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Central auditory processing: a view from auditory neuroscience.

The purpose of this report is to overview some recent advances in basic science that help us understand the roles of the central auditory nervous system in hearing. Particularly at rostral levels, neural representations of the acoustic signal are shaped by convergent inputs and show some degree of plasticity, even in adults. The fidelity with which brain regions represent a stimulus dimension is heterogeneous, and this has demonstrable implications for the perceptual consequences of damage to those regions. So-called higher-level disorders (e.g., phonologic ones) have become increasingly understandable, largely through work in cognitive neuroscience, which has begun to describe the functional architecture of the processes mediating sound recognition and comprehension.

Animals↗

Leanna Standish, ND, PhD. From neuroscience to naturopathy. Interview by Bonnie Horrigan.

Leanna Standish, ND, PhD, is the principal investigator for the Bastyr University AIDS Research Center and codirector of the Bastyr Research Institute. She also serves as director of research at Bastyr University and as a staff physician at the University Health Clinic. She is a licensed naturopathic physician and will soon complete her training as an acupuncturist. Dr Standish received her doctoral degree in biopsychology from the University of Massachusetts. She completed a postdoctoral fellowship in psychopharmacology at the Yerbes Primate Research Center, co-directed Smith College's neuroscience program, and served for 2 years as a visiting scientist/senior fellow in the University of Washington's Department of Physiology and Biophysics. Alternative Therapies interviewed Dr Standish at her office at Bastyr University in Seattle, Wash.

Complementary Therapies↗

Neuroscience nursing research: challenges for the next decade.

Nurses are making a significant difference in health care today and research is the key to making our practice the best that it can be. Our goal is to facilitate that research and to promote excellence in the knowledge underlying clinical practice. We should be proud of the accomplishments so far, but challenges and opportunities exist for the future. Neuroscience nurses are at the forefront of some of the most exciting avenues for scientific discovery. NINR research, past, present, and future will contribute to these efforts.

Forecasting↗

Gender disparity in the academic pipeline: women in neuroscience.

The percentages of females at critical steps in the academic career ladder were examined for one specific field, neuroscience. There was a slight attrition among females completing the Ph.D. However, the major drop-off occurred when qualified post-doctorates did not apply for faculty positions. Remedial actions should focus on not only the graduate school environment but also on the more critical postdoctoral experience.

Career Mobility↗

Toward a cognitive neuroscience of metacognition.

The relationship between metacognition and executive control is explored. According to an analysis by Fernandez-Duque, Baird, and Posner (this issue), metacognitive regulation involves attention, conflict resolution, error correction, inhibitory control, and emotional regulation. These aspects of metacognition are presumed to be mediated by a neural circuit involving midfrontal brain regions. An evaluation of the proposal by Fernandez-Duque et al. is made, and it is suggested that there is considerable convergence of issues associated with metacognition, executive control, working memory, and frontal lobe function. By integrating these domains and issues, significant progress could be made toward a cognitive neuroscience of metacognition.

Attention↗

Will neuroscience explain consciousness?

This paper is a defence of a pragmatic version of mind-brain reductionism from a neuroscientist's point of view. It is claimed that there are good reasons to believe that future neuroscience will be able to explain (in a weak and pragmatic sense) the puzzling aspects of mind and consciousness. Opposition to reductionism comes from both philosophical and empirical quarters. It is argued here that philosophical arguments, such as semantic problems with the concept of identity, are unconvincing and should be regarded with the greatest suspicion. The most influential empirical result that has been claimed to constitute a problem for reductionism is the temporal delay and mental antedating of consciousness found by Benjamin Libet. It is argued that these results, far from being a problem for reductionism, constitute evidence for a particular view of the physiological origins of consciousness. Finally, it is argued that many subjective aspects of experience can already be given satisfactory scientific explanations and that scientific progress is likely to rob the mind and subjective experience of their mystery.

Brain↗

An account of consciousness in physical and functional terms: a target for research in the neurosciences.

The neurophysiology of mental events cannot be fully understood unless that of consciousness is understood. As the first step in a top-down approach to that problem, one needs to find an account of consciousness as a property of the biological organism that can be clearly defined as such. However, if it is to deliver what must be expected of it, it should address what is commonly meant by the word consciousness. Unless the last condition is satisfied, the theory will fail to deliver what must ultimately be expected of it. Although current interest lies mainly in the higher functions of consciousness, such as its role in language and social relationships, the common usage of the word relates to modes of awareness that are not denied to creatures lacking language or social relationships. The basic features to be covered include awareness of the surrounding world, of the self, and of one's thoughts and feelings; the subjective qualities of phenomenal experience (qualia); the conditions a brain event must satisfy to enter consciousness; and the main divisions of mental events, such as sensations, feelings, perceptions, desires, volitions, and mental images. In the first four chapters we argue that these basic features of consciousness can all be accounted for in terms of just three categories of internal representations, each supported by the empirical evidence and each accurately definable in physical and functional terms. In the fifth, and last, chapter we take a closer look at two of the categories and what these in particular suggest as the most relevant lines of research in the contemporary spectrum of the neurosciences.

Animals↗

The AIDS dementia complex: clinical and basic neuroscience with implications for novel molecular therapies.

The AIDS dementia complex (ADC, also referred to as HIV-associated cognitive impairment) is a common disorder among HIV-infected patients associated with both inflammatory and neurodegenerative processes. This review describes recent advances in the clinical and basic neurosciences of HIV infection and discusses the multivariable nature of what has become a chronic disorder in the context of highly active antiretroviral therapies (HAART). Since its initial description twenty years ago, advances in cell and molecular biology along with those in neuroimaging have furthered our understanding of the underlying pathogenic mechanisms. The clinical and neuropsychological profile of ADC is generally consistent with a "frontal-subcortical" pattern of injury. Neuropathogenesis is largely driven by indirect mechanisms mediated by infected, or more commonly, immune activated macrophages, which secrete viral and host-derived factors. Magnetic resonance spectroscopy (MRS) provides a robust in vivo method to measure the inflammatory and neurotoxic events triggered by these factors and their associated signals. Although the use of combined or highly active antiretroviral therapies (HAART) has significantly improved survival rates, cerebral injury and cognitive impairment remain common events. Factors such as aging and chronic infection will likely impact the course of this disease, its pathogenesis, and treatment. The combined observations presented in this review suggest a number of critical areas for future inquiry.

AIDS Dementia Complex↗

The cognitive-affective neuroscience of obsessive-compulsive disorder.

There is substantial evidence that obsessive-compulsive disorder (OCD) is mediated by specific cortico-striatal- thalamic-cortical (CTSC) circuits. Here we discuss very recent publications that address the following questions: How does damage to CSTC circuitry come about?; What are the neurochemical systems involved in mediating this circuitry?; and What are the implications of such damage for understanding the pathogenesis and management of OCD? A cognitive-affective neuroscience perspective is helpful in advancing our understanding of the role of these circuits in OCD and the dysfunctional procedural strategies that appear to characterize this disorder. Furthermore, this model is becoming integrated with a range of data including brain imaging, genetic, immunologic, and neurochemical findings.

Affect↗

Fundamental neuroscience and the classification of psychiatric disorders.

Non-Darwinian views of evolution of nervous systems (e.g., Jacksonian evolution) conceive the present structure of the human brain as composed of a series of additive layers representing successive phylogenetic stages in evolution, layers which remain static after their emergence. In contrast to this view, recent allometric studies clearly show that limbic structures scale with the growth of the human brain (i.e., they do not remain stable but reach the size expected for the brain of a primate with the weight of a human brain). Data also show that limbic structures are significantly involved in cognitive functions such as memory and attention. Hence overlap of lesions in similar brain loci, especially in limbic regions, in both manic-depression and schizophrenia should come as no surprise. In the psychobiological sphere, the need for cognitive perceptual evaluation of the external world and internal state for emotional experience, further to the necessary visceral arousal, leads to a breakdown of the platonic, essentialist position, emotion vs. cognition at the psychological level, a problematic issue for the Kraepelinean view. Neural networks operation depend upon multiple nonlinear processes at the cellular, synaptic and network levels. Afferent input may serve not only to activate, but also to configure them into one of several circuit modes. These networks have been named polymorphic and can, at least to a measure, account for commonalities in lesion sites, in both affective and schizophrenic diseases. It is proposed that fundamental neuroscience should serve as one of the bases for the classification of psychiatric disorders.

Animals↗

Chemosensory transduction in eukaryotic microorganisms: trends for neuroscience?

It might appear curious to read about yeast, slime molds and protozoa in a journal dedicated to neuroscience. However, despite their distinct lack of synapses, eukaryotic microorganisms hold a wealth of information relevant to the signal-transduction pathways that underly activity in neuronal receptor cells, particularly those subserving the chemical senses. Microorganisms are sensitive to chemical stimuli from their environment and thus have similarities to receptor neurons of the olfactory system and the taste bud. Here, we introduce receptors, second messengers and effectors responsible for chemosensory signal transduction in yeast mating, sea-urchin spermatozoan chemotaxis, slime-mold aggregation and development, and ciliate chemoresponses.

Animals↗

Technology transfer in Europe: a case study of invertebrate neuroscience research.

Originally identified and defined as a concept in industrial and business communities, technology transfer is now being recognized as an important factor within the scientific research community. A recent study undertaken within the field of UK invertebrate neuroscience research generates several interesting conclusions. In this article, Huw A. Edwards and Elizabeth R.J. Bell discuss the study and its conclusions of a need for increased post-doctoral research mobility, the formation of consortia of research laboratories to apply for funding on an international scale, and the increased interest of the pharmaceutical industry in molecular and cellular techniques developed from fundamental invertebrate research.

Animals↗

The neonate-6-hydroxydopamine-lesioned rat: a model for clinical neuroscience and neurobiological principles.

In 1973, a technique of administering 6-hydroxydopamine (2,4,5-trihydroxyphenylethylamine) intracisternally to neonate rats was introduced to selectively reduce brain dopamine (neonate-lesioned rat). This neonate treatment proved unique when compared to rats lesioned as adults with 6-hydroxydopamine--prompting the discovery of differing functional characteristics resulting from the age at which brain dopamine is reduced. A realization was that neonate-lesioned rats modeled the loss of central dopamine and the increased susceptibility for self-injury in Lesch-Nyhan disease, which allowed identification of drugs useful in treating self-injury in mentally retarded patients. The neonate-lesioned rat has also been proposed to model the hyperactivity observed in attention-deficit hyperactivity disorder. Because the neonate-lesioned rat exhibits enhanced sensitization to repeated NMDA receptor antagonist administration and has functional changes characteristic of schizophrenia, the neonate lesioning is believed to emulate the hypothesized NMDA hypofunction in this psychiatric disorder. Besides modeling features of neurological and psychiatric disorders, important neurobiological concepts emerged from pharmacological studies in the neonate-lesioned rats. One was the discovery of coupling of D1/D2-dopamine receptor function. Another was the progressive increase in responsiveness to repeated D1-dopamine agonist administration referred to as "priming" of D1-dopamine receptor function. Additionally, a unique profile of signaling protein expression related to neonate reduction of dopamine has been identified. Thus, from modeling characteristics of disease to defining adaptive mechanisms related to neonatal loss of dopamine, the neonate-lesioned rat has had a persisting influence on neuroscience. Despite an extraordinary legacy from studies of the neurobiology of this treatment, a host of unknowns remain that will inspire future investigations.

Age Factors↗

Prospect theory on the brain? Toward a cognitive neuroscience of decision under risk.

Most decisions must be made without advance knowledge of their consequences. Economists and psychologists have devoted much attention to modeling decisions made under conditions of risk in which options can be characterized by a known probability distribution over possible outcomes. The descriptive shortcomings of classical economic models motivated the development of prospect theory (D. Kahneman, A. Tversky, Prospect theory: An analysis of decision under risk. Econometrica, 4 (1979) 263-291; A. Tversky, D. Kahneman, Advances in prospect theory: Cumulative representation of uncertainty. Journal of Risk and Uncertainty, 5 (4) (1992) 297-323) the most successful behavioral model of decision under risk. In the prospect theory, subjective value is modeled by a value function that is concave for gains, convex for losses, and steeper for losses than for gains; the impact of probabilities are characterized by a weighting function that overweights low probabilities and underweights moderate to high probabilities. We outline the possible neural bases of the components of prospect theory, surveying evidence from human imaging, lesion, and neuropharmacology studies as well as animal neurophysiology studies. These results provide preliminary suggestions concerning the neural bases of prospect theory that include a broad set of brain regions and neuromodulatory systems. These data suggest that focused studies of decision making in the context of quantitative models may provide substantial leverage towards a fuller understanding of the cognitive neuroscience of decision making.

Animals↗

Integrative neuroscience: linking levels of analyses.

If we are to understand how the brain performs different integrated functions in cellular terms, we need both to understand all relevant levels of analysis from the molecular to the behavioural and cognitive levels and to realize an integration of such levels. This is currently a major challenge for neuroscience. Most research, whether dealing with perception, action or learning, focuses on a few levels of organization, for instance the molecular level and brain imaging, and leaves other crucial areas practically untouched. To reach the level of understanding that we desire, a multi-level approach is required in which the different levels link into each other. It is possible to bridge across the different levels for one system, and this has been demonstrated, for example, in the lamprey in generation of goal-directed locomotion. It can be argued that an integrated analysis of any neural system cannot be performed without the aid of a close interaction between experiments and modelling. The dynamic processing within any neural system is such that an intuitive interpretation is rarely sufficient.

Animals↗

The neuroscience of impulsive and self-controlled decisions.

Impulsiveness and self-control are two antagonistic choice patterns. Whereas impulsive decisions can be exemplified by the preference for a small, immediate over a large, delayed reward, self-control can be characterised as the opposite preference order. This review focuses on current developments in investigating the neuroscience of impulsiveness and self-control, with particular emphasis on the neuroanatomy, psychopharmacology, and electrophysiology of this class of decision making. The role of the avian forebrain in representing and processing temporal reward discounting - a chief psychological mechanism responsible for producing impulsiveness - is especially highlighted. In addition to its role in impulsive decision making, the avian forebrain also appears to be involved in processing the key functions required for action- and self-control. In particular, recent electrophysiological studies indicate that single forebrain neurons reflect aspects of response omission strategy and the temporal scheduling of response withholding when execution of action needs to be controlled. In conclusion, the significant advances in this field of research may help to explain neuropathologies that are characterised by exaggerated impulsivity, or lack of self-control, as for instance attention deficit disorders, frontal lobe syndrome, drug addiction, or pathological gambling.

Animals↗

A simple and inexpensive light source for research in visual neuroscience.

Investigating the properties of light responsive neurons and their networks requires appropriate control of stimulus parameters, such as intensity, spectral composition, spatial and temporal profile. In the present paper, we describe how to build a simple, versatile and low-cost light source for use in visual neuroscience. The light source is a InGaN-based ultrabright light-emitting diode (LED), which may generate conventional light flashes as well as a variety of time varying stimuli to be used in quantitative studies of the visual system. In particular, with this instrument one may generate light stimuli sinusoidally modulated in time at frequencies ranging from 0.05 to 50 Hz, with less than 1% harmonic distortion at a contrast exceeding 85%. The relationship between applied voltage and energy emitted by the source is linear over an intensity range that exceeds 4.5 log-units, up to the full suppression of the light-sensitive currents in mammalian rods. The light source has minimal space requirement and does not generate appreciable radiating heat and hum, allowing its use for single cell work "in vitro" as well as for "in vivo" recording of the electroretinogram (ERG).

Animals↗