A pragmatic dementia risk score for patients with mild cognitive impairment in a memory clinic population: Development and validation of a dementia risk score using routinely collected data

Introduction

This study aimed to develop and validate a 3-year dementia risk score in individuals with mild cognitive impairment (MCI) based on variables collected in routine clinical care.

Methods

The prediction score was trained and developed using data from the National Alzheimer's Coordinating Center (NACC). Selection criteria included aged 55 years and older with MCI. Cox models were validated externally using two independent cohorts from the Prospective Registry of Persons with Memory Symptoms (PROMPT) registry and the Alzheimer's Disease Neuroimaging Initiative (ADNI) database.

Results

Our Mild Cognitive Impairment to Dementia Risk (CIDER) score predicted dementia risk with c-indices of 0.69 (95% confidence interval [CI] 0.66-0.72), 0.61 (95% CI 0.59-0.63), and 0.72 (95% CI 0.69-0.75), for the internally validated and the external validation PROMPT, and ADNI cohorts, respectively.

Discussion

The CIDER score could be used to inform clinicians and patients about the relative probabilities of developing dementia in patients with MCI.

Associations of medical comorbidity, psychosis, pain, and capacity with psychiatric hospital length of stay in geriatric inpatients with and without dementia

ABSTRACT Background: Geriatric psychiatry hospital beds are a limited resource. Our aim was to determine predictors of hospital length of stay (LOS) for geriatric patients with dementia admitted to inpatient psychiatric beds. Methods: Admission and discharge data from a large urban mental health center, from 2005 to 2010 inclusive, were retrospectively analyzed. Using the resident assessment instrument - mental health (RAI-MH), an assessment that is used to collect demographic and clinical information within 72 hours of hospital admission, 169 geriatric patients with dementia were compared with 308 geriatric patients without dementia. Predictors of hospital LOS were determined using a series of general linear models. Results: A diagnosis of dementia did not predict a longer LOS in this geriatric psychiatry inpatient population. The presence of multiple medical co-morbidities had an inverse relationship to length of hospital LOS - a greater number of co-morbidities predicted a shorter hospital LOS in the group of geriatric patients who had dementia compared to the without dementia study group. The presence of incapacity and positive psychotic symptoms predicted longer hospital LOS, irrespective of admission group (patients with dementia compared with those without). Conversely, pain on admission predicted shorter hospital LOS. Conclusions: Specific clinical characteristics generally determined at the time of admission are predictive of hospital LOS in geriatric psychiatry inpatients. Addressing these factors early on during admission and in the community may result in shorter hospital LOS and more optimal use of resources.

Short-latency single unit processing in olfactory cortex

Abstract Single-unit recording of layer II-III cells in olfactory (piriform) cortex was performed on awake, unrestrained rats actively engaged in learning novel odors in an olfactory discrimination task. Five of the 67 cells tested had very brief monophasic action potentials and high spontaneous firing rates (30-80 Hz); it is suggested that these units were interneurons. The remainder of the neurons had broader spikes and did not discharge for prolonged periods. Thirty-nine percent of the broad spike cells responded to at least one and usually more of the odors presented to the rats during either of the first two trials on which that odor was present, but, in most cases, these responses occurred only very infrequently over the course of subsequent trials. Six percent of the broad-spike group, how ever, continued firing robustly to a single odor but not to others. From these results it appears that most cells in piriform cortex do not respond to most odors, i.e., coding is exceedingly sparse. A subgroup of the predominant broad-spike cell type does react to several odors but this response drops out with repeated exposure, perhaps because of training. However, a few members of this class (a small fraction of the total cell population) do go on responding to a particular odor, thus exhibiting a form of odor specificity. The results are discussed with regard to predictions from recently developed models of the olfactory cortex.

Pentagastrin-induced hemoconcentration in healthy volunteers and patients with panic disorder: effect of pretreatment with ethinyl estradiol

Panic disorder has been associated with both an increased risk of coronary events as well as an increased risk of stroke. Hemoconcentration, with both a decrease in plasma volume and an increase in plasma viscosity, is a possible contributor to the risk of acute ischemic events. Our objectives were to demonstrate the process of hemoconcentration in response to induced panic symptoms and to assess the effect of pretreatment with ethinyl estradiol on panic-induced hemoconcentration. Fifteen male patients with panic disorder and 10 male healthy volunteers were included in a double-blind cross-over placebo-controlled design consisting of two injections of pentagastrin following randomized pretreatment with placebo and ethinyl estradiol. Plasma levels of hematocrit and hemoglobin were assessed at baseline and post-injections, and used to calculate an indirect estimation of the change in plasma volume. Pentagastrin-induced panic symptoms were associated with a mean decrease in plasma volume of 4.8% in the placebo pretreatment condition. Pretreatment with ethinyl estradiol attenuated this effect. The acute hemoconcentration observed in relation to pentagastrin-induced panic symptoms may be relevant to the increased risk of stroke and acute coronary events found in patients with panic disorder.

Improving adolescent and young adult health - training the next generation of physician scientists in transdisciplinary research

To address the critical shortage of physician scientists in the field of adolescent medicine, a conference of academic leaders and representatives from foundations, National Institutes of Health, Maternal and Child Health Bureau, and the American Board of Pediatrics was convened to discuss training in transdisciplinary research, facilitators and barriers of successful career trajectories, models of training, and mentorship. The following eight recommendations were made to improve training and career development: incorporate more teaching and mentoring on adolescent health research in medical schools; explore opportunities and electives to enhance clinical and research training of residents in adolescent health; broaden educational goals for Adolescent Medicine fellowship research training and develop an intensive transdisciplinary research track; redesign the career pathway for the development of faculty physician scientists transitioning from fellowship to faculty positions; expand formal collaborations between Leadership Education in Adolescent Health/other Adolescent Medicine Fellowship Programs and federal, foundation, and institutional programs; develop research forums at national meetings and opportunities for critical feedback and mentoring across programs; educate Institutional Review Boards about special requirements for high quality adolescent health research; and address the trainee and faculty career development issues specific to women and minorities to enhance opportunities for academic success.

Injectable vaccines for preventing pneumococcal infection in patients with chronic obstructive pulmonary disease

BACKGROUND

As chronic obstructive pulmonary disease (COPD) progresses, exacerbations can occur with increasing frequency. One goal of therapy in COPD is to try and prevent these exacerbations, thereby reducing disease morbidity and associated healthcare costs. Pneumococcal vaccinations are considered to be one strategy for reducing the risk of infective exacerbations.

OBJECTIVES

To determine the safety and efficacy of pneumococcal vaccination in COPD. The primary outcome assessed was acute exacerbations. Secondary outcomes of interest included episodes of pneumonia, hospital admissions, adverse events related to treatment, disability, change in lung function, mortality, and cost effectiveness.

SEARCH STRATEGY

We searched the Cochrane Airways Group COPD trials register using pre-specified terms. We also conducted additional handsearches of conference abstracts. The last round of searches were performed in April 2006.

SELECTION CRITERIA

Only randomised controlled trials assessing the effects of injectable pneumococcal vaccine in people with COPD were included.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and three review authors independently assessed trial quality.

MAIN RESULTS

Although 10 studies cited in 11 publications were identified that met the inclusion criteria for this review, only four of these provided data on participants with COPD. The studies which did provide data for this review consisted of two trials using a 14-valent vaccine, and two using a 23-valent injectable vaccine. Data for the primary outcome, acute exacerbation of COPD, was available from only one of the four studies. The odds ratio of 1.43 (95% confidence interval (CI) 0.31 to 6.69) between interventions was not statistically significant. Of the secondary outcomes for which data were available and could be extracted, none reached statistical significance. Three studies provided dichotomous data for persons who developed pneumonia (OR 0.89, 95% CI 0.58 to 1.37, n = 748). Rates of hospital admissions and emergency department visits came from a single study. There was no significant reduction in the odds of all-cause mortality 1 to 48 months post-vaccination (Peto odds ratio 0.94, 95% CI 0.67 to 1.33, n = 888), or for death from cardiorespiratory causes (OR 1.07, 95% CI 0.69 to 1.66).

AUTHORS' CONCLUSIONS

There is no evidence from randomised controlled trials that injectable pneumococcal vaccination in persons with COPD has a significant impact on morbidity or mortality. Further large randomised controlled trials would be needed to ascertain if the small benefits suggested by individual studies are real.

Population-based analysis of severe injuries from nonmotorized wheeled vehicles

BACKGROUND

Bicycling, skateboarding, and inline skating are popular recreational activities, with the potential of causing severe injury.

METHODS

A retrospective, population-based, trauma registry analysis of severe injuries and deaths from nonmotorized wheeled vehicles (NMWV) over a 10-year period was performed.

RESULTS

During the study period, 1475 cyclists, 141 skateboarders, and 112 inline skaters sustained injury meeting registry criteria (length of stay > or = 3 days or death). The majority were male. Lone crashes were the most common mechanism of injury, although collisions with motor vehicles accounted for 63.6% (n = 44) of observed deaths. Thoracic trauma and head injuries were more common in nonsurvivors.

CONCLUSION

NMWV injuries pose a public health concern. We recommend enforcement of mandatory helmet laws and expansion of the existing law to include skateboarders and inline skaters. Education initiatives should also be expanded to include the adult population. NMWV should be separated from motorized vehicles as much as possible.

Derivation and analysis of basic computational operations of thalamocortical circuits

Shared anatomical and physiological features of primary, secondary, tertiary, polysensory, and associational neocortical areas are used to formulate a novel extended hypothesis of thalamocortical circuit operation. A simplified anatomically based model of topographically and nontopographically projecting ("core" and "matrix") thalamic nuclei, and their differential connections with superficial, middle, and deep neocortical laminae, is described. Synapses in the model are activated and potentiated according to physiologically based rules. Features incorporated into the models include differential time courses of excitatory versus inhibitory postsynaptic potentials, differential axonal arborization of pyramidal cells versus interneurons, and different laminar afferent and projection patterns. Observation of the model's responses to static and time-varying inputs indicates that topographic "core" circuits operate to organize stored memories into natural similarity-based hierarchies, whereas diffuse "matrix" circuits give rise to efficient storage of time-varying input into retrievable sequence chains. Examination of these operations shows their relationships with well-studied algorithms for related functions, including categorization via hierarchical clustering, and sequential storage via hash- or scatter-storage. Analysis demonstrates that the derived thalamocortical algorithms exhibit desirable efficiency, scaling, and space and time cost characteristics. Implications of the hypotheses for central issues of perceptual reaction times and memory capacity are discussed. It is conjectured that the derived functions are fundamental building blocks recurrent throughout the neocortex, which, through combination, gives rise to powerful perceptual, motor, and cognitive mechanisms.

Blunt vascular neck injuries: diagnosis and outcomes of extracranial vessel injury

BACKGROUND

Blunt vascular neck injuries (BVNIs) are rare, often occult, and potentially devastating injuries. The purpose of this study was to identify a high-risk group, which would benefit from screening.

METHODS

Patients with BVNIs were identified from our trauma registry and charts were reviewed. Potential risk factors for BVNI were evaluated by univariate and multivariate logistic regression.

RESULTS

Thirty-one BVNIs were identified in 22 patients. The stroke rate was 60% and the mortality rate was 25%. Univariate analysis showed Glasgow Coma Scale score < or = 8, head injury (Abbreviated Injury Scale [AIS] score > or = 3), basal skull fracture, facial injury, other neck injury, thorax injury (AIS score > or = 3), abdominal injury, and cervical spine injury to be significant (p < 0.05). The multivariate predictive model had two predictors remaining significant: thorax injury (AIS [thorax] score > or = 3) and Glasgow Coma Scale score < or = 8.

CONCLUSION

Screening should be undertaken for patients at increased risk for BVNI: those with risk factors identified in our regression analysis and factors previously reported.

Identifying patients at risk for intracranial and extracranial blunt carotid injuries

BACKGROUND

Blunt carotid injuries are rare, often occult, and potentially devastating. Angiographic screening programs have detected this injury in up to 1% of blunt trauma patients. Implementing a liberal angiographic screening program at our hospital is impractical and we want to identify a high-risk group to target for screening. We hypothesize that intracranial and extracranial carotid injuries have different risks, presentations, and outcomes.

METHODS

Patients with intracranial and extracranial carotid injuries were identified from the British Columbia trauma registry. Presentation and outcome were reviewed. To facilitate statistical modeling the analysis was done by matching cases to 5 randomly selected controls. Risk factors for injury were evaluated by univariate and multiple logistic regression.

RESULTS

A total of 35 carotid injuries were identified. Thirteen intracranial injuries were identified in 10 patients. Twenty-two extracranial injuries were identified in 18 patients. Sixty-seven percent of patients with intracranial injuries and 31% of those with extracranial injuries died (P = 0.11). Eleven percent of intracranial injuries and 56% of extracranial injuries were occult (P = 0.04). Glasgow outcome scores were 2.04 intracranial and 3.12 extracranial (P = 0.18). For intracranial injuries the multiple variable predictive model had two predictors: Glasgow Coma Score </=8 and facial fractures. For extracranial the predictors were GCS < or =8 and thoracic injury (Abbreviated Injury Score > or =3).

CONCLUSIONS

Intracranial injuries were frequently detected on initial investigations and have very poor outcomes. Extracranial injuries were more frequently occult and stand to benefit from early detection by screening programs. As independent risk factors for these two injuries differ, limited screening resources should focus on risk factors for occult extracranial injury: namely, low GCS and significant thoracic injury.

Intraoperative decrease in pulse oximeter readings following injection of isosulfan blue

PURPOSE

Sentinel lymph node mapping, involving injection of isosulfan blue dye around a tumour, is beginning to be used in patients with carcinoma of the breast. Absorption of the dye into the circulation may interfere with pulse oximetry, causing falsely low readings. This report describes changes in pulse oximeter readings following injection of isosulfan blue for sentinel lymph node mapping in a patient with carcinoma of the breast.

CLINICAL FEATURES

An 83-yr-old female patient underwent sentinel node biopsy of the axilla followed by partial mastectomy for carcinoma of the left breast. Isosulfan blue was injected in the area of the tumour in the left breast. The SpO2 began to decrease 15 min after dye injection, reaching a nadir of 89-90% 30 min after injection. Arterial blood gas analysis showed normal arterial partial pressure of oxygen. Pulse oximeter readings did not return to normal until more than six hours after dye injection.

CONCLUSION

Review of the literature reveals a small number of case reports of similar occurrences of low pulse oximeter readings following injection of isosulfan blue or patent blue dye for lymphatic mapping. Data from these reports and the case described here suggest that the latency, magnitude and duration of effect on pulse oximeter readings following injection of these dyes is highly variable. It is important to rule out other causes of low pulse oximeter readings when this effect occurs; normal oxygenation can be verified with arterial blood gas analysis. Co-oximetry can be done to rule out methemoglobinemia as a cause of decreased SpO2.

Work-based antipoverty programs for parents can enhance the school performance and social behavior of children

We assess the impact of the New Hope Project, an antipoverty program tested in a random assignment experimental design, on family functioning and developmental outcomes for preschool- and school-aged children (N = 913). New Hope offered wage supplements sufficient to raise family income above the poverty threshold and subsidies for child care and health insurance to adults who worked full-time. New Hope had strong positive effects on boys' academic achievement, classroom behavior skills, positive social behavior, and problem behaviors, as reported by teachers, and on boys' own expectations for advanced education and occupational aspirations. There were not corresponding program effects for girls. The child outcomes may have resulted from a combination of the following: Children in New Hope families spent more time in formal child care programs and other structured activities away from home than did children in control families. New Hope parents were employed more, had more material resources, reported more social support, and expressed less stress and more optimism about achieving their goals than did parents in the control sample. The results suggest that an anti-poverty program that provides support for combining work and family responsibilities can have beneficial effects on the development of school-age children.

Origins and distribution of cholinergically induced beta rhythms in hippocampal slices

Regional variations and substrates of high-frequency rhythmic activity induced by cholinergic stimulation were studied in hippocampal slices with 64-electrode recording arrays. (1) Carbachol triggered beta waves (17.6 +/- 5.7 Hz) in pyramidal regions of 75% of the slices. (2) The waves had phase shifts across the cell body layers and were substantially larger in the apical dendrites than in cell body layers or basal dendrites. (3) Continuous, two-dimensional current source density analyses indicated apical sinks associated with basal sources, lasting approximately 10 msec, followed by apical sources and basal sinks, lasting approximately 20 msec, in a repeating pattern with a period in the range of 15-25 Hz. (4) Carbachol-induced beta waves in the hippocampus were accompanied by 40 Hz (gamma) oscillations in deep layers of the entorhinal cortex. (5) Cholinergically elicited beta and gamma rhythms were eliminated by antagonists of either AMPA or GABA receptors. Benzodiazepines markedly enhanced beta activity and sometimes introduced a distinct gamma frequency peak. (6) Twenty Hertz activity after orthodromic activation of field CA3 was distributed in the same manner as carbachol-induced beta waves and was generated by a current source in the apical dendrites of CA3. This source was eliminated by high concentrations of GABA(A) receptor blockers. It is concluded that cholinergically driven beta rhythms arise independently in hippocampal subfields from oscillatory circuits involving (1) bursts of pyramidal cell discharges, (2) activation of a subset of feedback interneurons that project apically, and (3) production of a GABA(A)-mediated hyperpolarization in the outer portions of the apical dendrites of pyramidal neurons.

A distinct member of the aspartic proteinase gene family from the human malaria parasite Plasmodium falciparum

A gene (hap) transcribed during the intra-erythrocytic life cycle stages of the human malaria parasite Plasmodium falciparum was cloned and sequenced. It was found to encode a protein belonging to the aspartic proteinase family but which carried replacements of catalytically crucial residues in the hallmark sequences contributing to the active site of this type of proteinase. Consideration is given as to whether this protein is the first known parasite equivalent of the pregnancy-associated glycoproteins that have been documented in ungulate mammals. Alternatively, it may be operative as a new type of proteinase with a distinct catalytic mechanism. In this event, since no counterpart is known to exist in humans, it affords an attractive potential target against which to develop new anti-malarial drugs.

The effects of retroperitoneal carbon dioxide insufflation on hemodynamics and arterial carbon dioxide

BACKGROUND

Laparoscopic techniques are being increasingly used for retroperitoneal surgery. However, hemodynamic and ventilatory efforts of retroperitoneal carbon dioxide (CO2) insufflation have not been studied. We hypothesized that differences in absorptive surface, anatomy, and compartment compliance could result in different hemodynamic and ventilatory effects between retroperitoneal and intraperitoneal insufflation.

METHODS

Pigs (n = 7) were anesthetized and stabilized. The peritoneal cavity was incrementally insufflated with CO2 to a maximum pressure of 25 cm H2O and the gas released. Hemodynamics and arterial blood gas values were recorded initially, at each level of insufflation, and following the pneumoperitoneum release until baseline values were reached. This insufflation protocol was repeated in the retroperitoneum.

RESULTS

Mean arterial pressure (111 mm Hg, 95% confidence interval 99 to 156) and cardiac output (3.7 L/min, 2.8 to 5.2) did not change with increasing insufflation pressure of either intraperitoneum or retroperitoneum. PaCO2 was directly related to insufflation pressure in both spaces, increasing from 41.2 mm Hg (37.3 to 43.4) at baseline to 57.7 mm Hg (47.6 to 82.1) at insufflation pressure of 25 cm H2O. After release of the insufflation gas, time to return to baseline PaCO2 was slightly less from the retroperitoneal space (73 minutes, 45 to 105) than the intraperitoneal (107 minutes, 35 to 175).

CONCLUSIONS

The effects of CO2 insufflation on hemodynamics and PaCO2 are the same in the retroperitoneal and intraperitoneal spaces.

Regulation of arousal and attention in preschool children exposed to cocaine prenatally

Four lines of evidence suggest a plausible link between prenatal cocaine exposure (CE) and specific effects on the mechanisms subserving arousal and attention regulation in infants and preschool-aged children. These are (1) the association of prenatal CE with alterations in monoaminergic system ontogeny; (2) neurobehavioral effects of prenatal CE in animals consistent with an enduring increased level of activity in response to novelty and inhibited exploration and altered responses to stress, suggesting overarousal in the face of novel/stressful situations and disrupted attention and exploration; (3) altered norepinephrine system function in cocaine-exposed human infants; and (4) neurobehavioral findings in infants and preschool-aged children suggestive of disrupted arousal regulation in the face of novelty, increased distractibility, and consequent impaired attention to novel, structured tasks. This paper summarizes findings on response to novel challenges from a cohort of prenatally cocaine-exposed infants and preschool-aged children followed longitudinally since birth. Arousal regulation in the face of novel challenges is operationalized behaviorally as state and emotional reactivity and neurophysiologically as the startle response and heart rate variability. Across different ages and tasks, behavioral and neurophysiological findings suggest that prenatally cocaine-exposed children are more likely to exhibit disrupted arousal regulation. Because the regulation of arousal serves as a gating mechanism to optimize orientation and attention, arousal regulation has important implications for ongoing information processing, learning, and memory. Furthermore, impaired arousal regulation predisposes children to a lower threshold for activation of "stress circuits" and may increase their vulnerability to the developmentally detrimental effects of stressful conditions particularly when such children are also exposed to the chaotic environmental conditions often characterizing substance-abusing families.

Triazolam impairs delayed recall but not acquisition of various everyday memory tasks in humans

A double-blind test battery was administered to 24 human subjects (8 control, 16 drug) to assess the effects of 0.125 mg triazolam (oral) on memory encoding and retention across delay intervals ranging from seconds to 1 week after presentation. Although the drug reduced immediate psychomotor performance, it did not impair recall of previously learned information, nor did it significantly impair encoding of new information. The drug enhanced immediate recall of the location and identity of playing cards, without affecting 4-h delayed recall. The drug treatment impaired correct recall of object names after a delay of 20 min. At 4 h delay, the drug impaired olfactory recognition and free-recall of object names. At both 1 day and 1 week delay, the drug impaired recall of biographical information and correct identification of picture-photographer pair associations. The drug also impaired the daily improvement of the drug group as compared with the control group in a geometric puzzle solving task. The time course of these memory impairments compares well with the known effects of triazolam on long-term potentiation (LTP), a candidate biological mechanism underlying telencephalic memory formation and expression.

Differential patterns of c-fos mRNA expression in amygdala during successive stages of odor discrimination learning

Expression of the activity-dependent gene c-fos was used to assess relative levels of neuronal activation in the amygdala and related structures of rats at different stages of odor discrimination learning. In situ hybridization was used to evaluate c-fos mRNA content within the amygdalar subdivisions, the bed nucleus of the stria terminalis, and the hippocampus. After initial exploration of the test apparatus, c-fos mRNA levels were increased in the medial and, to lesser extent, basolateral subdivisions and remained low in the central division. The balance of amygdala to hippocampal labeling favored hippocampus. Rats engaged in familiar nose-poke responses had comparably elevated labeling in the medial and basolateral divisions and low labeling densities in the central division. The ratio of hippocampal to amygdala labeling was at control levels. Rats required to switch from ad libitum responding to cued responding to odors had high basolateral to medial labeling ratios. This was in marked contrast to the medial dominance found in control and exploration rats. Hybridization was substantially more dense in basolateral amygdala than in hippocampal CA1; this imbalance was unique to the group required to form first associations between odors and rewards. Rats performing an overtrained odor discrimination had the least differentiation between amygdalar subdivisions of any behavioral group. The hippocampus-to-amygdala labeling ratio favored hippocampus and was nearly identical to the ratio in exploration rats. These results demonstrate that the balance of activity within the between limbic structures shifts according to behavioral demands. It is suggested that the balances reflect the availability of pertinent afferent cues, interactions between hippocampus and the extended amygdala, and relative levels of activity in the diffuse projections to the limbic system.

A profile of the behavioral changes produced by facilitation of AMPA-type glutamate receptors

A newly developed group of benzoylpiperidine drugs that enhance AMPA-receptor-gated currents ("ampakines") has been shown to improve memory encoding in rats across a variety of experimental paradigms. The present experiments were intended to i) provide a partial profile of the behavioral changes produced by ampakines, ii) test if two ampakines (BDP-12 and BDP-20) that differ significantly in their effects on AMPA receptor kinetics produce similar behavioral profiles, and iii) determine if physiological potency is reflected in behavioral potency. BDP-20 reduced two measures of exploratory activity in aged rats but increased speed of performance in a radial maze; the drug also caused substantially improved retention of spatial information. These results are similar to those obtained with BDP-12, an analog that differs from BDP-20 in its effects on ligand binding to the AMPA receptor and on the physiological responses of the receptors to glutamate. BDP-20 was approximately ten-fold more potent in behavioral effects than BDP-12, which agrees with the relative potencies of the two drugs as assessed with excised patches and excitatory synaptic responses. These findings indicate that ampakines, though differing in their effects on AMPA-receptor-mediated responses, have similar effects at the behavioral level.

Enhancement by an ampakine of memory encoding in humans

Acentrally active drug that enhances AMPA receptor-mediated currents was tested for its effects on memory in humans. Evidence for a positive influence on encoding was obtained in four tests: (i) visual associations, (ii) recognition of odors, (iii) acquisition of a visuospatial maze, and (iv) location and identity of playing cards. The drug did not improve scores in a task requiring cued recall of verbal information. The selectivity of drug effects on memory was confirmed using tests of visual recognition, motor performance, and general intellectual functioning. These results suggest that positive modulators of AMPA receptors selectively improve at least some aspects of memory.

Evidence that a positive modulator of AMPA-type glutamate receptors improves delayed recall in aged humans

Elderly subjects (65-76 years) were tested for recall of nonsense syllables prior to and after oral administration of 1-(quinoxalin-6 ylcarbonyl)piperidine (CX516), a centrally active drug that enhances currents mediated by AMPA-type glutamate receptors. A significant and positive drug effect was found for delayed (5 min) recall at 75 min posttreatment; average scores for the highest dose group were more than twofold greater than for the placebo group. The drug had no evident influence on heart rate or self-assessment of several psychological variables.

Facilitation of glutamate receptors reverses an age-associated memory impairment in rats

The accuracy of memory for recent events is reported to decay between young adulthood and middle age in humans (Crook et al., 1990; Crook and West, 1990; Thomas et al., 1977) due to impairments in acquisition and/or retention (Craik, 1977; Huppert and Kopelman, 1989). Effects of this kind are also found in comparisons of middle-aged (12-18 months) vs. young adult (3 months) rats in tests requiring retention of recently sampled spatial cues (Kadar et al., 1990a; Kadar et al., 1990b; Goudsmit et al., 1990; Weiss and Thompson, 1991). The causes of such changes in memory processing are unknown but might be expected to involve age-related losses in forebrain glutamate receptors (Bahr et al., 1992; Magnusson and Cotman, 1993; Wenk et al., 1991); these receptors mediate fast excitatory transmission in many brain regions and play an essential role in the production of long-term potentiation (LTP), a form of synaptic plasticity that has been implicated in memory encoding (Landfield and Lynch, 1977; Moore et al., 1993). In the present communication we report results indicating that a drug that enhances AMPA-type glutamate receptors acts centrally to selectively increase hippocampal spatial cell firing and improves both acquisition performance and memory retention in middle-aged rats to levels equivalent to those found in young adult animals.

Psychological effects of a drug that facilitates brain AMPA receptors

The effects of 1-(quinoxalin-6-ylcarbonyl)piperidine (CX516), a centrally active compound that facilitates AMPA receptor-mediated synaptic responses, were tested in human subjects. Separate tests of delayed recall were given prior to and nearly 3 h after administration of placebo (n = 12) or drug (n = 36). Control subjects exhibited poorer performance in the second session than in the first while subjects given 600-1200 mg of the drug did not. There were no pre- vs post-treatment differences in immediate recall in either group. The drug did not reliably affect self-assessment scores for any of several psychological variables but did disrupt the normally present correlations for within-subject changes in the variables. These results suggest that AMPA receptor modulators may (1) improve memory under some circumstances and (2) produce psychological effects that are subtle or not related to specific mood states.

Distinct memory circuits composing the hippocampal region

The very different anatomical designs of the adjacent circuitries of the cortico-hippocampal pathway, along with their somewhat different synaptic plasticity mechanisms, suggest a nearly serial pathway of distinct memory circuits each contributing its own specialized processing operation to overall hippocampal function. Modeling and formal theoretical analysis of the prominent anatomical design features of particular circuits (piriform/entorhinal cortex; hippocampal field CA3; hippocampal field CA1) are found to identify potential emergent function not readily arrived at in the absence of these formal models, and yet which once derived can be seen potentially to confer unique capabilities to an integrated hippocampal mechanism for processing memories during behavior.

Necrotizing fasciitis in childhood

Necrotizing fasciitis is a rare entity in the pediatric population. Five cases of this soft tissue infection were treated at the authors' institution between January and December 1993. Three of the children were profoundly neutropenic secondary to chemotherapy. All five were treated with aggressive surgical debridement, frequent dressing changes, broad-spectrum antibiotics, and nutritional support. In addition, the patients with neutropenia received a combination of granulocyte-colony stimulating factor and granulocyte transfusions. One child died of overwhelming sepsis and bone marrow graft failure. The others eventually made a complete recovery. Necrotizing fasciitis may be becoming a more common problem in children. Aggressive chemotherapeutic regimens and more frequent use of bone marrow transplantation could be a factor in this. Early diagnosis and aggressive surgical therapy is critical. However, mortality may be significant, especially in patients with neutropenia. Leukocyte response to the infection may be a prognostic marker. Pseudomonas and enteric gram-negative organisms are seen frequently in immunocompromised children with necrotizing fasciitis. Antimicrobial selection should supply adequate coverage of these organisms.

Non-Hebbian properties of long-term potentiation enable high-capacity encoding of temporal sequences

A hypothesis commonly found in biological and computational studies of synaptic plasticity embodies a version of the 1949 postulate of Hebb that coactivity of pre- and postsynaptic elements results in increased efficacy of their synaptic contacts. This general proposal presaged the identification of the first and still only known long-lasting synaptic plasticity mechanism, long-term potentiation (LTP). Yet the detailed physiology of LTP induction and expression differs in many specifics from Hebb's rule. Incorporation of these physiological LTP constraints into a simple non-Hebbian network model enabled development of "sequence detectors" that respond preferentially to the sequences on which they were trained. The network was found to have unexpected capacity (e.g., 50 x 10(6) random sequences in a network of 10(5) cells), which scales linearly with network size, thereby addressing the question of memory capacity in brain circuitry of realistic size.