Functional Neuroanatomy of the Basal Ganglia

Abstract

The "basal ganglia" refers to a group of subcortical nuclei responsible primarily for motor control, as well as other roles such as motor learning, executive functions and behaviors, and emotions. Proposed more than two decades ago, the classical basal ganglia model shows how information flows through the basal ganglia back to the cortex through two pathways with opposing effects for the proper execution of movement. Although much of the model has remained, the model has been modified and amplified with the emergence of new data. Furthermore, parallel circuits subserve the other functions of the basal ganglia engaging associative and limbic territories. Disruption of the basal ganglia network forms the basis for several movement disorders. This article provides a comprehensive account of basal ganglia functional anatomy and chemistry and the major pathophysiological changes underlying disorders of movement. We try to answer three key questions related to the basal ganglia, as follows: What are the basal ganglia? What are they made of? How do they work? Some insight on the canonical basal ganglia model is provided, together with a selection of paradoxes and some views over the horizon in the field.T he basal ganglia and related nuclei consist of a variety of subcortical cell groups engaged primarily in motor control, together with a wider variety of roles such as motor learning, executive functions and behavior, and emotions. The term basal ganglia in the strictest sense refers to nuclei embedded deep in the brain hemispheres (striatum or caudate-putamen and globus pallidus), whereas related nuclei consist of structures located in the diencephalon (subthalamic nucleus), mesencephalon (substantia nigra), and pons ( pedunculopontine nucleus). Ideas and concepts regarding the functions of the basal ganglia were strongly influenced by clinical observations during the 20th century, which showed that lesions of the lenticular nucleus ( putamen and globus pallidus) and the subthalamic nucleus (STN) were associated with parkinsonian signs, dystonia, and hemiballismus (Wilson 1925;Purdon-Martin 1927). Thus, the terms extra-pyramidal system and extra-pyramidal syndrome were frequently used in the past to refer to the pathological basis of movement disorders in an attempt to make a clear distinction from the pyramidal system (corticofugal neurons that give rise to corticospinal projections). At present, these terms and distinctions are considered obsolete and misleading and, therefore, will not be used in

Evolutionary and Developmental Contributions for Understanding the Organization of the Basal Ganglia

“…This is due to the high complexity of these nuclei, each comprising many different subtypes of neurons with different chemical features (expression of neurotransmitters, neuropeptides and receptors, for example), connections and physiological properties [reviewed by Reiner et al, 1998;Medina, 2009;Lanciego et al, 2012].…”

“…These nuclei are not only involved in the execution of tasks, they also play important roles in cognitive functions essential for adaptive behavior, such as planning, attention, learning and memory [reviewed by Reiner et al, 1998;Gerfen, 2004;Graybiel and Saka, 2004;Medina, 2009;Lanciego et al, 2012]. Basal ganglia dysfunction is associated with a variety of human diseases or disorders, including Parkinson's disease, obsessive-compulsive disorder or drug addiction, and understanding the basis of their clinical manifestations requires deep knowledge of the function of each single neuron subpopulation [Albin et al, 1989;Reiner et al, 1998].…”

Innate Inflammation in Parkinson's Disease

“…As the disease progresses, the degeneration becomes more widespread and involves other regions of the brain (Braak et al 2003). The affected circuits and the clinical consequences are described in more detail in other articles in this collection (Lanciego et al 2012;Massano and Bhatia 2012).…”

Fusion of Intraoperative 3D B-mode and Contrast-Enhanced Ultrasound Data for Automatic Identification of Residual Brain Tumors

“…Therefore, the basal ganglia area was mainly out of our focus, and in the remaining cases, we found no remarkable higher enhancement. Because this region plays a relevant role in the brain [43], a study taking into account the problem of tumor residual detection based on CEUS close to this area is important in the future. However, the iCEUS modality is still at the evaluation stage for brain tumor applications.…”