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Neuroimaging in Nuclear Medicine
Published in Michael Ljungberg, Handbook of Nuclear Medicine and Molecular Imaging for Physicists, 2022
Anne Larsson Strömvall, Susanna Jakobson Mo
The neurons have thin extensions, called axons, through which they interconnect via electrical impulses, causing the release of neurotransmitters. An isolating fatty covering called the myelin sheath often encases axons in order to enhance and speed up the transmission of the electrical impulses. The brain tissue beneath the cortex – that is, the subcortical white matter – is dominated by myelinated nerve fibres. Deep within the white matter of each cerebral hemisphere, there are defined areas, nuclei, of grey matter, for example, the basal ganglia. The basal ganglia include the striatum, which in turn is divided into the caudate nucleus and the putamen. A tiny, paired area of grey matter in the brainstem is called the substantia nigra, which is also considered part of the basal ganglia. The thalamus is another important subcortical nucleus lying medial to the striatum. The cerebellum also has two hemispheres and a middle part called the vermis. The cerebellum is heavily folded, and its proportion of white matter is smaller compared to the cerebrum.
Brain Motor Centers and Pathways
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
A wide range of functions of the basal ganglia is postulated to fall under a broadened umbrella of goal-oriented behavior and reinforcement learning, which lends itself to computational modeling of the basal ganglia based on this formalism. The basic hypothesis is that, in response to a number of inputs competing for limited motor or cognitive resources, the basal ganglia select the most rewarding action. In this context, it is proposed that the dorsal striatum, receiving extensive sensory inputs from the cortex and thalamus, as well as dopaminergic inputs from the SNc, develops an internal model for estimation of the expected future reward. The GPe-STN loop is postulated to support reward-seeking exploratory activity. The dynamics of the thalamo-cortico-striatal loop are believed to underlie the ability to time intervals in the seconds-to-minutes range, which is important in addressing the temporal relationship between the stimulus and the rewarding action.
Naturally Occurring Polymers—Animals
Published in Charles E. Carraher, Carraher's Polymer Chemistry, 2017
Recently, we have been working on Parkinson's disease. Parkinson's disease and other similar diseases are due to a depletion of dopamine in the corpus striatum. Direct addition of dopamine is not effective in the treatment presumably because it does not cross the blood–brain barrier. However, levodopa, the metabolic precursor of dopamine, does cross the blood–brain barrier and is believed to then be converted to dopamine in the basal ganglia.
A Ranking-based Weakly Supervised Learning model for telemonitoring of Parkinson’s disease
Published in IISE Transactions on Healthcare Systems Engineering, 2022
Dhari F. Alenezi, Hang Shi, Jing Li
Specifically related to PD, the movement disorder of PD occurs largely due to the selective loss of neurons that results in depletion of dopamine in the striatum (Jankovic, 2008; Samii et al., 2004; Sveinbjornsdottir, 2016). Dopaminergic drugs designed to replace the action of dopamine in the deplete striatum. Generally, the clinical effect of dopaminergic drugs is noticed quickly, and may last for several hours, particularly in the early stages of the disease (Zahoor et al., 2018). As a result, it is reasonable to use medication as the criterion to create pairs of ranked samples for each patient. It can be assumed that the disease is more severe before medication than relatively immediately after medication. Also, it is common for telemonitoring apps to collect samples with respect to the timing of medication, which naturally creates ranked samples. For example, the mPower app requests the users to perform their activities three times a day with at least one time before and one time after medication. Finally, our model is designed to address the scenario of limited labeled samples by compensating for that shortage with ranked samples; however, the model is expected to perform as good as a supervised learning model for patients without ranked samples.
Myelin Quantification in the Basal Ganglia and the Cerebral Peduncles of Human Brains
Published in IETE Journal of Research, 2022
Jacily Jemila, A. Brintha Therese, R. Rajeswaran
The basal ganglia and cerebral peduncles are very important regions of myelination. Basal ganglia are also called basal nuclei, which are made up of a group of neurons. These regions have different shapes and they are responsible for the control of movement. They are responsible for cognitive functions, habit learning, eye movement, emotion, and procedural learning. The main function of basal ganglia is the selection of action which is suitable to execute for a particular circumstance and is decided by it. It receives the signal from the cerebral cortex for the upcoming movement and processes and adjusts the impulse. The basal ganglia send the information to the thalamus. For proper brain function and behaviour basal ganglia is an important part of the brain. So proper myelination is very important for proper function. Dystonia, Huntington’s disease, and Parkinson's disease are associated with basal ganglia dysfunction. The basal ganglia have four parts: the striatum, the globus pallidus, the substantia nigra, and the subthalamic nucleus. Striatum plays an important role in sensorimotor activities and reward-based learning. The globus pallidus participates in different neural circuits. The substantia nigra is used to maintain the equilibrium of the nigrostriatal pathway. The subthalamic nucleus produces an excitatory neurotransmitter:
A scientometric analysis and review of spatial cognition studies within the framework of neuroscience and architecture
Published in Architectural Science Review, 2021
The difference between ‘map-based navigation’ and ‘route-based navigation’ is worth discussing within the research theme of Cluster 3. Although it is now evident that cognitive maps underpin navigation in animals and humans, not all navigation tasks are map-based. The spatial cognition research has indicated that, whenever the navigation route is familiar and well-rehearsed, a different brain system called the striatum controls interpretation. Thus, route-based navigation is a kind of automatic process which operates differently from the cognitive-map-based wayfinding processes (Iaria et al. 2003).