Striatum in the context of "Medial pallium"

The basal ganglia (BG) or basal nuclei are a group of subcortical nuclei found in the brains of vertebrates. Positioned at the base of the forebrain and the top of the midbrain, they have strong connections with the cerebral cortex, thalamus, brainstem and other brain areas. The basal ganglia are associated with a variety of functions, including regulating voluntary motor movements, procedural learning, habit formation, conditional learning, eye movements, cognition, and emotion.

The main functional components of the basal ganglia include the striatum, consisting of both the dorsal striatum (caudate nucleus and putamen) and the ventral striatum (nucleus accumbens and olfactory tubercle), the globus pallidus, the ventral pallidum, the substantia nigra, and the subthalamic nucleus. Each of these components has complex internal anatomical and neurochemical structures. The largest component, the striatum (dorsal and ventral), receives input from various brain areas but only sends output to other components of the basal ganglia. The globus pallidus receives input from the striatum and sends inhibitory output to a number of motor-related areas. The substantia nigra is the source of the striatal input of the neurotransmitter dopamine, which plays an important role in basal ganglia function. The subthalamic nucleus mainly receives input from the striatum and cerebral cortex and projects to the globus pallidus.

In neuroanatomy, pallium (pl.: pallia or palliums) refers to the layers of grey and white matter that cover the upper surface of the cerebrum in vertebrates. The non-pallial part of the telencephalon builds the subpallium. In basal vertebrates, the pallium is a relatively simple three-layered structure, encompassing 3–4 histogenetically distinct domains, plus the olfactory bulb.

It used to be thought that pallium equals cortex and subpallium equals telencephalic nuclei, but it has turned out, according to comparative evidence provided by molecular markers, that the pallium develops both cortical structures (allocortex and isocortex) and pallial nuclei (claustroamygdaloid complex), whereas the subpallium develops striatal, pallidal, diagonal-innominate and preoptic nuclei, plus the corticoid structure of the olfactory tuberculum.

Disorders of diminished motivation (DDM) are a group of disorders involving diminished motivation and associated emotions. Many different terms have been used to refer to diminished motivation. Often however, a spectrum is defined encompassing apathy, abulia, and akinetic mutism, with apathy the least severe and akinetic mutism the most extreme.

DDM can be caused by psychiatric disorders like depression and schizophrenia, brain injuries, strokes, and neurodegenerative diseases. Damage to the anterior cingulate cortex and to the striatum, which includes the nucleus accumbens and caudate nucleus and is part of the mesolimbic dopamine reward pathway, have been especially associated with DDM. Diminished motivation can also be induced by certain drugs, including antidopaminergic agents like antipsychotics, selective serotonin reuptake inhibitors (SSRIs), and cannabis, among others.

A neural network, also called a neuronal network, is an interconnected population of neurons (typically containing multiple neural circuits). Biological neural networks are studied to understand the organization and functioning of nervous systems.

Closely related are artificial neural networks, machine learning models inspired by biological neural networks. They consist of artificial neurons, which are mathematical functions that are designed to be analogous to the mechanisms used by neural circuits.

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.

Although the substantia nigra appears as a continuous band in brain sections, anatomical studies have found that it actually consists of two parts with very different connections and functions: the pars compacta (SNpc) and the pars reticulata (SNpr). The pars compacta serves mainly as a projection to the basal ganglia circuit, supplying the striatum with dopamine. The pars reticulata conveys signals from the basal ganglia to numerous other brain structures.

The nucleus accumbens (NAc or NAcc; also known as the accumbens nucleus, or formerly as the nucleus accumbens septi, Latin for 'nucleus adjacent to the septum') 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.

Different NAcc subregions (core vs shell) and neuron subpopulations within each region (D1-type vs D2-type medium spiny neurons) are responsible for different cognitive functions. As a whole, the nucleus accumbens has a significant role in the cognitive processing of motivation, aversion, reward (i.e., incentive salience, pleasure, and positive reinforcement), and reinforcement learning (e.g., Pavlovian-instrumental transfer); hence, it has a significant role in addiction. In addition, part of the nucleus accumbens core is centrally involved in the induction of slow-wave sleep. The nucleus accumbens plays a lesser role in processing fear (a form of aversion), impulsivity, and the placebo effect. It is involved in the encoding of new motor programs as well.