We studied time estimation in patients with frontal damage (F) and alcoholic Korsakoff (K) patients in order to differentiate between the contributions of working memory and episodic memory to temporal cognition. In Experiment 1, F and K patients estimated time intervals between 10 and 120 s less accurately than matched normal and alcoholic control subjects. F patients were less accurate than K patients at short (< 1 min) time intervals whereas K patients increasingly underestimated durations as intervals grew longer. F patients overestimated short intervals in inverse proportion to their performance on the Wisconsin Card Sorting Test. As intervals grew longer, overestimation yielded to underestimation for F patients. Experiment 2 involved time estimation while counting at a subjective 1/s rate. F patients' subjective tempo, though relatively rapid, did not fully explain their overestimation of short intervals. In Experiment 3, participants produced predetermined time intervals by depressing a mouse key. K patients underproduced longer intervals. F patients produced comparably to normal participants, but were extremely variable. Findings suggest that both working memory and episodic memory play an individual role in temporal cognition. Turnover within a short-term working memory buffer provides a metric for temporal decisions. The depleted working memory that typically attends frontal dysfunction may result in quicker turnover, and this may inflate subjective duration. On the other hand, temporal estimation beyond 30 s requires episodic remembering, and this puts K patients at a disadvantage. (JINS, 2000, 6, 517–528.)

We studied a group of 31 temporal lobe epilepsy patients (25 left, 6 right) with unilateral hippocampal sclerosis evident on magnetic resonance imaging. Single slice T2 relaxation times were acquired for the left and right hippocampi. Principal components analysis of preoperative memory data resulted in two factors that reflect a distinction between arbitrary and semantic forms of verbal recall. The former component correlated with left hippocampal T2 relaxation time, while the latter component did not. This study suggests that variation in left hippocampal integrity is more related to the acquisition of arbitrary associates than semantically structured material, and reinforces the possibility that the left temporal lobe is functionally heterogeneous with respect to memory. (JINS, 2000, 6, 529–538.)

As noted by Satz, the prevalence of lateralized language in the general population is underestimated substantially by the proportion of people who show the typical asymmetry on a laterality task. In a series of two dichotic listening experiments with a total of 171 right-handers and 170 left-handers, we tested the hypothesis that increased reliability of measurement will lead to increased classification accuracy. Experiment 1 showed that neither the frequency nor magnitude of the right-ear advantage (REA) for fused rhyming words increased as the number of trials increased from 120 to 480. Ear-difference scores were highly reliable (r = .85), even when based on 120 trials. Experiment 2, which involved lists of dichotic word pairs, yielded similar results. Even though retest reliability of the ear-difference score for 132 word pairs was only .45, neither the incidence nor strength of the REA increased significantly when the number of pairs was increased to 528. The results indicate that the poor classification accuracy of dichotic listening tasks cannot be attributed to unreliability. (JINS, 2000, 6, 539–547.)

Recent evidence suggests that HIV-seropositive drug users are impaired on tasks of visuospatial working memory compared with drug users seronegative for HIV. In the current study we evaluated the performance of 30 HIV-seropositive male drug users and 30 risk-matched seronegative controls on two measures of verbal working memory, the Listening Span and the verbal Self Ordered Pointing Task. Impaired working memory performance was significantly more common among HIV-seropositive persons compared to controls, with the highest incidence of deficit among symptomatic participants. These findings indicate that working memory deficits in persons with HIV are not domain-specific and can be demonstrated reliably in drug users. (JINS, 2000, 6, 548–555.)

Evidence is presented for the efficacy of a new method of assessing reading comprehension using a standardized reading test that was formatted for computer presentation with simultaneous event-related brain potential (ERP) recordings. Reading comprehension abilities of 23 healthy undergraduate students were evaluated using ERPs. The results revealed a differential ERP response pattern for correct and incorrect test items. These response patterns were observed at individual participant levels. The findings provided further support for the use of ERPs in the neuropsychological assessment of patients who are difficult or impossible to assess using behavioral responses because of concomitant motoric and/or communicative limitations. (JINS, 2000, 6, 556–567.)

This study aimed to investigate outcome in adults with mild traumatic brain injury (TBI) at 1 week and 3 months postinjury and to identify factors associated with persisting problems. A total of 84 adults with mild TBI were compared with 53 adults with other minor injuries as controls in terms of postconcussional symptomatology, behavior, and cognitive performance at 1 week and 3 months postinjury. At 1 week postinjury, adults with mild TBI were reporting symptoms, particularly headaches, dizziness, fatigue, visual disturbance, and memory difficulties. They exhibited slowing of information processing on neuropsychological measures, namely the WAIS–R Digit Symbol subtest and the Speed of Comprehension Test. By 3 months postinjury, the symptoms reported at 1 week had largely resolved, and no impairments were evident on neuropsychological measures. However, there was a subgroup of 24% of participants who were still suffering many symptoms, who were highly distressed, and whose lives were still significantly disrupted. These individuals did not have longer posttraumatic amnesia (PTA) duration. They were more likely to have a history of previous head injury, neurological or psychiatric problems, to be students, females, and to have been injured in a motor vehicle accident. The majority were showing significant levels of psychopathology. A range of factors, other than those directly reflecting the severity of injury, appear to be associated with outcome following mild TBI. (JINS, 2000, 6, 568–579.)

What we call computational neuroscience involves construction of mathematical and numerical models for understanding cognitive phenomena. This issue is devoted to showing how it can also be used to help in the analysis of cognitive defects. Although the models may seem abstract to clinicians, they are based on the reality of brain anatomy. The theoretical papers presented here are connectionist: They posit a network of cells connected by synapses whose weights are modified during learning. Architecture of connectionist models has progressed and ramified considerably since they were first introduced, and we include some examples of the current state of the art. The final work presented here is concerned with the connection of the constructed models with clinical experience and experiment.

This article suggests how brain mechanisms of learning, attention, and volition may give rise to hallucinations during schizophrenia and other mental disorders. The article suggests that normal learning and memory are stabilized through the use of learned top-down expectations. These expectations learn prototypes that are capable of focusing attention upon the combinations of features that comprise conscious perceptual experiences. When top-down expectations are active in a priming situation, they can modulate or sensitize their target cells to respond more effectively to matched bottom-up information. They cannot, however, fully activate these target cells. These matching properties are shown to be essential towards stabilizing the memory of learned representations. The modulatory property of top-down expectations is achieved through a balance between top-down excitation and inhibition. The learned prototype is the excitatory on-center in this top-down network. Phasic volitional signals can shift the balance between excitation and inhibition to favor net excitatory activation. Such a volitionally mediated shift enables top-down expectations, in the absence of supportive bottom-up inputs, to cause conscious experiences of imagery and inner speech and thereby to enable fantasy and planning activities to occur. If these volitional signals become tonically hyperactive during a mental disorder, the top-down expectations can give rise to conscious experiences in the absence of bottom-up inputs and volition. These events are compared with data about hallucinations. The article predicts where these top-down expectations and volitional signals may act in the laminar circuits of visual cortex and, by extension, in other sensory and cognitive neocortical areas, and how the level of abstractness of learned prototypes may covary with the abstractness of hallucinatory content. A similar breakdown of volition may lead to delusions of control in the motor system. (JINS, 2000, 6, 583–592.)

Amnesia in its various forms is characterized by defects in one or more components of a complex system. Implantation of short-term memory occurs in the hippocampus, while long-term memory is essentially located in the neocortex; these regions are interconnected through complex synaptic structures. In the hippocampus, physiological data show that, as predicted by Hebb, excitatory synapses between nearby excitatory cells become strengthened by simultaneous activation. In contrast with this local process, the preponderance of clinical and experimental evidence indicates that cortical recall of a “memory” is the reconstruction of fragments stored in different synaptically distant brain regions. A mathematical model of memory must reconcile this apparent contradiction as well as explain how many different memories and “ideas” can be assembled within a given anatomical area. Continuum theory, which treats an ensemble of “cell assemblies” or neural networks, offers a step in this direction. Linear analysis using this approach shows that it is the nature of the neural continuum to generate activity waves of wavelength greater than synaptic connection ranges. These waves grow under certain circumstances, and their wavelength is controlled by the synaptic parameters. Both hippocampal and cortical tissue are subject to such wave growth. In the hippocampus, the local Hebbian strengthening controls the global wave growth, making the difference between wave decay and growth. The cortical wave structure can become very complex, so that reproducible memory recall as well as “creative thought” can be accommodated in the theory. Deficits in the functioning of the system may also be evaluated potentially by means of “goodness-of-fit” of the clinical and spatially resolved data with the model. (JINS, 2000, 6, 593–607.)

A neural network model with dynamic thresholds, asymmetric connections, and clustered memories simulates spread activation that is hypothesized for semantic networks in the brain. By altering the parameters of the dynamic threshold a large range of disturbances can be generated in the model. These disturbances show metaphorical resemblance to certain general clinical descriptions of mental disturbances found in psychiatric patients engaged in various cognitive tasks. Even though the model is highly theoretical and metaphoric, it may help to gain certain insights into the relation between alterations of certain neural parameters, for example, thresholds and connectivity, and clinical symptoms in patients. (JINS, 2000, 6, 608–619.)

One of the most fascinating aspects of brain research is the subject of language. As in many other cases, the malfunctions that occur in different persons for various reasons give us insight on the mechanisms that support our ability to talk, read and listen. Following the work of Plaut and associates, we deal with the dyslexia disorder, which is the overall name for a large number of reading disorders. A Boltzmann machine neural network scheme was trained to implement the nonlinear mapping task of graphic representation into semantic representation, which may model the brain sections responsible for the translation of a written word into meanings and syllables. After training, various types of lesions were applied and the performance of the network was tested in order to measure the effect of each lesion on the error rate and type distribution that were detected. The system's errors were classified into several categories and the distribution of errors between the categories was studied. Using the simulations, it is demonstrated that a finite scheduling process in the Boltzmann machine causes the distribution of the network's errors to be unique and different from its expected error distribution. The phenomenon is given a mathematical explanation rooted in the statistical mechanics basics of the Boltzmann machine. Test results suggest the localization of certain reading functions within the network. Comparison is made to relevant types of dyslexia and shows resemblance in major symptoms as well as in certain known side effects. (JINS, 2000, 6, 620–626.)

Because lesions usually affect contiguous areas of the brain, cognitive neuropsychology has generally posited modularity of brain function, assuming that specific regions of the brain have specific dedicated functions. However, a review of 36 published functional neuroimaging studies suggests that functions are distributed over multiple regions. Or, in other words, specific brain regions are usually multifunctional. By a technique of “virtual lesions,” I measure the contribution that regions of the brain make to tasks imaged in 36 PET experiments, and propose a new and more detailed interlink between neuropsychology and functional neuroimaging. (JINS, 2000, 6, 627–635.)

This edited book addresses the important topic of child development in the last half of this century. The central focus of the book is the development of skilled motor actions by children, such as maintaining posture, walking, reaching, and grasping. The contents are based on the papers contributed in the first Mac Keith Meeting held at the Royal Society of Medicine in London in 1994. According to the preface to the book, the meeting aimed at making connections between levels of explanation, normal and pathological processes, basic and clinical research, and so on. Therefore, underlying themes are linking neurophysiological and psychological explanations, pre- and postnatal behavior, input and output processes, ballistic and graded movements, stability and variability, and so forth. In fact, the book succeeds in integrating findings from clinical and basic sciences to both normal and pathological motor development.

While the fact of litigation in neuropsychological assessment is about as subtle as a horse in a bedroom, it does not necessarily follow that the nature of malingering behaviors is also obvious or that the logic and techniques of malingering assessment have achieved “mature” validity. Despite the dramatic increase in studies on malingering in recent years, detection of malingering in head injury litigation continues to be a challenge for neuropsychologists. Numerous studies, most published since 1994, have attempted to search for the best technique for identifying malingering and/or malingerers. Unfortunately, this effort has been hampered by the lack of clinical data regarding the complexity and diversity of malingering behaviors themselves. In addition, the research is being conducted by clinical neuroscientists who, in various ways, are somewhat unsophisticated in their views of malingering detection statistics, paradigms and proofs (vs. forensic psychologists, maybe?).

This is an excellent clinical textbook by a group steeped in a quarter of a century's clinical experience and basic research experience. For members of INS who desire a rich and deep resource book on Tourette syndrome (this reviewer was trained to omit the possessive ‘s’ for all eponymous genetic designations) this one from the Yale Child Study Center provides the best choice. The organization of the book is also praiseworthy, as each chapter ends with a “look back” summary and a preview of the next chapter. It has the virtues of harmonious voices, coming as it does from a single center. The medical (including but not limited to neuropsychiatric) and biological sciences are presented in depth, clearly and thoughtfully, and well integrated with the clinical breadth of coverage of the core disorder and Tourette syndrome's (TS) comorbidities. Attention Deficit Hyperactivity Disorder (ADHD), and Obsessive Compulsive Disorder (OCD).

The aim of this compact, well-organized volume is to guide the hopeful brain and behavioral sciences researcher through the entire proposal and funding process, from conceptualizing an initial project idea all the way to preparation of final reports and competing renewal applications. Particularly for the novice grant-seeker, this volume is a useful aid to cracking the often mystifying world of research funding opportunities.