Biomedical subjects

J Polich

Publications and source records attributed to J Polich.

At least 19 recordsLinked to original sources

PubMed2001

P300 asymmetry in schizophrenia: a meta-analysis.

P300 event-related brain potential (ERP) amplitude is smaller in patients with schizophrenia compared to unaffected controls, but whether left temporal component amplitude is also smaller is debated. The present study employed meta-analytical methods to quantitatively assess previous P300 schizophrenia asymmetry findings. All P300 articles on schizophrenia using an auditory oddball paradigm published before January 2000 were obtained by comprehensive literature searches and cross-referencing for related articles. A total of 19 original articles reporting complete midline electrode data and 11 articles reporting lateral asymmetry electrode data were reviewed, which included different independent conditions that yielded 50 independent data sets. P300 amplitude differences between patients with schizophrenia and control subjects from the midline electrodes yielded effect sizes that differed among recording sites, such that Fz was significantly smaller than Pz, with Cz effect sizes smaller than Pz but larger than Fz. Comparison of P300 amplitude from the lateral data for the T3 and T4 electrodes found no reliable effect size difference when these electrodes were analyzed separately. However, comparison of P300 amplitude effect sizes from the TCP1 was significantly larger than that from the TCP2 when these electrodes were analyzed separately. P300 amplitude is smaller overall in patients with schizophrenia compared to control subjects and differs in its effect size topography across the midline and temporal electrode sites, with the strongest effect sizes obtained for the Pz midline and TCP1 lateral electrodes.

Cerebral Cortex↗

PubMed2001

Auditory P3a deficits in male subjects at high risk for alcoholism.

BACKGROUND: Substantial evidence indicates that alcoholism is biologically mediated by a genetic predisposition. As the decreased P300 (P3b) event-related brain potential component does not recover with prolonged abstinence, it is unlikely to be related to drinking history but is more likely to be genetically influenced. This is supported by findings that P3b amplitudes are reduced in subjects at high-risk compared to low-risk for alcoholism. Although there are few studies of P3a in HR subjects, lower P3a amplitudes have been reported with a novel nontarget stimulus paradigm, as well as with a difficult three-stimulus visual paradigm. Using a similar three-tone auditory paradigm in which the discriminability between the target and standard tone is difficult, the P3a component can also be reliably elicited with a rare nontarget perceptually distinct stimulus. This technique was employed in young adult subjects at low-risk and high-risk for alcoholism. METHODS: A total of 17 low-risk and 24 high-risk male subjects were employed as subjects in an auditory paradigm that yielded a large amplitude P3a with a centro-frontal maximum to the nontarget and a robust low amplitude prolonged P3b with a parietal maximum amplitude to the target stimulus. Current source density maps were derived to assess topographic differences between low-risk and high-risk subjects. RESULTS: The high-risk group manifested significantly lower P3a amplitudes than the low-risk group at the frontal electrodes to rare nontarget stimuli. High-risk subjects also demonstrated a more disorganized current source density map for P3a compared to low-risk subjects. CONCLUSIONS: The reduction of P3a in the high-risk group may be due to cortical dysfunction including the frontal and prefrontal cortex. The lower P3a amplitude coupled with more disorganized current source density maps suggest inefficient brain functioning in high-risk subjects.

Acoustic Stimulation↗

PubMed2001

Hemispheric differences for visual matrix processing: stimulus size and spatial frequency effects.

Hemispheric processing differences were assessed by presenting square matrices that varied in size and the number of filled-in cells. Subjects judged whether the matrix contained an even or odd number of filled cells. Experiment 1 employed relatively small matrix sizes (2 x 2, 3 x 3, and 4 x 4), and Experiment 2 employed relatively large matrix sizes (4 x 4, 6 x 6, and 8 x 8). Response time was shorter and error rates lower for left visual field/right hemisphere (LVF/RH) presentations compared to right visual field/left hemisphere (RVF/LH) presentations, with the larger matrices demonstrating the strongest visual field/hemispheric effects. Increases in the number of filled cells contributed to increases for the LVF/RH response time advantage only for the larger arrays. Analysis of the data from both studies collapsed across the number of filled cells produced highly consistent LVF/RH advantages for both response time and error rate, with stronger LVF/RH advantages found for the larger matrix sizes of both studies. The findings suggest that visual stimulus spatial frequency is a key determinant of hemispheric processing advantages, but that this factor is constrained by stimulus size variation. Theoretical implications with respect to the hemispheric processing double filtering by frequency model are discussed.

Adult↗

PubMed2001

Tobacco smoking and event-related brain potentials in a Stroop task.

Behavioral and event-related brain potential (ERP) measures were used to assess the effects of tobacco smoking on selective attention. Two groups of abstinent smokers performed a Stroop color-naming task. The display color of a stimulus word determined the correct response, whereas word meaning was irrelevant. Meaning was congruent, neutral, or incongruent with respect to color. After completing two blocks of trials under abstinent conditions, subjects received a 15-min break before performing two more blocks. Subjects in the Smoking group (N=12) smoked two cigarettes during the break. Matched Control subjects (N=12) did not smoke during the break. Typical Stroop effects were found, as reaction time (RT) was shortest to congruent words, intermediate to neutral words, and longest to incongruent words. Overall RT decreased after the break equally for the Smoking and Control groups, whereas the magnitude of the Stroop effect was unchanged for either group. P300 amplitude decreased after the break for the Smoking group but not for the Control group, which implied that smoking rather than practice produced component decline. Error rate and P300 latency did not change after the break for either group. The results suggest that tobacco smoking may decrease the availability of general attentional resources required to evaluate colored word stimuli, whereas the specific stimulus processing mechanisms responsible for the Stroop effect are relatively unaffected.

Adult↗

PubMed2001

P3a from a passive visual stimulus task.

OBJECTIVE: Visual event-related brain potentials (ERPs) were elicited using a 3-stimulus oddball paradigm to assess the P3a with passive stimulus processing. METHODS: Young adults (n=12) were presented with a series of visual stimuli consisting of a solid circle standard stimulus (P=0.76) that was difficult to discriminate from a larger target circle (P=0.12), with a large square distractor stimulus (P=0.12) presented randomly in the series. Subjects were instructed in the passive condition to simply look at the stimuli and in the active condition to press a mouse key only to the target stimulus. ERPs were recorded from 15 scalp electrodes, with the amplitude and latency of the P300 from the distractor and target stimuli assessed. RESULTS: The P3a from the distractor stimulus was similar in amplitude, scalp topography, and peak latency across the passive and active task conditions. The P3b from the target stimulus demonstrated much smaller amplitude, highly altered scalp topography, and longer latency for the passive compared to active task conditions. CONCLUSIONS: The P3a can be obtained with visual stimuli in the 3-stimulus paradigm under passive viewing conditions. Theoretical implications and clinical applications are discussed.

Adult↗

PubMed2001

Wavelet analysis of P3a and P3b.

Target/standard discrimination difficulty and the degree of stimulus "novelty" were manipulated systematically in a three-stimulus odd-ball task to assess how these variables affect target and non-target P300 scalp distributions for visual stimuli. Wavelet transformation (WT) analyses were performed on the non-target (P3a) and target (P3b) ERPs to assay how the underlying electroencephalographic (EEG) activity was affected by both the difficulty and novelty factors. When target/standard discrimination was easy, P300 amplitude was higher for the target than the non-target across all electrode sites, and both demonstrated parietal maximums. In contrast, when target/standard discrimination was difficult, non-target amplitude (P3a) was higher and earlier over the frontal/central electrode sites for both levels of novelty, whereas target amplitude (P3b) was greater parietally and occurred later than the non-target components and was generally unaffected by non-target novelty level. The WT analyses indicated that appreciable theta activity was related to the more novel non-target stimuli; primarily target component delta coefficients were affected by the discrimination difficulty variable. The findings suggest that target/standard discrimination difficulty, rather than stimulus novelty, determines P3a generation for visual stimuli but that the underlying theta oscillations are differentially affected by stimulus novelty. WT analysis methods are discussed along with the theoretical and neurophysiological implications of the findings.

Adult↗

PubMed2001

P300 and alpha event-related desynchronization (ERD).

In the present study we evaluated the relationships between the P300 event-related potential and event-related desynchronization (ERD) of electroencephalographic alpha activity by simultaneously analyzing P300 as well as 7-10- and 10-14-Hz alpha ERD responses from auditory passive and active oddball conditions. We compared the effects of task (target vs. nontarget) and electrode (Fz, Cz, Pz) on P300 and ERD, and correlated P300 amplitude/latency with ERD maximal amplitude/latency across individuals. The major findings were that P300 as well as slow and fast alpha ERD manifested similar task and electrode effects. P300 preceded ERD and predicted individual variance of both slow and fast alpha ERD. The relationships of P300 with alpha ERD were different for the slow and fast alpha frequencies. These findings indicate that P300 and ERD are related such that slow and fast alpha ERDs are specifically guided or modified by the internal event(s) indexed by P300.

Adolescent↗

PubMed2000

Auditory P3a assessment of male alcoholics.

BACKGROUND: P3a amplitude differences between alcoholic and control groups have not been well defined. Because event-related potential (ERP) differences between these groups appear to be influenced by task difficulty, the present study employed a new auditory ERP paradigm, in which target/standard tone discriminability was difficult, with infrequent nontarget stimuli used to elicit the P3a. METHODS: A total of n = 27 male alcoholics and n = 25 male controls were assessed using a three-tone discrimination paradigm, in which the discriminability between the target and standard was difficult, with easily discriminable infrequent nontarget tones also presented. A P3a component with a centro-frontal maximum to the rare nontargets and a P3b with a parietal maximum amplitude to the target stimulus were obtained. Current Source Density (CSD) maps were derived from the potential data and employed to assay topographical differences between subject groups. RESULTS: Alcoholics produced smaller P3a amplitudes than control subjects to the rare nontargets with no peak latency differences observed. The most prominent current sources are apparent more anteriorly for the nontarget compared to the target stimulus in both groups. There were more sources and sinks in the alcoholics than in the control subjects for P3a. A bootstrap analysis method showed that P3a CSD maps evinced distinct topographic distributions between alcoholics and control subjects in all brain regions. CONCLUSIONS: The lower P3a amplitude and weaker sources in alcoholics coupled with less topographic specificity in their CSD maps, suggests disorganized inefficient brain functioning. This global electrophysiological pattern suggests cortical disinhibition perhaps reflecting underlying CNS hyperexcitability in alcoholics.

Adult↗

PubMed2000

The P300 brain potential is reduced in smokers.

RATIONALE: Tobacco smoking is the most prevalent type of substance abuse, yet its biobehavioral etiology is little understood. Identification of differences between smokers and non-smokers on basic characteristics of neurocognitive functioning may help to elucidate the mechanisms of tobacco dependence. OBJECTIVES: This study assessed the relationship between smoking status and the P300 component of event-related potential (ERP) while controlling for potential confounders such as alcoholism, drug abuse, and psychopathology. METHODS: The ERP responses elicited by a visual oddball task were measured at the mid-parietal site in 905 current smokers, 463 ex-smokers, and 979 never smokers. RESULTS: P300 amplitude was significantly lower in current cigarette smokers compared to never-smokers. Ex-smokers did not differ significantly from never-smokers. P300 reduction was also associated with alcoholism, drug dependence, and family density of alcoholism. However, after controlling for smoking, only family density of alcoholism remained a significant predictor of P300 amplitude. CONCLUSIONS: The results indicate a significant effect of smoking status on P300 amplitude which is additive to family history of alcoholism and suggest that either (1) long-term tobacco smoking may produce a reversible change in brain function, or (2) reduced P300 may be a marker of risk for nicotine dependence.

Adolescent↗

PubMed2000

Introduction

Explore the source record for details and available documents.

Journal Article↗

PubMed2000

P300 as a clinical assay: rationale, evaluation, and findings.

Use of the P300 event-related brain potential (ERP) as a clinical assay is reviewed and assessed by comparing its distribution qualities with normative biomedical testing data from published studies. The coefficient of variation statistic was calculated for P300 data and a variety of clinical testing data. P300 amplitude and latency variability was found to be highly comparable and sometimes superior to routinely employed biomedical assays. These results are discussed in terms of how to control inter-group ERP variability and the application of normative P300 data in clinical settings.

Acoustic Stimulation↗

PubMed2000

Neuroelectric assessment of HIV: EEG, ERP, and viral load.

The effects of the human immunodeficiency virus (HIV) infection on the central nervous system function were studied with electroencephalographic (EEG) and auditory event-related brain potentials (EPRs) in patients infected with HIV and unaffected young adult control subjects (n=10/group). All subjects were assessed once every 15 min for four trial blocks at the same time of day to assess EEG/ERP changes with time on task-induced fatigue. Spectral analysis was applied to the pre- and post-stimulus EEG segments. ERP values were evaluated with respect to group differences for component amplitude and latency measures. Spectral analysis demonstrated that HIV patients evinced greater pre-stimulus delta power over frontal areas compared to control subjects, and less post-stimulus spectral power for the delta, theta, and alpha bands over the central/parietal areas. P300 amplitude was smaller, and latency was marginally longer for the HIV patients compared to control subjects. P300 latency correlated positively with increases in the patient HIV viral load. Time-on-task generally did not affect EEG or ERP measures for either group other than contributing to an overall decrease in neuroelectric responsivity. Group spectral power effects were consistent with differences in arousal/fatigue level. P300 group differences were consistent with declines in cognitive capability, and P300 latency increased with increased viral load. HIV infection negatively affected central nervous system function as measured by EEG and cognitive ERPs in a manner that suggests decreased arousal and increased fatigue in HIV patients.

AIDS Dementia Complex↗

PubMed2000

P300 and blink instructions.

OBJECTIVES: The effects of instructions to refrain from blinking on the P300 event-related brain potential (ERP) from auditory and visual stimuli were assessed. METHODS: An oddball paradigm was employed in which young adult subjects (n = 20) silently counted the infrequent target stimuli and were given either no instructions or told "do not blink" in different conditions, with auditory and visual stimulus tasks employed for all subjects. ERPs were recorded from the midline electrodes, with amplitude and latency of the P300 and other components obtained. RESULTS: P300 amplitude for both modalities and target/standard stimulus conditions was smaller and visual peak latency longer in the "do not blink" condition. Blink instructions did not directly affect the other components. CONCLUSIONS: Instructions to refrain from blinking can decrease P300 amplitude and can increase peak latency.

Acoustic Stimulation↗

PubMed1999

Heritability of event-related brain potentials in families with a history of alcoholism.

Event-related brain potentials (ERPs) are altered in patients with a variety of psychiatric disorders and may represent quantitative correlates of disease liability that are more amenable to genetic analysis than disease status itself. Estimates of heritability are presented for amplitude and latency of the N1 and P3 components of the ERP measured at 19 scalp locations in response to visual and auditory stimuli for 604 individuals in 100 pedigrees ascertained as part of the Collaborative Study on the Genetics of Alcoholism. Significant heritabilities were found for visual P3 amplitude in response to all stimuli and for visual P3 latency in response to target and novel, but not non-target, stimuli. Heritability of visual N1 latencies was uniformly low, whereas heritability of visual N1 amplitude was significant for all electrodes in response to the non-target stimuli but only for posterior electrodes in the other two stimulus conditions. Heritabilities for auditory target P3 were similar to those of the visual stimuli, with auditory target P3 amplitudes and latencies both demonstrating significant heritability. For auditory P2 in response to non-target stimuli, peak amplitude was heritable, but latency was not. Auditory N1 amplitude and latency were significantly heritable for both target and non-target conditions and did not demonstrate the anterior/posterior patterning obtained for visual N1 amplitude. This study represents the first systematic assessment of heritability of these potential neurophysiological markers in families with a history of alcoholism and suggests that many of these ERP phenotypes have heritabilities strong enough to justify genomic screening for loci jointly influencing ERP abnormalities and liability to alcoholism.

Adolescent↗

PubMed1999

Visual P3a in male subjects at high risk for alcoholism.

BACKGROUND: Voltage of the P300 component of event-related potentials (ERPs) has been proposed as a phenotypic marker of risk for alcoholism. P3a elicited by intrusive events is important in the context of deficits in inhibition found during psychophysiological and behavioral evaluations in children of alcoholics. METHODS: ERPs were recorded from a group of adult children of alcoholics (n = 26) and controls (n = 23) with a three-stimulus visual oddball paradigm. The task required a difficult perceptual discrimination between a frequent (.80) vertical line and an infrequent (.10) 2 degrees tilted line (target). An easily discriminable nontarget infrequent horizontal line also occurred (.10). Subjects were required to press a button to the target. P3a was compared using mixed-model ANCOVAs at 31 sites organized in 5 scalp regions. Current source density (CSD) maps were also analyzed. RESULTS: High-risk (HR) subjects manifested reduced P3a amplitudes compared to controls at frontal, central, parietal, and temporal electrodes. CSD analyses supported these findings with group differences found for all the scalp regions. CONCLUSIONS: The results are discussed in relation to previous HR studies. P3a reductions may be related to deficits in neuronal inhibition during stimulus processing. These results suggest that P3a amplitude may be important as a marker for vulnerability to alcoholism.

Adult↗

PubMed1999

P300, handedness, and corpus callosal size: gender, modality, and task.

The P300 event-related potential (ERP) was elicited in left- and right-handed young adult male and female subjects (n = 20/group), with auditory and visual stimulus modalities from single-stimulus and oddball tasks. P300 amplitude was larger across all conditions for left- compared to right-handed subjects at anterior and central electrode sites. P300 latency was shorter across all conditions for left- compared to right-handers. Task type did not affect the ERP handedness differences. Male and female subjects demonstrated comparable ERP handedness effects, although smaller P300 components were obtained for males compared to females. When considered in the context of previously reported corpus callosal size differences for left- vs. right-handed and male vs. female participants, the findings suggest that the P300 reflects callosal size and inter-hemispheric transmission efficacy.

Acoustic Stimulation↗

PubMed1999

Neuroelectric assessment of nutrient intake.

Electroencephalographic (EEG) activity and auditory event-related brain potentials (ERPs) were assessed in two groups (n = 12 each) of subjects. The 'food-nutrient' group had fasted from the night before and consumed a 500 cal nutrient drink; the 'control' group consumed breakfast but did not consume any nutrients during the recordings. All subjects were assessed every 15 min for six trial blocks at the same time of day, with the fast/nutrient group measured initially before and after consuming the nutrient drink. No effects of the nutrient drink were obtained on the post-stimulus EEG spectral power or mean frequency measures. However, the fast/nutrient group demonstrated less delta, theta, and alpha-1 power than the no-fast/control group. Increases in spectral power were generally observed across trial blocks especially for the alpha and beta bands, and are consistent with increases in arousal level. P300 amplitude was unaffected by the nutrient consumption, but target stimulus N100 amplitude was smaller for the food-nutrient compared to the control group. Taken together, the results suggest that nutrient consumption does not directly affect EEG or cognitive ERP measures.

Adolescent↗

PubMed1999

Normal aging and odor intensity effects on the olfactory event-related potential.

Olfactory event-related potentials (OERPs) were recorded in 14 young and 14 older adults, with odor strength of isoamyl acetate manipulated to assess olfactory stimulus intensity. Young participants produced significantly larger N1/P2, N2/P3 amplitudes and shorter N1, P2 and N2 latencies than older participants. Medium- and high-odor concentrations elicited significantly shorter P2 and N2 latencies than the lowest concentration for both age groups. Odor concentration appears to affect the speed of olfactory stimulus information processing regardless of age.

Adult↗