Biomedical subjects

John Polich

Publications and source records attributed to John Polich.

17 recordsLinked to original sources

PubMed2006

P3a from auditory white noise stimuli.

OBJECTIVE: P3a and P3b event-related brain potentials (ERPs) were elicited with an auditory 3-stimulus (target, distracter, standard) paradigm in which subjects responded only to the target. METHODS: Distracter stimuli consisted of white noise, novel sounds, or a high frequency tone, with stimulus characteristics perceptually controlled. Task difficulty was varied as easy and hard by changing the pitch difference between the target and standard stimuli. RESULTS: Error rate was greater and response time longer for the hard task. P3a distracter amplitude was largest for the white noise and novel stimuli, with maximum amplitude over the central recording sites, and larger for the hard discrimination task. P3b target amplitude was unaffected by distracter type, maximum over the parietal recording sites, and smaller and later for the hard task. CONCLUSIONS: The findings indicate that white noise stimuli can produce reliable P3a components. SIGNIFICANCE: White noise can be useful for clinical P3a applications, as it removes the variability of stimulus novelty.

Acoustic Stimulation↗

PubMed2006

Neuropsychology and neuropharmacology of P3a and P3b.

Perspectives on the P300 event-related brain potential (ERP) are reviewed by outlining the distinction between the P3a and P3b subcomponents. The critical factor for eliciting P3a is how target/standard discrimination difficulty rather than novelty modulates task processing. The neural loci of P3a and P3b generation are sketched and a theoretical model is developed. P3a originates from stimulus-driven disruption of frontal attention engagement during task processing. P3b originates when temporal-parietal mechanisms process the stimulus information for memory storage. The neuropharmacological implications of this view are then outlined by evaluating how acute and chronic use of ethanol, marijuana, and nicotine affect P3a and P3b. The findings suggest that the circuit underlying ERP generation is influenced in a different ways for acute intake and varies between chronic use levels across drugs. Theoretical implications are assessed.

Animals↗

PubMed2006

Meditation states and traits: EEG, ERP, and neuroimaging studies.

Neuroelectric and imaging studies of meditation are reviewed. Electroencephalographic measures indicate an overall slowing subsequent to meditation, with theta and alpha activation related to proficiency of practice. Sensory evoked potential assessment of concentrative meditation yields amplitude and latency changes for some components and practices. Cognitive event-related potential evaluation of meditation implies that practice changes attentional allocation. Neuroimaging studies indicate increased regional cerebral blood flow measures during meditation. Taken together, meditation appears to reflect changes in anterior cingulate cortex and dorsolateral prefrontal areas. Neurophysiological meditative state and trait effects are variable but are beginning to demonstrate consistent outcomes for research and clinical applications. Psychological and clinical effects of meditation are summarized, integrated, and discussed with respect to neuroimaging data.

Brain↗

PubMed2005

P3a from visual stimuli: task difficulty effects.

The P3a event-related brain potential (ERP) was elicited using a visual three-stimulus oddball paradigm (target, standard, distracter) in which participants responded only to the target. Discrimination task difficulty between the target and the standard was manipulated by varying the size of the standard stimulus circle relative to a constant target stimulus circle across three conditions (easy, medium, hard). A large checkerboard pattern was employed for the distracter stimulus across all tasks. Error rate and response time increased with increases in task difficulty, so that the task difficulty manipulation was successful. Distracter P3a amplitude increased and target P3b decreased somewhat with increases in task difficulty. The findings suggest that increased perceptual discrimination difficulty between the target and standard stimuli increases P3a amplitude. Theoretical implications are discussed.

Adult↗

PubMed2005

Alzheimer's disease and P300: review and evaluation of task and modality.

Early stage Alzheimer disease patients and matched elderly unaffected controls (n = 16/group) were evaluated with the P300 event-related brain potential (ERP). All subjects performed four oddball tasks that varied systematically in task difficulty and were each presented in the auditory and visual modalities. P300 amplitude was smaller and peak latency longer for the Alzheimer patients compared to elderly control subjects across tasks and modalities. P300 differences between Alzheimer patients and controls were largest for the relatively easy tasks, with little influence of stimulus modality observed. The results suggest that the P300 brain potential is sensitive to Alzheimer's disease processes during its early stages, and that easily performed stimulus discrimination tasks are the clinically most useful. Theoretical and practical implications are reviewed.

Acoustic Stimulation↗

PubMed2004

Alcoholism risk, tobacco smoking, and P300 event-related potential.

OBJECTIVE: The P300 event-related potential (ERP) is sometimes larger for individuals at low- compared to high-risk for alcoholism. These effects are inconsistent, and how P300 is affected by tobacco smoking in the context of alcoholism risk is unknown. The present study used P300 to examine the inter-relationship between alcoholism heritability and smoking status. METHODS: P300 was elicited with a visual discrimination task from young adults at low- and high-risk for alcoholism. Half of the subjects in each risk category reported that they did not smoke cigarettes, and the other half reported that they smoked regularly, with equal numbers of male and female subjects assessed. ERPs were recorded, and subjects were instructed to respond only to an infrequently presented target stimulus that occurred in a series of standard and distracter stimuli. RESULTS: P300 amplitude from the target stimuli was larger for the low-risk compared to high-risk subjects overall. However, smoking status demonstrated even stronger effects, with non-smokers producing consistently larger component amplitudes than smokers and accounting for more variance than alcoholism risk. These group factors also significantly affected P300 scalp topography. No reliable alcoholism risk or smoking group effects were obtained for the ERPs from the other stimuli. CONCLUSIONS: The findings suggest that P300 measures of alcoholism risk in young adults are moderated by smoking status. Theoretical implications are discussed.

Adolescent↗

PubMed2004

Olfactory, auditory, and visual ERPs from single trials: no evidence for habituation.

Event-related potentials (ERPs) using olfactory, auditory, and visual stimuli were recorded from young adults to assess possible component habituation across single trials among modalities. A single-stimulus ERP paradigm was used that employed a 10-min inter-stimulus interval (ISI) to minimize possible sensory adaptation and three stimulus trials for each modality to assess initial habituation effects. The present findings were: (1) P3 amplitude does not habituate appreciably over the initial three trials but may increase from the first to second trial. (2) ERPs from a single-stimulus paradigm with a very long ISI produce significantly correlated component amplitudes for the olfactory, auditory, and visual modalities. (3) P3 amplitude from olfactory stimuli demonstrated scalp topography similar to that for auditory and visual ERPs. These findings suggest that the single-stimulus task using a long ISI produces highly comparable and stable P3 components from olfactory, auditory, and visual stimuli. Application of single-stimulus paradigm to olfactory ERP methods is supported.

Adult↗

PubMed2004

Clinical application of the P300 event-related brain potential.

The P300 brain potential can provide information about cognition that is quantitatively comparable to other clinically used biomedical assays. Causes of P300 variability with respect to task and biologic determinants have been well characterized so that refinement of ERP methods for clinical applications is possible. Elaboration of how P300 and other ERP components reflect neuropsychologic processes would help to increase their clinical relevance. In particular, development of reliable P3a paradigms used in conjunction with P3b tasks promises to augment dramatically the applicability and sensitivity of ERPs. Use of P300 as a clinical evaluation tool should be revisited with contemporary theory, methods, and analysis procedures because a reliable neuroelectric measure of mental function would redefine the assessment of cognitive disorders.

Aging↗

PubMed2003

Alcoholism risk and the P300 event-related brain potential: modality, task, and gender effects.

The P300 event related potential (ERP) was elicited from young adults at low- (LR) and high-risk (HR) for alcoholism (n = 24/risk group), with equal numbers of male and female subjects employed. The effects of stimulus modality, task difficulty, and gender were assessed with analogous auditory and visual paradigms (tone location/head rotation and tone matching/shape matching). Although task performance was generally comparable across risk groups, LR subjects produced smaller P300 amplitudes than HR subjects for the visual matching tasks. No consistent risk group P300 latency effects were obtained. Gender, task difficulty, and scalp topography differentially modulated the risk group outcomes across paradigms. These findings suggest that P300 amplitude reflects risk-for-alcoholism in male and female young adults, but the specific task conditions and electrode location affect the strength of risk group differences.

Acoustic Stimulation↗

PubMed2003

P3a from visual stimuli: typicality, task, and topography.

A visual three-stimulus (target, nontarget, standard) paradigm was employed in which subjects responded only to the target. Nontarget stimulus properties were varied systematically to evaluate how stimulus typicality (non-novel vs. novel) across task discrimination (easy vs. difficult) conditions affects P3a scalp topography. Nontarget stimuli consisted of letters, small squares, large squares, and novel patterns; discrimination difficulty between the target and standard was varied across conditions. When the discrimination was easy, P300 amplitude was larger for the target than the nontarget with parietal maximums for both. In contrast, when the discrimination was difficult, nontarget amplitude (P3a) was larger and earlier than the target P300 over the frontal/central electrode sites, whereas target amplitude (P3b) was larger parietally and occurred later. P3a was largest when elicited by either the large square or novel pattern stimuli. The findings suggest that stimulus context as defined by the target/standard discrimination difficulty rather than stimulus novelty determines P3a generation.

Adolescent↗

PubMed2003

Meta-analysis of P300 and schizophrenia: patients, paradigms, and practical implications.

The goal of the present meta-analysis was to identify factors that contribute to P300 event-related brain potential (ERP) differences in patients with schizophrenia compared to unaffected controls in an attempt to characterize the clinically relevant dimensions underlying P300 deficits in patients with schizophrenia. P300 effect size (d) was smaller in amplitude and longer in latency in schizophrenic patients compared to normal controls, with the strongest effects obtained from the auditory oddball. Paranoid subtype demonstrated larger P300 amplitude effect sizes than other disease subtypes, and P300 latency effect size decreased with disease duration. Psychopathology severity and antipsychotic medications were unrelated to P300 amplitude effect size. Gender proportion, educational level, and stimulus and task variables also affected P300 amplitude and latency effect sizes. The findings are used to formulate a theoretical account of the empirical data and provide suggestions for maximizing the utility of the P300 component in the assessment of schizophrenia.

Clinical Trials as Topic↗

PubMed2002

N2 and P3 components of event-related potential in first-episode schizophrenic patients: scalp topography, medication, and latency effects.

Auditory N2 and P3 components of event-related potentials were assessed in first-episode schizophrenic and normal control subjects (n=12/group). P3 amplitude was decreased in the patients most prominently over the frontal areas in contrast to a widespread P3 amplitude decrease reported in chronic schizophrenia. Moreover, frontal attenuation of P3 amplitude was greater in the non-medicated compared with medicated patients, a finding that suggests frontal areas are primarily affected at the onset of the first schizophrenic episode. Prolongation of N2 and P3 latencies was also observed in the patients, which indicates that stimulus classification and memory updating processes were slowed even in early stages of schizophrenia. These findings indicate that first-episode schizophrenic patients produce N2 and P3 abnormalities that are distinct from those in chronic patients, and that psychotropic medication can attenuate event-related potential effects in specific ways.

Acoustic Stimulation↗

PubMed2002

P300 and slow wave from oddball and single-stimulus visual tasks: inter-stimulus interval effects.

The effects of inter-stimulus intervals on P300 from an oddball task (target and standard stimuli) and a single-stimulus task (targets only) employing simple visual stimuli were assessed in order to determine how a relatively long ISI affects event-related brain potentials (ERPs). Young adult subjects (n=16) responded by pressing a button to a visual target stimulus of each task condition. ISI was either 2.5 or 30 s and paradigm type was either the oddball or single-stimulus task. ERPs were recorded from the midline electrodes, with amplitude, mean area, and latency of the P300 and other components assessed. The results showed that P300 morphology was dramatically affected by task and ISI such that under the 2.5 s condition, the oddball paradigm produced typical ERP components, whereas the single-stimulus condition demonstrated minimal P300 amplitude. When ISI was 30 s, both the oddball and single-stimulus tasks produced robust P300 components but also evinced strong slow wave (SW) potentials, which contributed to the ERP measurement outcomes. It is concluded that P300 from visual stimuli can be elicited with both oddball and single-stimulus tasks when ISI is relatively long. ERPs from both paradigms produced appreciable SW activity, which needs to be considered when long ISI procedures are employed.

Adult↗

PubMed2002

P300 amplitude is determined by target-to-target interval.

P300 event-related brain potential (ERP) measures are affected by target stimulus probability, the number of nontargets preceding the target in the stimulus sequence structure, and interstimulus interval (ISI). Each of these factors contributes to the target-to-target interval (TTI), which also has been found to affect P300. The present study employed a variant of the oddball paradigm and manipulated the number of preceding nontarget stimuli (0, 1, 2, 3) and ISI (1, 2, 4 s) in order to systematically assess TTI effects on P300 values from auditory and visual stimuli. Number of preceding nontargets generally produced stronger effects than ISI in a manner suggesting that TTI determined P300 measures: Amplitude increased as TTI increased for both auditory and visual stimulus conditions, whereas latency tended to decrease with increased TTI. The finding that TTI is a critical determinant of P300 responsivity is discussed within a resource allocation theoretical framework.

Acoustic Stimulation↗

PubMed2002

P3a and P3b auditory ERPs in HIV patients receiving anti-viral medication.

The effects of human immunodeficiency virus (HIV) infection on central nervous system function were studied with the P3a and P3b event-related brain potentials (ERPs) in patients with HIV compared to unaffected matched controls (n = 14/group). All patients were on anti-viral medication for at least 2 months before testing. Auditory stimuli were employed in an easy 2-stimulus oddball discrimination task to obtain a typical P3b (P300) subcomponent. A 3-stimulus distractor paradigm also was employed in which the target/standard discrimination was very difficult, and an infrequent high-pitched tone non-target was presented to elicit the P3a subcomponent. Subjects responded only to the target stimulus in each task. P3a amplitude was significantly smaller for HIV compared to control subjects. No reliable P3b effects were obtained. The findings suggest that P3a rather than P3b may be a more sensitive measure of cognitive impairment in HIV patients on anti-viral medication.

Acoustic Stimulation↗

PubMed2002

P300 stimulus sequence effects in children and adults.

Immediate memory capability for 12 children (8 years) and 12 adults (21 years) was assessed electrophysiologically by using P300 event-related brain potential (ERP) stimulus sequences. These were derived from an auditory discrimination paradigm in which participants detected target stimuli in a series of target (T) and standard (S) tones that were varied by randomly presenting one of four sequence patterns (SSSS, TTTT, TTTS, SSST). Short-term memory capability was assessed behaviorally by recall performance of a 20-word list. Children and adults showed virtually identical P300 amplitude sequence patterns, such that for both groups component size increased systematically as the discrepancy between standard and target stimuli increased across sequence patterns. P300 latency evinced similar, albeit weaker, stimulus sequence effects, with children having longer component peak latencies. Memory recall performance was substantially weaker for the children than for adult participants, especially for recency effects. The findings suggest that immediate memory for stimulus sequences is fully developed in young children, although long-term memory is not.

Adolescent↗

PubMed2001

Cognitive effects of a Ginkgo biloba/vinpocetine compound in normal adults: systematic assessment of perception, attention and memory.

A computerized test battery was used in a double-blind design to assess the cognitive effects of a nutrient compound containing Ginkgo biloba in 24 normal adults. Ten tasks (perceptual, attention and short-term memory) were presented in a standardized manner designed to maximize performance, with substantial pre-test practice employed to minimize response variability. Subjects were given either placebo or Ginkgo biloba extract capsules to consume for 14 days, after which they performed all tasks twice. They then received the other condition, and after 14 days completed the final test session. Response time and error rate stabilized after pre-test practice. A 'working memory capacity' paradigm demonstrated a reliable 50 ms response time decrease between the placebo and Ginkgo biloba testing, suggesting that Ginkgo biloba speeds short-term working memory processing in normal adults. Copyright 2001 John Wiley & Sons, Ltd.

Journal Article↗