52 research outputs found
A neural mass computational framework to study synaptic mechanisms underlying alpha and theta rhythms
No full textComputational modelling in neuroscience is gaining in popularity towards investigating neurological and psychiatric disorders. One of the major obstacles in faster progress in this field has been the current state-of-the-art computational platforms and frameworks that struggle to simulate, in terms of time and memory, the complex brain structures and functions. Thus, modelling of neuronal population that are packed in dense spatial clusters and show local synchrony has been a popular methodology towards simulating higher level brain functions recorded via electroencephalogram (EEG); neural mass modelling has been one such paradigm. The drawback in these models of population level dynamics, however, is a lack of correlation with the underlying cellular mechanisms, which is crucial in investigating disease conditions. The neural mass model presented in this work approaches both these issues: first, kinetic models of synaptic information transfer replaces Rall’s alpha function that are traditionally used in these models, thus allowing correlation of model output simulating EEG-like dynamics with lower-level synaptic attributes; second, computational time for this modified approach in neural mass models is faster than the existing traditional approach and up to an order of ten. Here, the objective is to understand the underlying cellular mechanisms of alpha and theta rhythms that are EEG biomarkers in several neurological and psychiatric disorders. A biologically-inspired model of the thalamic Lateral Geniculate Nucleus using the modified neural mass modelling framework is tuned and parameterised to simulate EEG alpha and theta rhythms. The results suggest that low-levels of neurotransmitter concentration in the synaptic cleft along with a reduced GABA-ergic activity from the thalamic interneurons may play a role in alpha to theta band transition, a symptom implicated in several brain disorders. Furthermore, the model validates reports from experimental observations that similar thalamic mechanisms underlie alpha and theta band oscillations. In addition, the model predicts that the GABA-ergic pathways from the thalamic interneurons and the thalamic reticular nucleus may have distinct roles in EEG during cognitive state and state of sleep, and in both healthy and diseased brains
Combined study of time-series bifurcation and power spectral behaviour of a thalamo-cortico-thalamic neural mass model
No full textBiologically inspired means for rank-order encoding images:a quantitative analysis
No full textIn this paper, we present biologically inspired means to enhance perceptually important information retrieval from rank-order encoded images. Validating a retinal model proposed by VanRullen and Thorpe, we observe that on average only up to 70% of the available information can be retrieved from rank-order encoded images. We propose a biologically inspired treatment to reduce losses due to a high correlation of adjacent basis vectors and introduce a filter-overlap correction algorithm (FoCal) based on the lateral inhibition technique used by sensory neurons to deal with data redundancy. We observe a more than 10% increase in perceptually important information recovery. Subsequently, we present a model of the primate retinal ganglion cell layout corresponding to the foveal-pit. We observe that information recovery using the foveal-pit model is possible only if FoCal is used in tandem. Furthermore, information recovery is similar for both the foveal-pit model and VanRullen and Thorpe's retinal model when used with FoCal. This is in spite of the fact that the foveal-pit model has four ganglion cell layers as in biology while VanRullen and Thorpe's retinal model has a 16-layer structure. © 2006 IEEE
Implementing the cellular mechanisms of synaptic transmission in a neural mass model of the thalamo-cortical circuitry
No full textA novel direction to existing neural mass modelling technique is proposed where the commonly used `alpha function' for representing synaptic transmission is replaced by a kinetic framework of neurotransmitter and receptor dynamics. The aim is to underpin neuro-transmission dynamics associated with abnormal brain rhythms commonly observed in neurological and psychiatric disorders. An existing thalamocortical neural mass model is modified by using the kinetic framework for modelling synaptic transmission mediated by glutamatergic and GABA (gamma-aminobutyric-acid)-ergic receptors. The model output is compared qualitatively with existing literature on in-vitro experimental studies of ferret thalamic slices, as well as on single-neuron-level model based studies of neuro-receptor and transmitter dynamics in the thalamocortical tissue. The results are consistent with these studies: the activation of ligand-gated GABA receptors is essential for generation of spindle waves in the model, while blocking this pathway leads to low-frequency synchronised oscillations such as observed in slow-wave sleep; the frequency of spindle oscillations increase with increased levels of post-synaptic membrane conductance for AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic-acid) receptors, and blocking this pathway effects a quiescent model output. In terms of computational efficiency, the simulation time is improved by a factor of ten compared to a similar neural mass model based on alpha functions. This implies a dramatic improvement in computational resources for large-scale network simulation using this model. Thus, the model provides a platform for correlating high-level brain oscillatory activity with low-level synaptic attributes, and makes a significant contribution towards advancements in current neural mass modelling paradigm as a potential computational tool to better the understanding of brain oscillations in sickness and in health
Assistive Chatbots for healthcare: a succinct review
No full textBrief Survey paper on Chatbots that are designed to be of assistance in mental and physical healthcare. Focuss on the last 10 years 2013-2023, and on AI-enabled technology only.</p
Combined study of time-series bifurcation and power spectral behaviour of a thalamo-cortico- thalamic neural mass model
Get PDFA combined power spectral and time-series bifurcation analysis of a neural mass model is presented. Such 'multimodal' analytical techniques are being used in several researches to understand Electroencephalograph (EEG) anomalies in brain disorder
A thalamo-cortico-thalamic neural mass model to study alpha rhythms in Alzheimer's disease
No full textWe present a lumped computational model of the thalamo-cortico-thalamic circuitry. The model essentially consists of two modules: a thalamic module and a cortical module. The thalamic module circuitry is a modified version of a classic neural mass computational model of the thalamic circuitry to simulate cortical alpha rhythms and which we have used in previous research to study EEG abnormality associated with Alzheimer's Disease (AD). Here, we introduce a modified synaptic structure representing a neuronal population in the thalamic model. Furthermore, the synaptic organisation and connectivity parameter values in the model are based on experimental data reported from the dorsal Lateral Geniculate Nucleus of different species. The cortical module circuitry is based on a recent work studying cortical brain rhythms. We vary the synaptic connectivity parameters in the thalamic module of the model to simulate the effects of AD on brain synaptic circuitry and study power within the alpha frequency bands. The power and dominant frequencies of the model output are studied in three sub-bands within the alpha band: lower alpha (7-9 Hz), middle alpha (9-11 Hz) and upper alpha (11-13 Hz). Such an analytical method conforms to recent comparative EEG studies on young adults, healthy aged adults and MCI or early stage AD patients. The results show a remarkable role of the synaptic connectivities in the inhibitory thalamic cell populations on the alpha band power and frequency. Furthermore, the total number of active synapses in the thalamic cell populations produces the slowing of alpha rhythms and a simultaneous decrease of alpha band power in the brain as a result of AD.</p
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