Ventral striatum
Encyclopedia
The ventral striatum is generally considered that part of the striatum
that is connectionally associated with limbic structures, such as the amygdala, hippocampus, midline thalamus, and certain regions of the prefrontal cortex. In addition, the ventral striatum is strongly innervated by dopaminergic fibers from the ventral tegmental area (VTA), known as the mesolimbic dopamine system, and has the highest density of serotonergic inputs in the striatum. The ventral striatum consists of the nucleus accumbens
and the olfactory tubercle
. Although, some sources also include the ventromedial parts of the caudate nucleus
and putamen
.
In its present connotation, the term “ventral striatum” was introduced in 1975 by Lennart Heimer
and Richard Wilson to differentiate it from the dorsal, sensorimotor-related part of the striatum (ie, the caudate-putamen complex). This inclusion of ventrally located striatal tissue in a “unified” striatum, along with the recognition of connectionally associated pallidal elements in the substantia innominata and deep layers of the olfactory tubercle (ie, the ventral pallidum), has had great impact on the functional-anatomical concept of the basal ganglia. Whereas traditionally, the basal ganglia were thought to be primarily involved in sensory-motor functions, it has now become accepted that the basal ganglia, as a result of their involvement in a set of parallel, functionally segregated basal ganglia-thalamocortical circuits, which primarily entertain the premotor and prefrontal cortical cortices, are also involved in cognitive and “limbic” functions.
Thus, in line with the characteristics of its inputs, the ventral striatum is functionally strongly associated with emotional and motivational aspects of behavior. Moreover, structural and functional disturbances of ventral striatal areas have been shown to be correlated with various forms of psychopathology, such as schizophrenia, addictive behavior, and obsessive–compulsive disorder. Based on the character of the afferents of the nucleus accumbens, the ventral striatum may be viewed as a site for integration of signals with emotional content (amygdala
); contextual information (hippocampus
); motivational significance (dopaminergic inputs); information about the state of arousal (midline thalamus); and executive/cognitive information (prefrontal cortex
).
The accumbens’ outputs, directly or via ventral pallidal and dopaminergic and non-dopaminergic nigral relays, lead to brain areas involved in basic functions, such as feeding and drinking behavior (lateral hypothalamus); motivational behavior (VTA and nigral dopaminergic neurons); locomotor behavior (caudal mesencephalon); and more complex cognitive and executive functions (via medial thalamic nuclei to the prefrontal cortex). Thus, Mogenson and colleagues’ original concept of the nucleus accumbens as a functional interface between the limbic and motor systems, in general terms, is still valid. However, current insights are, of course, much more differentiated. In particular, the functional differentiation between the shell and core has received much attention in the past two decades.
Primarily based on animal experimental work, it may be concluded that the shell stands out from the core and the rest of the striatum through its involvement in the expression of certain innate, unconditioned behaviors, such as feeding or defensive behavior. The shell and core subregions play important but distinct roles in Pavlovian and instrumental conditioned learning that may be potentiated by psychostimulants. The core subregion seems to be preferentially involved in response-reinforcement learning, whereas the shell is not involved in motor or response learning, per se, rather, it integrates basic biological “drives” with the viscero-limbic and motor-effector systems. Dopamine in the nucleus accumbens may have a role in enhancing the gain by which conditioned stimuli and contexts exert control over behavior.It is considered a reward center.
Striatum
The striatum, also known as the neostriatum or striate nucleus, is a subcortical part of the forebrain. It is the major input station of the basal ganglia system. The striatum, in turn, gets input from the cerebral cortex...
that is connectionally associated with limbic structures, such as the amygdala, hippocampus, midline thalamus, and certain regions of the prefrontal cortex. In addition, the ventral striatum is strongly innervated by dopaminergic fibers from the ventral tegmental area (VTA), known as the mesolimbic dopamine system, and has the highest density of serotonergic inputs in the striatum. The ventral striatum consists of the nucleus accumbens
Nucleus accumbens
The nucleus accumbens , also known as the accumbens nucleus or as the nucleus accumbens septi , is a collection of neurons and forms the main part of the ventral striatum...
and the olfactory tubercle
Olfactory tubercle
The olfactory tubercle is a structure involved in Olfaction.It is present in humans, but much smaller than it is in some other animals.It is a frequent subject of research.-External links:...
. Although, some sources also include the ventromedial parts of the caudate nucleus
Caudate nucleus
The caudate nucleus is a nucleus located within the basal ganglia of the brains of many animal species. The caudate nucleus is an important part of the brain's learning and memory system.-Anatomy:...
and putamen
Putamen
The putamen is a round structure located at the base of the forebrain . The putamen and caudate nucleus together form the dorsal striatum. It is also one of the structures that comprises the basal ganglia. Through various pathways, the putamen is connected to the substantia nigra and globus pallidus...
.
In its present connotation, the term “ventral striatum” was introduced in 1975 by Lennart Heimer
Lennart Heimer
Lennart Heimer , was a Swedish-American neuroscientist and educator most noted for mapping circuits of the brain in the limbic lobe and basal ganglia, structures that play central roles in emotion processing and movement....
and Richard Wilson to differentiate it from the dorsal, sensorimotor-related part of the striatum (ie, the caudate-putamen complex). This inclusion of ventrally located striatal tissue in a “unified” striatum, along with the recognition of connectionally associated pallidal elements in the substantia innominata and deep layers of the olfactory tubercle (ie, the ventral pallidum), has had great impact on the functional-anatomical concept of the basal ganglia. Whereas traditionally, the basal ganglia were thought to be primarily involved in sensory-motor functions, it has now become accepted that the basal ganglia, as a result of their involvement in a set of parallel, functionally segregated basal ganglia-thalamocortical circuits, which primarily entertain the premotor and prefrontal cortical cortices, are also involved in cognitive and “limbic” functions.
Thus, in line with the characteristics of its inputs, the ventral striatum is functionally strongly associated with emotional and motivational aspects of behavior. Moreover, structural and functional disturbances of ventral striatal areas have been shown to be correlated with various forms of psychopathology, such as schizophrenia, addictive behavior, and obsessive–compulsive disorder. Based on the character of the afferents of the nucleus accumbens, the ventral striatum may be viewed as a site for integration of signals with emotional content (amygdala
Amygdala
The ' are almond-shaped groups of nuclei located deep within the medial temporal lobes of the brain in complex vertebrates, including humans. Shown in research to perform a primary role in the processing and memory of emotional reactions, the amygdalae are considered part of the limbic system.-...
); contextual information (hippocampus
Hippocampus
The hippocampus is a major component of the brains of humans and other vertebrates. It belongs to the limbic system and plays important roles in the consolidation of information from short-term memory to long-term memory and spatial navigation. Humans and other mammals have two hippocampi, one in...
); motivational significance (dopaminergic inputs); information about the state of arousal (midline thalamus); and executive/cognitive information (prefrontal cortex
Prefrontal cortex
The prefrontal cortex is the anterior part of the frontal lobes of the brain, lying in front of the motor and premotor areas.This brain region has been implicated in planning complex cognitive behaviors, personality expression, decision making and moderating correct social behavior...
).
The accumbens’ outputs, directly or via ventral pallidal and dopaminergic and non-dopaminergic nigral relays, lead to brain areas involved in basic functions, such as feeding and drinking behavior (lateral hypothalamus); motivational behavior (VTA and nigral dopaminergic neurons); locomotor behavior (caudal mesencephalon); and more complex cognitive and executive functions (via medial thalamic nuclei to the prefrontal cortex). Thus, Mogenson and colleagues’ original concept of the nucleus accumbens as a functional interface between the limbic and motor systems, in general terms, is still valid. However, current insights are, of course, much more differentiated. In particular, the functional differentiation between the shell and core has received much attention in the past two decades.
Primarily based on animal experimental work, it may be concluded that the shell stands out from the core and the rest of the striatum through its involvement in the expression of certain innate, unconditioned behaviors, such as feeding or defensive behavior. The shell and core subregions play important but distinct roles in Pavlovian and instrumental conditioned learning that may be potentiated by psychostimulants. The core subregion seems to be preferentially involved in response-reinforcement learning, whereas the shell is not involved in motor or response learning, per se, rather, it integrates basic biological “drives” with the viscero-limbic and motor-effector systems. Dopamine in the nucleus accumbens may have a role in enhancing the gain by which conditioned stimuli and contexts exert control over behavior.It is considered a reward center.
External links
- http://www.nimh.nih.gov/images1/news-items/braindorsal1.jpg
- http://www.hnl.bcm.tmc.edu/fmri.html