RESUMO
Associative memory (AM) reflects the ability to remember and retrieve multiple pieces of information bound together thus enabling complex episodic experiences. Despite growing interest in the use of transcranial direct current stimulation (tDCS) for the modulation of AM, there are inconsistent evidence regarding its benefits. An alternative to standard constant tDCS could be the application of frequency-modulated tDCS protocols, that mimic natural function-relevant brain rhythms. Here, we show the effects of anodal tDCS oscillating in theta rhythm (5 Hz; 1.5 ± 0.1 mA) versus constant anodal tDCS and sham over left posterior parietal cortex on cued recall of face-word associations. In a crossover design, each participant completed AM assessment immediately following 20-min theta-oscillatory, constant, and sham tDCS, as well as 1 and 5 days after. Theta oscillatory tDCS increased initial AM performance in comparison to sham, and so did constant tDCS. On the group level, no differences between oscillatory and constant tDCS were observed, but individual-level analysis revealed that some participants responded to theta-oscillatory but not to constant tDCS, and vice versa, which could be attributed to their different physiological modes of action. This study shows the potential of oscillatory tDCS protocols for memory enhancement to produce strong and reliable memory-modulating effects which deserve to be investigated further.
Assuntos
Cognição/fisiologia , Lobo Parietal/fisiologia , Córtex Pré-Frontal/fisiologia , Ritmo Teta/fisiologia , Adulto , Cognição/efeitos da radiação , Feminino , Humanos , Masculino , Memória , Rememoração Mental/fisiologia , Rememoração Mental/efeitos da radiação , Lobo Parietal/diagnóstico por imagem , Lobo Parietal/efeitos da radiação , Córtex Pré-Frontal/efeitos da radiação , Ritmo Teta/efeitos da radiação , Estimulação Transcraniana por Corrente Contínua/métodos , Adulto JovemRESUMO
Creativity pervades many areas of everyday life and is considered highly relevant in several human living domains. Previous literature suggests that the posterior parietal cortex (PPC) is related to creativity. However, none of previous studies have compared the effect of transcranial random noise stimulation (tRNS) over bilateral PPC on both verbal and visual divergent thinking (DT) and Remote Associates Test (RAT) in the same experimental design. Forty healthy participants were randomly assigned to tRNS (100-500 Hz) over bilateral PPC or sham group, for 15 min and current was set at 1.5 mA. Participants' creativity skills were assessed before and after brain stimulation with the Unusual Uses and the Picture Completion subtests from the Torrance Test of Creative Thinking and the RAT. ANCOVA (baseline scores as covariate) results indicated that tRNS group had significantly higher scores at post-test in RAT and visual originality compared to sham group. Unusual Uses, on the other hand, was not significant. Improvement in RAT suggests the involvement of PPC during via insight solution which may reflect internally directed attention that helps the recombination of remotely associated information. The improvement in visual originality dimension from DT may be due to a higher internally directed attention while reducing externally oriented attention.
Assuntos
Cognição/fisiologia , Lobo Parietal/fisiologia , Pensamento/efeitos da radiação , Estimulação Transcraniana por Corrente Contínua/efeitos adversos , Adulto , Atenção/fisiologia , Atenção/efeitos da radiação , Cognição/efeitos da radiação , Criatividade , Feminino , Voluntários Saudáveis , Humanos , Masculino , Testes Neuropsicológicos , Lobo Parietal/efeitos da radiação , Adulto JovemRESUMO
Recent research indicates that tinnitus is related to alterations of neural networks including temporal, parietal, and prefrontal brain regions. The current study examines a rTMS protocol which targets three central nodes of these networks in a two-arm randomized parallel group trial. Overall, 49 patients with chronic tinnitus were randomized to receive either triple-site stimulation (left dorsolateral prefrontal stimulation, 1000 pulses, 20 Hz plus left and right temporoparietal stimulation, 1000 pulses each, 1 Hz) or single-site stimulation (left temporoparietal stimulation, 3000 pulses, 1 Hz). Both groups were treated in ten sessions. Tinnitus severity as measured by the tinnitus questionnaire was assessed before rTMS (day1), after rTMS (day12) and at two follow-up visits (day 90 and day 180). The triple-site protocol was well tolerated. There was a significant reduction in tinnitus severity for both treatment groups. The triple-site group tended to show a more pronounced treatment effect at day 90. However, the measurement time point x group interaction effect was not significant. The current results confirm former studies that indicated a significant reduction of tinnitus severity after rTMS treatment. No significant superiority of the multisite protocol was observed. Future approaches for the enhancement of treatment effects are discussed.
Assuntos
Lobo Parietal/efeitos da radiação , Córtex Pré-Frontal/efeitos da radiação , Lobo Temporal/efeitos da radiação , Zumbido/terapia , Estimulação Magnética Transcraniana/métodos , Adulto , Doença Crônica , Feminino , Audição , Humanos , Masculino , Pessoa de Meia-Idade , Rede Nervosa/fisiologia , Resultado do TratamentoRESUMO
The current report assessed the effects of low-level proton irradiation in inbred adult male Fischer 344 and Lewis rats performing an analog of the human Psychomotor Vigilance Test (PVT), commonly utilized as an object risk assessment tool to quantify fatigue and sustained attention in laboratory, clinical, and operational settings. These strains were used to determine if genetic differences in dopaminergic function would impact radiation-induced deficits in sustained attention. Exposure to head-only proton irradiation (25 or 100 cGy) disrupted rPVT performance in a strain-specific manner, with 25 cGy-exposed Fischer 344 rats displaying the most severe deficits in sustained attention (i.e., decreased accuracy and increased premature responding); Lewis rats did not display behavioral deficits following radiation. Fischer 344 rats displayed greater tyrosine hydroxylase and dopamine transporter levels in the frontal cortex compared to the Lewis rats, even though radiation exposure increased both of these proteins in the Lewis rats only. Tyrosine hydroxylase was decreased in the parietal cortex of both rat strains following radiation exposure, regardless of proton dose. Strain-specific cytokine changes were also found in the frontal cortex, with the Lewis rats displaying increased levels of putative neurotrophic cytokines (e.g., CNTF). These data support the hypothesis that basal dopaminergic function impacts the severity of radiation-induced deficits in sustained attention.
Assuntos
Atenção/efeitos da radiação , Encéfalo/efeitos da radiação , Proteínas da Membrana Plasmática de Transporte de Dopamina/metabolismo , Dopamina/metabolismo , Prótons , Tirosina 3-Mono-Oxigenase/metabolismo , Animais , Atenção/fisiologia , Western Blotting , Encéfalo/metabolismo , Fator Neurotrófico Ciliar/metabolismo , Citocinas/metabolismo , Lobo Frontal/metabolismo , Lobo Frontal/efeitos da radiação , Humanos , Masculino , Lobo Parietal/metabolismo , Lobo Parietal/efeitos da radiação , Ratos , Ratos Endogâmicos F344 , Ratos Endogâmicos Lew , Especificidade da EspécieAssuntos
Neoplasias Encefálicas/patologia , Neurilemoma/patologia , Lobo Parietal/patologia , Neoplasias Encefálicas/radioterapia , Neoplasias Encefálicas/cirurgia , Criança , Feminino , Humanos , Neurilemoma/radioterapia , Neurilemoma/cirurgia , Lobo Parietal/efeitos da radiação , Lobo Parietal/cirurgiaRESUMO
OBJECTIVE: To visualize the dynamic expression of endothelial barrier antigen (EBA) and S100B in the rat parietal cortex at the acute phase of radiation-induced brain injury using computed tomography (CT). METHODS: A rat model of brain injury was established by CT scanning. The expression of EBA and S100B in the parietal cortex was analyzed at different time points by immunohistochemistry (IHC) and western blotting. RESULTS: Significantly increased EBA expression was detected in the animals in the control group compared with the animals receiving CT radiation, which exhibited significantly reduced EBA levels within the vessel walls (F=33.29, p<0.05), particularly at day 3 after radiation. Both immunohistochemical staining and western blot analysis indicated that the positive expression levels of S100B among radiation groups were increased compared with the control group (IHC, F=28.05, p<0.05; WB, F=175.3, p<0.05). The expression of S100B peaked at day 3 (IHC, 102718±8710; WB, 2320±0.129), and subsequently decreased. CONCLUSION: CT radiation can induce altered EBA and S100B protein expression. Decreased EBA expression levels indicated that the integrity of the blood-brain barrier (BBB) was affected by radiation. The destruction of the BBB and the expression of S100B might play important roles in the incidence and repair of the early radiation-induced brain injury, and radiation represents a cause of mental disorders.
Assuntos
Antígenos de Superfície/metabolismo , Regulação da Expressão Gênica/efeitos da radiação , Lobo Parietal/efeitos da radiação , Radiação , Subunidade beta da Proteína Ligante de Cálcio S100/metabolismo , Análise de Variância , Animais , Masculino , Ratos , Ratos Sprague-Dawley , Fatores de TempoRESUMO
Atypical teratoid/rhabdoid tumours (ATRT) of the central nervous system are uncommon embryonal carcinomas that predominantly affect infants and young children, and less commonly adults. We report a 58 year old woman who presented with ATRT involving the right parietal lobe which was treated with surgery and adjuvant radiotherapy. Her history was significant for soft tissue sarcoma of the right ear treated with surgery and adjuvant radiotherapy at age 3, thus raising the possibility of radiation-induced aetiology.
Assuntos
Neoplasias Encefálicas/etiologia , Tumor Rabdoide/etiologia , Neoplasias Encefálicas/cirurgia , Feminino , Humanos , Imageamento por Ressonância Magnética , Pessoa de Meia-Idade , Lobo Parietal/patologia , Lobo Parietal/efeitos da radiação , Tumor Rabdoide/cirurgia , Sarcoma/radioterapia , Neoplasias Cutâneas/radioterapia , Tomógrafos ComputadorizadosRESUMO
The extracellular matrix metalloproteinase inducer (EMMPRIN) has been known to play a key regulatory role in pathological angiogenesis. A elevated activation of vascular endothelial growth factor (VEGF) following radiation injury has been shown to mediate blood-brain barrier (BBB) breakdown. However, the roles of EMMPRIN and VEGF in radiation-induced brain injury after gamma knife surgery (GKS) are not clearly understood. In this study, we investigated EMMPRIN changes in a rat model of radiation injury following GKS and examined potential associations between EMMPRIN and VEGF expression. Adult male rats were subjected to cerebral radiation injury by GKS under anesthesia. We found that EMMPRIN and VEGF expression were markedly upregulated in the target area at 8-12 weeks after GKS compared with the control group by western blot, immunohistochemistry, and RT-PCR analysis. Immunofluorescent double staining demonstrated that EMMPRIN signals colocalized with caspase-3 and VEGF-positive cells. Our data also demonstrated that increased EMMPRIN expression was correlated with increased VEGF levels in a temporal manner. This is the first study to show that EMMPRIN and VEGF may play a role in radiation injuries of the central nervous system after GKS.
Assuntos
Basigina/metabolismo , Encéfalo/efeitos da radiação , Raios gama/efeitos adversos , Fator A de Crescimento do Endotélio Vascular/metabolismo , Animais , Encéfalo/irrigação sanguínea , Encéfalo/metabolismo , Encéfalo/patologia , Lesões Encefálicas/metabolismo , Lesões Encefálicas/patologia , Caspase 3/metabolismo , Imuno-Histoquímica , Masculino , Microscopia Eletrônica de Transmissão , Lobo Parietal/metabolismo , Lobo Parietal/patologia , Lobo Parietal/efeitos da radiação , Lesões Experimentais por Radiação/metabolismo , Radiocirurgia/efeitos adversos , Ratos , Ratos Wistar , Fatores de TempoRESUMO
Neuroimaging studies have shown both dorsolateral prefrontal (DLPFC) and inferior parietal cortex (iPARC) activation during probabilistic association learning. Whether these cortical brain regions are necessary for probabilistic association learning is presently unknown. Participants' ability to acquire probabilistic associations was assessed during disruptive 1 Hz repetitive transcranial magnetic stimulation (rTMS) of the left DLPFC, left iPARC, and sham using a crossover single-blind design. On subsequent sessions, performance improved relative to baseline except during DLPFC rTMS that disrupted the early acquisition beneficial effect of prior exposure. A second experiment examining rTMS effects on task-naive participants showed that neither DLPFC rTMS nor sham influenced naive acquisition of probabilistic associations. A third experiment examining consecutive administration of the probabilistic association learning test revealed early trial interference from previous exposure to different probability schedules. These experiments, showing disrupted acquisition of probabilistic associations by rTMS only during subsequent sessions with an intervening night's sleep, suggest that the DLPFC may facilitate early access to learned strategies or prior task-related memories via consolidation. Although neuroimaging studies implicate DLPFC and iPARC in probabilistic association learning, the present findings suggest that early acquisition of the probabilistic cue-outcome associations in task-naive participants is not dependent on either region.
Assuntos
Aprendizagem por Associação/fisiologia , Lobo Parietal/fisiologia , Córtex Pré-Frontal/fisiologia , Aprendizagem por Probabilidade , Adolescente , Adulto , Aprendizagem por Associação/efeitos da radiação , Estudos Cross-Over , Feminino , Humanos , Estudos Longitudinais , Masculino , Lobo Parietal/anatomia & histologia , Lobo Parietal/efeitos da radiação , Córtex Pré-Frontal/anatomia & histologia , Córtex Pré-Frontal/efeitos da radiação , Estudos Prospectivos , Método Simples-Cego , Estimulação Magnética Transcraniana/efeitos adversos , Estimulação Magnética Transcraniana/métodos , Adulto JovemRESUMO
Few studies have shown that local exposure to radiofrequency electromagnetic fields (RF) induces intensity-dependent physiological changes, especially in the brain. The aim of the present study was to detect reproducible responses to local RF exposure in the parietal cortex of anesthetized rats and to determine their dependence on RF intensity. The target cortex tissue was locally exposed to 2-GHz RF using a figure-eight loop antenna within a range of averaged specific absorption rates (10.5, 40.3, 130, and 263 W/kg averaged over 4.04 mg) in the target area. Local cerebral blood flow (CBF) and temperatures in three regions (target area, rectum, and calf hypodermis) were measured using optical fiber blood flow meters and thermometers during RF exposure. All parameters except for the calf hypodermis temperature increased significantly in exposed animals compared with sham-exposed ones during 18-min exposures. Dependence of parameter values on exposure intensity was analyzed using linear regression models. The elevation of local CBF was correlated with temperature rise in both target and rectum at the end of RF exposure. However, the local CBF elevation seemed to be elevated by the rise in target temperature, but not by that of the rectal temperature, in the early part of RF exposure or at low-intensity RF exposure. These findings suggest that local RF exposure of the rat cortex drives a regulation of CBF accompanied by a local temperature rise, and our findings may be helpful for discussing physiological changes in the local cortex region, which is locally exposed to RF.
Assuntos
Temperatura Corporal/fisiologia , Circulação Cerebrovascular/fisiologia , Circulação Cerebrovascular/efeitos da radiação , Lobo Parietal/fisiologia , Animais , Temperatura Corporal/efeitos da radiação , Relação Dose-Resposta à Radiação , Campos Eletromagnéticos , Exposição Ambiental , Masculino , Lobo Parietal/efeitos da radiação , Doses de Radiação , Ondas de Rádio , Ratos , Ratos Sprague-DawleyRESUMO
Radionecrosis with brain edema is a complication of radiosurgery. Three female patients harbouring a frontal pole, petrous and parasagital parietoocipital meningiomas respectively who had been treated with LINAC radiosurgery are presented. Those patients developed, between two and eight months later, a severe symptomatic radionecrosis with a huge brain edema resistant to the usual steroid therapy. Only after 40 sessions of hyperbaric oxygen, a good remission of the lesions was obtained. There are few cases reported in the literature with such a good outcome. Consequentely, this therapy must be taken into account to treat this type of radiosurgical complication before considering surgery.
Assuntos
Edema Encefálico/terapia , Lesões Encefálicas/terapia , Oxigenoterapia Hiperbárica , Lesões por Radiação/terapia , Radiocirurgia/efeitos adversos , Idoso , Dano Encefálico Crônico/etiologia , Dano Encefálico Crônico/prevenção & controle , Edema Encefálico/etiologia , Edema Encefálico/patologia , Lesões Encefálicas/etiologia , Lesões Encefálicas/patologia , Neoplasias Cerebelares/cirurgia , Ângulo Cerebelopontino/patologia , Ângulo Cerebelopontino/efeitos da radiação , Endotélio Vascular/patologia , Endotélio Vascular/efeitos da radiação , Feminino , Humanos , Imageamento por Ressonância Magnética , Neoplasias Meníngeas/cirurgia , Meningioma/cirurgia , Pessoa de Meia-Idade , Necrose , Lobo Parietal/patologia , Lobo Parietal/efeitos da radiação , Lesões por Radiação/etiologia , Lesões por Radiação/patologia , Resultado do TratamentoRESUMO
Audio-visual stimuli typically yield faster responses than isolated modality-specific ones. This crossmodal speed advantage depends upon efficient multisensory integration mechanisms in the brain. Here, we used repetitive transcranial magnetic stimulation (rTMS) to address the role of the posterior parietal cortex, in particular of the inferior parietal lobule (IPL), in speeding up responses to crossmodal stimuli. The results show that rTMS over IPL impairs the response to contralateral modality-specific visual and auditory targets without affecting the response speed advantage following audio-visual targets. Furthermore, this speed advantage is subserved by a neural coactivation mechanism suggesting a summation in a given neural site. Control rTMS over V1 impaired only contralateral visual responses without affecting the response to auditory or audio-visual targets. These results suggest that the response speed advantage for crossmodal targets is maintained in spite of the IPL interference that impairs modality-specific responses. The possible role of alternative sites for the audio-visual advantage, such as the superior colliculus, is discussed.
Assuntos
Percepção Auditiva/fisiologia , Lobo Parietal/fisiologia , Tempo de Reação/fisiologia , Estimulação Magnética Transcraniana/métodos , Percepção Visual/fisiologia , Estimulação Acústica , Adulto , Vias Auditivas/fisiologia , Vias Auditivas/efeitos da radiação , Percepção Auditiva/efeitos da radiação , Lateralidade Funcional/fisiologia , Humanos , Testes Neuropsicológicos , Orientação/fisiologia , Lobo Parietal/anatomia & histologia , Lobo Parietal/efeitos da radiação , Estimulação Luminosa , Desempenho Psicomotor/fisiologia , Radiação , Tempo de Reação/efeitos da radiação , Percepção Espacial/fisiologia , Colículos Superiores/fisiologia , Córtex Visual/anatomia & histologia , Córtex Visual/fisiologia , Córtex Visual/efeitos da radiação , Vias Visuais/fisiologia , Vias Visuais/efeitos da radiação , Percepção Visual/efeitos da radiação , Adulto JovemRESUMO
Phosphenes represent a perceptual effect of transcranial magnetic stimulation (TMS) or electric stimulation of visual cortical areas. One likely neural basis for the generation of static phosphenes is the primary visual cortex (V1) although evidence is controversial. A peculiar feature of V1 is that it has sparse callosal connections with the exception of a central portion of visual field representation. In contrast, visually responsive cortical areas in the parietal lobe have widespread callosal connections. Thus, interhemispheric transfer (IT) time of off-centre phosphenes should be slower when generated by V1 than by visual parietal areas. To verify this possibility, in Exp. 1 we measured IT of phosphenes generated by TMS applied to V1 and in Exp. 2 we measured IT of phosphenes obtained by TMS applied to posterior parietal cortex. In both experiments, we obtained static bright circular phosphenes appearing in the contralateral hemifield. We measured IT time behaviorally by comparing unimanual simple reaction time to the onset of a phosphene under crossed or uncrossed hemifield-hand condition (Poffenberger paradigm). In keeping with our prediction, we found a substantially longer IT time for V1 than for parietal phosphenes. Additionally, an IT similar to that obtained with V1 stimulation was found when participants were asked to imagine the phosphenes previously experienced during TMS. In conclusion, the present results suggest that IT of phosphenes either generated by V1 TMS or imagined is subserved by slower callosal channels than those of real visual stimuli or parietal phosphenes.
Assuntos
Corpo Caloso/fisiologia , Lateralidade Funcional/fisiologia , Lobo Occipital/fisiologia , Lobo Parietal/fisiologia , Fosfenos/fisiologia , Córtex Visual/fisiologia , Adulto , Mapeamento Encefálico/métodos , Corpo Caloso/anatomia & histologia , Campos Eletromagnéticos , Feminino , Lateralidade Funcional/efeitos da radiação , Humanos , Masculino , Vias Neurais/anatomia & histologia , Vias Neurais/diagnóstico por imagem , Vias Neurais/fisiologia , Lobo Occipital/anatomia & histologia , Lobo Occipital/efeitos da radiação , Lobo Parietal/anatomia & histologia , Lobo Parietal/efeitos da radiação , Fosfenos/efeitos da radiação , Radiografia , Tempo de Reação/fisiologia , Fatores de Tempo , Estimulação Magnética Transcraniana , Córtex Visual/anatomia & histologia , Córtex Visual/efeitos da radiação , Percepção Visual/fisiologiaRESUMO
BACKGROUND: The term of low-grade glioma addresses a favorable clinical outcome with indolent histological features in general consideration; however, recent studies underline the inconsistency, which originates from the accumulation of different histologic subtypes in this terminology. The malignant transformation of a low-grade glioma is unusual but presents a poor prognosis. CASE HISTORY: We report a case of a 12-year-old boy, who was referred for complaints of recurrent seizures. His physical examination was unremarkable, but it was learned that a peripheral mass lesion located on the left posterior parietal lobe--which had been thought to be a low-grade glioma--had been detected on a magnetic resonance imaging 2 years ago at a different hospital. The patient was then treated with valproate and carbamazepine for the seizures and advised to be followed up without any additional diagnostic and therapeutic studies for his suspected low-grade glioma. A recent magnetic resonance imaging study showed enlargements of the mass and surrounding edema with additional necrosis. Surgical excision of the tumor was performed. After the diagnosis of glioblastoma multiforme, the patient received radiation therapy and chemotherapy with a good clinical recovery without any evidence of residue or recurrence at 12-month follow-up. CONCLUSION: The first line treatment modality in the management of low-grade glioma--especially in suitable patients--is clearly surgery. The gross total resection guarantees the distinguishing of the histological types of the low-grade gliomas and reflects the biologic behavior of these tumors. Observation without surgery must be reserved for selected inoperable cases.
Assuntos
Neoplasias Encefálicas/patologia , Glioblastoma/patologia , Glioma/patologia , Neoplasias Encefálicas/terapia , Criança , Terapia Combinada , Progressão da Doença , Glioblastoma/terapia , Glioma/terapia , Humanos , Imageamento por Ressonância Magnética/métodos , Masculino , Lobo Parietal/efeitos dos fármacos , Lobo Parietal/efeitos da radiação , Lobo Parietal/cirurgia , Prognóstico , Resultado do TratamentoRESUMO
The posterior parietal cortex (PPC) plays a role in spatial updating of goals for eye and arm movements across saccades, but less is known about its role in updating perceptual memory. We reported previously that transsaccadic memory has a capacity for storing the orientations of three to four Gabor patches either within a single fixation (fixation task) or between separate fixations (saccade task). Here, we tested the role of the PPC in transsaccadic memory in eight subjects by simultaneously applying single-pulse transcranial magnetic stimulation (TMS) over the right and left PPC, over several control sites, and comparing these to behavioral controls with no TMS. In TMS trials, we randomly delivered pulses at one of three different time intervals around the time of the saccade, or at an equivalent time in the fixation task. Controls confirmed that subjects could normally retain at least three visual features. TMS over the left PPC and a control site had no significant effect on this performance. However, TMS over the right PPC disrupted memory performance in both tasks. This TMS-induced effect was most disruptive in the saccade task, in particular when stimulation coincided more closely with saccade timing. Here, the capacity to compare presaccadic and postsaccadic features was reduced to one object, as expected if the spatial aspect of memory was disrupted. This finding suggests that right PPC plays a role in the spatial processing involved in transsaccadic memory of visual features. We propose that this process uses saccade-related feedback signals similar to those observed in spatial updating.
Assuntos
Transtornos da Memória/fisiopatologia , Memória/fisiologia , Lobo Parietal/fisiologia , Movimentos Sacádicos/fisiologia , Estimulação Magnética Transcraniana/métodos , Adulto , Mapeamento Encefálico , Campos Eletromagnéticos/efeitos adversos , Retroalimentação/fisiologia , Retroalimentação/efeitos da radiação , Feminino , Fixação Ocular/fisiologia , Fixação Ocular/efeitos da radiação , Lateralidade Funcional/fisiologia , Humanos , Masculino , Memória/efeitos da radiação , Transtornos da Memória/etiologia , Pessoa de Meia-Idade , Testes Neuropsicológicos , Lobo Parietal/efeitos da radiação , Reconhecimento Visual de Modelos/fisiologia , Reconhecimento Visual de Modelos/efeitos da radiação , Estimulação Luminosa , Movimentos Sacádicos/efeitos da radiação , Percepção Espacial/fisiologia , Percepção Espacial/efeitos da radiação , Fatores de Tempo , Estimulação Magnética Transcraniana/efeitos adversosRESUMO
BACKGROUND AND PURPOSE: Radiotherapy is an integral part of various therapeutic regimens in pediatric and adult oncology. Endocrine dysfunction, neurologic and psychiatric deficits, secondary malignancies and radiation-induced necrosis are well-known possible late effects of cranial irradiation. However, only sporadic cases of radiation-induced cavernous hemangiomas (RICH) have been reported so far. PATIENTS AND METHODS: Pediatric patients who underwent cranial radiation therapy for malignant diseases between January 1980 and December 2003 were retrospectively analyzed. After the end of therapy they entered a detailed follow-up program. RESULTS: Of 171 patients, eight (three patients with medulloblastoma, three patients with acute lymphoblastic leukemia, and one patient each with ependymoma and craniopharyngioma) developed intracerebral cavernoma 2.9-18.4 years after irradiation representing a cumulative incidence (according to the Kaplan-Meier method) of 2.24%, 3.86%, 4.95%, and 6.74% within 5, 10, 15, and 20 years following radiation therapy, respectively. In patients treated in the first 10 years of life, RICH occurred with shorter latency and significantly more often (p = 0.044) resulting in an even higher cumulative incidence. CONCLUSION: These findings and previously published cases show that cavernous hemangiomas may occur after irradiation of the brain several years after the end of therapy irrespective of the radiation dose and type of malignancy. Particularly children < 10 years of age at the time of irradiation are at higher risk. Since patients with RICH frequently do not show symptoms but hemorrhage is a possible severe complication, imaging of the central nervous system should be performed routinely for longer follow- ups, particularly in patients who were treated as young children.
Assuntos
Neoplasias Encefálicas/etiologia , Irradiação Craniana/efeitos adversos , Hemangioma Cavernoso do Sistema Nervoso Central/etiologia , Neoplasias Induzidas por Radiação/etiologia , Adolescente , Adulto , Neoplasias Encefálicas/diagnóstico , Neoplasias Encefálicas/radioterapia , Neoplasias Cerebelares/radioterapia , Criança , Pré-Escolar , Craniofaringioma/radioterapia , Ependimoma/radioterapia , Feminino , Seguimentos , Lobo Frontal/patologia , Lobo Frontal/efeitos da radiação , Hemangioma Cavernoso do Sistema Nervoso Central/diagnóstico , Humanos , Lactente , Imageamento por Ressonância Magnética , Masculino , Meduloblastoma/radioterapia , Neoplasias Induzidas por Radiação/diagnóstico , Lobo Parietal/patologia , Lobo Parietal/efeitos da radiação , Neoplasias Hipofisárias/radioterapia , Leucemia-Linfoma Linfoblástico de Células Precursoras/radioterapia , Dosagem Radioterapêutica , Fatores de Risco , Lobo Temporal/patologia , Lobo Temporal/efeitos da radiação , Tomografia Computadorizada por Raios XRESUMO
A possible dissociation of duration and numerosity processing was tested in an off-line repetitive transcranial magnetic stimulation (rTMS) design. Participants had to compare the numerosity of flashed dot sequences or the duration of single dot displays before and after 15 min of 1 Hz rTMS over one of three sites (the left or right intraparietal sulcus (IPS), or the vertex chosen as a control site). Compared to the control site, performance was only slowed down for the numerosity comparison task after the left IPS stimulation, whereas it was not affected for the duration comparison task for any of the parietal sites. These results show that the parietal area critically involved in numerosity processing is not involved in duration processing, revealing at least one cerebral site where duration and numerosity comparison processes dissociate.
Assuntos
Formação de Conceito/fisiologia , Discriminação Psicológica/fisiologia , Matemática , Lobo Parietal/fisiologia , Mascaramento Perceptivo/fisiologia , Percepção do Tempo/fisiologia , Adulto , Atenção/fisiologia , Formação de Conceito/efeitos da radiação , Discriminação Psicológica/efeitos da radiação , Feminino , Área de Dependência-Independência , Lateralidade Funcional/fisiologia , Lateralidade Funcional/efeitos da radiação , Humanos , Masculino , Lobo Parietal/efeitos da radiação , Estimulação Luminosa , Resolução de Problemas/fisiologia , Resolução de Problemas/efeitos da radiação , Valores de Referência , Percepção Espacial/fisiologia , Percepção Espacial/efeitos da radiação , Percepção do Tempo/efeitos da radiação , Estimulação Magnética Transcraniana/métodosRESUMO
PURPOSE: To test the hypothesis that fractional anisotropy (FA) is more severely reduced in white matter of the frontal lobe compared with the parietal lobe after receiving the same whole-brain irradiation dose in a cohort of childhood medulloblastoma survivors. METHODS AND MATERIALS: Twenty-two medulloblastoma survivors (15 male, mean [+/- SD] age = 12.1 +/- 4.6 years) and the same number of control subjects (15 male, aged 12.0 +/- 4.2 years) were recruited for diffusion tensor magnetic resonance imaging scans. Using an automated tissue classification method and the Talairach Daemon atlas, FA values of frontal and parietal lobes receiving the same radiation dose, and the ratio between them were quantified and denoted as FFA, PFA, and FA(f/p), respectively. The Mann-Whitney U test was used to test for significant differences of FFA, PFA, and FA(f/p) between medulloblastoma survivors and control subjects. RESULTS: Frontal lobe and parietal lobe white matter FA were found to be significantly less in medulloblastoma survivors compared with control subjects (frontal p = 0.001, parietal p = 0.026). Moreover, these differences were found to be discrepant, with the frontal lobe having a significantly larger difference in FA compared with the parietal lobe. The FA(f/p) of control and medulloblastoma survivors was 1.110 and 1.082, respectively (p = 0.029). CONCLUSION: Discrepant FA changes after the same irradiation dose suggest radiosensitivity of the frontal lobe white matter compared with the parietal lobe. Special efforts to address the potentially vulnerable frontal lobe after treatment with whole-brain radiation may be needed so as to balance disease control and treatment-related morbidity.
Assuntos
Neoplasias Cerebelares/radioterapia , Lobo Frontal/efeitos da radiação , Meduloblastoma/radioterapia , Lobo Parietal/efeitos da radiação , Tolerância a Radiação , Adolescente , Anisotropia , Estudos de Casos e Controles , Neoplasias Cerebelares/patologia , Criança , Irradiação Craniana/efeitos adversos , Irradiação Craniana/métodos , Estudos Transversais , Imagem de Difusão por Ressonância Magnética , Feminino , Lobo Frontal/patologia , Humanos , Masculino , Meduloblastoma/patologia , Lobo Parietal/patologia , Estatísticas não Paramétricas , SobreviventesRESUMO
BACKGROUND: Little is known about the immediate effects of whole-brain gamma-irradiation. The authors hypothesize that Egr1 as an immediate early gene and microglia both participate in early reactions. MATERIAL AND METHODS: Both, expression of Egr1 and cellular distribution were studied in a temporal sequence in different brain regions of rats subjected to irradiation with 10 Gy. Brain tissue was examined using immunohistochemistry, real-time RT-PCR (reverse transcription-polymerase chain reaction), and Western blotting. RESULTS: Astroglia and oligodendroglia showed increased Egr1 immunoreactivity within the first hours following irradiation. This was accompanied by a strong peak in CD68 immunoreactivity histologically attributable to activated microglia. A high constitutive expression of Egr1 protein in the nuclei of activated neurons was reduced following irradiation and RT-PCR demonstrated significantly reduced levels of egr1-lv as a neuronal activity-related mRNA variant. CONCLUSION: The induction of Egr1 in glial cells, as well as the activation of microglia take place earlier than histological changes reported so far. The authors revealed a temporal sequence of reactions that point toward the initiation of an immediate inflammatory response including reduced neuronal activity.
Assuntos
Encéfalo/efeitos da radiação , Irradiação Craniana/efeitos adversos , Proteína 1 de Resposta de Crescimento Precoce/genética , Microglia/efeitos da radiação , RNA Mensageiro/genética , Lesões Experimentais por Radiação/genética , Animais , Antígenos CD/genética , Antígenos de Diferenciação Mielomonocítica/genética , Astrócitos/patologia , Astrócitos/efeitos da radiação , Encéfalo/patologia , Núcleo Celular/patologia , Núcleo Celular/efeitos da radiação , Cerebelo/patologia , Cerebelo/efeitos da radiação , Citoplasma/patologia , Citoplasma/efeitos da radiação , Giro Denteado/patologia , Giro Denteado/efeitos da radiação , Lobo Frontal/patologia , Lobo Frontal/efeitos da radiação , Expressão Gênica/efeitos da radiação , Hipocampo/patologia , Hipocampo/efeitos da radiação , Masculino , Neurônios/patologia , Neurônios/efeitos da radiação , Lobo Parietal/patologia , Lobo Parietal/efeitos da radiação , Reação em Cadeia da Polimerase , Lesões Experimentais por Radiação/patologia , Ratos , Ratos Sprague-DawleyRESUMO
Reflexive spatial attention is critical for controlling perception and action. An established body of evidence suggests that mechanisms of spatial attention operate both within and between sensory modalities; however the attentional mechanisms that link modalities in the human brain are unclear. Here we used transcranial magnetic stimulation (TMS) to explore the role of the parietal cortex in coordinating reflexive shifts of spatial attention between vision and touch. In two experiments, healthy participants localised visual and somatosensory targets that were preceded by non-informative visual or somatosensory spatial cues. To determine the role of parietal cortex in spatial orienting, TMS was delivered synchronously with cue onset for 100 ms. Results revealed a critical role of the right angular gyrus and supramarginal gyrus in reflexive orienting to visual and somatosensory targets that followed a somatosensory cue. In contrast, the same TMS protocol was ineffective in modulating reflexive orienting based on visual cues. This dependence on cue modality may reflect subcortical redundancy of visual orienting mechanisms. Overall, our results indicate a critical role of the inferior parietal cortex in mediating reflexive shifts of attention within and between sensory modalities.