Basal ganglia

As basal ganglia ( basal nuclei lat ) are " subcortical " that is below the cerebral cortex (cortex cerebri) located summarized in each hemisphere of the brain, so both sides -scale cores or core areas for important functional aspects of motor, cognitive and limbic systems are of great importance. The basal ganglia form an integral part of the structures designated by Kinner Wilson in 1912 as extrapyramidalmotorisches System ( EPMS ). The term EPMS, which is today still used in many places, was abandoned because it came at a time when it was still assumed that the charge of the motor so-called pyramidal tract system, a extrapyramidalmotorisches system had to be faced, the only indirectly special motor and other brain functions had jurisdiction because it had no direct connections to the spinal cord. The long held notion that the basal ganglia are solely responsible for the control of voluntary motor function is now no longer tenable. Rather, the basal ganglia are involved in a much wider context in the whole complex of executive services such as spontaneity, affect, initiative, willpower, drive, sequential planning, anticipation, motor selection, etc..

Anatomy

Referred to the basal ganglia, partly as basal ganglia or, according to recent nomenclature ( basal nuclei ) as the basal ganglia, one counts in the narrow sense ( anatomy ):

• The caudate nucleus ( curly core) and
• The lentiform nucleus ( lenticular nucleus). This consists of: Putamen ( shell body ) and
• Pallidum or globus pallidus ( pale globe) with an internal ( internum pallidum / medial globus pallidus internus or / medial GPI ) and an external segment ( globus pallidus externum / or lateral globus pallidus externus / lateralis, GPE ).

Caudate nucleus and putamen are together in early embryonic development and are then separated by grow through the internal capsule, the longest projection path of the CNS. However, they remain thin strips of gray matter linked and together therefore referred as the striatum ( the Striped ). This summary is not only morphologically, but also functionally relevant. Ventral caudate nucleus and putamen are still connected. This place is called " fundus striati " or nucleus accumbens.

One of the basal ganglia in the broader sense ( functional) if we include:

• The substantia nigra ( black substance ), one located in the midbrain central area consisting of Pars compacta ( SNc )
• Pars reticularis ( SNr ) and lateralis

The entrance station in the basal ganglia is the striatum dar. It not only projections from the cerebral cortex and substantia nigra, but not from different core areas of the central nervous system, such as raphe nuclei, reticular formation. The starting point is the pallidum internum (GPI ), which GABAergic ( inhibitory ) projected directly onto the thalamus and him ( and thus the cerebral cortex ) inhibits. Both the pallidum and subthalamic nucleus are evolutionarily to the thalamus ventralis.

Function

About the until now only partially understood complex function of the basal ganglia is currently postulated hypothetical, that they are instrumental in both the selection and processing of currently required " motor " and " non-motor " ( higher - inclusive ) action patterns as well as simultaneously on the suppression or inhibition currently this is not required, so unwanted and thus suppressing activation patterns. The basal ganglia are in a sense as a " filtering process " ( gating, see below) in a complex loop (loop) included emanating from the cerebral cortex and the basal ganglia and the thalamus back to the cerebral cortex ( frontal lobe ) runs. From almost the entire cerebral cortex, specifically from the nerve cells of layer V, arrive with a few exceptions (primary visual and auditory cortex) information to the striatum as the input station of the basal ganglia in the form of cortico- striatal connections ( excitatory glutamatergic transmission ). About the output station of the basal ganglia, the substantia nigra ( pars reticulata SNR) and the globus pallidus internus (GPI ), which processed by the basal ganglia end information ( inhibitory GABAergic transmission ) reaches the thalamus and from the thalamus ( excitatory, glutamatergic ) primarily to the frontal cortex back. The basal ganglia provide an elementary, in detail yet poorly understood functional contribution of the frontal, the so-called executive part of the brain dar.

Today it delimits a direct ( excitatory ) connection from the striatum to the initial structures (SNR and GPI) against indirect ( inhibitory ) compound. The striatum and the GPI are both GABAergic ( inhibitory ). Thus, a direct projection of the striatum leads to the GPI to an inhibition of its inhibition ( disinhibition ), which now means a stimulation of the thalamus and the cerebral cortex. In the indirect connection, it is a bit more complicated: The striatum inhibits the globus pallidus externus, GPE, which inhibits the subthalamic nucleus. Thus, it comes back to an inhibition of inhibition, ie the subthalamic nucleus is excited. He now acts in turn exciting the GPI, which is now the thalamus and thus indirectly inhibits the cerebral cortex. If the GPE is inhibited, a direct inhibition of GPI, which the inhibitory effect of GPI even more enhanced disappears. This is the output modulation of Basalganglienaktivität speak to two oppositely directed reins, causing a more (positive ) or below ( negative) movement or action patterns ( in the broad sense " behavior ").

The of the nerve cells of the substantia nigra ( pars compacta ) outgoing dopaminergic projection to the striatum is today therefore represents a particularly strong researched modulation path within the basal ganglia, because it has been recognized that his fault due to a premature degeneration ( " aging " ) to the symptoms of Parkinson's disease results.

Diseases

The neurological diseases associated with a dysfunction of the basal ganglia, including:

• Parkinsonian syndromes, such as Parkinson 's disease, multiple system atrophy (MSA), Hallervorden -Spatz syndrome ( HSS)
• Dystonia syndromes, such as spasmodic torticollis, athetosis, dystonia tardive
• Choreatic syndromes, such as Huntington's disease, Hemiballism, Tardive dyskinesia, choreoathetosis
• PANS / PANDAS
• ADHD
• Tic disorders, e.g. Tourette's syndrome

The " Parkinson's disease " it comes as a result of chronic progressive degeneration of the substantia nigra pars compacta ( SNc ) outgoing dopaminergic transmission to a pathological change in the striatal modulation in very varying degrees to Muskeltonusveränderungen (rigor ), motion depletion ( hypokinesia ), shaking (tremor ), postural instability, reduced sense of smell ( hyposmia ), and other symptoms can result.

In early childhood, perinatal brain damage (eg, kernicterus, lack of oxygen) are lesions of the basal ganglia with changes in muscle tone (eg athetosis ) frequently. In Wilson's disease occurs due to copper deposition, inter alia, in the basal ganglia to complex motor and mental disorders.

Gating theory

As described above, the filter function of the basal ganglia or striatum is referred to as gating. The gating theory itself is neuroanatomically and physiologically relatively well established, however, can be found under this name at present almost exclusively in neuropsychological publications. This is in favor of the validity of the gating theory important as gating the content is nothing new in itself, but just a different name. From the gating theory can be a number of other theories derived to explain diseases and describe inter-individual differences in human personality:

• Tic disorders as Fehlverschaltung the basal ganglia, where a recurrent pattern of movement is carried out by certain behavior plans will be processed incorrectly by the striatum.
• ADHD (Attention Deficit and Hyperactivity Disorder ). Is here some researchers suggest similar interconnection pattern as in tic disorders, except that in this case not a particular behavior pattern would processed incorrectly, but a general inadequate filter function is present in the redundant or " inappropriate " behavior is energized ( hyperactivity), while new behavior plans flawed be inhibited ( attention deficit ).
• Obsessive Compulsive Disorder: The gating theory of obsessive-compulsive disorder is comparable with that of the tic disorders, which they rather " shaky " is, scientifically and according to many experts since although they can explain compulsions, but not obsessive thoughts, nor the affective component of OCD.

Another explanation of the gating theory of the inter-individual differences in personality: Hans Jürgen Eysenck described one of today 's most established personality factors as extraversion vs.. Introversion and told him about basic cortical arousal. These neurophysiological explanation is, however, now questioned more often. Recent research has tried to explain this personality dimension on the gating. Thus, introverts have a more efficient gating compared to extraverts, why extraverts their gating ( ie the ability of the striatum to process behavior adequately plans ) need to step by seeking additional internal locus of external signals or sensory stimuli. In this way, according to the theory, the glutamatergic projection of the cerebral cortex to the striatum amplified, whereby this can now better filtering. This theory explains for example why extraverts better learning when they listen to music, for example, while introverts are thereby rather distracted.

The gating theory in the broader sense is promising, but currently lies still in its infancy. Many of the subtheories are scientifically sound, which linkages partly (though logical) are still difficult or impossible to examine.

Swell

• Jonathan W. Mink: The Basal Ganglia Chapter 31 - Fundamental Neuroscience 2003 Academic Press
• Bastian Conrad, Andres Ceballos - Baumann: Movement disorders in neurology - recognize and properly treat. 1st edition. Thieme Verlag, Stuttgart / New York 1996, ISBN 3-13-102391-0.
• Andres Ceballos -Baumann, Bastian Conrad: movement disorders. 2nd edition. Thieme Verlag, Stuttgart / New York 2005, ISBN 3-13-102392-9.
• G. Percheron, G. Fénelon, V. Leroux - Hugon, A. Feve (1994 ): Histoire du système de la base of the ganglions. La lente d'un système émergence cérébral majeur. Revue Neurologique August-September; 150 (8-9) :543 - 54th
• Lennart Heimer: The Human Brain and Spinal Cord: Functional Neuroanatomy and Dissection Guide. Springer, New York 1995, ISBN 0-387-94227-0.