The clinical use of deep brain stimulation (DBS) is among the most important advances in the clinical neurosciences in the past two decades. As a surgical tool, DBS can directly measure pathological ...brain activity and can deliver adjustable stimulation for therapeutic effect in neurological and psychiatric disorders correlated with dysfunctional circuitry. The development of DBS has opened new opportunities to access and interrogate malfunctioning brain circuits and to test the therapeutic potential of regulating the output of these circuits in a broad range of disorders. Despite the success and rapid adoption of DBS, crucial questions remain, including which brain areas should be targeted and in which patients. This Review considers how DBS has facilitated advances in our understanding of how circuit malfunction can lead to brain disorders and outlines the key unmet challenges and future directions in the DBS field. Determining the next steps in DBS science will help to define the future role of this technology in the development of novel therapeutics for the most challenging disorders affecting the human brain.
Recognition of epileptic seizure type is essential for the neurosurgeon to understand the cortical connectivity of the brain. Though automated early recognition of seizures from normal ...electroencephalogram (EEG) was existing, no attempts have been made towards the classification of variants of seizures. Therefore, this study attempts to classify seven variants of seizures with non-seizure EEG through the application of convolutional neural networks (CNN) and transfer learning by making use of the Temple University Hospital EEG corpus. The objective of our study is to perform a multi-class classification of epileptic seizure type, which includes simple partial, complex partial, focal non-specific, generalized non-specific, absence, tonic, and tonic–clonic, and non-seizures. The 19 channels EEG time series was converted into a spectrogram stack before feeding as input to CNN. The following two different modalities were proposed using CNN: (1) Transfer learning using pretrained network, (2) Extract image features using pretrained network and classify using the support vector machine classifier. The following ten pretrained networks were used to identify the optimal network for the proposed study: Alexnet, Vgg16, Vgg19, Squeezenet, Googlenet, Inceptionv3, Densenet201, Resnet18, Resnet50, and Resnet101. The highest classification accuracy of 82.85% (using Googlenet) and 88.30% (using Inceptionv3) was achieved using transfer learning and extract image features approach respectively. Comparison results showed that CNN based approach outperformed conventional feature and clustering based approaches. It can be concluded that the EEG based classification of seizure type using CNN model could be used in pre-surgical evaluation for treating patients with epilepsy.
•We propose a CNN and transfer learning-based 8-class seizure type classification using the Temple University Hospital EEG corpus.•We propose a CNN and transfer learning-based 8-class seizure type classification•ReLU layer showed the highest accuracy using extract image feature approach•The highest accuracy of 82.85% and 88.30% was achieved using Googlenet and Inceptionv3 respectively•Extract image features approach outperformed transfer learning approach
During treatment with deep brain stimulation (DBS), electrical current is delivered into the brain parenchyma through implanted electrodes. Although this technique is routinely used in the treatment ...of Parkinson's disease, essential tremor, and dystonia, a growing number of neuropsychiatric applications for DBS are being investigated. Investigators can use animal models of these diseases to study the mechanisms through which DBS exerts its effects, to explore new applications of this therapy, and to identify and characterize alternative stimulation targets. Here, we discuss preclinical DBS research that provides insight into the mechanisms underlying cognitive and psychiatric applications of this technique, emphasizing the predictive validity of animal models and their potential use in translational research.
Deep brain stimulation (DBS) has long been used to alleviate symptoms in patients suffering from psychiatric and neurological disorders through stereotactically implanted electrodes that deliver ...current to subcortical structures via wired pacemakers. The application of DBS to modulate neural circuits is, however, hampered by its mechanical invasiveness and the use of chronically implanted leads, which poses a risk for hardware failure, hemorrhage, and infection. Here, we demonstrate that a wireless magnetothermal approach to DBS (mDBS) can provide similar therapeutic benefits in two mouse models of Parkinson's disease, the bilateral 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and in the unilateral 6-hydroxydopamine (6-OHDA) model. We show magnetothermal neuromodulation in untethered moving mice through the activation of the heat-sensitive capsaicin receptor (transient receptor potential cation channel subfamily V member 1, TRPV1) by synthetic magnetic nanoparticles. When exposed to an alternating magnetic field, the nanoparticles dissipate heat, which triggers reversible firing of TRPV1-expressing neurons. We found that mDBS in the subthalamic nucleus (STN) enables remote modulation of motor behavior in healthy mice. Moreover, mDBS of the STN reversed the motor deficits in a mild and severe parkinsonian model. Consequently, this approach is able to activate deep-brain circuits without the need for permanently implanted hardware and connectors.
Deep brain stimulation is used to alleviate symptoms of neurological and psychiatric disorders including Parkinson’s disease, epilepsy, and obsessive–compulsive-disorder. Electrically stimulating ...limbic structures has been of great interest, and in particular, the region of the fornix. We conducted a systematic search for studies that reported clinical and preclinical outcomes of deep brain stimulation within the fornix up to July 2019. We identified 13 studies (7 clinical, 6 preclinical) that examined the effects of fornix stimulation in Alzheimer’s disease (
n
= 9), traumatic brain injury (
n
= 2), Rett syndrome (
n
= 1), and temporal lobe epilepsy (
n
= 1). Overall, fornix stimulation can lead to decreased rates of cognitive decline (in humans), enhanced memory (in humans and animals), visuo-spatial memorization (in humans and animals), and improving verbal recollection (in humans). While the exact mechanisms of action are not completely understood, studies suggest fornix DBS to be involved with increased functional connectivity and neurotransmitter levels, as well as enhanced neuroplasticity.
After publication of the original article it came to the authors’ attention that there was an error under the subheading
Traumatic Brain Injury (TBI)
as well as Table 1.
Deep brain stimulation (DBS) of the nucleus basalis of Meynert (NBM) has gained interest as a potential therapy for treatment-resistant dementia. However, optimal stimulation parameters and ...mechanisms of action are yet to be elucidated.
First, we assessed NBM DBS at different stimulation parameters in a scopolamine-induced rat model of dementia. Rats were tested in the object location task with the following conditions: (i) low and high frequency (20 Hz or 120 Hz), (ii) monophasic or biphasic pulse shape (iii) continuous or intermittent DBS (20s on, 40s off) and 100 μA amplitude. Thereafter, rats were stimulated with the most effective parameter followed by 5-bromo-2′-deoxyuridine (BrdU) administration and perfused 4 weeks later. We then evaluated the effects of NBM DBS on hippocampal neurogenesis, synaptic plasticity and on cholinergic fibres in the perirhinal and cingulate cortex using immunohistochemistry. We also performed in-vivo microdialysis to assess circuit-wide effects of NBM DBS on hippocampal acetylcholine levels during on and off stimulation.
Biphasic, low frequency and intermittent NBM DBS reversed the memory impairing effects of scopolamine when compared to sham rats. We found that acute stimulation promoted proliferation in the dentate gyrus, increased synaptic plasticity in the CA1 and CA3 subregion of the hippocampus and increased length of cholinergic fibres in the cingulate gyrus. There was no difference regarding hippocampal acetylcholine levels between the groups.
These findings suggest that the potential mechanism of action of the induced memory enhancement through NBM DBS might be due to selective neuroplastic and neurochemical changes.
•NBM DBS at specific parameters enhances spatial and recognition memory.•NBM DBS induces neurogenesis, growth of cholinergic fibres, and synaptic plasticity.•NBM DBS increases neuronal activity in various brain regions associated with memory.
The emerging field of ultra-high field MRI (UHF-MRI, 7 Tesla and higher) provides the opportunity to image human brains at a higher resolution and with higher signal-to-noise ratios compared to the ...more widely available 1.5 and 3T scanners. Scanning postmortem tissue additionally allows for greatly increased scan times and fewer movement issues leading to improvements in image quality. However, typical postmortem neuroimaging routines involve placing the tissue within plastic bags that leave room for susceptibility artifacts from tissue-air interfaces, inadequate submersion, and leakage issues. To address these challenges in postmortem imaging, a custom-built nonferromagnetic container was developed that allows whole brain hemispheres to be scanned at sub-millimeter resolution within typical head-coils.
The custom-built polymethylmethacrylaat container consists of a cylinder with a hemispheric side and a lid with valves on the adjacent side. This shape fits within common MR head-coils and allows whole hemispheres to be submerged and vacuum sealed within it reducing imaging artifacts that would otherwise arise at air-tissue boundaries. Two hemisphere samples were scanned on a Siemens 9.4T Magnetom MRI scanner. High resolution T2* weighted data was obtained with a custom 3D gradient echo (GRE) sequence and diffusion-weighted imaging (DWI) scans were obtained with a 3D kT-dSTEAM sequence along 48 directions.
The custom-built container proved to submerge and contain tissue samples effectively and showed no interferences with MR scanning acquisition. The 3D GRE sequence provided high resolution isotropic T2* weighted data at 250 μm which showed a clear visualization of gray and white matter structures. DWI scans allowed for dense reconstruction of structural white matter connections via tractography.
Using this custom-built container worked towards achieving high quality MR images of postmortem brain material. This procedure can have advantages over traditional schemes including utilization of a standardized protocol and the reduced likelihood of leakage. This methodology could be adjusted and used to improve typical postmortem imaging routines.
Vestibular schwannoma (VS) is a benign primary brain tumor that occurs sporadic or as part of a genetic syndrome. The most common cause is the mutation of the NF2 tumor suppressor gene that is ...involved in the production of the protein merlin. Merlin plays a role in cell growth and cell adhesion. In patients with NF2, the VSs arise bilaterally and coincide with other brain tumors. In sporadic VS, the tumor is typically unilateral and does not coincide in combination with other tumors. MRI is the standard imaging technique and can be used to assess the size and aspect of the tumor as well as the progression of disease. The preferred management of large VS in both VS types is surgery with or without adjuvant radiation. The management for the medium- or small-sized VS includes wait and scan, radiotherapy and/or surgery. This choice depends on the preference of the patient and institutional protocols. The outcomes of surgical and radiotherapy treatments are improving due to progress in surgical equipment/approaches, advances in radiation delivery techniques and dose optimizations protocols. The main purpose of the management of VS is preserving function as long as possible in combination with tumor control.
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