Efficacy of repeated psychophysiological detection of deception testing.

Physiological measures were recorded during repeated psychophysiological detection of deception (PDD) tests to determine if reaction levels change with test repetition. Two groups of 22 healthy male subjects completed six peak of tension PDD tests on each of two test days. A minimum between test day interval of six days was maintained. The treatment group was programmed to respond deceptively to one of seven test questions while the control group was programmed to respond truthfully to all questions. The respiration and galvanic skin resistance (GSR) line lengths, GSR peak response amplitude and latency, and cardiovascular inter-beat-interval (IBI) were calculated for each response. Analyses indicated that, except for GSR peak response latency, differential physiological reactivity during a PDD test did not change significantly over repeated tests or days; there was a decrease in average respiration line lengths at the initial test(s) of each day; and differential changes in average respiration line length, GSR peak latency, and cardiovascular IBI responses corresponded to deception. Power analyses were calculated to assist in result interpretation. It is suggested that PDD decision accuracy, concerning subject veracity, should not decrease during repeated testing.

Effects of crack cocaine on neurocognitive function.

Because crack cocaine appears to have a preferential effect on the metabolic and electrophysiological activity of the frontal and temporal regions of the brain (Pascual-Leone et al., 1991a, 1991b; Volkow, 1992), we hypothesized that cognitive measures of those regions would be impaired in crack cocaine users relative to measures in normal volunteers. We used logistic regression to determine the relationship of cocaine usage to neuropsychological test performance. We compared 38 patients with an average of 3.6 (SD = 2.5) years of crack cocaine use and 24.5 (SD = 28.1) days of abstinence to 54 normal volunteers on a battery of neuropsychological tests. Statistical adjustments were made for the effects of age, education, socioeconomic class, and level of depression. Our findings were mixed with regard to purported measures of executive/frontal functioning, with worse performance associated with cocaine usage on the Booklet Categories Test, but better performance associated on others (number of categories on the Wisconsin Card Sorting Test, Controlled Oral Word Association). Cocaine usage was associated with impairment on measures of spatial, but not verbal memory, confrontation naming, and Trail-making Test, Part B, a measure of perceptual-motor speed and cognitive flexibility. In summary, it appears that continuous crack cocaine use produces a dissociative pattern in neuropsychological test performance with improvement on some measures, but deterioration on others. The permanence of these effects remains to be determined with longitudinal studies.

Functional importance of ventricular enlargement and cortical atrophy in healthy subjects and alcoholics as assessed with PET, MR imaging, and neuropsychologic testing.

The authors assessed the relationship between ventricular enlargement, cortical atrophy, regional brain glucose metabolism, and neuropsychologic performance in 10 alcoholics and 10 control subjects. Regional brain glucose metabolism was measured with fluorine-18 fluorodeoxyglucose (FDG) and positron emission tomography (PET). Cortical atrophy and ventricular size were evaluated quantitatively with magnetic resonance (MR) imaging. Alcoholics had decreased brain glucose metabolism and more cortical atrophy but did not have significantly greater ventricular size than did control subjects. The degree of ventricular enlargement and of cortical atrophy was associated with decreased metabolism predominantly in the frontal cortices and subcortical structures in both alcoholics and control subjects. There were no significant correlations between neuropsychologic performance and MR imaging structural changes, whereas various subtest scores were significantly correlated with frontal lobe metabolism. These data show that F-18 FDG PET is a sensitive technique for detecting early functional changes in the brain due to alcohol and/or aging before structural changes can be detected with MR imaging.

Brain imaging of an alcoholic with MRI, SPECT, and PET.

A medically healthy chronic alcoholic without evidence of neurological and neuropsychological impairment was studied with magnetic resonance imaging (MRI), single photon emission computerized tomography (SPECT), and positron emission tomography (PET). An age-matched normal volunteer was evaluated with the same scans for comparison. The MRI of the alcoholic revealed prominent ventricles and mild cortical atrophy. SPECT and PET revealed predominant involvement of the frontal cortex as shown by decreased frontal blood flow and metabolism. This case illustrates the sensitivity of brain imaging techniques in detecting cerebral abnormalities even in the absence of neurologic and/or neuropsychological impairments.

Individual differences in cortical evoked potentials as a function of heartbeat detection ability.

Much work has been done to assess individual differences in the ability to detect visceral activity, and most of this work has focused on heartbeat detection ability. This experiment attempted to determine if some underlying cortical event is associated with heartbeat detection ability, and further, to assess whether this cortical event is lateralized to the right hemisphere. Event-related cortical potentials, time-locked to the EKG R-wave and averaged over 400 samples, were studied at Fz, Cz, F7, and F8 in 12 subjects. The primary dependent measure of heartbeat detection accuracy was the standard deviation of the mean temporal latency, measured from peak EKG R-waves to the subjects' report of physical sensation of heartbeats. A significant relationship was found between the amplitudes of event related potentials (ERPs) in the right hemisphere and heartbeat detection accuracy.