Theodore R. Bashore

Dynamics of brain electrical activity

SummaryIn addition to providing important theoretical insights into chaotic deterministic systems, dynamical systems theory has provided techniques for analyzing experimental data. These methods have been applied to a variety of physical and chemical systems. More recently, biological applications have become important. In this paper, we report applications of one of these techniques, estimation of a signals correlation dimension, to the characterization of human electroencephalographic (EEG) signals and event-related brain potentials (ERPs). These calculations demonstrate that the magnitude of the technical difficulties encountered when attempting to estimate dimensions from noisy biological signals are substantial. However, these results also suggest that this procedure can provide a partial characterization of changes in cerebral electrical activity associated with changes in cognitive behavior that complements classical analytic procedures.

On the transmission of partial information: inferences from movement-related brain potentials.

Results are reported from a new paradigm that uses movement-related brain potentials to detect response preparation based on partial information. The paradigm uses a hybrid choice-reaction go/nogo procedure in which decisions about response hand and whether to respond are based on separate stimulus attributes. A lateral asymmetry in the movement-related brain potential was found on nogo trials without overt movement. The direction of this asymmetry depended primarily on the signaled response hand rather than on properties of the stimulus. When the asymmetry first appeared was influenced by the time required to select the signaled hand, and when it began to differ on go and nogo trials was influenced by the time to decide whether to respond. These findings indicate that both stimulus attributes were processed in parallel and that the asymmetry reflected preparation of the response hand that began before the go/nogo decision was completed.

Critical issues in assessing the behavioral effects of amphetamine

Amphetamine induces a behavioral syndrome in mammals that includes a variety of repetitive behaviors. An integral component of this syndrome in humans is the presence of a thought disturbance not unlike that manifest in idiopathic paranoid schizophrenia. The consistent pattern of behavioral changes produced by amphetamine across species, when considered in light of the psychosis it elicits in humans, has suggested to many that these drug-induced changes in animals may provide a model of the endogenous psychosis in humans. Amphetamine-induced changes in open-field behavior in the rat have been the most widely studied in attempts to formulate a model for investigating the neurobiological mechanisms underlying amphetamine psychosis and paranoid schizophrenia in humans and for testing the therapeutic efficacy of new antipsychotic drugs. The procedures used to assess the behavioral response to amphetamine, however, typically include rating scales or automated recordings that by their very nature ignore those components of the behavioral response that may be most critical for developing a viable animal model of the naturally occurring psychosis. Further, open-field behavior is often recorded during arbitrarily selected intervals without consideration for the multiphasic nature of the entire amphetamine response. We discuss how incomplete descriptive analyses of the amphetamine behavioral response in rats has led to confusion in the literature and describe behavioral research that is paradigmatic of the work we believe is most likely to eventuate in significant progress in the field.

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.

Are there alternatives to traditional polygraph procedures

The most commonly used method for detecting deception is based on the assumption that lies given by a person in response to critical questions posed during a polygraph examination will elicit an identifiable pattern of autonomic reactivity. Critics of this method argue that a polygraph examination cannot detect lying because lying does not produce a distinct physiological response. They assert that the possession of information only the guilty person would be expected to have can be revealed in a polygraph examination, however, by the pattern of autonomic arousal presentation of this information elicits in a person who possesses it. In this article, the position is taken that the dependence of both procedures on autonomic measures diminishes their effectiveness and inhibits the development of alternatives. A few studies are reviewed that suggest that measures of brain electrical activity can be used to infer the possession of information in persons attempting to conceal it

“Classical” and “atypical” antipsychotic drugs: Differential antagonism of amphetamine- and apomorphine-induced alterations of spontaneous neuronal activity in the neostriatum and nucleus accumbens

The ability of clozapine and haloperidol to antagonize the depression of firing rate produced by d-amphetamine and apomorphine in the neostriatum and nucleus accumbens was tested in immobilized, locally anesthetized rats. In the neostriatum, an intraperitoneal injection of 2.5 mg/kg d-amphetamine or 1.0 mg/kg apomorphine produced a prolonged inhibition of neuronal activity that was reversed by a subjsequent injection of either 20 mg/kg clozapine or 2.0 mg/kg haloperidol. An analysis of the onset and magnitude of the blockade revealed that clozapine was more effective than haloperidol in reversing the amphetamine response but that both antipsychotic drugs produced a comparable blockade of the apomorphine-induced depression. Similar results were obtained in the nucleus accumbens. The data indicate that although clozapine acts equieffectively in the neostriatum and nucleus accumbens, this atypical antipsychotic drug, aside from blocking postsynaptic dopamine receptors, may exert at least some of its effects by preventing dopamine release.

Perception of emotion among schizophrenic patients

The relationship of problems in social perception to the social dysfunction of schizophrenic patients has not been adequately addressed. The present study compared the responses of patients diagnosed as schizophrenic and affective disorder and nonpatient subjects on a measure of perception of emotional cues. A measure of general attention/perception was also administered. Schizophrenics exhibited selective deficits in perception of emotional stimuli in relationship to control groups. They differed in their perceptions of negative emotion, but not positive or neutral emotion, in comparison to affective disorder and control subjects. This selective distortion in social perception was apparent even though schizophrenics also performed poorly on the general attentional measure. A number of alternatives are discussed as possible explanations for the specific deviations which schizophrenics exhibited in perceiving negative emotion.

Discovery of the P300 : a tribute

The significant and enduring contributions made to cognitive psychophysiology by Samuel Sutton and his colleagues in the first two papers on the P300 component of the event-related brain potential are discussed. The remarkable quality of these contributions is revealed in the fact that the issues that motivated the series of experiments reported by these investigators continue to be of core importance to the field.

Age, Physical Fitness, and Mental Processing Speed

In the past 25 years, encouraged perhaps by the programs initiated during the Kennedy administration and by Kenneth Cooper’s book Aerobics (1968), interest in the benefits, both physiological and psychological, that accrue to individuals who exercise on a regular basis has grown tremendously. Indeed, the importance of incorporating a program of systematic exercise into one’s lifestyle is now advocated by organizations such as the American Medical Association (AMA) and the Department of Health and Human Services. Where in the early 1960s under the leadership of President Kennedy, the emphasis was on exercise in the early years of life, today’s recommendations are that all age groups, including the elderly, participate in regular, systematic exercise programs. The current rather ambitious objective of the U.S. Public Health Service is to have 50% of older Americans exercising regularly by 1990. This would represent a substantial increase from the 28% of people over 65 who reported exercising regularly in the National Health Interview Survey of 1985 (National Center for Health Studies, 1986). At that time, although 41% reported having walked for exercise in the previous two weeks, only 12% reported having done calisthenics, 5% biked and 1% jogged.

Neostriatal and mesolimbic neurons: Dose-dependent effects of clozapine

Abstract To determine whether clozapine, an antipsychotic drug devoid of extrapyramidal side effects, acts preferentially on neurons in the nucleus accumbens rather than in the neostriatum, an analysis of clozapine-induced changes in spontaneous neuronal activity was performed on locally anesthetized, immobilized rats. In both brain sites, intraperitoneal administration of clozapine (10, 20 or 80 mg/kg) produced a comparable dose-dependent increase in neuronal activity. Haloperidol, at a dose (2.0mg/kg) that typically elicits extrapyramidal side effects in rats, also increased the firing rate of neurons in the neostriatum and nucleus accumbens. However, haloperidol produced a greater effect on neuronal activity in the neostriatum during the first 15 min after injection, whereas 80 mg/kg clozapine was more effective during this period in the nucleus accumbens. In contrast, the neuronal response to the lower doses of clozapine paralleled that produced by haloperidol in the neostriatum; no differential regional effects were recorded at any time after injection of 10 or 20 mg/kg clozapine. The results suggest that the lack of extrapyramidal side effects associated with clozapine cannot be simply explained by a selective action of this drug on neurons in the nucleus accumbens.