Search results
Results from the WOW.Com Content Network
The loop has also been divided into limbic, associative, oculomotor, and motor circuits [4] to explain the role of dopamine in the basal ganglia on motivational states. [10] A five loop division based on primary cortical targets has been described as follows: [11]
The limbic basal ganglia circuits are influenced heavily by extracellular dopamine. Increased dopamine results in inhibition of the Ventral pallidum , entopeduncular nucleus, and substantia nigra pars reticulata , resulting in disinhibition of the thalamus.
Due to the location of the structures in the circuit, the resulting shape is a limbus. This is what drove MacLean to call the circuit the limbic system when he later modified the circuit. Various studies indicate that the Papez circuit is greatly influenced by the cerebellum and that perhaps the hippocampus is not the starting point of the circuit.
The limbic system also interacts with the basal ganglia. The basal ganglia are a set of subcortical structures that direct intentional movements. The basal ganglia are located near the thalamus and hypothalamus. They receive input from the cerebral cortex, which sends outputs to the motor centers in the brain stem.
An example of a neural circuit is the trisynaptic circuit in the hippocampus. Another is the Papez circuit linking the hypothalamus to the limbic lobe. There are several neural circuits in the cortico-basal ganglia-thalamo-cortical loop. These circuits carry information between the cortex, basal ganglia, thalamus, and
The mesolimbic pathway and its positioning in relation to the other dopaminergic pathways. The mesolimbic pathway is a collection of dopaminergic (i.e., dopamine-releasing) neurons that project from the ventral tegmental area (VTA) to the ventral striatum, which includes the nucleus accumbens (NAcc) and olfactory tubercle. [9]
The dopaminergic pathways that project from the substantia nigra pars compacta (SNc) and ventral tegmental area (VTA) into the striatum (i.e., the nigrostriatal and mesolimbic pathways, respectively) form one component of a sequence of pathways known as the cortico-basal ganglia-thalamo-cortical loop.
Simplified diagram of frontal cortex to striatum to thalamus pathways. There are five defined frontostriatal circuits: motor and oculomotor circuits originating in the frontal eye fields are involved in motor functions; while dorsolateral prefrontal, orbital frontal, and anterior cingulate circuits are involved in executive functions, social behavior and motivational states. [2]