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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.
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.
The striatum (pl.: striata) or corpus striatum [5] is a cluster of interconnected nuclei that make up the largest structure of the subcortical basal ganglia. [6] 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 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.
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.
Frontostriatal circuits are neural pathways that connect frontal lobe regions with the striatum and mediate motor, cognitive, and behavioural functions within the brain. [1] They receive inputs from dopaminergic , serotonergic , noradrenergic , and cholinergic cell groups that modulate information processing. [ 2 ]
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