Mechanisms Of Spontaneous Recovery Research Articles

Brain network characteristics between subacute and chronic stroke survivors in active, imagery, passive movement task: a pilot study.

The activation patterns and functional network characteristics between stroke survivors and healthy individuals based on resting-or task-state neuroimaging and neurophysiological techniques have been extensively explored. However, the discrepancy between stroke patients at different recovery stages remains unclear. To investigate the changes in brain connectivity and network topology between subacute and chronic patients, and hope to provide a basis for rehabilitation strategies at different stages after stroke. Fifteen stroke survivors were assigned to the subacute group (SG, N = 9) and chronic group (CG, N = 6). They were asked to perform hand grasping under active, passive, and MI conditions when recording EEG. The Fugl-Meyer Assessment Upper Extremity subscale (FMA_UE), modified Ashworth Scale (MAS), Manual Muscle Test (MMT), grip and pinch strength, modified Barthel Index (MBI), and Berg Balance Scale (BBS) were measured. Functional connectivity analyses showed significant interactions on frontal, parietal and occipital lobes connections in each frequency band, particularly in the delta band. The coupling strength of premotor cortex, M1, S1 and several connections linked to frontal, parietal, and occipital lobes in subacute subjects were lower than in chronic subjects in low alpha, high alpha, low beta, and high beta bands. Nodal clustering coefficient (CC) analyses revealed that the CC in chronic subjects was higher than in subacute subjects in the ipsilesional S1 and occipital area, contralesional dorsolateral prefrontal cortex and parietal area. Characteristic path length (CPL) analyses showed that CPL in subacute subjects was lower than in chronic subjects in low beta, high beta, and gamma bands. There were no significant differences between subacute and chronic subjects for small-world property. Subacute stroke survivors were characterized by higher transfer efficiency of the entire brain network and weak local nodal effects. Transfer efficiency was reduced, the local nodal role was strengthened, and more neural resources needed to be mobilized to perform motor tasks for chronic survivors. Overall, these results may help to understand the remodeling pattern of the brain network for different post-stroke stages on task conditions and the mechanism of spontaneous recovery.

Neuronal activity reorganization in motor cortex for successful locomotion after a lesion in the ventrolateral thalamus.

Thalamic stroke leads to ataxia if the cerebellum-receiving ventrolateral thalamus (VL) is affected. The compensation mechanisms for this deficit are not well understood, particularly the roles that single neurons and specific neuronal subpopulations outside the thalamus play in recovery. The goal of this study was to clarify neuronal mechanisms of the motor cortex involved in mitigation of ataxia during locomotion when part of the VL is inactivated or lesioned. In freely ambulating cats, we recorded the activity of neurons in layer V of the motor cortex as the cats walked on a flat surface and horizontally placed ladder. We first reversibly inactivated ∼10% of the VL unilaterally using glutamatergic transmission antagonist CNQX and analyzed how the activity of motor cortex reorganized to support successful locomotion. We next lesioned 50%-75% of the VL bilaterally using kainic acid and analyzed how the activity of motor cortex reorganized when locomotion recovered. When a small part of the VL was inactivated, the discharge rates of motor cortex neurons decreased, but otherwise the activity was near normal, and the cats walked fairly well. Individual neurons retained their ability to respond to the demand for accuracy during ladder locomotion; however, most changed their response. When the VL was lesioned, the cat walked normally on the flat surface but was ataxic on the ladder for several days after lesion. When ladder locomotion normalized, neuronal discharge rates on the ladder were normal, and the shoulder-related group was preferentially active during the stride's swing phase.NEW & NOTEWORTHY This is the first analysis of reorganization of the activity of single neurons and subpopulations of neurons related to the shoulder, elbow, or wrist, as well as fast- and slow-conducting pyramidal tract neurons in the motor cortex of animals walking before and after inactivation or lesion in the thalamus. The results offer unique insights into the mechanisms of spontaneous recovery after thalamic stroke, potentially providing guidance for new strategies to alleviate locomotor deficits after stroke.

임플란트에 둘러싸인 채 압하된 치아의 자연회복: 증례보고

자연치아와 연결한 임플란트 수복물에서 종종 자연치아의 압하가 보고되곤 하지만 임플란트에 둘러싸인 자연치아의 압하에 대한 보고는 매우 드물다. 56세의 여성을 하악 우측 제1소구치는 임플란트로, 제 2소구치 치근은 포스트 수복 후 지르코니아로 각각 수복했다. 제 1대구치와 제 2대구치는 이미 임플란트로 수복되어 있었다. 기능 4개월 후 제 2소구치의 압하로 인한 대합치와의 간격이 분명히 관찰되었으나 불편감을 비롯한 이상증상은 없었다. 예후에 대한 자세한 설명 후 별다른 조치 없이 경과 관찰을 시작하였다. 3개월 후 치근단 방사선 사진상에서 원위치로의 치아 회복 시작이 관찰되었으며 다시 11개월이 경과한 후 치아의 추가 정출로 교합의 완전한 회복이 이루어졌다. 압하를 인지한지 2년 3개월째 관찰 중이다. 임플란트에 둘러싸인 자연치가 압하되고 저절로 회복되는 과정의 관찰을 통해 압하가 생기는 원인과 저절로 회복된 기전을 추정할 수 있었다. Reports about the intrusion of a natural tooth bounded by implants are very rare, although some concerns have been discussed on the intrusion of teeth connected to implants. A female aged 56 years received an implant (mandibular right first premolar) and post/core onto root rest (mandibular right second premolar) and was restored by single zirconia crown, respectively. Molars were implant restorations. Four month after loading, second premolar was intruded and prominent gap was shown between opposite tooth. Because nonspecific discomfort was expressed, observation was decided after explanation of prognosis of tooth without treatment. Three month later reversal to original position was detected on the periapical radiographs and fully recovered position with intimate contact was completed 11 more months later. Till now 2 years and 3 month observation is being performed. Through the observation of spontaneous recovery of a natural tooth bounded by implants, the cause of intrusion and a mechanism of spontaneous recovery could be estimated.

Rehabilitation is Initiated Early After Stroke, but Most Motor Rehabilitation Trials Are Not

Stroke is the third most common cause of death and the most common cause of acquired adult disability in developed countries.1 Motor impairment is common after stroke, and a critical factor influencing the patient’s ability to live independently.2,3 The neurobiological mechanisms of plasticity and spontaneous recovery during the initial days and weeks after stroke have been reasonably well characterized using animal models.4,5 These mechanisms include cell genesis, functional plasticity, and structural adaptations, such as axonal sprouting and synaptogenesis. The nature and time course of these mechanisms map onto the trajectory of motor recovery observed in human patients, most of whom reach their recovery plateau within 3 months of stroke.6,7 Rehabilitation is primarily delivered in this time period, to capitalize on the unique physiological conditions that prevail, and shape the spontaneous recovery process for the patient’s benefit. Recovery of function is likely to be enhanced by novel treatments that interact with and facilitate the underlying mechanisms of spontaneous recovery. A variety of neurorehabilitation techniques aimed at improving motor recovery after stroke have been developed and trialed over the past 3 decades. These include repetitive task training, biofeedback, constraint-induced movement therapy, robotics, virtual reality, motor imagery, noninvasive brain stimulation, and pharmacological agents.8,9 However, despite almost 1000 randomized control trials (RCTs) in stroke rehabilitation,10 there is very little translation of this evidence base into clinical practice.11,12 Research efforts to develop the evidence base are challenged by difficulties in recruiting patients, resulting in small sample sizes; the heterogeneity of impairments after stroke and the complexity of their interactions with factors affecting recovery; and limited collaboration between scientists, clinicians, patient groups, and industry.11 Even when the research evidence base supports the development of clinical guidelines, significant barriers …

A biologically realistic network model of acquisition and extinction of conditioned fear associations in lateral amygdala neurons.

The basolateral amygdala plays an important role in the acquisition and expression of both fear conditioning and fear extinction. To understand how a single structure could encode these "opposite" memories, we developed a biophysical network model of the lateral amygdala (LA) neurons during auditory fear conditioning and extinction. Membrane channel properties were selected to match waveforms and firing properties of pyramidal cells and interneurons in LA, from published in vitro studies. Hebbian plasticity was implemented in excitatory AMPA and inhibitory GABA(A) receptor-mediated synapses to model learning. The occurrence of synaptic potentiation versus depression was determined by intracellular calcium levels, according to the calcium control hypothesis. The model was able to replicate conditioning- and extinction-induced changes in tone responses of LA neurons in behaving rats. Our main finding is that LA activity during both acquisition and extinction can be controlled by a balance between pyramidal cell and interneuron activations. Extinction training depressed conditioned synapses and also potentiated local interneurons, thereby inhibiting the responses of pyramidal cells to auditory input. Both long-term depression and potentiation of inhibition were required to initiate and maintain extinction. The model provides insights into the sites of plasticity in conditioning and extinction, the mechanism of spontaneous recovery, and the role of amygdala NMDA receptors in extinction learning.

Repairing the human brain after stroke: I. Mechanisms of spontaneous recovery

Stroke remains a leading cause of adult disability. Some degree of spontaneous behavioral recovery is usually seen in the weeks after stroke onset. Variability in recovery is substantial across human patients. Some principles have emerged; for example, recovery occurs slowest in those destined to have less successful outcomes. Animal studies have extended these observations, providing insight into a broad range of underlying molecular and physiological events. Brain mapping studies in human patients have provided observations at the systems level that often parallel findings in animals. In general, the best outcomes are associated with the greatest return toward the normal state of brain functional organization. Reorganization of surviving central nervous system elements supports behavioral recovery, for example, through changes in interhemispheric lateralization, activity of association cortices linked to injured zones, and organization of cortical representational maps. A number of factors influence events supporting stroke recovery, such as demographics, behavioral experience, and perhaps genetics. Such measures gain importance when viewed as covariates in therapeutic trials of restorative agents that target stroke recovery.

Mechanisms of spontaneous recovery in DC gate bias stressed power VDMOSFETs

The effects of spontaneous recovery on threshold voltage and channel carrier mobility in DC gate bias stressed power VDMOSFETs, as well as the underlying changes in gate oxide-trapped charge and interface trap densities, are analysed in terms of the mechanisms responsible. Various mechanisms, including drift of oxide-trapped charge to the SiO2–Si interface, charge neutralisation, interface trap redistribution and electrochemical reactions near the interface are considered, in order to explain the experimental results. A major difference in the results for post-stress recovery obtained by subthreshold midgap and single transistor mobility techniques, both indicating mostly decrease in interface trap and oxide-trapped charge densities and the charge pumping technique, which signified a remarkable post-stress increase of true interface trap density, is ascribed to both interface trap redistribution within the silicon bandgap and to the inability of the former two techniques to assess the contribution of border traps to the estimated densities of interface traps. Drift of positive oxide charge to the interface, accompanied by subsequent charge neutralisation and interface trap redistribution, is found to dominate in the early stage of post-stress recovery, whereas the chain of electrochemical reactions involving hydrogen species (passivation of interface traps, dissociation of interfacial trap precursors, hydrogen dimerisation and cracking at charged oxide traps) is shown to become more important in the advanced stage of recovery.

Transkranielle Magnetstimulation - eine neue Therapieoption bei Aphasie?

Repetitive transcranial magnetic stimulation (rTMS) is a painless, non-invasive method of brain stimulation, which induces electric currents by using magnetic fields. The electric currents affect about 1-cm square area of the cortex. Slow frequency 1 Hz rTMS reduces cortical excitability whereas fast frequency (5, 10 or 20 Hz) leads to increasing cortical excitability. Therefore, rTMS can suppress (compensatory) over activation in the damaged hemisphere or increase cortical excitability in the non affected hemisphere. rTMS bears the potential for a new therapeutic procedure in patients with aphasia. One can assume that the treatment with rTMS supports the mechanisms of spontaneous recovery. Here we describe the procedure of rTMS. We will then present an overview of preliminary results from current neurolinguistic studies employing rTMS. Finally, the results of recent rTMS trials in aphasia treatment will be discussed.

Spontaneous recovery from acalculia

A topic much considered in research on acalculia was its relationship with aphasia. Far less attention has been given to the natural course of acalculia. In this retrospective study, we examined the relationship between aphasia and acalculia in an unselected series of 98 left-brain-damaged patients and the spontaneous recovery from acalculia in 92 acalculic patients with follow-up. There was a significant association between aphasia and acalculia although 19 participants exhibited aphasia with no acalculia and six acalculia with no aphasia. We observed significant improvement between a first examination carried out between 1 and 5 months post-onset and a second examination carried out between 3 and 11 months later (mean: 5 months). The mechanisms of spontaneous recovery are discussed.

Mechanisms of spontaneous recovery in positive gate bias stressed power VDMOSFETs

Mechanisms of spontaneous recovery in positive gate bias stressed power VDMOSFETs

Spinal cord injury in small animals 1. Mechanisms of spontaneous recovery

Spinal cord injury causes obvious clinical deficits early in the course of lesion evolution, but it is commonly observed that recovery can occur spontaneously during a period of days, weeks...

Spontaneous spinal epidural haematomas with repeated remission and relapse.

We present a case of spontaneous spinal epidural haematoma (SSEH) with a rare clinical course of repeated spontaneous recovery and relapse. The patient suffered three episodes of upper-back pain of sudden onset followed by sensory and motor dysfunction after weight lifting. In the first two episodes, the neurological deficits recovered spontaneously and completely. In the last episode, paraplegia persisted even after emergency surgery. Serial studies with computed tomographic (CT) myelography and magnetic resonance imaging (MRI) demonstrated the remitting and relapsing course of the SSEHs. The possible causes of the SSEHs and the mechanisms of spontaneous recovery are discussed.