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Biomedical subjects

J Polich

Publications and source records attributed to J Polich.

At least 37 records · Page 2Linked to original sources
PubMed1999

Comparison of P300 from passive and active tasks for auditory and visual stimuli.

The P300 event-related brain potential (ERP) was elicited with a stimulus-sequence paradigm for auditory and visual stimuli in separate active and passive task response conditions. Auditory stimuli in the passive task yielded P300 waveforms similar to those obtained from the active task condition. Visual stimuli in the passive task yielded much smaller P300 waveforms that were not morphologically consistent with those from the active task. The results suggest that auditory stimuli produce more robust P300 components than visual stimuli in passive task situations.

Acoustic Stimulation↗
PubMed1999

P3a and P3b from typical auditory and visual stimuli.

OBJECTIVE: Target/standard discrimination difficulty was manipulated systematically to assess how this variable affects target and nontarget P300 scalp distributions for both auditory and visual stimuli. DESIGN AND METHODS: A 3-stimulus paradigm (target, standard, nontarget) was employed in which subjects (n = 16) responded only to an infrequently occurring target stimulus. The perceptual discrimination difficulty between the target and more frequently occurring standard stimuli was varied as Easy or Difficult in different conditions, while holding the nontarget stimulus properties constant. RESULTS: When target/standard discrimination was Easy, P300 amplitude was larger for the target than the nontarget across all electrode sites, and both demonstrated parietal maximums. In contrast, when target/standard discrimination was Difficult, target amplitude (P3b) was larger parietally and occurred later than nontarget components, whereas nontarget amplitude (P3a) was larger and earlier than the target P300 over the frontal electrode sites. Similar outcomes across task conditions were obtained for both auditory and visual stimuli. CONCLUSIONS: The findings suggest that target/standard discrimination difficulty, rather than stimulus novelty, determines P3a generation for both auditory and visual stimulus modalities.

Acoustic Stimulation↗
PubMed1999

P300 and response time from a manual Stroop task.

OBJECTIVES: Manual response time (RT) and P300 event-related potential (ERP) measures were recorded in a Stroop color naming task to determine if previous results with vocal responses would be obtained using an arbitrary stimulus-response (S-R) mapping. METHODS: Subjects (n = 32) were instructed to respond to the display color of a word but to ignore its meaning. Display color was congruent, neutral, or incongruent with word meaning. RESULTS: Stroop facilitation and interference effects were observed, as RT was shortest in the congruent condition, intermediate in the neutral condition, and longest in the incongruent condition. In contrast, P300 latency did not vary across color/word congruence conditions, suggesting that the RT difference between congruence conditions originated after stimulus evaluation. CONCLUSIONS: These manual RT/P300 findings support the view that Stroop interference and facilitation originate from response competition between the relevant and irrelevant stimulus attributes. By employing an arbitrary mapping of color words onto buttons, the present results indicate that the disparate effects of Stroop stimuli on RT and P300 latency do not depend on the nature of the S-R translation.

Adolescent↗
PubMed1999

On P300 measurement stability: habituation, intra-trial block variation, and ultradian rhythms.

P300 event-related brain potentials (ERPs) were elicited using a simple discrimination task in which participants discriminated two different equiprobable visual stimuli with button-press responses (n = 20). A total of ten trial blocks were presented at 10-min intervals. P300 amplitude declined significantly, but peak latency did not change reliably across trial blocks. P300 amplitude demonstrated a reliable cyclical fluctuation across trial blocks, although P300 latency did not. Intra-trial block ERP variability was assessed by computing the correlation coefficients between the target and standard stimuli for amplitude and latency measures across participants within each trial block. P300 amplitude correlations were weakest at the Fz electrode, more strongly associated at Cz, and were most strongly correlated at Pz across trial blocks. P300 latency correlations were somewhat weaker and similar in strength across electrodes sites. The correlational patterns for both P300 amplitude and latency demonstrated reliable cyclical variation. The N100 component produced strong and consistent correlations for both amplitude and latency, whereas the P200 and N200 component measures evinced cyclical correlational patterns similar to the P300 across trial blocks. These results suggest that the stability of P300 and other component measures can vary appreciably within and across trial blocks in a manner that reflects ultradian variation in arousal level.

Activity Cycles↗
PubMed1999

P300, alcoholism heritability, and stimulus modality.

The P300 event-related brain potential (ERP) was elicited with auditory and visual stimuli from members of 13 families who were at high risk (HR) for alcoholism (father diagnosed as alcoholic) and 13 families at low risk (LR) for alcoholism. Each family consisted of a father, mother, and at least two biological children. The intrafamily member correlations (father vs. child, mother vs. child, child vs. child) for P300 amplitude were obtained for 15 electrode sites. P300 amplitude from auditory stimuli was not correlated among HR family members, but was positively correlated among LR family members. P300 amplitude from visual stimuli was positively correlated among both HR and LR family members. When taken in conjunction with previous findings, the present results suggest that P300 amplitude from auditory stimuli may not be as reliable as ERPs from visual stimuli for the assessment of alcoholism heritability.

Adolescent↗
PubMed1999

Auditory and visual P300 topography from a 3 stimulus paradigm.

OBJECTIVE: The P300 event-related brain potential (ERP) was elicited with auditory and visual stimuli in a separate session of a 3 stimulus oddball paradigm, and the scalp topography was assessed with 15 electrode locations. METHODS: Target (0.10), standard (0.80), and infrequent non-target (0.10) stimuli in the auditory task were 2000, 1000 and 500 Hz tone, and in the visual task, 'X', 'O', and 'H', respectively. The stimuli were presented in a random series, once every 2 s, and participants responded only to the target (N = 12). RESULTS: Target stimuli elicited larger P300 components than non-target did in both stimulus modalities. For both target and non-target stimuli, P300 amplitude was larger and latency longer for the visual compared with the auditory stimulus. Analysis of normalized P300 amplitude data indicated that the target and non-target P300s from both modalities had identical topography. CONCLUSION: The findings suggest that both target and non-target stimuli in 3 stimulus oddball paradigm elicited the same type of P300 (P3b) for both stimulus modalities.

Acoustic Stimulation↗
PubMed1999

Olfactory P3 in young and older adults.

Olfactory event-related potentials (OERPs) were recorded monopolarly at the Fz, Cz, and Pz electrode sites in 16 young adults and 16 older adults to assess aging effects on the olfactory P3. Amyl acetate was used to elicit the OERPs, with an intertrial interval of 45 s. Young adults produced significantly larger P3 amplitudes and shorter P3 peak latencies than older adults. The olfactory P3 response appears to be sensitive to age-related changes in the olfactory system and may reflect cognitive slowing in the central nervous system.

Adult↗
PubMed1999

Tobacco smoking and memory scanning: behavioral and event-related potential effects.

The behavioral and electrophysiological effects of tobacco smoking in a memory-scanning task were investigated in two groups of regular cigarette smokers. After overnight abstinence, subjects performed memory scanning with both small and large memory sets. Subjects in the Smoking group (n = 12) then smoked two cigarettes of their preferred brand. Subjects in the Control group (n = 12) also received a rest break, but did not smoke. Both groups then performed the same tasks again after the break. Behavioral performance was segregated into response time (RT)--the time required to make the memory set decision--and movement time (MT)--the time required to execute the response. Increases in RT and MT were observed after Smoking subjects smoked cigarettes, but similar increases were observed in the Control group. Analysis of event-related brain potentials (ERPs) revealed that P300 amplitude decreased somewhat after the break, but that this decrease did not differ between the Smoking and Control groups. The results suggest that tobacco smoking's effects on performance and electrophysiological variables in memory comparison tasks are slight relative to individual differences and time-on-task effects.

Adolescent↗
PubMed1999

Olfactory event-related potentials in young and elderly adults: evaluation of tracking task versus eyes open/closed recording.

The purpose of the present study was to evaluate olfactory event-related potentials (OERPs) elicited by amyl acetate from subjects performing a visuomotor tracking task compared with the no-task conditions of eyes open and eyes closed. Task condition did not produce any reliable effects for any amplitude measure. Task type weakly influenced only P2 latency. Elder adults evinced smaller P2 and N1/P2 amplitudes and longer N1 and P2 latencies than young adults. The results suggest that tracking task performance is not necessary to obtain robust OERPs from normal subjects of a wide age range.

Adult↗
PubMed1999

P300 habituation patterns: individual differences from ultradian rhythms.

Event-related brain potentials (ERPs) were elicited with auditory stimuli from normal subjects every 10 min. for 10 successive trial blocks to assess ultradian influences on the P300 component. Based on a theoretical analysis of the underlying relationship between background EEG activity and P300 variability, subjects were divided into two groups according to whether P300 amplitude increased or decreased initially over trial blocks. P300 amplitude habituated across trial blocks. P300 latency produced systematic cyclical variation with approximately a 90-min. period that was opposite in phase for the different subject groups. The findings suggest that ultradian rhythms contribute to P300 latency variability. The implications of the results for P300 in applied settings are discussed.

Acoustic Stimulation↗
PubMed1999

Poststimulus EEG spectral analysis and P300: attention, task, and probability.

Event-related potentials (ERPs) were elicited with auditory stimuli, and spectral analysis was performed on the poststimulus electroencephalographic (EEG) activity to assess how variables that influence the P300 affect spectral parameters of the resultant ERP. In Experiment 1, a no-stimulus condition was compared with a single repeated tone that was either ignored or counted. In Experiment 2, an auditory oddball paradigm was used in which the subject ignored all stimuli, counted only the target, or counted both the target and the standard stimuli in different conditions. In Experiment 3, stimulus probability was manipulated in separate conditions (.20, .50, .80), with the subject required to count the target stimulus. Delta and theta band spectral power increased whenever P300 amplitude increased. However, as the attentional requirements increased across tasks, alpha-1 and alpha-2 power and mean frequency increased. The findings indicate that auditory stimulus processing modulates the EEG more than just by adding ERP components to the epoch.

Adult↗
PubMed1999

Visual P3a in male alcoholics and controls.

The goal of this study was to assess the P3a component of event-related potentials in a population of abstinent, chronic alcoholics. A three-stimulus visual oddball paradigm was used to elicit robust P3a components in a large group of well-characterized male alcoholics (n = 44) and controls (n = 28). The task required subjects to make a difficult perceptual discrimination between randomly presented, frequently occurring vertical lines (.80) and infrequent target lines that were tilted 2 degrees to the right of vertical (.10) by only responding with a button press to the target stimuli. A nontarget infrequent horizontal line occurred (.10) randomly to which no response was made. The target stimulus elicited robust late P3b components with a parietal maximum amplitude, and the nontarget stimulus elicited reliable P3a components with a fronto-central maximum amplitude distribution. Group differences in P3a were assessed using repeated measures ANCOVA analyses in five scalp regions. Alcoholic subjects produced smaller P3a amplitudes over the central, parietal, temporal, and occipital areas compared with controls. Current source density analyses supported these findings with extension of the differences between the groups to the frontal region. The results suggest that the P3a may be important in the evaluation of alcoholism and its heritability. Theoretical implications are discussed.

Adult↗
PubMed1998

Habituation of P300 from visual stimuli.

The P300 event-related brain potential (ERP) was elicited with visual stimuli using an oddball task in which the subjects made button press responses to discriminate target and standard stimuli. Each stimulus occurred randomly with a 0.50 probability, and 10 trial blocks were presented at 10-min inter-block-intervals (IBIs). P300 amplitude declined reliably across trial blocks, and an interaction between trial block number and electrode site was observed. No habituation effects were found for P300 latency or for N100, P200, or N200 amplitude. The results suggest that P300 amplitude from visual stimuli habituates when short IBIs and a sufficient number of trial blocks are employed. Theoretical implications are discussed with respect to attentional resource allocation and context updating.

Adult↗
PubMed1998

Quantitative trait loci analysis of human event-related brain potentials: P3 voltage.

The P3 event-related brain potential (ERP) is a positive-going voltage change of scalp-recorded electroencephalographic activity that occurs between 300-500 ms after stimulus onset. It is elicited when a stimulus is perceived, memory operations are engaged, and attentional resources are allocated toward its processing. Because this ERP component reflects fundamental cognitive processing, it has found wide utility as an assessment of human mental function in basic and clinical studies. In particular, P3 attributes are heritable and have demonstrated considerable promise as a means to identify individuals at genetic risk for alcoholism. We have conducted a quantitative linkage analysis on a large sample from families with a high density of affected individuals. The analyses suggest that several regions of the human genome contain genetic loci related to the generation of the P3 component of the ERP, which are possible candidate loci underlying the functional organization of human neuroelectric activity.

Alcoholism↗
PubMed1998

EEG, ERPs and food consumption.

Baseline electroencephalographic (EEG) and auditory event-related brain potentials (ERPs) were assessed in subjects before and after consuming food and under eyes open and closed recording conditions in an attempt to replicate and extend previous food--ERP effects. Subjects were assessed the morning after fasting from the previous night, before and after eating a standard lunch. Delta- band EEG spectral power decreased and theta- and early alpha-band frequency increased after food consumption. However, in contrast to previous reports, P300 amplitude was unaffected by food consumption and peak latency increased. The strength of the correlational association between background EEG activity and P300 measures decreased for the delta- and theta- bands, but increased for the early and late alpha- bands. The findings suggest that food consumption affects general arousal, rather than specific cognitive EEG or ERP factors and are discussed with respect to previous EEG-ERP findings on food intake.

Adult↗
PubMed1998

P3a, perceptual distinctiveness, and stimulus modality.

A three-stimulus oddball paradigm (target, standard, nontarget) was employed in which subjects responded to an infrequent target, when its discrimination from the frequent standard was difficult. In separate auditory and visual modality conditions, the stimulus characteristics of an infrequent nontarget were manipulated such that its perceptual distinctiveness from the target was varied systematically. For both the low and high distinctiveness conditions, target stimulus P300 amplitude was larger than the nontarget only at the parietal electrode. In contrast, nontarget P3a amplitude was larger and earlier than the target P300 over the frontal/central electrode sites. The distinctiveness manipulation between the target and nontarget produced larger P3a component profiles for the auditory compared to visual stimuli. The results support previous findings that target/standard stimulus context determines P3a generation for both auditory and visual stimulus modalities and suggest that the distinctiveness of the eliciting stimulus contributes to P3a amplitude. Theoretical implications are discussed.

Acoustic Stimulation↗
PubMed1998

P300 and handedness: on the possible contribution of corpus callosal size to ERPs.

The P300 event-related potential (ERP) was elicited in left- and right-handed young adult male and female participants (n = 20/group) with both auditory and visual stimulus discrimination tasks that varied systematically in difficulty. P300 amplitude was larger across all task conditions for left- than for right-handed participants at anterior and central electrode sites. P300 latency was shorter across all task conditions for left- than for right-handers. Task difficulty did not affect the ERP handedness differences. Male and female subjects demonstrated comparable ERP handedness effects, although smaller P300 components were obtained for males than for females. When considered in the context of corpus callosal size differences for left-versus right-handed and male versus female participants, the findings suggest that the P300 reflects callosal size and interhemispheric transmission efficacy.

Acoustic Stimulation↗