EEG biomarkers of free recall.

Brain activity in the moments leading up to spontaneous verbal recall provide a window into the cognitive processes underlying memory retrieval. But these same recordings also subsume neural signals unrelated to mnemonic retrieval, such as response-related motor activity. Here we examined spectral EEG biomarkers of memory retrieval under an extreme manipulation of mnemonic demands: subjects either recalled items after a few seconds or after several days. This manipulation helped to isolate EEG components specifically related to long-term memory retrieval. In the moments immediately preceding recall we observed increased theta (4-8 Hz) power (+T), decreased alpha (8-20 Hz) power (-A), and increased gamma (40-128 Hz) power (+G), with this spectral pattern (+T-A + G) distinguishing the long-delay and immediate recall conditions. As subjects vocalized the same set of studied words in both conditions, we interpret the spectral +T-A + G as a biomarker of episodic memory retrieval.

Multitrial free recall for evaluating memory.

OBJECTIVE: Much of our knowledge concerning the neural basis of human memory derives from lab-based verbal recall tasks. Outside of the lab, clinicians use validated and normed neuropsychological tests to assess patients' memory function and to evaluate clinical interventions. Here we sought to establish the clinical validity of examining memory through multitrial free recall of semantically organized and unrelated word lists. METHOD: We compare memory performance in multitrial free recall tasks with the Rey Auditory Verbal Learning Test and the California Verbal Learning Test, two common neuropsychological tests aimed at evaluating memory function in clinical settings. We compare predictive validity between the tasks by evaluating deficits in a patient sample and examining age-related declines in memory. We additionally compare test-retest reliability, establish convergent validity, and show the emergence of common recall dynamics between the tasks. RESULTS: We demonstrate that both laboratory free recall tasks have better predictive validity and test-retest reliability than the established neuropsychological tests. We further show that all tasks have good convergent validity and reveal core memory processes, including temporal and semantic organization. However, we also demonstrate the benefits of repeated trials for evaluating the dynamics of memory search and their neuropsychological sequelae. CONCLUSIONS: These results provide evidence for the clinical validity of lab-based multitrial free recall tasks and highlight their psychometric benefits over neuropsychological measures. Based on these results, we discuss the need to bridge the gap between clinical understanding of putative mechanisms underlying memory disorders and neuroscientific findings obtained using lab-based free recall tasks. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Medial temporal lobe functional connectivity predicts stimulation-induced theta power.

Focal electrical stimulation of the brain incites a cascade of neural activity that propagates from the stimulated region to both nearby and remote areas, offering the potential to control the activity of brain networks. Understanding how exogenous electrical signals perturb such networks in humans is key to its clinical translation. To investigate this, we applied electrical stimulation to subregions of the medial temporal lobe in 26 neurosurgical patients fitted with indwelling electrodes. Networks of low-frequency (5-13 Hz) spectral coherence predicted stimulation-evoked increases in theta (5-8 Hz) power, particularly when stimulation was applied in or adjacent to white matter. Stimulation tended to decrease power in the high-frequency broadband (HFB; 50-200 Hz) range, and these modulations were correlated with HFB-based networks in a subset of subjects. Our results demonstrate that functional connectivity is predictive of causal changes in the brain, capturing evoked activity across brain regions and frequency bands.

Widespread theta synchrony and high-frequency desynchronization underlies enhanced cognition.

The idea that synchronous neural activity underlies cognition has driven an extensive body of research in human and animal neuroscience. Yet, insufficient data on intracranial electrical connectivity has precluded a direct test of this hypothesis in a whole-brain setting. Through the lens of memory encoding and retrieval processes, we construct whole-brain connectivity maps of fast gamma (30-100 Hz) and slow theta (3-8 Hz) spectral neural activity, based on data from 294 neurosurgical patients fitted with indwelling electrodes. Here we report that gamma networks desynchronize and theta networks synchronize during encoding and retrieval. Furthermore, for nearly all brain regions we studied, gamma power rises as that region desynchronizes with gamma activity elsewhere in the brain, establishing gamma as a largely asynchronous phenomenon. The abundant phenomenon of theta synchrony is positively correlated with a brain region's gamma power, suggesting a predominant low-frequency mechanism for inter-regional communication.

Theta returns.

Recent physiological studies have implicated theta - a high-amplitude 4-8 Hz oscillation that is prominent in rat hippocampus during locomotion, orienting and other voluntary behaviors - in synaptic plasticity, information coding and the function of working memory. Intracranial recordings from human cortex have revealed evidence of high-amplitude theta oscillations throughout the brain, including the neocortex. Although its specific role is largely unknown, the observation of human theta has begun to reveal an intriguing connection between brain oscillations and cognitive processes.

Gating of human theta oscillations by a working memory task.

Electrode grids on the cortical surface of epileptic patients provide a unique opportunity to observe brain activity with high temporal-spatial resolution and high signal-to-noise ratio during a cognitive task. Previous work showed that large-amplitude theta frequency oscillations occurred intermittently during a maze navigation task, but it was unclear whether theta related to the spatial or working memory components of the task. To determine whether theta occurs during a nonspatial task, we made recordings while subjects performed the Sternberg working memory task. Our results show event-related theta and reveal a new phenomenon, the cognitive "gating" of a brain oscillation: at many cortical sites, the amplitude of theta oscillations increased dramatically at the start of the trial, continued through all phases of the trial, including the delay period, and decreased sharply at the end. Gating could be seen in individual trials and varying the duration of the trial systematically varied the period of gating. These results suggest that theta oscillations could have an important role in organizing multi-item working memory.

Increased incidence of severe breastfeeding malnutrition and hypernatremia in a metropolitan area.

OBJECTIVE: To identify common characteristics among infants with breastfeeding malnutrition in a region with an increasing incidence of breastfeeding malnutrition. DESIGN: Retrospective case series. SETTING: A 361-bed regional tertiary care children's hospital in a 1.7 million population metropolitan area. CASE SERIES: five infants with severe breastfeeding malnutrition and hypernatremia admitted to a tertiary care children's hospital over a 5-month period. Retrospective case review: 166 infants admitted between 1990 and 1994 with the diagnosis of dehydration, hypernatremia, or malnutrition. MAIN OUTCOME MEASURES: Maternal characteristics, age at presentation, percent loss from birth weight, serum sodium, average age at birth hospital discharge, neurologic, or cardiovascular complications. RESULTS: Five infants were admitted to a children's hospital over a 5-month period with severe breastfeeding malnutrition and hypernatremia. The average weight loss at time of readmission was 23% (+/- 8%) from birth weight. The average presenting sodium was 186 +/- 19 mmol/L. Three suffered significant complications. From 1990 through 1994, there was a statistically significant (P < .05) annual increase in the number of infants admitted with breastfeeding malnutrition and hypernatremia. CONCLUSIONS: While breastfeeding malnutrition and hypernatremia is not a new problem, this cluster of infants represents an increase in frequency and severity of the problem and could be a consequence of several factors, including inadequate parent education about breastfeeding problems and inadequate strategies for infant follow-up.

Glutamine reduces cytokine release, organ damage, and mortality in a rat model of endotoxemia.

Clinical trials have demonstrated that glutamine (GLN) supplementation can decrease infectious morbidity and improve survival in a number of settings of critical illness. The mechanism of this protection remains unclear. The objective of this study was to evaluate the effect of GLN on cytokine release, organ injury, and survival from endotoxin-induced septic shock. Endotoxemia was induced in Male Sprague-Dawley rats by intravenous administration of 5 mg/kg Escherichia coli lipopolysaccharide (LPS). Concomitantly, animals were fluid resuscitated with a lactated ringers (LR) solution and given GLN (0.75 g/kg i.v.) or LR alone. Blood samples were obtained at multiple time points post-LPS injury for cytokine analysis. Survival rates were monitored for 72 h. Organ injury was evaluated in a separate set of animals via pathologic exam of tissues harvested 6 h post-LPS injury. A single dose of GLN significantly attenuated the release of TNF-alpha at 2 h (P < 0.005) and IL-1 beta at 4 h (P < 0.0001). This attenuation of cytokine release was associated with a significant decrease in mortality (P < 0.003). Pathologic exam demonstrated significant protection of both lung and small bowel tissue by GLN. Blood gas values 6-h post-LPS injury showed increased PaO2 and bicarbonate concentration in GLN treated animals. These data indicate that GLN can significantly attenuate pro-inflammatory cytokine release, protect against end-organ damage, and decrease mortality from endotoxemia. GLN confers protection even when administered at the onset of endotoxemia, rather then as pre-treatment. Thus, one explanation for the clinical benefits observed from GLN-supplementation may be related to the attenuation of pro-inflammatory cytokines.

The clinicopathologic features of cryoglobulinemic nephropathy.

Renal biopsy specimens from eight patients with cryoglobulinemic nephropathy were examined by light, electron, and immunofluorescence microscopy. The light microscopic features were not diagnostic. Characteristic ultrastructural findings were observed in all except one specimen and consisted of glomerular electron-dense deposits, which had a coarse, granular appearance at low-power magnifications and revealed tubular, annular and in a few cases, also fibrillar structures at high-power magnifications. Subendothelial deposits were a constant finding. The presence of intravascular thrombi (deposits), osmiophilic bodies, and crystals within the cytoplasm of the glomerular cells are also helpful for the diagnosis of this entity. Because of these specific findings, cryoglobulinemic nephropathy should be recognized as a clinicopathologic entity.

Glutamine induces heat shock protein and protects against endotoxin shock in the rat.

Enhanced expression of heat shock protein (HSP) has been shown to be protective against laboratory models of septic shock. Induction of HSPs to improve outcome in human disease has not been exploited because laboratory induction agents are themselves toxic and not clinically relevant. In this study, we demonstrate that a single dose of intravenous glutamine causes a rapid and significant increase in HSP25 and HSP72 expression in multiple organs of the unstressed Sprague-Dawley rat. With the utilization of a fluid-resuscitated rat model of endotoxemia, mortality was dramatically reduced by glutamine administration concomitant with the endotoxin injury. Endotoxin-treated animals given glutamine exhibited dramatic increases in tissue HSP expression and marked reduction of end-organ damage. These data suggest glutamine may protect against mortality and attenuate end-organ injury in endotoxemic shock via enhanced HSP expression. Furthermore, glutamine confers protection when administered at the initiation of sepsis, rather than as pretreatment. Thus glutamine appears to be a clinically viable enhancer of HSP expression and may prove beneficial in the therapy of sepsis and sepsis-induced organ injury.

The predictive value of discriminatory human chorionic gonadotropin levels in the diagnosis of implantation outcome in in vitro fertilization cycles.

OBJECTIVE: To determine if early serum hCG levels are predictive of implantation outcome in patients undergoing IVF-ET. DESIGN: Retrospective study of IVF cycles using receiver operator characteristic curve (ROC) analysis. SETTING: Tertiary-care, university hospital-affiliated IVF program. PATIENTS: Three hundred fifty-one conception cycles were studied. INTERVENTIONS: None. MAIN OUTCOME MEASURE: Implantation failure, defined as chemical pregnancies, ectopic gestations, and first trimester abortions, or implantation success, defined as delivered singleton and multiple pregnancies, and second trimester abortions. RESULTS: For each post-ET day 14 to 20, mean hCG levels of the implantation success group were significantly greater than implantation failure outcomes (P < 0.0001). Using ROC curve analysis, hCG cutoff values for each post-ET day were calculated for optimal discrimination of implantation failure from implantation success cycles. A patient with an hCG measurement greater than the calculated cutoff value had a > or = 90% chance of having an implantation success after IVF-ET. CONCLUSION: Discriminatory hCG cutoff values may be useful in predicting implantation outcome in IVF-ET cycles and may guide clinicians in identifying those pregnancies at risk for adverse outcomes and instituting more intensive surveillance in this population. This information also may be useful in providing counseling to IVF patients regarding pregnancy prognosis and result in cost savings.

Intrathecal morphine for postoperative analgesia in children after selective dorsal root rhizotomy.

The authors report their experience with low doses (0.007-0.015 mg/kg), moderate doses (0.016-0.025 mg/kg), and high doses (0.026-0.035 mg/kg) of intrathecal morphine for postoperative analgesia after selective dorsal root rhizotomy surgery in 50 children, aged 3 to 12 years. After closure of the dura, a single dose of preservative-free morphine was injected into the subarachnoid space, and patients were assessed for 48 hours for level of comfort and side effects. The three doses of morphine provided equivalent analgesia and similar side effects. The duration of postoperative analgesia ranged from 3 to 48 hours (mean, 12.2 +/- 9.5 h). Common side effects were limited to nausea and vomiting (42%) and mild facial pruritus. No patient experienced late respiratory depression or generalized pruritus. The authors conclude that low doses of intrathecal morphine is as effective as moderate or high doses of morphine for reducing pain in the immediate postoperative period. Intrathecal morphine provides excellent analgesia after selective dorsal rhizotomy.

Adult age differences in the temporal characteristics of category free recall.

Two experiments are reported that examined the temporal structure of recall for categorizable word lists by younger and older adults. All participants showed response bursting, in which recall order is clustered by semantic category, with longer interresponse times (IRTs) appearing between categories than within categories. Experiment 1 demonstrated that older adults, even when matched to younger adults in overall accuracy, differed in the rate of increase of between-category IRTs with output position, but not in within-category IRTs. Experiment 2 showed that this interaction is eliminated when the names of the response categories are provided to the participants. Results are interpreted in terms of combined effects of an age-compromised episodic memory system (between-category IRTs) accompanied by a comparatively preserved semantic system (within-category IRTs) in healthy aging.

Interresponse times in serial recall: effects of intraserial repetition.

The authors examined the effects of intraserial repetition on multitrial serial learning of random consonant lists, analyzing both learning rates and perfect trial interresponse times (IRTs). Lists varied along 3 dimensions: list length, presence or absence of a repeated element, and lag between repeated elements. After achieving a forward-recall criterion on a given list, participants (N = 20) attempted backward recall. At small lags, IRTs between the repeated elements were very short (compared with IRTs from identical positions in nonrepetition lists). At larger lags, the IRT to recall the second repeated item was substantially longer than in control lists. These results reveal a latency analogue of the Ranschburg pattern seen in accuracy data. A Ranschburg pattern was also found in participants' learning rates. These results both generalize the Ranschburg phenomenon and present further challenges to theories of serial order memory.

Contextual variability and serial position effects in free recall.

In immediate free recall, words recalled successively tend to come from nearby serial positions. M. J. Kahana (1996) documented this effect and showed that this tendency, which the authors refer to as the lag recency effect, is well described by a variant of the search of associative memory (SAM) model (J. G. W. Raaijmakers & R. M. Shiffrin, 1980, 1981). In 2 experiments, participants performed immediate, delayed, and continuous distractor free recall under conditions designed to minimize rehearsal. The lag recency effect, previously observed in immediate free recall, was also observed in delayed and continuous distractor free recall. Although two-store memory models, such as SAM, readily account for the end-of-list recency effect in immediate free recall, and its attenuation in delayed free recall, these models fail to account for the long-term recency effect. By means of analytic simulations, the authors show that both the end of list recency effect and the lag recency effect, across all distractor conditions, can be explained by a single-store model in which context, retrieved with each recalled item, serves as a cue for subsequent recalls.

A functional relation between learning and organization in free recall.

It is well known that multitrial free recall is accompanied by increased organization of output over learning trials, even when the order of presentation is randomized. We compared the relation between learning and organization in 30 young and 30 older adults as they learned categorized materials to a criterion of 100% recall. The importance of this age manipulation was that it allowed us to examine, using two groups that differ significantly in their learning ability, whether organization and learning follow the same function. As was expected, older adults showed less organization on any given learning trial. However, when equated for degree of learning, the older adults showed approximately the same level of organization as the young. This finding suggests that the organization-learning relation remains invariant in the face of significant differences in participants' mnemonic abilities.

Anesthetic considerations in neonatal neurosurgical patients.

Neonatal neurosurgery patients have specific considerations throughout the perioperative course in addition to the usual care of neonates undergoing other surgical procedures. Prematurity, with its associated comorbidity, temperature, and glucose control are important topics to consider in this age group. This article addresses practical aspects of preoperative assessment, intraoperative management, and postoperative care. Because CSF shunting and myelomeningocele repair are common neonatal procedures, these specific procedures are the focus of this article.

Transient acantholytic dermatosis occurring during pregnancy.

A case of transient acantholytic dermatosis (TAD) in pregnancy is reported. The eruption appeared in the third month of the pregnancy and completely resolved two months later. Reports concerning the occurrence of this disorder in young people are rare, and, to the best of our knowledge, this is the first patient in whom onset of the disease has been detected during pregnancy.

Prayer nodules in Moslem men.

Seven cases of Israeli Moslem men with hyperkeratotic nodular callosities of the legs and forehead are reported. These patients were randomly encountered over a two-year period in our dermatology clinic. The nodules were attributed to repeated trauma to the legs and forehead sustained during Moslem prayer. This article familiarizes the clinician with the morphologic characteristics of these lesions, which may occur in some Moslem men.

Dermatophytosis of the diaper area.

Six cases of dermatophytosis of the diaper area due to either Epidermophyton floccosum or Trichophyton rubrum are described herein. The clinical and laboratory features of these patients and those reported in the literature are highlighted. Dermatophytosis should be considered in the differential diagnosis of rashes in the diaper area. Most standard remedies for diaper rash will not be effective or may exacerbate diaper dermatophytosis. Recognition of this condition by the clinician will lead to earlier rational treatment and may avoid the delay caused by therapy.