Presidential address, 1982. The pharmacology of human information processing

Perceptual and cognitive processes in augmented reality - comparison between binocular and monocular presentations

In the present study, we investigated the difference between monocular augmented reality (AR) and binocular AR in terms of perception and cognition by using a task that combines the flanker task with the oddball task. A right- or left-facing arrowhead was presented as a central stimulus at the central vision, and participants were instructed to press a key only when the direction in which the arrowhead faced was a target. In a small number of trials, arrowheads that were facing in the same or opposite direction (flanker stimuli) were presented beside the central stimulus binocularly or monocularly as an AR image. In the binocular condition, the flanker stimuli were presented to both eyes, and, in the monocular condition, only to the dominant eye. The results revealed that participants could respond faster in the binocular condition than in the monocular one; however, only when the flanker stimuli were in the opposite direction was the response faster in the monocular condition. Moreover, the results of event-related brain potentials (ERPs) showed that all stimuli were processed in both the monocular and the binocular conditions in the perceptual stage; however, the influence of the flanker stimuli was attenuated in the monocular condition in the cognitive stage. The influence of flanker stimuli might be more unstable in the monocular condition than in the binocular condition, but more precise examination should be conducted in a future study.

The response relevance of visual stimuli modulates the P3 component and the underlying sensorimotor network

The functional meaning and neural basis of the P3b component of ERPs are still under debate. One of the main issues is whether P3b reflects only stimulus-related processes (stimulus evaluation hypothesis) or response-related processes as well (stimulus-response or S-R link activation hypothesis). Here, we conducted an EEG experiment examining whether P3b may indeed reflect an S-R link activation, followed by an fMRI experiment in which we explored the brain areas and functional connectivity possibly constituting the neural basis of these sensorimotor links. In both experiments, two successive visual stimuli, S1 and S2, were presented with a 1 sec interval, and responses were defined either by S1 or S2, while participants responded only after S2 onset. The obtained EEG results suggest that P3b may be interpreted in terms of the S-R link activation account, although further studies are needed to disentangle P3-related activity from overlapping anticipatory activity. The obtained fMRI results showed that processing of the relevant S1 involved activation of a distributed postero-anterior sensorimotor network, and increased strength of functional connectivity within this network. This network may underlie activation of the S-R links, thus possibly also the P3b component, forming a bridging step between sensory encoding and response execution.

Toward the Language Oscillogenome

Language has been argued to arise, both ontogenetically and phylogenetically, from specific patterns of brain wiring. We argue that it can further be shown that core features of language processing emerge from particular phasal and cross-frequency coupling properties of neural oscillations; what has been referred to as the language ‘oscillome.’ It is expected that basic aspects of the language oscillome result from genetic guidance, what we will here call the language ‘oscillogenome,’ for which we will put forward a list of candidate genes. We have considered genes for altered brain rhythmicity in conditions involving language deficits: autism spectrum disorders, schizophrenia, specific language impairment and dyslexia. These selected genes map on to aspects of brain function, particularly on to neurotransmitter function. We stress that caution should be adopted in the construction of any oscillogenome, given the range of potential roles particular localized frequency bands have in cognition. Our aim is to propose a set of genome-to-language linking hypotheses that, given testing, would grant explanatory power to brain rhythms with respect to language processing and evolution.

Effects of response delays and of unknown stimulus-response mappings on the oddball effect on P3

P3b is a prominent component of human event-related EEG potentials. P3b has been related to consciousness, encoding into memory, and updating of strategic schemata, among others, yet evidence has also been provided for its close relationship with deciding how to respond to the presented stimuli. P3b is large with rarely occurring stimuli and small with frequent ones. Here, we investigate the extent to which this oddball effect depends on selecting and executing responses. Participants pressed one of two keys in response to one of two letters, one of which was presented rarely and one frequently. Information about letter-key mapping was provided by a second stimulus. In different blocks, this mapping stimulus was either constant across trials or varied randomly, and either preceded or followed the letter. The oddball effect was reduced when responses were delayed (by waiting for the constant mapping stimulus following the letter) and was further reduced when responses could not be assigned to the letters (because letters were followed by varying mapping stimuli). This evidence suggests that P3b is closely related to decision processes, possibly reflecting reactivation of stimulus-response links.

Genetic influences on composite neural activations supporting visual target identification

Behavior genetic studies of brain activity associated with complex cognitive operations may further elucidate the genetic and physiological underpinnings of basic and complex neural processing. In the present project, monozygotic (N=51 pairs) and dizygotic (N=48 pairs) twins performed a visual oddball task with dense-array EEG. Using spatial PCA, two principal components each were retained for targets and standards; wavelets were used to obtain time-frequency maps of eigenvalue-weighted event-related oscillations for each individual. Distribution of inter-trial phase coherence (ITC) and single trial power (STP) over time indicated that the early principal component was primarily associated with ITC while the later component was associated with a mixture of ITC and STP. Spatial PCA on point-by-point broad sense heritability matrices revealed data-derived frequency bands similar to those well established in EEG literature. Biometric models of eigenvalue-weighted time-frequency data suggest a link between physiology of oscillatory brain activity and patterns of genetic influence.

Prescription stimulants in individuals with and without attention deficit hyperactivity disorder: misuse, cognitive impact, and adverse effects

Prescription stimulants are often used to treat attention deficit hyperactivity disorder (ADHD). Drugs like methylphenidate (Ritalin, Concerta), dextroamphetamine (Dexedrine), and dextroamphetamine-amphetamine (Adderall) help people with ADHD feel more focused. However, misuse of stimulants by ADHD and nonaffected individuals has dramatically increased over recent years based on students' misconceptions or simple lack of knowledge of associated risks. In this review, we discuss recent advances in the use and increasing misuse of prescription stimulants among high school and college students and athletes. Given the widespread belief that stimulants enhance performance, there are in fact only a few studies reporting the cognitive enhancing effects of stimulants in ADHD and nonaffected individuals. Student athletes should be apprised of the very serious consequences that can emerge when stimulants are used to improve sports performance. Moreover, misuse of stimulants is associated with dangers including psychosis, myocardial infarction, cardiomyopathy, and even sudden death. As ADHD medications are prescribed for long-term treatment, there is a need for long-term safety studies and education on the health risks associated with misuse is imperative.

The acute effects of d-amphetamine and d-methamphetamine on ERP components in humans

While a number of behavioural studies have been conducted to investigate the acute effects of amphetamines on tasks of attention and information processing, there is currently a scarcity of research concerning their electrophysiological effects in healthy adults. It is also unclear as to whether amphetamines exert effects on stimulus evaluation or response selection. In two studies, independent groups of twenty healthy illicit stimulant users aged between 21 and 32 years were administered 0.42 mg/kg d-amphetamine versus placebo, and 0.42 mg/kg d-methamphetamine versus placebo respectively, and completed an auditory oddball task on two separate testing days. A 62-channel EEG was recorded during the completion of the task, and the effects of amphetamines on N200 and P300 ERP components were analysed. d-amphetamine significantly decreased reaction time, improved accuracy, and reduced the latency of the P300 component relative to placebo, while having no effect on the N200 component. d-methamphetamine had no effect on reaction time, accuracy or the P300 component, but reduced the amplitude of the N200 component, relative to placebo. It was concluded that there is tentative support to suggest that d-amphetamine at a dose of 0.42 mg/kg may enhance speed of information processing while d-methamphetamine at a dose of 0.42 mg/kg may reflect changes to stimulus evaluation.

Are prescription stimulants "smart pills"? The epidemiology and cognitive neuroscience of prescription stimulant use by normal healthy individuals

Use of prescription stimulants by normal healthy individuals to enhance cognition is said to be on the rise. Who is using these medications for cognitive enhancement, and how prevalent is this practice? Do prescription stimulants in fact enhance cognition for normal healthy people? We review the epidemiological and cognitive neuroscience literatures in search of answers to these questions. Epidemiological issues addressed include the prevalence of nonmedical stimulant use, user demographics, methods by which users obtain prescription stimulants, and motivations for use. Cognitive neuroscience issues addressed include the effects of prescription stimulants on learning and executive function, as well as the task and individual variables associated with these effects. Little is known about the prevalence of prescription stimulant use for cognitive enhancement outside of student populations. Among college students, estimates of use vary widely but, taken together, suggest that the practice is commonplace. The cognitive effects of stimulants on normal healthy people cannot yet be characterized definitively, despite the volume of research that has been carried out on these issues. Published evidence suggests that declarative memory can be improved by stimulants, with some evidence consistent with enhanced consolidation of memories. Effects on the executive functions of working memory and cognitive control are less reliable but have been found for at least some individuals on some tasks. In closing, we enumerate the many outstanding questions that remain to be addressed by future research and also identify obstacles facing this research.

Event-Related Oscillations in Alcoholism Research: A Review

Alcohol dependence is characterized as a multi-factorial disorder caused by a complex interaction between genetic and environmental liabilities across development. A variety of neurocognitive deficits/dysfunctions involving impairments in different brain regions and/or neural circuitries have been associated with chronic alcoholism, as well as with a predisposition to develop alcoholism. Several neurobiological and neurobehavioral approaches and methods of analyses have been used to understand the nature of these neurocognitive impairments/deficits in alcoholism. In the present review, we have examined relatively novel methods of analyses of the brain signals that are collectively referred to as event-related oscillations (EROs) and show promise to further our understanding of human brain dynamics while performing various tasks. These new measures of dynamic brain processes have exquisite temporal resolution and allow the study of neural networks underlying responses to sensory and cognitive events, thus providing a closer link to the physiology underlying them. Here, we have reviewed EROs in the study of alcoholism, their usefulness in understanding dynamical brain functions/dysfunctions associated with alcoholism as well as their utility as effective endophenotypes to identify and understand genes associated with both brain oscillations and alcoholism.

A review of brain oscillations in cognitive disorders and the role of neurotransmitters

The analysis of the functional correlates of "brain oscillations" has become an important branch of neuroscience. Although research on the functional correlates of brain oscillation has progressed to a high level, studies on cognitive disorders are rare and mainly limited to schizophrenia patients. The present review includes the results of the changes in brain oscillations in patients with Alzheimer's, schizophrenia, bipolar disorders, mild cognitive impairment, attention-deficit hyperactivity disorder (ADHD), alcoholism and those with genetic disorders. Furthermore, the effects of pharmaca and the influence of neurotransmitters in patients with cognitive disorders are also reviewed. Following the review, a short synopsis is given related to the analysis of brain oscillations.

Uncovering genes for cognitive (dys)function and predisposition for alcoholism spectrum disorders: a review of human brain oscillations as effective endophenotypes

Brain oscillations provide a rich source of potentially useful endophenotypes (intermediate phenotypes) for psychiatric genetics, as they represent important correlates of human information processing and are associated with fundamental processes from perception to cognition. These oscillations are highly heritable, are modulated by genes controlling neurotransmitters in the brain, and provide links to associative and integrative brain functions. These endophenotypes represent traits that are less complex and more proximal to gene function than either diagnostic labels or traditional cognitive measures, providing a powerful strategy in searching for genes in psychiatric disorders. These intermediate phenotypes identify both affected and unaffected members of an affected family, including offspring at risk, providing a more direct connection with underlying biological vulnerability. Our group has utilized heritable neurophysiological features (i.e., brain oscillations) as endophenotypes, making it possible to identify susceptibility genes that may be difficult to detect with diagnosis alone. We have discussed our findings of significant linkage and association between brain oscillations and genes in GABAergic, cholinergic and glutamatergic systems (GABRA2, CHRM2, and GRM8). We have also shown that some oscillatory indices from both resting and active cognitive states have revealed a common subset of genetic foci that are shared with the diagnosis of alcoholism and related disorders. Implications of our findings have been discussed in the context of physiological and pharmacological studies on receptor function. These findings underscore the utility of quantitative neurophysiological endophenotypes in the study of the genetics of brain function and the genetic diathesis underlying complex psychiatric disorders.

The Posterior Contralateral Negativity as a Temporal Indicator of Visuo-Spatial Processing

Abstract. The temporal segmentation of the processing stream between stimulus and response is a declared aim of many EEG-studies on cognitive processing. This goal, however, can only be reached when measures of high temporal sensitivity are available that are unequivocally assigned to a particular cognitive process. The present study evaluates the peak latency of the posterior contralateral negativity (PCN) as a temporal measure of visual spatial processing. In three experiments, we show systematic variability of the PCN latency with task demands. In visual search, PCN latency varied in the same direction as response times with the number of distractors. These effects, however, were smaller than the effects observed on response times, indicating that the process underlying the PCN might contribute to but did not determine response time effects. In contrast, in attentional cueing tasks and a stimulus localization task, where stimulus detection was the primarily addressed process, PCN latency varied to the same amount as manual response times. Thus, it is suggested that the latency of the PCN provides a reliable and valid temporal measure of target localization.

Effects of acute bouts of exercise on cognition

A review was conducted of studies that assessed the effects of acute bouts of physical activity on adults' cognitive performance. Three groups of studies were constituted on the basis of the type of exercise protocol employed. Each group was then evaluated in terms of information-processing theory. It was concluded that submaximal aerobic exercise performed for periods up to 60 min facilitate specific aspects of information processing; however, extended exercise that leads to dehydration compromises both information processing and memory functions. The selective effects of exercise on cognitive performance are explained in terms of Sanders' [Acta Psychol. 53 (1983) 61] cognitive-energetic model.

Older age, traumatic brain injury, and cognitive slowing: some convergent and divergent findings

Reaction time (RT) meta-analyses of cognitive slowing indicate that all stages of processing slow equivalently and task independently among both older adults (J. Cerella & S. Hale, 1994) and adults who have suffered a traumatic brain injury (TBI; F. R. Ferraro, 1996). However, meta-analyses using both RT and P300 latency have revealed stage-specific and task-dependent changes among older individuals (T. R. Bashore, K. R. Ridderinkhof, & M. W. van der Molen, 1998). Presented in this article are a meta-analysis of the effect of TBI on processing speed, assessed using P300 latency and RT, and a qualitative review of the literature. They suggest that TBI induces differential slowing. Similarities in the effects of older age and TBI on processing speed are discussed and suggestions for future research on TBI-induced cognitive slowing are offered.

[Opioid addiction: P300 assessment in treatment by methadone substitution]

The aim of this study was to assess cognitive functions in two clinical conditions, namely during heroin detoxification and during substitution treatment by methadone. Two groups of chronic heroin user inpatients, meeting DSM-III-R criteria for concurrent opiate dependence, were tested using an auditory oddball paradigm of P300. The first group (four women and six men) were drug-free and the second (five women, ten men) received methadone treatment. Patients were also compared to a control group of non-dependent healthy subjects (five women, nine men). The patients were recorded 6-10 days after the beginning of either detoxification or methadone treatment. There were significant P300 alterations in the two patient groups, with amplitude decrease and latency increase, at a time when self-reported signs of withdrawal were absent or minimal. Paradoxically, the reaction time was accelerated in the two groups of patients, who also showed increased discrimination errors. These abnormalities were found with a lesser degree in the methadone-treated group than in detoxification patients.

Event-related potentials in posttraumatic headache

OBJECTIVES

To assess impairment of cognitive functions occurring in patients with posttraumatic headache as a consequence of a minor cranial trauma in the absence of organic damage involving the central nervous system.

BACKGROUND

The term posttraumatic syndrome defines a stereotypic set of symptoms following traumatic brain injury that are subjective and varied. A deficit of cognitive function and impairment of the rapid processes of learning, attention, and short-term memory have frequently been identified. Moreover, headache is the most frequent symptom reported by the patients. Due to the nature of the symptoms, a great limitation in defining the posttraumatic syndrome is represented by the lack of methods and diagnostic tools that allow quantification of the subjective disturbances and evidence of the signs indicative of central nervous system involvement in this pathological condition.

METHODS

Twenty-five subjects (16 women, 9 men; mean age, 28 +/- 9 years) were examined between 3 and 6 months after the traumatic event. The P300 event-related potential was recorded by an odd-ball paradigm with an acoustic modality. The patients underwent electroencephalography and brain stem auditory evoked potentials; magnetic resonance imaging was performed to exclude the presence of cerebral lesions.

RESULTS

The mean latency of P300 was increased in both central electrodes (Cz and Pz) in patients with posttraumatic syndrome compared with controls (P<.001); assuming the value of mean +/- 2 SD was the cutoff point between normal and abnormal results, the P300 latency results were altered in 13 patients (52%). In the patient group, a significant correlation was demonstrated between Zung Depression Scale score and P3 and N2 wave latencies (r = 0.54, P <.004; r = 0.56, P<.003) and between Zung Anxiety Scale scores and P3 wave latencies (r = 0.46, P<.02).

CONCLUSIONS

These data suggest the usefulness of the P300 event-related potential in evaluating cognitive disturbances in patients affected by posttraumatic syndrome. Alteration of cognitive potential in such patients, even in the absence of lesions detectable by neuroimaging, indicate the functional impairment of specific cerebral areas that can occur after a traumatic event.

Delayed P300 during Sternberg and color discrimination tasks in poor readers

The P300 ERP component was studied in poor and normal readers, using Sternberg and color discrimination (Spaceships) tasks. During the first one, subjects must decide if a probe item belongs or not to a set of digits previously presented. In the second one, the participants must shoot violet spaceships with one key and other than violet spaceships with another key. There were no significant differences between groups with respect to reaction times, but a larger proportion of errors was observed in poor readers. Longer P300 latencies were recorded for poor readers than controls in both tasks. P300 amplitudes showed topographical differences between the two groups: Poor readers' P300 is larger frontally during the Sternberg task, but smaller at posterior sites during the Spaceships task. These results suggest that poor readers may have deficiencies during the early processing stage, such as visual stimulus evaluation. Poor readers also appear to have deficits for classifying and memorizing visual stimuli.

Transdermal nicotine: single dose effects on mood, EEG, performance, and event-related potentials

A 21-mg dose of nicotine was administered transdermally to 16 overnight smoking-deprived smokers in a double-blind, placebo-controlled design. Mood ratings, electroencephalography (EEG), behavioral performance and event-related potential (ERP: P300) indices of attention and information processing speed were assessed before and 4 h after placebo/nicotine treatment. Although nicotine, relative to placebo, failed to alter mood, it increased absolute and relative power indices of EEG arousal, shortened reaction times, and increased P300 amplitudes. The results are discussed in relation to nicotine's actions on cholinergic transmission and its role in smoking behavior.