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The mesolimbic pathway and a specific set of the pathway's output neurons (e.g. D1-type medium spiny neurons within the nucleus accumbens) play a central role in the neurobiology of addiction. [20] [21] [22] Drug addiction is an illness caused by habitual substance use that induces chemical changes in the brain's circuitry. [23]
The reward system (the mesocorticolimbic circuit) is a group of neural structures responsible for incentive salience (i.e., "wanting"; desire or craving for a reward and motivation), associative learning (primarily positive reinforcement and classical conditioning), and positively-valenced emotions, particularly ones involving pleasure as a core component (e.g., joy, euphoria and ecstasy).
Once the neurons have reached their regional positions, they extend axons and dendrites, which allow them to communicate with other neurons via synapses. Synaptic communication between neurons leads to the establishment of functional neural circuits that mediate sensory and motor processing, and underlie behavior. [12]
While individual neurons are simple, many of them together in a network can perform complex tasks. There are two main types of neural network. In neuroscience , a biological neural network is a physical structure found in brains and complex nervous systems – a population of nerve cells connected by synapses .
The development of the nervous system in humans, or neural development, or neurodevelopment involves the studies of embryology, developmental biology, and neuroscience.These describe the cellular and molecular mechanisms by which the complex nervous system forms in humans, develops during prenatal development, and continues to develop postnatally.
As we age, our brain experiences both structural and functional changes. Over time, this can cause a decline in cognitive abilities, memory, and even emotional regulation.
Network models can be classified as either network of neurons propagating through different levels of cortex or neuron populations interconnected as multilevel neurons. The spatial positioning of neuron could be 1-, 2- or 3-dimensional; the latter ones are called small-world networks as they are related to local region.
Neurons may be termed by their associated neurotransmitter such as excitatory dopaminergic neurons and inhibitory GABAergic neurons. [ 5 ] Cortical interneurons only make up around a fifth of the neuronal population but they play a major role in modulating cortical activity needed for cognition and many aspects of learning and memory.