Joel E. Alexander

P300 topography of amplitude/latency correlations

SummaryThe 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.

Omega-3 polyunsaturated fatty acids and cognition throughout the lifespan: A review

Abstract With increasing awareness of the effects of nutrition on physical and mental health, researchers have begun to further investigate the benefits of omega-3 polyunsaturated fatty acids (n-3 PUFA) on health and the brain; however, these benefits remain unclear across different age groups. Objectives The purpose of this article is to summarize the current evidence on the cognitive effects of n-3 PUFA throughout the lifespan. Methods An exhaustive review of the literature on the effects of n-3 PUFA on various aspects of cognition, across the lifespan, was conducted. Results The research suggests that n-3 PUFA positively affect pre-natal neurodevelopment; however, this cognitive-enhancing effect might diminish post-natally with maturation, as no research on child populations has clearly tied dietary n-3 PUFA to improved cognitive skills. Overall, few studies have examined the cognitive effects of n-3 PUFA through childhood, young adulthood, and middle age. At later ages, multiple studies found evidence suggesting that n-3 PUFA can protect against neurodegeneration and possibly reduce the chance of developing cognitive impairment. Discussion Age groups central to the lifespan require further investigation into the effects that n-3 PUFA might have on their cognitive skills. The research examining the extremities of the lifespan provides evidence that n-3 PUFA are essential for neurodevelopment and cognitive maintenance in older adulthood. Future research must develop more consistent methodologies, as variable dosages, supplementation periods, and cognitive measures across different studies have led to disparate results, making the evidence less comparable and difficult to synthesize.

Sex differences, hemispheric laterality, and associated brain activity in the intellectually gifted

Benbow (1986) proposed that enhanced development of the right cerebral hemisphere may be associated with extreme intellectual giftedness. Here we report on a series of studies conducted to evaluate the viability of this hypothesis, using several neurop‐sychological methods (e.g., dichotic listening, concurrent finger‐tapping, chimeric face, and word processing). Also presented are new data from electroencepha‐lographic recordings of brain activity taken from precocious and average‐ability male and female adolescents while they performed two of the aforementioned tasks. These experiments provide convergent lines of evidence suggesting that enhanced right‐hemisphere involvement during basic information processing, as well as superior coordination and allocation of cortical resources within and between the hemispheres, are unique characteristics of the gifted brain. The evidence is especially compelling for precocious male adolescents, as gifted female adolescents tend to exhibit a somewhat more bilateral an...

Hemispheric differences for P300 amplitude from an auditory oddball task

The P3(00) event-related potential (ERP) was elicited in 80 normal, right-handed male subjects using a simple auditory stimulus discrimination task, with electroencephalographic (EEG) activity recorded at 19 electrodes. P300 amplitude was larger over the right compared to left hemisphere electrode sites primarily at anterior-medial locations (F3/4, C3/4) for both target and standard stimuli. The N100, P200, and N200 components also demonstrated several similar, albeit less robust, hemispheric asymmetries. No hemispheric effects for P300 latency were observed, with few consistent latency findings for any of the other components obtained. The results suggest that the discrimination process underlying P300 generation may originate with right frontal activation.

Developmentally advanced EEG alpha power in gifted male and female adolescents

An electroencephalographic (EEG) study of gifted and average ability male and female adolescents, as well as college students of both sexes, was conducted to investigate further the relative contributions the left and right cerebral hemispheres during an eyes open (baseline) task in all groups. A total of 90 subjects had baseline EEG recorded in three groups with equal numbers of males and females: 30 gifted adolescents, 30 average ability adolescents, and 30 college-age subjects. Overall alpha power (8-12 Hz resting potential) was significantly greater in average ability subjects compared to both college-age subjects. Moreover, there were no significant differences in overall alpha power between college-age and gifted adolescent subjects. However, college-age and gifted adolescent subjects had different RH/LH patterns of activation such that at temporal and parietal locations college-age and gifted adolescent subjects had greater LH alpha power levels whereas gifted adolescents had greater RH alpha power. These findings suggest that gifted adolescents may have a developmentally enhanced state of brain activity, one that more closely resembles that of college-age adults to whom they also resemble in terms of cognitive development.

P300 from an auditory oddball task: inter-laboratory consistency

Event-related potentials (ERPs) were recorded from normal subjects for the purpose of evaluating measurement consistency among six laboratories located in different cities within the United States. At each laboratory location 15 male subjects were tested using a simple auditory stimulus discrimination task and identical electrophysiological equipment and recording methods. Assessment of the N1, P2, N2, and P3(00) potentials from both the target and standard stimuli resulted in no reliable differences among laboratories for component amplitudes, latencies, and scalp distributions. Quantitative evaluation of overall waveform and specific component morphology yielded good to excellent agreement across laboratories. The findings suggest that large-scale inter-laboratory human electrophysiological studies are feasible and may prove of value when using ERPs to evaluate cognitive function in humans.

Omega-3 polyunsaturated fatty acids and cognition in a college-aged population.

The cognitive influences of omega-3 polyunsaturated fatty acids (n-3 PUFA) remain unclear throughout the life span. Dietary n-3 PUFA appear cognitively beneficial prenatally and neuroprotective at later age; however, researchers using supplementation designs have reported disparate findings across age groups. Few studies have examined the cognitive impact of n-3 PUFA during young adulthood. This study assessed the cognitive effects of fish oil supplementation at college age, hypothesizing benefits on affect, executive control, inhibition, and verbal learning and memory. College-aged participants were assigned to active (n = 20, 5 men; age = 19.9, sage = 1.8) or placebo (n = 21, 7 men; age = 20.4, sage = 1.6) treatments, receiving fish oil (480 mg DHA/720 mg EPA) or coconut oil, respectively. Both groups completed four weeks of supplementation. At baseline and posttreatment, the researchers administered the Rey Auditory Verbal Learning Test (RAVLT; Lezak, 1995), Stroop Color and Word Test (SCWT; Golden & Freshwater, 2002), Trail Making Test (TMT; Corrigan & Hinkeldey, 1987; Gaudino, Geisler, & Squires, 1995; Lezak, 1995), and Positive and Negative Affect Schedule (PANAS; Watson, Clark, & Tellegen, 1988). Repeated-measures ANOVAs indicated no benefits of fish oil on the SCWT, RAVLT Stages 1 to 5, or PANAS. An interaction occurred between condition and time of measurement (i.e., baseline and posttreatment) on RAVLT Stages 6 and 7, and placebo significantly improved TMT performance over fish oil. The benefits of n-3 PUFA on RAVLT performance derived more from depreciated placebo performance than improved performance due to fish oil. The placebo gain on TMT performance likely derived from a learning effect. Together, these results present limited cognitive benefits of n-3 PUFA at college age; however, the treatment may have been subtherapeutic, with a larger sample needed to generalize these results.

P300 differences between sinistrals and dextrals

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

Cerebral lateralization in homosexual males: a preliminary EEG investigation

A preliminary investigation was conducted to determine whether hemispheric patterns of electrophysiological activation in male homosexuals differ from that of male and female heterosexuals. Electroencephalographic (EEG) activity was recorded over left and right cerebral hemispheric locations while subjects performed verbal and spatial cognitive tasks. Male homosexuals demonstrated different patterns of alpha power compared to heterosexual males and females during baseline recording. Different hemispheric patterns of alpha activity also were observed between homosexual and heterosexual males during affective judgments of both verbal and spatial stimuli, but not between homosexual males and heterosexual females. These results provide further evidence of biologically-mediated functional differences between homosexuals and heterosexuals.

A Graphical Technique for Displaying Correlation Matrices

Abstract A recent multilaboratory study to investigate phenotypic and genotypic markers for alcoholism is described. A preliminary investigation of the reliability of electroencephalographic data amassed at six laboratories was undertaken; data from each laboratory could be usefully summarized with sample correlation matrices. A graphical method for depicting these correlation matrices is presented. The Larntz-Perlman procedure for assessing the equality of correlation matrices can immediately be incorporated into this graphical technique. The experimental data from the preliminary investigation are illustrated with the graphical method, which readily conveys large amounts of correlational information and reveals meaningful patterns in the electroencephalographic responses.