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Passive observation of motor actions induces cortical activity in the primary motor cortex (M1) of the onlooker, which could potentially contribute to motor learning. While recent studies report modulation of motor performance following action observation, the neurophysiological mechanism supporting these behavioral changes remains to be specifically defined. Here, we assessed whether the observation of a repetitive thumb movement--similarly to active motor practice--would inhibit subsequent long-term potentiation-like (LTP) plasticity induced by paired-associative stimulation (PAS). Before undergoing PAS, participants were asked to either 1) perform abductions of the right thumb as fast as possible; 2) passively observe someone else perform thumb abductions; or 3) passively observe a moving dot mimicking thumb movements. Motor evoked potentials (MEP) were used to assess cortical excitability before and after motor practice (or observation) and at two time points following PAS. Results show that, similarly to participants in the motor practice group, individuals observing repeated motor actions showed marked inhibition of PAS-induced LTP, while the "moving dot" group displayed the expected increase in MEP amplitude, despite differences in baseline excitability. Interestingly, LTP occlusion in the action-observation group was present even if no increase in cortical excitability or movement speed was observed following observation. These results suggest that mere observation of repeated hand actions is sufficient to induce LTP, despite the absence of motor learning.

Context: The known detrimental effects of sport concussions on motor system function include balance problems, slowed motor execution, and abnormal motor cortex excitability., Objective: To assess whether these concussion-related alterations of motor system function are still evident in collegiate football players who sustained concussions but returned to competition more than 9 months before testing., Design: Case-control study., Setting: University laboratory., Patients or Other Participants: A group of 21 active, university-level football players who had experienced concussions was compared with 15 university football players who had not sustained concussions., Intervention(s): A force platform was used to assess center-of-pressure (COP) displacement and COP oscillation regularity (approximate entropy) as measures of postural stability in the upright position. A rapid alternating-movement task was also used to assess motor execution speed. Transcranial magnetic stimulation over the motor cortex was used to measure long-interval intracortical inhibition and the cortical silent period, presumably reflecting y-aminobutyric acid subtype B receptor-mediated intracortical inhibition., Main Outcome Measure(s): COP displacement and oscillation regularity, motor execution speed, long-interval intracortical inhibition, cortical silent period., Results: Relative to controls, previously concussed athletes showed persistently lower COP oscillation randomness, normal performance on a rapid alternating-movement task, and more M1 intracortical inhibition that was related to the number of previous concussions., Conclusions: Sport concussions were associated with pervasive changes in postural control and more M1 intracortical inhibition, providing neurophysiologic and behavioral evidence of lasting, subclinical changes in motor system integrity in concussed athletes.

Alzheimer's disease (AD)-the most common type of dementia among the elderly-represents one of the most challenging and urgent medical mysteries affecting our aging population. Although dominant inherited mutation in genes involved in the amyloid metabolism can elicit familial AD, the overwhelming majority of AD cases, dubbed sporadic AD, do not display this Mendelian inheritance pattern. Apolipoprotein E (APOE), the main lipid carrier protein in the central nervous system, is the only gene that has been robustly and consistently associated with AD risk. The purpose of the current paper is thus to highlight the pleiotropic roles and the structure-function relationship of APOE to stimulate both the functional characterization and the identification of novel lipid homeostasis-related molecular targets involved in AD.

Sports concussions affect thousands of individuals every year and are a major public health concern. Still, little is known about the long-term and cumulative effects of concussions on brain neurophysiology. The principal objective of this study was to investigate the long-lasting effects of multiple sports concussions on sensorimotor integration and somatosensory processing in a sample of 12 concussed athletes and 14 non-concussed athletes of similar age (mean, 23 years) and education (mean, 16 years). Right median nerve stimulation was paired with transcranial magnetic stimulation (TMS) of the left primary motor cortex to investigate sensorimotor integration with short latency afferent inhibition (SAI) and long latency afferent inhibition (LAI) at five interstimulus intervals (18, 20, 22, 100, 200 msec). Somatosensory evoked potentials (SEP) were recorded from the left centro-parietal region. We also investigated primary motor cortex inhibitory mechanisms with three TMS protocols: cortical silent period, long interval intracortical inhibition, and short interval intracortical inhibition. Motor evoked potentials were recorded from the right abductor pollicis brevis muscle. No differences were observed between groups for SAI, LAI, and SEP. However, cortical silent period duration was prolonged and long interval intracortical inhibition was enhanced in the concussed group. These findings suggest that multiple sports concussions lead to specific, long-term neurophysiological dysfunctions of intracortical inhibitory mechanisms in primary motor cortex while somatosensory processing and sensorimotor integration are spared. This study provides additional evidence for the presence of specific and stable alterations of GABA(B) receptor activity in primary motor cortex that may be of clinical value for prognosis and diagnosis.

Event-related potentials (ERPs) have been useful to detect subtle, pervasive alterations of cognition-related waveforms in athletes with multiple concussions. This study used the sustained posterior contralateral negativity (SPCN) waveform component recorded while participants performed a visual short-term memory task to investigate how working memory (WM) storage capacity was affected among athletes who differed according to their history of sports concussions. Fifty-five university-level football players were assigned to three groups: 1-2 concussion athletes; 3+ concussion athletes; non-concussed athletes. The main finding of the present study was that athletes with a history of three concussions or more exhibited significantly attenuated SPCN amplitude relative to both concussed athletes with only one or two prior concussions and athletes without concussions. The latter finding adds to previous evidence of disproportionately worse outcome in athletes presenting with a history of three or more concussions relative to those with fewer concussions. In addition, SPCN amplitude was found to correlate significantly with a visual memory capacity estimate (K), but this K value did not significantly differ across groups. This suggests that attenuated SPCN amplitude after three or more concussions did not interfere with apparent WM function. Taken together, these findings suggest that the altered neurophysiological index of WM storage might be a more sensitive measure of a latent WM function abnormality which may well worsen with aging, or perhaps additional brain insults.

Objective: The present study was aimed at characterizing the short- and long-term effects of multiple concussions using an electrophysiological approach., Method: Participants for this study were recruited from college football teams. They included athletes who never sustained concussions compared to two groups of asymptomatic multiple concussed athletes, one that sustained their last concussion within the year and the other more than 2 years prior to testing. All participants were submitted to an auditory three-tone Oddball paradigm while event-related potentials (ERP) were recorded., Results: Results from ERP recordings reveal significantly reduced P3a and P3b amplitudes in the recent concussed group in the three-tone task compared to control athletes. In contrast, athletes who sustained their concussions more than 2 years prior to testing had equivalent P3a and P3b amplitude to that of controls., Conclusion: These findings suggest that, despite functioning normally in their daily lives, concussed athletes still show subtle neuronal changes in information processing. Thus, the persistence of sub-clinical abnormalities on ERP components despite normal overt functioning may indicate sub-optimal compensation in multiple concussed athletes and leave them vulnerable to subsequent concussions.

Although post-combustion emissions from power plants are a major source of air pollution, they contain excess CO2 that could be used to fertilize commercial greenhouses and stimulate plant growth. We addressed the combined effects of ultrahigh [CO2] and acidic pollutants in flue gas on the growth of Alternanthera philoxeroides. When acidic pollutants were excluded, the biomass yield of A. philoxeroides saturated near 2000 micromol mol(-1) [CO2] with doubled biomass accumulation relative to the ambient control. The growth enhancement was maintained at 5000 micromol mol(-1) [CO2], but declined when [CO2] rose above 1%, in association with a strong photosynthetic inhibition. Although acidic components (SO2 and NO2) significantly offset the CO2 enhancement, the aboveground yield increased considerably when the concentration of pollutants was moderate (200 times dilution). Our results indicate that using excess CO2 from the power plant emissions to optimize growth in commercial green house could be viable.

The number of concussions and other head injuries are increasing in the National Hockey League (NHL). The factors that may influence concussion risk in hockey remain largely unknown. In the current study, data on 787 NHL players from the 2001-2002 season were examined. It was found that a player's average ice time per game was a significant predictor of concussion. A player's total ice time for the season was not a significant predictor, however, and there was no significant difference found in the number of games played in the season between those who suffered a concussion and those who did not. These data suggest that in-game fatigue is an important factor when considering concussions.

Objective: Using transcranial magnetic stimulation paradigms, this study investigated motor cortex integrity as a function of an athlete's prior history of concussions., Patients and Methods: Motor cortex excitatory and inhibitory mechanisms were studied in athletes using four different transcranial magnetic stimulation protocols, namely 1) resting motor threshold, 2) intracortical inhibition and intracortical facilitation in a paired-pulse paradigm, 3) excitability of the corticospinal system using an input-output curve, and 4) intracortical inhibition in a cortical silent-period paradigm. Motor-evoked potentials were recorded from the first dorsal interosseous muscle of the right hand., Results: Cortical silent-period duration in athletes who have experienced multiple concussions was prolonged when compared to that of normal control participants. Linear regression suggested that concussion severity was the main factor explaining motor cortex dysfunction. Moreover, when we retested the athletes, the cortical silent period was more prolonged in those who sustained another concussion after baseline testing had occurred., Conclusion: Findings from this study indicate that sports-related concussions result in long-term motor system dysfunctions that seem to be attributable to subclinical intracortical inhibitory system abnormalities. This study also shows that sustaining subsequent concussions exacerbates this deficit, and thus provides additional support for the contention that the adverse effects of sports-related concussions on intracortical inhibitory systems are cumulative.

Primary Objective: This event-related potentials study investigated the long-term effects associated with a history of one or multiple concussions on the N2pc and P3 components using a visual search oddball paradigm., Methods and Procedure: A total of 47 university football players were assigned to three experimental groups based on prior concussion history: Athletes with a history of one concussion (single-concussion group); Athletes with two or more concussions (multi-concussion group); non-concussed athletic controls. The average post-concussion period was 31 months for athletes in the multi-concussion group and 59 months for the single-concussion group., Results: This study found significantly suppressed P3 amplitude in the multi-concussed athletes group compared to the single-concussion and non-concussed athletes even when using the time since the latest concussion as a covariate., Conclusion: This finding suggests that the multi-concussed athletes group showed long-lasting P3 amplitude suppression when compared with single-concussion or non-concussed athletes despite equivalent neuropsychological test scores and post-concussion symptoms self-reports. This pattern of results is important because it shows that 'old' concussions do not cause general or ubiquitous electrophysiological suppression. The specificity of the long-term effects of previous concussions to the P3, along with an intact N2pc response, suggests that further work may allow one to pinpoint the cognitive system that is specifically affected by multiple concussions.

Background: Recently, the effect of hyperbaric oxygen (HBO(2)) therapy was explored in the treatment of chronic TBI. It has been speculated that idling neurons in the penumbra zone remain viable several years after injury and might be reactivated by enhanced oxygenation. We studied the therapeutic potential of HBO(2) therapy in a 54-year-old man who had sustained traumatic brain injuries one year before testing that resulted in permanent neurological symptoms., Methods: Two treatment series separated by a one-year inter-session interval were administered. Treatment series consisted of 20 and 60 daily one-hour exposures to 100% oxygen at 2 ATA. Electrophysiological (event-related potentials), metabolic and behavioral (sensorimotor and neuropsychological) measurements were obtained to evaluate the effects of hyperbaric oxygen therapy on neurocognitive functioning., Results: Following the initial treatment, the patient showed improvements in sensorimotor functions, as well as enhanced P300 amplitude in the damaged hemisphere. Although most of these gains were no longer observed one year after treatment, these were reinstated with an additional series of 60 exposures. Neuropsychological improvements were also observed after the completion of the second series of treatments., Conclusion: The present single-case study provides preliminary evidence of neuropsychological and electrophysiological improvements after series of 20 and 60 treatments, although the first dosage appeared to be insufficient to produce permanent benefits. Longitudinal studies using different treatment parameters should be conducted if we are to systematically investigate long-term improvements resulting from HBO(2) therapy.

Our ability to discriminate and recognize human voices is amongst the most important functions of the human auditory system. The current study sought to determine whether electrophysiological markers could be used as objective measures of voice familiarity, by looking at the electrophysiological responses [mismatch negativity (MMN) and P3a] when the infrequent stimulus presented is a familiar voice as opposed to an unfamiliar voice. Results indicate that the MMN elicited by a familiar voice is greater than that elicited by an unfamiliar voice at FCz. The familiar voice also produced a greater P3a wave than that triggered by the unfamiliar voice at Fz. As both the MMN and the P3a were elicited as participants were instructed not to pay attention to incoming stimulation, these findings suggest that voice recognition is a particularly potent preattentive process whose neural representations can be objectively described through electrophysiological assessments.

Background: Osteopenia has been reported in children surviving acute lymphoblastic leukemia and brain tumors, apparently as a consequence of therapy. It has been suggested that cranial irradiation may play a role in the development of this complication. In order to explore that possibility, we examined survivors of brain tumors treated with and without radiation in childhood to investigate associations between radiation, osteopenia, physical activity, health status and overall health-related quality of life (HRQL)., Procedure: Subjects were survivors of posterior fossa tumors (astrocytoma or medulloblastoma) or optic glioma, < 18 years of age at diagnosis and > 1 year off treatment. Measurements of growth velocity, body composition, bone densitometry, physical activity and HRQL were undertaken., Results: Twenty-five (62.5%) of the 40 eligible patients participated in the study. Of the 25 patients, 12 (48%) received radiation therapy (R group) while 13 received no radiation (NR group). Growth hormone (GH) deficiency had been detected in three subjects, one had completed GH therapy while two were still on hormone replacement. The prevalence of osteopenia was 44% in the entire group, and 67% versus 27% in the R and NR groups. Florid osteoporosis was present in 20% of the entire group, more than 40% of the R group but none of the NR group. A significant correlation (P < 0.01) was observed between overall HRQL and Z scores of bone mineral density (BMD) of the lumbar spine. Pain and ambulation/mobility utility scores correlated significantly (P < 0.05) with BMD, while levels of physical activity correlated (P < 0.05) with overall HRQL utility scores., Conclusions: This pilot study demonstrates that in survivors of brain tumors treated in childhood, radiation therapy is associated with significant loss of bone mineral. Among these survivors, HRQL is less, pain is more severe and ambulation is more restricted in those with low BMD scores. The reduction in HRQL is reflected in diminished physical activity. A larger multi-center study is needed to confirm these results.

Since there is almost no information on whether the concomitant use of diagnostic radioisotopes and radiographic contrast media interferes with dual-energy X-ray absorptiometry (DXA), we investigated these potentially confounding effects. At routine scheduled radiographic follow-up, 40 patients previously treated for malignant lymphomas or solid tumors in Hamilton and Ottawa, Canada were evaluated, 10 in each of the following 4 categories of diagnostic procedure: (1) computed tomography (CT) with intravenous, iodine-based contrast (+/-oral contrast), (2) magnetic resonance imaging (MRI) with gadolinium-based contrast, (3) gallium scan (GS), and (4) technetium bone scan (TBS). Whole body bone mineral content (WB-BMC) and lumbar spine bone mineral density (LS-BMD), total fat mass (TFM), and lean body mass (LBM) were measured by DXA immediately before and after the other radiological studies (on the same day) and then 7 days later. No statistically significant differences were found among WB-BMC, LS-BMD, TFM, and LBM Z-scores immediately before and after MRI, GS, TBS, and 7 days later. The DXA measurements performed immediately before and after CT showed statistically significant differences in WB-BMC (100% vs 124.5%, p<0.001), TFM (100% vs 75.4%, p<0.001), and LBM (100% vs 110%, p<0.001), resulting from the CT contrast agents compromising the precision of the DXA. The DXA results after 7 days were not statistically different from those at baseline. Dual-energy X-ray absorptiometry can be performed in association with other radiological techniques, with the exception of CT conducted with contrast within 1 week. This study provides information that applies not only to patients with cancer but to the general population undergoing diagnostic procedures.

Lumbar spine and mid-radius bone mineral density was measured repeatedly in 48 postmenopausal women who completed 7 years of taking either a 500 mg x day(-1) calcium supplement (n = 22) or calcium supplementation with hormone replacement therapy. The hormone replacement was either a low dose (n = 15) or a moderate dose (n = regime. The purpose of the measurements was to establish the long-term pattern of change in bone mineral mass produced by continued hormone replacement. The calcium-only group lost bone mineral mass at the radius, while the spine, bone was preserved. Low dose hormone replacement preserved radius bone. Moderate dose replacement increased bone mineral mass at the spine and preserved radius bone.

Physical and lifestyle data were collected from 62 postmenopausal women who had declined hormone replacement therapy. Potential predictor variables were examined for their associations with bone mineral density (BMD) of the lumbar spine and femoral neck as assessed by dual x-ray absorptiometry. Body weight demonstrated the strongest association with lumbar BMD; lean body mass demonstrated the strongest association with femoral BMD. Together with the natural logarithm of the number of years since menopause (ln YSM) these anthropometric variables explained 36 and 34% of the variability of femoral and lumbar BMD, respectively. Serum estradiol levels demonstrated a weak positive association with BMD, which lost statistical significance after adjustment for body mass. Similarly, cardiovascular fitness was positively associated with femoral BMD prior to but not following adjustment for body mass. Controlling for years since menopause and body mass, the product of dietary calcium and calcium absorption demonstrated a weak positive correlation with femoral BMD (partial r = 0.30). The intake of tea was positively and significantly associated with both bone density measurements. In multiple regression analysis, femoral BMD was best explained by the lean body mass, ln YSM, and the daily intake of tea (r2 = 0.50). Similarly, lumbar BMD was best explained by body weight, ln YSM, and intake of tea (r2 = 0.44). Body mass is a major predictor of postmenopausal bone density at the hip and spine. A positive association between dietary calcium and BMD was detected only by taking into account the intestinal absorptive efficiency.

The authors studied the effects of peritoneal macrophages on the growth of HP2 cells, a continuous line isolated from the transplanted Harding-Passey mouse melanoma. They found that normal peritoneal macrophages can exert a strong cytostatic effect on HP2 cells, as expressed by cell number and tritiated thymidine uptake by the target cells. The data indicates that normal heat inactivated sera from various species can render macrophages cytostatic. In addition, normal serum can amplify the cytostatic properties of macrophages from immunized animals. The results are discussed in the light of present knowledge of macrophage metabolism.

A simple and inexpensive method to assess the contamination of environmental surfaces and the associated potential risk of exposure of autopsy room personnel to potentially hazardous materials is described. Blood was selected as a marker of contamination and HEMASTIX reagent strips were used to determine its presence on selected surfaces. The surfaces selected for examination typically do not come into direct contact with cadavers or tissues during a routine postmortem examination and thus are not included in routine cleanup. We documented the presence of blood on a variety of environmental surfaces in the autopsy suite and suggest that the contamination resulted from a breakdown in good work practices, most probably the indiscriminate handling or touching of materials and equipment with contaminated gloves. The risk of exposure to blood by the indirect route was deemed significant. The results of this study underscore the importance of establishing and consistently following good work practices and cleanup procedures to minimize the risk of exposure to blood before, during, and after postmortem examinations.