RESUMO
BACKGROUND: Recent studies of photobiomodulation (PBM) in patients with cognitive or psychological disorders (including traumatic brain injury, stroke, and dementia) have yielded some encouraging results. OBJECTIVE: In this study, we aimed to investigate the effect of a single stimulation on memory in older adults with mild cognitive impairment (MCI). METHODS: After PBM, hemodynamic changes, as a measure of functional brain activity, were evaluated using functional near-infrared spectroscopy (fNIRS). Eighteen subjects who met the criteria of MCI were randomly assigned to control and experimental groups. A single real or sham PBM session was administered to the forehead of each patient in the experimental and control groups, respectively. All subjects performed a visual memory span test before and after the stimulation, and their hemodynamic responses during the tasks were measured using fNIRS. RESULTS: The results showed that among the MCI subjects, only those who received PBM, but not those who received the sham stimulation, demonstrated significant improvement in the visual memory performance and a reduction in the hemodynamic response during the tasks. CONCLUSION: These findings suggest that PBM may reduce the cognitive efforts needed to complete tasks that require high memory loads, and thus improve the cognitive performance of individuals with MCI.
Assuntos
Disfunção Cognitiva/terapia , Terapia com Luz de Baixa Intensidade , Memória de Curto Prazo/efeitos da radiação , Espectroscopia de Luz Próxima ao Infravermelho , Idoso , Cognição/efeitos da radiação , Feminino , Hemodinâmica/efeitos da radiação , Humanos , Masculino , Testes Neuropsicológicos/estatística & dados numéricosRESUMO
Radiation exposure has multiple effects on the brain, behavior and cognitive functions. It has been reported that high-dose (>20 Gy) radiation-induced behavior and cognitive aberration partly associated with severe tissue destruction. Low-dose (<3 Gy) exposure can occur in radiological disasters and cerebral endovascular treatment. However, only a few reports analyzed behavior and cognitive functions after low-dose irradiation. This study was undertaken to assess the relationship between brain neurochemistry and behavioral disruption in irradiated mice. The irradiated mice (0.5 Gy, 1 Gy and 3 Gy) were tested for alteration in their normal behavior over 10 days. A serotonin (5-HT), Dopamine, gamma-Aminobutyric acid (GABA) and cortisol analysis was carried out in blood, hippocampus, amygdala and whole brain tissue. There was a significant decline in the exploratory activity of mice exposed to 3 Gy and 1 Gy radiation in an open field test. We observed a significant short-term memory loss in 3 Gy and 1 Gy irradiated mice in Y-Maze. Mice exposed to 1 Gy and 3 Gy radiation exhibited increased anxiety in an elevated plus maze (EPM). The increased anxiety and memory loss patterns were also seen in 0.5 Gy irradiated mice, but the results were not statistically significant. In this study we observed that neurotransmitters are significantly altered after irradiation, but the neuronal cells in the hippocampus were not significantly affected. This study suggests that the low-dose radiation-induced cognitive impairment may be associated with the neurochemical in low-dose irradiation and unlike the high-dose scenario might not be directly related to the morphological changes in the brain.
Assuntos
Comportamento Animal/efeitos da radiação , Encéfalo/efeitos da radiação , Animais , Química Encefálica/efeitos da radiação , Cognição/efeitos da radiação , Dopamina/análise , Dopamina/sangue , Relação Dose-Resposta à Radiação , Hipocampo/química , Hipocampo/efeitos da radiação , Hidrocortisona/análise , Hidrocortisona/sangue , Masculino , Aprendizagem em Labirinto/efeitos da radiação , Memória de Curto Prazo/efeitos da radiação , Camundongos , Camundongos Endogâmicos C57BL , Teste de Campo Aberto/efeitos da radiação , Distribuição Aleatória , Serotonina/análise , Serotonina/sangue , Comportamento Espacial/efeitos da radiação , Ácido gama-Aminobutírico/análise , Ácido gama-Aminobutírico/sangueRESUMO
OBJECTIVES: Exposure to light can have acute alerting and circadian phase-shifting effects. This study investigated the effects of evening exposure to blue-enriched polychromatic white (BEL) vs. polychromatic white light (WL) on sleep inertia dissipation the following morning in older adults. METHODS: Ten healthy older adults (average ageâ¯=â¯63.3 yrs; 6F) participated in a 13-day study comprising three baseline days, an initial circadian phase assessment, four days with 2-h evening light exposures, a post light exposure circadian phase assessment and three recovery days. Participants were randomized to either BEL or WL of the same irradiance for the four evening light exposures. On the next mornings at 2, 12, 22 and 32â¯min after each wake time, the participants completed a 90-s digit-symbol substitution test (DSST) to assess working memory, and objective alertness was assessed using a wake EEG recording. DSST and power density from the wake EEG recordings were compared between the two groups. RESULTS: DSST performance improved with time awake (pâ¯<â¯0.0001) and across study days in both light exposure groups (pâ¯<â¯0.0001). There was no main effect of group, although we observed a significant day x group interaction (pâ¯=â¯0.0004), whereby participants exposed to BEL performed significantly better on the first two mornings after light exposures than participants in WL (post-hoc, pâ¯<â¯0.05). On those days, the BEL group showed higher EEG activity in some of the frequency bins in the sigma and beta range (pâ¯<â¯0.05) on the wake EEG. CONCLUSION: Exposure to blue-enriched white light in the evening significantly improved DSST performance the following morning when compared to polychromatic white light. This was associated with a higher level of objective alertness on the wake EEG, but not with changes in sleep or circadian timing.
Assuntos
Cognição/efeitos da radiação , Fototerapia/métodos , Idoso , Atenção/efeitos da radiação , Ritmo Circadiano , Cor , Cromoterapia/métodos , Feminino , Humanos , Luz , Iluminação/métodos , Masculino , Memória de Curto Prazo/fisiologia , Memória de Curto Prazo/efeitos da radiação , Pessoa de Meia-Idade , Sono , VigíliaRESUMO
We investigated the effects of light wavelengths on cortical oscillatory activity associated with working memory processes. Cortical activity responses were measured using magnetoencephalography (MEG) while participants performed an auditory Sternberg memory task during exposure to light of different wavelength. Each trial of the memory task consisted of four words presented as a memory set and one word presented as a probe. All words were presented audibly. Participants were instructed to indicate whether the probe word was or was not presented within the memory set. A total of 90 trials were conducted under the light exposure. Event-related synchronization (ERS) and event-related desynchronization responses in the alpha frequency range during the task were analyzed. Results showed that, during memory encoding, ERS responses were significantly greater in the short-wavelength (blue) light condition than in the middle-wavelength (green) light condition, approximately 20-30min after the onset of light exposure. Behavioral performance was very high throughout the experiment and there was no difference between the light conditions. Although the light effects were not observed in behavior, the result of ERS suggests that 20-30min of exposure to blue light enhances cortical activity related to active memory maintenance and/or attention to auditory stimuli.
Assuntos
Sincronização Cortical/fisiologia , Potenciais Evocados/fisiologia , Luz , Magnetoencefalografia , Memória de Curto Prazo/fisiologia , Estimulação Acústica , Adulto , Análise de Variância , Mapeamento Encefálico , Sincronização Cortical/efeitos da radiação , Eletroencefalografia , Humanos , Masculino , Memória de Curto Prazo/efeitos da radiação , Aprendizagem Verbal , Vocabulário , Adulto JovemRESUMO
Fourteen healthy right-handed subjects were scanned using PET with a [15O]water tracer during exposure to electromagnetic field (EMF) emitted by a mobile phone and a sham-exposure under double-blind conditions. During scanning, the subjects performed a visual working memory task. Exposure to an active mobile phone produced a relative decrease in regional cerebral blood flow (rCBF) bilaterally in the auditory cortex but no rCBF changes were observed in the area of maximum EMF. It is possible that these remote findings were caused by the EMF emitted by the active mobile phone. A more likely interpretation of the present findings were a result of an auditory signal from the active mobile phone. Therefore, it is not reasoned to attribute this finding to the EMF emitted by the phone. Further study on human rCBF during exposure to EMF of a mobile phone is needed.
Assuntos
Córtex Auditivo/efeitos da radiação , Telefone Celular , Circulação Cerebrovascular/efeitos da radiação , Campos Eletromagnéticos/efeitos adversos , Estimulação Acústica , Adulto , Artefatos , Córtex Auditivo/diagnóstico por imagem , Córtex Auditivo/fisiologia , Percepção Auditiva/fisiologia , Percepção Auditiva/efeitos da radiação , Circulação Cerebrovascular/fisiologia , Humanos , Masculino , Memória de Curto Prazo/fisiologia , Memória de Curto Prazo/efeitos da radiação , Testes Neuropsicológicos , Estimulação Luminosa , Tomografia Computadorizada de EmissãoRESUMO
There is some concern that short-term memory loss or other cognitive effects may be associated with the use of mobile cellular telephones. In this experiment, the effect of repeated, acute exposure to a low intensity 900 MHz radiofrequency (RF) field pulsed at 217 Hz was explored using an appetitively-motivated spatial learning and working memory task. Adult male C57BL/6J mice were exposed under far field conditions in a GTEM cell for 45 min each day for 10 days at an average whole-body specific energy absorption rate (SAR) of 0.05 W/kg. Their performance in an 8-arm radial maze was compared to that of sham-exposed control animals. All behavioral assessments were performed without handlers having knowledge of the exposure status of the animals. Animals were tested in the maze immediately following exposure or after a delay of 15 or 30 min. No significant field-dependent effects on performance were observed in choice accuracy or in total times to complete the task across the experiment. These results suggest that exposure to RF radiation simulating a digital wireless telephone (GSM) signal under the conditions of this experiment does not affect the acquisition of the learned response. Further studies are planned to explore the effects of other SARs on learned behavior. Bioelectromagnetics 21:151-158, 2000. Published 2000 Wiley-Liss, Inc.