examined in relation to selected neuropsychological test data. RESULTS: In general, both AD and PD patients rate themselves as being less impaired than do their caregivers. The two diagnostic groups, AD and PD, differ significantly, however, on awareness discrepancy measures in the cognitive domain. In their ratings of patient cognitive skills, AD caregivers rate patients as significantly more impaired than patients rate themselves, whereas PD caregivers and patients do not differ significantly on these ratings. Impaired awareness in PD but not in AD is associated with poorer overall cognitive function and performance on tests measuring memory, attention, and constructional ability. CONCLUSIONS: Both AD and PD patients display impaired awareness of deficits in multiple domains, including motor-related neurologic function. Parkinson disease patients with comparatively intact cognitive function display relatively preserved awareness of motor and other deficits.

Aged↗