Biomedical subjects

J Polich

Publications and source records attributed to J Polich.

At least 55 records · Page 3Linked to original sources

PubMed1998

P300 clinical utility and control of variability.

The P300 event-related brain potential (ERP) has been used to study normal aging as well as patient populations with a variety of neurologic and psychiatric disorders. The P300 has demonstrated reasonable success as a means to assess disturbances in cognitive function, and its clinical utility has been enhanced by the identification of factors that contribute to the variability of ERP measurements. In this article, the neuropsychological theory of P300 is reviewed, ways in which this brain potential can be used as a measure of cognitive efficiency are defined, and methodologic issues that must be considered for successful clinical ERP applications are outlined. This approach is then extended to specific recommendations concerning the technical and practical aspects of P300 recording, so that a well-defined normative database can be developed for evaluating individual patients. When appropriate procedures are used, the P300 can provide a highly useful means to quantify human cognitive capability.

Aging↗

PubMed1998

Stimulus context determines P3a and P3b.

P300 differences for target (.10), nontarget (.10), and standard tones (.80) were assessed using a three-stimulus oddball paradigm in which participants responded only to the target (n = 12). Target/standard (easy or difficult) and nontarget/standard (large or small) pitch differences were manipulated orthogonally. In all conditions, target tones elicited a parietal P300, which was affected only by the target/standard discrimination ease. Nontarget in the easy/large and difficult/small conditions elicited a parietal but smaller P300 than the target but in the easy/small condition elicited similar ERPs to the standard. However, nontarget stimuli in the difficult/large condition elicited an anterior maximum and earlier P300 (P3a) component. The findings suggest that target P300s are not influenced by the nontarget stimulus configuration, whereas the nontarget P300 outcomes are determined directly by the stimulus context. The theoretical implications are discussed.

Acoustic Stimulation↗

PubMed1997

P300 from a single-stimulus paradigm: auditory intensity and tone frequency effects.

The P300 component of the event-related brain potential (ERP) was elicited with auditory stimuli in two different tasks. The oddball paradigm presented both target and standard stimuli; the single-stimulus paradigm presented a target but no standard tone stimulus, with the inter-target interval the same as that for the oddball condition. Experiment 1 manipulated stimulus intensity and Experiment 2 manipulated tone stimulus frequency, with the relative target probability maintained 0.20 for both tasks. P300 amplitude and latency were highly similar for the oddball and single-stimulus procedures in both experiments across independent variables. The findings suggest that the single-stimulus paradigm may prove useful in experimental and applied contexts that require very simple ERP task conditions.

Acoustic Stimulation↗

PubMed1997

Handedness and P300 from auditory stimuli.

The P3(00) event-related potential (ERP) was elicited in 20 left- and 20 right-handed normal young adult male subjects using a simple auditory stimulus discrimination task. P3 amplitude from the target stimuli was larger at anterior electrode sites for left- compared to right-handed subjects. P3 latency from the standard stimuli was shorter for left- compared to right-handers. The N1, P2, and N2 components generally demonstrated similar handedness effects. The relationship of ERP amplitude and handedness to anatomical variables and cognitive factors is discussed.

Adult↗

PubMed1997

P300 topography of amplitude/latency correlations.

The correlational association from 19 electrode sites between peak amplitude and latency for the P3(00) event-related brain potential (ERP) for n = 80 homogeneous subjects was assessed using a simple auditory discrimination task. The correlation strength varied systematically across scalp topography in different ways for the various ERP components. For the target stimuli, P3 amplitude and latency were negatively correlated and most tightly coupled over the frontal-central and right medial/lateral recording sites. In contrast, the N1 produced negative correlations that were strongest over the left and right central/lateral locations; P2 demonstrated a positive correlation that was strongest frontally and centrally; N2 demonstrated a positive correlations that was strongest over the central and parietal sites. ERPs from the standard stimuli produced generally similar patterns for the P3 and P2 components, with only weak or no reliable effects observed for the N1 and N2 potentials. Taken together, the findings suggest that analysis of amplitude/latency correlational relationships can provide information about ERP component generation. Theoretical implications are discussed.

Adult↗

PubMed1997

P300 and long-term physical exercise.

Electrophysiologic effects of physical exercise were investigated by comparing groups of individuals who engage in relatively low amounts of physical exercise (< 5 h/week) to subjects who engage in relatively high amounts of aerobic exercise (> 5 h/week). Event-related brain potentials (ERPs) were recorded using auditory and visual stimuli in separate oddball task conditions. P300 amplitude was affected by exercise frequency, such that increased amounts of exercise were associated with increased amplitude and somewhat more so for visual stimuli. No reliable exercise effects for P300 latency were observed, with little effect found for the other components. The findings suggest that a history of intensive physical exercise affects P300 amplitude. Theoretical mechanisms are discussed.

Acoustic Stimulation↗

PubMed1997

P300 sequence effects, probability, and interstimulus interval.

Probability and interstimulus interval effects on P3(00) event-related potential (ERP) stimulus sequences were examined in 2 experiments. ERPs were elicited with an auditory-discrimination paradigm in which subjects were instructed to detect target stimuli from a series of target (T) and standard (S) tones that were varied by randomly presenting 1 of 4 sequence patterns (SS, TS, TT, ST). Experiment 1 manipulated target stimulus probability as either 0.33 or 0.67; Experiment 2 kept target probability at 0.33 and manipulated the interstimulus interval (ISI) as either 2 or 6 s. Increases in target stimulus probability produced smaller P300 amplitudes that were additive with stimulus sequence type. ISI did not reliably affect P300 amplitude, although ISI interacted with stimulus sequence. P300 latency from the stimulus sequences was influenced weakly by the probability and ISI factors, with few consistent sequence effects obtained for the N1, P2, and N2 potentials. The results suggest that even relatively short sequences can affect P300 amplitude in the same way as longer sequences: as the number of standard stimuli preceding the target increased, P300 amplitude increased. The theoretical implications of the findings are discussed in the context of applied testing situations.

Adolescent↗

PubMed1997

P300 and probability: comparison of oddball and single-stimulus paradigms.

The P300 event-related brain potential (ERP) was elicited with auditory stimuli in two different tasks. The oddball paradigm presented both target and standard stimuli; the single-stimulus paradigm presented a target but no standard tone stimulus, with the inter-target interval the same as that for the oddball condition. Target stimulus probability was manipulated in the oddball task in different conditions (0.10, 0.30, 0.50, 0.70, 0.90). The single-stimulus paradigm employed the same procedures such that the inter-target interval was identical as that for the oddball condition across changes in probability. P300 amplitude and latency were similar for both the oddball and single-stimulus procedures across probability levels. Correlations between the P300 values from each task mimicked those from test-retest comparisons for the oddball paradigm. The findings suggest that P300 from the single-stimulus paradigm responds to target stimulus probability in the same fashion as the traditional oddball. The implications of the single-stimulus technique are discussed in terms of applied contexts that require very simple ERP task conditions.

Acoustic Stimulation↗

PubMed1997

On the number of trials needed for P300.

The P300 event-related brain potential (ERP) was elicited in n = 24 subjects using auditory and visual stimuli with target probabilities of 0.20 and 0.80 in different conditions. A total of 40 target stimulus ERPs were obtained from each subject and were averaged in two different ways: (1) single-trial averages were obtained by averaging each subsequent pairs of trial blocks (1-2, 3-4, 5-6, etc); (2) successive averages were obtained by averaging successive blocks of two trials (1-2, 1-4, 1-6, etc.). Statistical analyses demonstrated that for the single-trial averages, P300 measures are variable but not significantly different from one another across trial pairs, whereas successive averages demonstrated systematic decreases in amplitude and slight increases in peak latency. Auditory and visual stimuli produced similar patterns for the two averaging methods, as did target probability. The findings suggest that P300 amplitude stabilized with approximately 20 target trials for all conditions, and that peak latency changes relatively little during this time. The results are discussed in terms of applied/clinical contexts.

Acoustic Stimulation↗

PubMed1997

On the relationship between EEG and P300: individual differences, aging, and ultradian rhythms.

The literature on the relationship between background EEG and event-related brain potentials (ERPs) is reviewed, with the conclusion that variation in the former can contribute to individual variability in the latter. The effects of background EEG activity on the P300 component are then described using the results of three experiments. Study 1 assayed the association between EEG spectral power/mean frequency and P300 amplitude/latency measures in young adults. For the slower delta, theta, and alpha bands generally strong correlations who obtained for both types of measures. Study 2 employed similar techniques to assess a large sample of adults who varied in age from 20-80+ years. EEG power in the slower bands was correlated positively with P300 amplitude across the age range, but few effects for mean frequency/component latency were observed. Study 3 measured a group of young adults ten times very 20 min to assess for temporal changes in the relationship between EEG and ERPs. The correlations between spectral power and P300 amplitude measures were found to vary in a manner that suggested the influence of ultradian rhythms on neuroelectric activity. Taken together, the findings from all three study indicate that background EEG variation contributes significantly to the individual variability of the P300 ERP. Theoretical and applied implications of the findings are discussed.

Activity Cycles↗

PubMed1997

Olfactory event-related potentials: older males demonstrate the greatest deficits.

Olfactory event-related potentials (OERPs) were recorded monopolarly at the Fz, Cz, and Pz electrode sites in 16 young adults (8M/8F) and 16 older adults (8M/8F) with inter-stimulus intervals (ISI) of 45, 60 and 90 s using amyl acetate as the odorant stimulus. N1, P2, and N2 peak amplitudes and latencies were measured. Young participants demonstrated significantly shorter peak latencies than older participants. Older males demonstrated significantly smaller peak amplitudes than the other participant groups. Peak amplitudes also increased with longer ISIs for older males. The OERP is compared to traditional olfactory psychophysical testing.

Adult↗

PubMed1997

P300 from a single-stimulus paradigm: passive versus active tasks and stimulus modality.

The P300 component of the event-related brain potential (ERP) was elicited with auditory and visual stimuli in separate experiments. Each study compared an oddball paradigm that presented both target and standard stimuli with a single-stimulus paradigm that presented a target but no standard stimuli. Subjects were instructed in different conditions either to ignore the stimuli, press a response key to the target, or maintain a mental count of the targets. For the passive ignore conditions, P300 amplitude from the single-stimulus paradigm was larger than that from the oddball paradigm. For the active tasks, P300 amplitude from the oddball paradigm was larger than that from the single-stimulus paradigm. For the press and count conditions, P300 amplitude and latency were highly similar for the oddball and single-stimulus procedures. The findings suggest that the single-stimulus paradigm can provide reliable cognitive measures in clinical/applied testing for both passive and active response conditions.

Acoustic Stimulation↗

PubMed1997

EEG and ERP assessment of normal aging.

EEG was recorded from 120 normal adult subjects who ranged in age from 20 to 80+ years in separate eyes open/closed conditions. The P3(00) event-related brain potential (ERP) was elicited with auditory and visual stimuli in separate conditions in the same subjects. Spectral analysis indicated that overall EEG power decreased as subject age increased. P3 amplitude decreased and peak latency increased for both the auditory and visual stimulus conditions as subject age increased. Few age-related differences were observed for the N1, P2, or N2 components. Spectral power from the delta, theta, and alpha bands correlated positively with P3 amplitude across subject age, but mean band frequency demonstrated only weak associations with P3 latency. No strong relationships were found between EEG and the other ERP component variables. The results suggest that age contributes to EEG power shifts, and that such changes significantly affect age-related variability of the P3 ERP component.

Adult↗

PubMed1996

EEG changes from long-term physical exercise.

Electrophysiologic effects of physical exercise were investigated by comparing groups of individuals who engage in regular intensive physical exercise (12 + h/week) to control subjects (2 + h/week). Electroencephalographic (EEG) activity was recorded under eyes open/closed conditions to assess baseline differences between these groups. Spectral power was less for the exercise compared to the control group in the delta band, but greater in all other bands. Mean band frequency was higher for the exercise compared to controls in the delta, theta, and beta bands. Some differences in scalp distribution for power and frequency between the exercise and control groups also were found. The findings suggest that physical exercise substantially affects resting EEG. Theoretical mechanisms for these effects are discussed.

Adult↗

PubMed1996

P3(00) habituation from auditory and visual stimuli.

The P3(00) event-related brain potential (ERP) was elicited with auditory and visual stimuli using an oddball task in which the subject indicated with a button-press response the occurrence of a target stimulus that occurred randomly on 20% of the trials and refrained from responding to a standard stimulus. A total of four trial blocks were collected for each stimulus modality condition. P3 amplitude from the target stimuli decreased reliably across trial blocks for both the auditory and visual stimulus condition, with no interaction obtained between stimulus modality and trial block. P3 latency was shorter for the auditory compared to visual stimulus conditions, but did not vary with trial block. No changes in amplitude or latency independent of the P3 effects were obtained for the other ERP components with trial block, although the usual modality differences were observed. The results suggest that P3 components elicited by auditory and visual stimuli both habituate for actively discriminated target stimuli. The theoretical implications are discussed in the context of previous findings.

Acoustic Stimulation↗

PubMed1996

P300, probability, and the three-tone paradigm.

The effects of stimulus probability on P300 from a 3-tone paradigm were examined in two experiments. Experiment 1 manipulated the probability of the non-target tone as 0.10, 0.45, or 0.80, while the target tone probability was always 0.10. Experiment 2 manipulated the probability of 3 tones as 0.10, 0.30, or 0.60, with one of the infrequent tones assigned as the target in each condition. Subjects were required to press a button in response to the target stimulus in both experiments. The results indicated that the P300 to the target and the non-target were both affected by the probability of the eliciting stimulus, such that component amplitude was inversely related to probability; no reliable P300 latency effects were found. Target tones elicited larger P300 amplitude than the non-target tones at the same probability. The findings suggest that probability effects on P300 amplitude are independent of responding to a specific target stimulus and are discussed with reference to the clinical utility of the 3-tone paradigm.

Acoustic Stimulation↗

PubMed1996

P300, stimulus intensity, and modality.

Auditory and visual stimulus intensity levels were manipulated systematically in separate conditions to assess the influence of these variables on the P300 event-related brain potential (ERP). Increases in stimulus intensity produced increases in P300 amplitude and decreases in peak latency for both modalities, although the latency effects were stronger for visual stimulation. Similar, somewhat weaker stimulus intensity effects also were observed for the N100, P200, and N200 components. The findings suggest that stimulus intensity contributes to both P300 amplitude and latency measures in important ways and are discussed in relation to the use of ERPs in applied contexts.

Acoustic Stimulation↗

PubMed1996

Meta-analysis of P300 normative aging studies.

The theoretical and empirical backgrounds for the utility of the P300 event-related potential (ERP) as a measure of cognitive aging are summarized. P300 latency data from 32 different normative aging studies are then reviewed and assessed with meta-analytic procedures. Evaluation of moderator variables indicates that sample characteristics, stimulus factors, and task conditions contribute significantly to the "normal" change in peak latency that occurs with aging. These findings are critiqued in the context of previous reports, and implications are outlined for future applications of ERPs to normative aging. It is concluded that P300 latency can provide useful information about cognitive aging but that specific variables must be considered to obtain more precise results.

Acoustic Stimulation↗