Concussion history and postconcussion neurocognitive performance and symptoms in collegiate athletes

CONTEXT: Athletes are at an inherent risk for sustaining concussions. Research examining the long-term consequences of sport-related concussion has been inconsistent in demonstrating lingering neurocognitive decrements that may be associated with a previous history of concussion. OBJECTIVE: To determine the relationship between concussion history and postconcussion neurocognitive performance and symptoms in collegiate athletes. DESIGN: Repeated-measures design. SETTING: Multi-center analysis of collegiate athletes. PATIENTS OR OTHER PARTICIPANTS: Fifty-seven concussed collegiate athletes (36 without concussion history, 21 with a history of 2 or more concussions). INTERVENTION(S): All subjects were administered an Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) neurocognitive test battery, which measures verbal memory, visual memory, reaction time, and visual processing speed and 22 concussion symptoms. MAIN OUTCOME MEASURE(S): Subjects who sustained a concussion were administered 2 follow-up tests at days 1 and 5 postinjury. Independent variables were history of concussion (no history of concussion, 2 or more concussions) and time (baseline, day 1 postconcussion, or day 5 postconcussion). RESULTS: A within-subjects effect (time) on ImPACT performance (P < .001), a between-subjects multivariate effect of group (P < .001), and a group-by-time interaction (P = .034) were noted. Athletes with a concussion history performed significantly worse on verbal memory (P = .01) and reaction time (P = .023) at day 5 postconcussion compared with athletes who did not report a previous concussion. No significant group differences were seen at day 5 postinjury on visual memory (P = .167), processing speed (P = .179), or total concussion symptoms (P = .87). CONCLUSIONS: Concussed collegiate athletes with a history of 2 or more concussions took longer to recover verbal memory and reaction time than athletes without a history of concussion.     

Assessing the enduring residual neuropsychological effects of head trauma in college athletes who participate in contact sports.

The present study examined the enduring residual neuropsychological effects of head trauma in college athletes using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS), Postconcussion Syndrome Checklist, and the Stroop task. Based on a brief self-report concussion history survey, male and female athletes who participated in ice hockey, field hockey, lacrosse, and/or soccer were assigned to one of three concussion-history conditions: Non-concussed, Non-recent concussed (i.e., more than 2 years since last concussion), or Recent concussed (i.e., 2 years or less since last concussion). A fourth group of subjects consisting of non-concussed/non-athletes served in the control condition. Group differences emerged on the RBANS when immediate memory, delayed memory, and total scores were analyzed. Specifically, recent concussed athletes and, surprisingly, non-concussed athletes scored lower than control subjects in the two memory domains, whereas all three athlete groups had lower total RBANS scores than those of control subjects. Moreover, recent concussed athletes not only had lower immediate memory scores than control subjects, but also were impaired relative to non-recent concussed athlete subjects in this memory domain. No group differences were detected on the Stroop task or on the Postconcussion Syndrome Checklist. Interestingly, however, the severity of the Postconcussion Syndrome Checklist scores for the two athlete-concussed groups, taken in aggregate, correlated negatively with RBANS scores for attention (r = -.65) and delayed memory (r = -.61), and with the total RBANS score (r = -.59). In recent concussed athletes, lower delayed memory scores correlated with more severe Postconcussion Symptom Checklist scores (r = -.90), while more severe/higher number of concussions correlated with increased processing speed on the Stroop interference task (r = .90). These findings indicate that recent head injury produces alterations in neuropsychological function, especially that of memory, that resolve with time. More provocatively, the data also suggest that participation in contact sports may produce sub-clinical cognitive impairments in the absence of a diagnosable concussion presumably resulting from the cumulative consequences produced by multiple mild head trauma.     

Interpreting Clinical Reaction Time Change and Recovery After Concussion: A Baseline Versus Norm-Based Cutoff Score Comparison

ContextPreseason testing can be time intensive and cost prohibitive. Therefore, using normative data for postconcussion interpretation in lieu of preseason testing is desirable.ObjectiveTo establish the recovery trajectory for clinical reaction time (RT_clin) and assess the usefulness of changes from baseline (comparison of postconcussion scores with individual baseline scores) and norm-based cutoff scores (comparison of postconcussion scores with a normative mean) for identifying impairments postconcussion.DesignCase-control study.SettingMultisite clinical setting.Patients or Other ParticipantsAn overlapping sample of 99 participants (age = 19.0 ± 1.1 years) evaluated within 6 hours postconcussion, 176 participants (age = 18.9 ± 1.1 years) evaluated at 24 to 48 hours postconcussion, and 214 participants (age = 18.9 ± 1.1 years) evaluated once they were cleared to begin a return-to-play progression were included. Participants with concussion were compared with 942 control participants (age = 19.0 ± 1.0 years) who did not sustain a concussion during the study period but completed preseason baseline testing at 2 points separated by 1 year (years 1 and 2).Main Outcome Measure(s)At each time point, follow-up RT_clin (ie, postconcussion or year 2) was compared with the individual year 1 preseason baseline RT_clin and normative baseline data (ie, sex and sport specific). Receiver operating characteristic curves were calculated to compare the sensitivity and specificity of RT_clin change from baseline and norm-based cutoff scores.ResultsClinical reaction time performance declined within 6 hours (18 milliseconds, 9.2% slower than baseline). The decline persisted at 24 to 48 hours (15 milliseconds, 7.6% slower than baseline), but performance recovered by the time of return-to-play initiation. Within 6 hours, a change from baseline of 16 milliseconds maximized combined sensitivity (52%) and specificity (79%, area under the curve [AUC] = 0.702), whereas a norm-based cutoff score of 19 milliseconds maximized combined sensitivity (46%) and specificity (86%, AUC = 0.700). At 24 to 48 hours, a change from baseline of 2 milliseconds maximized combined sensitivity (64%) and specificity (61%, AUC = 0.666), whereas a norm-based cutoff score of 0 milliseconds maximized combined sensitivity (63%) and specificity (62%, AUC = 0.647).ConclusionsNorm-based cutoff scores can be used for interpreting RT_clin scores postconcussion in collegiate athletes when individual baseline data are not available, although low sensitivity and specificity limit the use of RT_clin as a stand-alone test.     

Neurocognitive performance of concussed athletes when symptom free

CONTEXT: Concussed athletes may underreport concussion-related symptoms in order to expedite return to play. Whether neurocognitive impairments persist once concussion-related symptoms resolve has yet to be determined. Reliance on athlete-reported, postconcussion symptoms when making return-to-play decisions may expose athletes to subsequent injury if complete recovery has not occurred. OBJECTIVE: To evaluate the presence of neurocognitive decrements in concussed athletes no longer reporting concussion-related symptoms. DESIGN: Within-groups design. SETTING: University research laboratory. PATIENTS OR OTHER PARTICIPANTS: Twenty-one National Collegiate Athletic Association Division I collegiate athletes (16 men, 5 women). Age = 19.81 +/- 1.25 years, height = 180.95 +/- 10.62 cm, mass = 93.66 +/- 27.60 kg, and previous concussions = 1.76 +/- 2.02. MAIN OUTCOME MEASURE(S): The ImPACT concussion assessment test was administered to concussed athletes at baseline, when symptomatic (within 72 hours of injury), and when asymptomatic. Index scores of verbal memory, visual memory, visual-motor speed, reaction time, and concussion-related symptoms were recorded at each session. The Symptom Assessment Scale was administered daily after injury to establish when the athlete became asymptomatic. RESULTS: When assessed within 72 hours of concussion, 81% of the athletes showed deficits on at least 1 ImPACT variable. At the asymptomatic time point, 38% of the concussed athletes continued to demonstrate neurocognitive impairment on at least 1 ImPACT variable. CONCLUSIONS: Neurocognitive decrements may persist when athletes no longer report concussion-related symptoms. The exclusive use of symptom reports in making a return-to-play decision is not advised. A multifaceted approach to concussion assessment that includes evaluation of a myriad of functions is warranted.     

Brain atrophy associated with baseline and longitudinal measures of cognition

The overall goal was to identify patterns of brain atrophy associated with cognitive impairment and future cognitive decline in non-demented elders. Seventy-one participants were studied with structural MRI and neuropsychological testing at baseline and 1-year follow-up. Deformation-based morphometry was used to examine the relationship between regional baseline brain tissue volume with baseline and longitudinal measures of delayed verbal memory, semantic memory, and executive function. Smaller right hippocampal and entorhinal cortex (ERC) volumes at baseline were associated with worse delayed verbal memory performance at baseline while smaller left ERC volume was associated with greater longitudinal decline. Smaller left superior temporal cortex at baseline was associated with worse semantic memory at baseline, while smaller left temporal white and gray matter volumes were associated with greater semantic memory decline. Increased CSF and smaller frontal lobe volumes were associated with impaired executive function at baseline and greater longitudinal executive decline. These findings suggest that baseline volumes of prefrontal and temporal regions may underlie continuing cognitive decline due to aging, pathology, or both in non-demented elderly individuals.     

Levels-of-processing effect on internal source monitoring in schizophrenia

BACKGROUND: Recognition can be normalized in schizophrenia by providing patients with semantic organizational strategies through a levels-of-processing (LOP) framework. However, patients may rely primarily on familiarity effects, making recognition less sensitive than source monitoring to the strength of the episodic memory trace. The current study investigates whether providing semantic organizational strategies can also normalize patients' internal source-monitoring performance. METHOD: Sixteen clinically stable medicated patients with schizophrenia and 15 demographically matched healthy controls were asked to identify the source of remembered words following an LOP-encoding paradigm in which they alternated between processing words on a 'shallow' perceptual versus a 'deep' semantic level. A multinomial analysis provided orthogonal measures of item recognition and source discrimination, and bootstrapping generated variance to allow for parametric analyses. LOP and group effects were tested by contrasting recognition and source-monitoring parameters for words that had been encoded during deep versus shallow processing conditions. RESULTS: As in a previous study there were no group differences in LOP effects on recognition performance, with patients and controls benefiting equally from deep versus shallow processing. Although there were no group differences in internal source monitoring, only controls had significantly better performance for words processed during the deep encoding condition. Patient performance did not correlate with clinical symptoms or medication dose. CONCLUSIONS: Providing a deep processing semantic encoding strategy significantly improved patients' recognition performance only. The lack of a significant LOP effect on internal source monitoring in patients may reflect subtle problems in the relational binding of semantic information that are independent of strategic memory processes.     

Evidence for the Factorial and Construct Validity of a Self-Report Concussion Symptoms Scale

OBJECTIVE: To evaluate the factorial and construct validity of the Head Injury Scale (HIS) among a sample of male and female collegiate athletes. DESIGN AND SETTING: Using a cross-sectional design, we established the factorial validity of the HIS scale with confirmatory factor analysis and the construct validity of the HIS with Pearson product moment correlation analyses. Using an experimental design, we compared scores on the HIS between concussed and nonconcussed groups with a 2 (groups) x 5 (time) mixed-model analysis of variance. SUBJECTS: Participants (N = 279) in the cross-sectional analyses were predominately male (n = 223) collegiate athletes with a mean age of 19.49 +/- 1.63 years. Participants (N = 33) in the experimental analyses were concussed (n = 17) and nonconcussed control (n = 16) collegiate athletes with a mean age of 19.76 +/- 1.49 years. MEASUREMENTS: All participants completed baseline measures for the 16-item HIS, neuropsychological testing battery, and posturography. Concussed individuals and paired controls were evaluated on days 1, 2, 3, and 10 postinjury on the same testing battery. RESULTS: Confirmatory factor analysis indicated that a theoretically derived, 3-factor model provided a good but not excellent fit to the 16-item HIS. Hence, the 16-item HIS was modified on the basis of substantive arguments about item-content validity. The subsequent analysis indicated that the 3-factor model provided an excellent fit to the modified 9-item HIS. The 3 factors were best described by a single second-order factor: concussion symptoms. Scores from the 16-item HIS and 9-item HIS were strongly correlated, but there were few significant correlations between HIS scores and scores from the neuropsychological and balance measures. A significant group-by-day interaction was noted on both the 9-item HIS and 16-item HIS, with significant differences seen between groups on days 1 and 2 postconcussion. CONCLUSIONS: We provide evidence for the factorial and construct validity of the HIS among collegiate athletes. This scale might aid in return-to-play decisions by physicians and athletic trainers.     

Functional abnormalities in normally appearing athletes following mild traumatic brain injury: a functional MRI study

Memory problems are one of the most common symptoms of sport-related mild traumatic brain injury (MTBI), known as concussion. Surprisingly, little research has examined spatial memory in concussed athletes given its importance in athletic environments. Here, we combine functional magnetic resonance imaging (fMRI) with a virtual reality (VR) paradigm designed to investigate the possibility of residual functional deficits in recently concussed but asymptomatic individuals. Specifically, we report performance of spatial memory navigation tasks in a VR environment and fMRI data in 15 athletes suffering from MTBI and 15 neurologically normal, athletically active age matched controls. No differences in performance were observed between these two groups of subjects in terms of success rate (94 and 92%) and time to complete the spatial memory navigation tasks (mean = 19.5 and 19.7 s). Whole brain analysis revealed that similar brain activation patterns were observed during both encoding and retrieval among the groups. However, concussed athletes showed larger cortical networks with additional increases in activity outside of the shared region of interest (ROI) during encoding. Quantitative analysis of blood oxygen level dependent (BOLD) signal revealed that concussed individuals had a significantly larger cluster size during encoding at parietal cortex, right dorsolateral prefrontal cortex, and right hippocampus. In addition, there was a significantly larger BOLD signal percent change at the right hippocampus. Neither cluster size nor BOLD signal percent change at shared ROIs was different between groups during retrieval. These major findings are discussed with respect to current hypotheses regarding the neural mechanism responsible for alteration of brain functions in a clinical setting.     

Immunity to vaginal herpes simplex virus-2 infection in B-cell knockout mice

We investigated the involvement of antibody in protection against vaginal herpes simplex virus type-2 (HSV-2) infection by comparing intact and B-cell knockout (KO) mice. Vaginal immunization of intact mice with attenuated HSV-2 markedly reduced an HSV-2 challenge infection in the vagina. In contrast, immunization of B-cell KO mice produced less immunity against the challenge infection and that immunity occurred in a different pattern. At 20 hr after challenge, immunostaining of virus proteins in the vaginal epithelium and shed virus protein titres in the vaginal secretions were not significantly different between immunized and non-immunized B-cell KO mice and were much greater than in immunized intact mice. At 48 hr after challenge, the vaginal infection in immunized B-cell KO mice was markedly less than at 20 hr but remained approximately sevenfold higher than in intact mice. This pattern of challenge infection in the vagina indicates that B cells, and probably the antibody derived from them, provided significant protection against reinfection in intact mice, especially during the first 20 hr after challenge, while other effector mechanisms became important between 20 and 48 hr after challenge. To determine whether T-cell immunity in immunized B-cell KO mice was equal to that in intact mice, we assessed interferon-gamma (IFN-gamma) secretion by memory T cells in vivo in the vagina at 20 hr after challenge. We found no significant differences in the up-regulation of major histocompatibility complex (MHC) class II antigens in the epithelium, up-regulation of vascular cell adhesion molecule-1 (VCAM-1) in vascular endothelium, or recruitment of T cells to the mucosa, indicating that the memory T-cell response to virus challenge was the same in intact and B-cell KO mice.     

Failing to get the gist: reduced false recognition of semantic associates in semantic dementia

In 2 experiments involving patients with semantic dementia, the authors investigated the impact of semantic memory loss on both true and false recognition. Experiment 1 involved recognition memory for categories of everyday objects that shared a predominantly semantic relationship. The patients showed preserved item-specific recollection for the pictorial stimuli but, compared with control participants, exhibited significantly reduced utilization of gist information regarding the categories of objects. The latter result is consistent with the patients' degraded semantic knowledge. Experiment 2 involved categories of abstract objects that were related to one another perceptually rather than semantically. Patients with semantic dementia obtained item-specific recollection and gist memory scores that were indistinguishable from those of control participants. These results suggest that the reduction in gist memory in semantic dementia is largely specific to semantic representations and cannot be attributed to general difficulty with abstracting and/or utilizing gistlike commonalities between stimuli.     

Expansion of plasmablasts and loss of memory B cells in peripheral blood from COVID-19 patients with pneumonia

Studies on the interactions between SARS-CoV-2 and humoral immunity are fundamental to elaborate effective therapies including vaccines. We used polychromatic flow cytometry, coupled with unsupervised data analysis and principal component analysis (PCA), to interrogate B cells in untreated patients with COVID-19 pneumonia. COVID-19 patients displayed normal plasma levels of the main immunoglobulin classes, of antibodies against common antigens or against antigens present in common vaccines. However, we found a decreased number of total and naïve B cells, along with decreased percentages and numbers of memory switched and unswitched B cells. On the contrary, IgM⁺ and IgM⁻ plasmablasts were significantly increased. In vitro cell activation revealed that B lymphocytes showed a normal proliferation index and number of dividing cells per cycle. PCA indicated that B-cell number, naive and memory B cells but not plasmablasts clustered with patients who were discharged, while plasma IgM level, C-reactive protein, D-dimer, and SOFA score with those who died. In patients with pneumonia, the derangement of the B-cell compartment could be one of the causes of the immunological failure to control SARS-Cov2, have a relevant influence on several pathways, organs and systems, and must be considered to develop vaccine strategies.     

抑郁障碍患者及Ⅰ级亲属的认知功能研究

目的探讨抑郁障碍患者的认知功能特点,以及认知功能障碍是否为抑郁障碍的候补内表型。方法选择符合美国精神障碍诊断和统计手册第4版（DSM-）诊断标准的抑郁障碍患者、患者级亲属及健康志愿者各71例,分别使用词汇学习测验,故事复述测验,图形临摹及线条定位测验,语义流畅性测验,编码测验,词汇,故事图形回忆测验,以及威斯康星卡分类测验,进行认知功能测评。结果患者组的词汇学习,故事复述,图形临摹,线条定位,语义流畅,编码测验,词汇回忆,故事回忆,图形临摹回忆,WCST完成分类数均比正常对照组差（P〈0.05和P〈0.001）。级亲属组的词汇学习,故事复述,图形临摹,线条定位,语义流畅,编码测验,词汇回忆,故事回忆,图形临摹回忆,WCST完成分类数,WCST正确应答数明显低于正常对照组,WCST持续错误数明显高于正常对照组（P〈0.05和P〈0.001）。级亲属组与患者组在词汇学习,故事复述,图形临摹,线条定位,语义流畅,编码测验,词汇回忆,故事回忆,图形临摹回忆,WCST总应答数,WCST正确应答数,持续错误数,非持续错误数,差别无统计学意义。结论抑郁障碍患者及其级亲属均存在认知功能的损害,认知功能可以作为抑郁障碍的候补内表型。     

Overinclusive thought and loosening of associations are not unique to schizophrenia and are produced in Alzheimer's dementia

Introduction. Bleuler's concept of loosening of associations which he believed epitomised psychotic thinking can manifest as overinclusion (merging of semantic categories) on semantic categorisation tasks. Overinclusion is explained by excessive activation within the semantic memory network to subordinate features with low associative strength. Therefore patients with degradation of subordinate semantic knowledge (e.g., with Alzheimer's Dementia—AD) should not produce overinclusion errors.

Methods. 22 people with schizophrenia and 26 people with AD (nonpsychotic, semantic memory impairment) were compared on a semantic categorisation test, the Category Generation Test (CGT). The CGT involves free-sorting 45 cards of pictured objects from five taxonomic groups (e.g., animals). Overinclusion and underinclusion (subdivision of categories) errors were recorded and the strategies used in generating these abnormal categories were explored qualitatively.

Results. Two-thirds of both groups generated abnormal categories, including frequent overinclusions. Using a semantic probes test, abnormal categorisations could not be attributed to knowledge degradation as this appeared preserved. Qualitatively, the two groups differed in their sorting strategies.

Conclusions. Loosening of associations is found in nonpsychotic people, who have semantic memory impairments (e.g., AD), using semantic knowledge tasks. However there may be different explanations; atypical semantic categorisation in schizophrenia appears to result from attention to thematic rather than feature-based associations.     

False memory and schizophrenia: evidence for gist memory impairment

BACKGROUND: In this study we examined patients' false memory, that is memory for a non-presented event, to search for a further source of converging evidence for the impairment of semantic memory in individuals with schizophrenia. In two experiments we compared the pattern of false memory created by the Deese-Roediger-McDermott (DRM) paradigm between individuals with schizophrenia and those of a normal control group. METHOD: Experiment 1 tested participants on both recall and recognition of lists of semantically related words. Experiment 2 adopted the meaning recognition test, in addition to the standard recognition test, to assess the participants' gist memory. RESULTS: Individuals with schizophrenia performed worse than normal controls on both recall and recognition of studied words. The schizophrenia patients had higher rates of false recall and false recognition for semantically unrelated words than did the normal controls, suggesting an abnormal pattern of semantic activation in the former group. More importantly, no differences were found between the two groups with regard to false recall and false recognition of semantically related words. When the participants were tested for meaning recognition, however, the schizophrenia patients gave fewer 'old' responses to non-studied semantically related words than did the control group, indicating an impaired gist memory in schizophrenia patients. CONCLUSIONS: When asked to consciously retrieve word lists, individuals with schizophrenia showed impairment not only in item-specific memory but also in gist memory. The pattern of results is consistent with the storage deficit view of semantic memory in schizophrenia.     

Concussion does not impact intraindividual response time variability

This investigation examined the effect of concussion on intraindividual variability in 5 processing speed tasks. Forty-four adults, including 22 concussed and 22 healthy age- and gender-matched participants, completed the Headminder Concussion Resolution Index (D. M. Erlanger, D. J. Feldman, K. C. Kutner,& M. McCrea, 2001) twice. The test consists of a series of tasks including 25 trials of simple response time task, 70 trials of cued response time task (CuRT), 60 trials each for 2 visual recognition tasks, and 30 trials of symbol scanning task. Concussed participants completed a preinjury baseline assessment and were retested within 48 hours of injury diagnosis. The nonconcussed participants were retested 45 days after initial assessment. Average response time (RT), standard deviation, and response accuracy were calculated for each individual. Overall, concussed individuals had increased RTs across all tasks and were less accurate in the CuRT. RT variability for all tasks was elevated in concussed individuals, but controlling for mean RT at follow-up eliminated group differences. These findings indicate that response-time-variability increases in concussed individuals are proportional to processing-time increases. As such, RT variability is not a unique identifier of cognitive dysfunction following concussion. These results highlight that transient brain injury has significantly different neurobiological consequences than chronic conditions have.     

Semantic knowledge and episodic memory for faces in semantic dementia

Previous studies have documented poor recognition memory for faces in patients with semantic dementia. Preserved face recognition memory was found in this study, however, so long as atrophy was confined predominantly to the left temporal lobe. Patients with structural damage to the right temporal lobe were typically impaired, with the status of the hippocampus and parahippocampal gyrus (including the perirhinal cortex) on the right being critical. Two single-case studies of patients with predominantly left temporal lobe pathology confirmed good recognition memory for famous faces, even if semantic knowledge about the celebrities depicted was severely degraded. An effect of semantic knowledge on recognition memory became apparent only when perceptually different photographs of the famous people were used at study and test. These results support the view that new episodic learning typically draws on information from both perceptual and semantic systems.     

Mathematical cognition in intellectually precocious first graders

Forty-six intellectually precocious (M age = 74 months) and 250 intellectually typical (M age = 75 months) children were administered a standardized working memory battery, speed of processing measures, and tasks that assessed skill at number line estimation and strategies used to solve simple and complex addition problems. Precocious children had an advantage over same-age peers for all components of working memory, and used a more mature mix of strategies to solve addition problems and to make number line estimates; there were no group differences for speed of processing. Many of the advantages of the precocious children on the number line and addition strategy tasks were significantly reduced or eliminated when group differences in working memory were controlled. Individual differences analyses revealed that each of the three components of working memory contributed to different aspects of skilled performance on the mathematics tasks.     

Amantadine therapy of epidemic influenza a(2) (Hong Kong)

In a double-blind comparison of the therapeutic effect of amantadine in a natural outbreak of Hong Kong influenza in January 1969 near Houston, Texas, the decrease in titers of virus in throat swabs from 12 treated patients during the first 10 hr of treatment was appreciably greater than similar titers of virus from 16 untreated patients (P = 0.06). The titer of shed virus decreased significantly more rapidly (P < 0.05) among amantadine-treated patients ill more than 48 hr before treatment than among five control patients who had been ill more than 48 hr. Cough, sore throat, and nasal obstruction cleared more rapidly in treated patients (P < 0.05), and decline of fever in 6 treated patients sick for less than 48 hr before treatment was more rapid than among 13 untreated patients who had been ill for less than 48 hr. These findings are considered to be consistent with a limited therapeutic effect of the drug.     

Semantic categorisation of novel objects in frontotemporal dementia

Impaired semantic memory is ubiquitous in frontotemporal dementia (FTD), including patients with semantic dementia (SD), progressive nonfluent aphasia (PNFA) and nonaphasic FTD patients with a deficit in executive and social functioning (EXEC/SOC). One hypothesis attributes this to the degradation of specific categories of knowledge in semantic memory. This study explores the alternate hypothesis that impaired semantic memory in FTD can also reflect limitations in the categorisation processes that determine object meaning. Patients were taught a novel semantic category under two conditions: rule-based categorisation, where executive resources support the evaluation of specific features to determine category membership; and similarity-based categorisation, where category membership is determined by the overall resemblance of an item to a prototype or recalled exemplars. In the first experiment, patients learned a novel category composed of highly salient features. For SD patients, we found category membership judgment profiles following rule-based and similarity-based training that resembled the performance of control subjects. Categorisation was impaired following rule-based training in PNFA and EXEC/SOC patients. In the second experiment, we modified the category so that membership was determined by less salient features, thus increasing the burden on executive resources. Under these circumstances, SD patients' categorisation profiles continued to resemble those of control subjects, PNFA patients' category judgments were governed by feature salience, and EXEC/SOC patients' judgments were limited by impaired executive resources. These observations suggest that the semantic memory deficit in SD largely reflects degraded feature knowledge for familiar objects, while impaired semantic memory in PNFA and in EXEC/SOC patients largely reflects a deficit in the processes associated with semantic categorisation.     

A viral-induced protein in the nuclei of cells infected with fowlpox virus.

The proteins found in the nuclear and cytoplasmic fractions of fowlpox virus-infected and mock-infected chick embryo cells were examined by SDS-polyacrylamide-gel electrophoresis. At 24 hr PI a viral-induced 37,000-dalton protein was present in infected cytoplasm, and was still being synthesized, although in lesser amounts, at 48 hr. No viral-induced proteins were identified in the nuclear fraction of infected cells at 24 hr PI, but by 36 hr PI a new 36,000-dalton protein had appeared; increased synthesis of this protein was seen at 48 hr PI. There was a general decline in the synthesis of host cell proteins during the period of viral infection.