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A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a synapse. The cell receiving the signal, or target cell, may be another neuron, but could also be a gland or muscle cell.
The striatum or corpus striatum is a cluster of interconnected nuclei that make up the largest structure of the subcortical basal ganglia. The striatum is a critical component of the motor and reward systems; receives glutamatergic and dopaminergic inputs from different sources; and serves as the primary input to the rest of the basal ganglia.
The substantia nigra (SN) is a basal ganglia structure located in the midbrain that plays an important role in reward and movement. Substantia nigra is Latin for "black substance", reflecting the fact that parts of the substantia nigra appear darker than neighboring areas due to high levels of neuromelanin in dopaminergic neurons. Parkinson's disease is characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta.
Dopamine is a neuromodulatory molecule that plays several important roles in cells. It is an organic chemical of the catecholamine and phenethylamine families. Dopamine constitutes about 80% of the catecholamine content in the brain. It is an amine synthesized by removing a carboxyl group from a molecule of its precursor chemical, L-DOPA, which is synthesized in the brain and kidneys. Dopamine is also synthesized in plants and most animals. In the brain, dopamine functions as a neurotransmitter—a chemical released by neurons to send signals to other nerve cells. Neurotransmitters are synthesized in specific regions of the brain, but affect many regions systemically. The brain includes several distinct dopamine pathways, one of which plays a major role in the motivational component of reward-motivated behavior. The anticipation of most types of rewards increases the level of dopamine in the brain, and many addictive drugs increase dopamine release or block its reuptake into neurons following release. Other brain dopamine pathways are involved in motor control and in controlling the release of various hormones. These pathways and cell groups form a dopamine system which is neuromodulatory.
The nucleus accumbens is a region in the basal forebrain rostral to the preoptic area of the hypothalamus. The nucleus accumbens and the olfactory tubercle collectively form the ventral striatum. The ventral striatum and dorsal striatum collectively form the striatum, which is the main component of the basal ganglia. The dopaminergic neurons of the mesolimbic pathway project onto the GABAergic medium spiny neurons of the nucleus accumbens and olfactory tubercle. Each cerebral hemisphere has its own nucleus accumbens, which can be divided into two structures: the nucleus accumbens core and the nucleus accumbens shell. These substructures have different morphology and functions.
Dopaminergic pathways in the human brain are involved in both physiological and behavioral processes including movement, cognition, executive functions, reward, motivation, and neuroendocrine control. Each pathway is a set of projection neurons, consisting of individual dopaminergic neurons.
The ventral tegmental area (VTA), also known as the ventral tegmental area of Tsai, or simply ventral tegmentum, is a group of neurons located close to the midline on the floor of the midbrain. The VTA is the origin of the dopaminergic cell bodies of the mesocorticolimbic dopamine system and other dopamine pathways; it is widely implicated in the drug and natural reward circuitry of the brain. The VTA plays an important role in a number of processes, including reward cognition and orgasm, among others, as well as several psychiatric disorders. Neurons in the VTA project to numerous areas of the brain, ranging from the prefrontal cortex to the caudal brainstem and several regions in between.
Motivational salience is a cognitive process and a form of attention that motivates or propels an individual's behavior towards or away from a particular object, perceived event or outcome. Motivational salience regulates the intensity of behaviors that facilitate the attainment of a particular goal, the amount of time and energy that an individual is willing to expend to attain a particular goal, and the amount of risk that an individual is willing to accept while working to attain a particular goal.
Temporal difference (TD) learning refers to a class of model-free reinforcement learning methods which learn by bootstrapping from the current estimate of the value function. These methods sample from the environment, like Monte Carlo methods, and perform updates based on current estimates, like dynamic programming methods.
The habenula is a small bilateral neuronal structure in the brain of vertebrates, that has also been called a microstructure since it is no bigger than a pea. The naming as little rein describes its elongated shape in the epithalamus, where it borders the third ventricle, and lies in front of the pineal gland.
Peter Dayan is a British neuroscientist and computer scientist who is director at the Max Planck Institute for Biological Cybernetics in Tübingen, Germany, along with Ivan De Araujo. He is co-author of Theoretical Neuroscience, an influential textbook on computational neuroscience. He is known for applying Bayesian methods from machine learning and artificial intelligence to understand neural function and is particularly recognized for relating neurotransmitter levels to prediction errors and Bayesian uncertainties. He has pioneered the field of reinforcement learning (RL) where he helped develop the Q-learning algorithm, and made contributions to unsupervised learning, including the wake-sleep algorithm for neural networks and the Helmholtz machine.
The reward system is a group of neural structures responsible for incentive salience, associative learning, and positively-valenced emotions, particularly ones involving pleasure as a core component. Reward is the attractive and motivational property of a stimulus that induces appetitive behavior, also known as approach behavior, and consummatory behavior. A rewarding stimulus has been described as "any stimulus, object, event, activity, or situation that has the potential to make us approach and consume it is by definition a reward". In operant conditioning, rewarding stimuli function as positive reinforcers; however, the converse statement also holds true: positive reinforcers are rewarding.The reward system motivates animals to approach stimuli or engage in behaviour that increases fitness. Survival for most animal species depends upon maximizing contact with beneficial stimuli and minimizing contact with harmful stimuli. Reward cognition serves to increase the likelihood of survival and reproduction by causing associative learning, eliciting approach and consummatory behavior, and triggering positively-valenced emotions. Thus, reward is a mechanism that evolved to help increase the adaptive fitness of animals. In drug addiction, certain substances over-activate the reward circuit, leading to compulsive substance-seeking behavior resulting from synaptic plasticity in the circuit.
Pendleton Read Montague, Jr. is an American neuroscientist and popular science author. He is the director of the Human Neuroimaging Lab and Computational Psychiatry Unit at the Fralin Biomedical Research Institute at VTC in Roanoke, Virginia, where he also holds the title of the inaugural Virginia Tech Carilion Vernon Mountcastle Research Professor. Montague is also a professor in the department of physics at Virginia Tech in Blacksburg, Virginia and professor of Psychiatry and Behavioral Medicine at Virginia Tech Carilion School of Medicine.
Ann Martin Graybiel is an Institute Professor and a faculty member in the Department of Brain and Cognitive Sciences at the Massachusetts Institute of Technology. She is also an investigator at the McGovern Institute for Brain Research. She is an expert on the basal ganglia and the neurophysiology of habit formation, implicit learning, and her work is relevant to Parkinson's disease, Huntington's disease, obsessive–compulsive disorder, substance abuse and other disorders that affect the basal ganglia.
The Department of Physiology, Development and Neuroscience, (PDN) is a part of the School of Biological Sciences at the University of Cambridge. Research in PDN focuses on three main areas: Cellular and Systems Physiology, Developmental and Reproductive Biology, and Neuroscience and is currently headed by Sarah Bray and William Colledge. The department was formed on 1 January 2006, within the School of Biological Sciences at the University of Cambridge from the merger of the Departments of Anatomy and Physiology. The department hosts the Centre for Trophoblast Research and has links with the Cambridge Centre for Brain Repair, the Cambridge Stem Cell Institute, and the Gurdon Institute.
Addiction is a state characterized by compulsive engagement in rewarding stimuli, despite adverse consequences. The process of developing an addiction occurs through instrumental learning, which is otherwise known as operant conditioning.
Robert H. Wurtz is an American neuroscientist working as a NIH Distinguished Scientist and Chief of the Section on Visuomotor Integration at the National Eye Institute. He is a member of the US National Academy of Sciences and the American Academy of Arts and Sciences. He is recognised for developing methods for studying the visual system in 'awake-behaving' primates, a technique now widely used for the study of higher brain functions. He pioneered the study of the neuronal basis of vision and its relation with cognitive functions.
Okihide Hikosaka is a neuroscience research professor who specializes in the mechanisms of motivation, learning, skill, decision-making, attention, and oculomotor control. His research into neuronal mechanisms of voluntary behavior and basal ganglia function created breakthroughs in the understanding of the neurochemistry behind information-seeking behavior and the efficacy of grouping motor sequence learning actions in order to remember more than individual actions.
Chantal Martin Soelch is a Swiss clinical psychologist, academic, and author. She is a Professor in Clinical and Health Psychology, and Vice-rector for Teaching, Continuing Education, Gender Equality, and Diversity and Inclusion at the University of Fribourg (Switzerland).
Anthony J. Dickinson, is a British psychologist, currently Emeritus Professor of Comparative Psychology in the Department of Psychology at the University of Cambridge. He is the author of the highly cited monograph Contemporary Animal Learning Theory and was elected a Fellow of the Royal Society in 2003 for "internationally recognised contributions to our understanding of learning, memory, motivation and planning".
References
- ↑ "Wolfram Schultz". royalsociety.org. Retrieved 2023-10-23.
- ↑ "Wolfram Schultz". www.wolframschultz.org. Retrieved 2023-10-23.
- 1 2 3 4 "Wolfram Schultz | Gruber Foundation". gruber.yale.edu. Retrieved 2023-10-23.
- 1 2 "Wolfram Schultz | The Lundbeck Foundation". lundbeckfonden.com. Retrieved 2023-10-23.
- ↑ "Prof Wolfram Schultz FRS". University of Cambridge. Retrieved 16 November 2023.
- 1 2 3 "Wolfram Schultz". Gruber Foundation. Yale University. Retrieved 16 November 2023.
- ↑ "Wolfram Schultz". scholar.google.co.uk. Retrieved 2023-10-23.
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