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Loss of specificity in Basal Ganglia related movement disorders.

Bronfeld M, Bar-Gad I - Front Syst Neurosci (2011)

Bottom Line: Studies of normal behavior have found that BG neurons tend to phasically modulate their activity in relation to different behavioral events.We review the existing evidence for LOS in BG-related movement disorders, the possible neural mechanisms underlying LOS, its effects on frequently used measures of neuronal activity and its relation to theoretical models of the BG.Thus, the concept of neuronal specificity may underlie a unifying conceptual framework for the BG role in normal and abnormal motor control.

View Article: PubMed Central - PubMed

Affiliation: The Leslie and Susan Gonda (Goldschmied) Multidisciplinary Brain Research Center, Bar-Ilan University Ramat-Gan, Israel.

ABSTRACT
The basal ganglia (BG) are a group of interconnected nuclei which play a pivotal part in limbic, associative, and motor functions. This role is mirrored by the wide range of motor and behavioral abnormalities directly resulting from dysfunction of the BG. Studies of normal behavior have found that BG neurons tend to phasically modulate their activity in relation to different behavioral events. In the normal BG, this modulation is highly specific, with each neuron related only to a small subset of behavioral events depending on specific combinations of movement parameters and context. In many pathological conditions involving BG dysfunction and motor abnormalities, this neuronal specificity is lost. Loss of specificity (LOS) manifests in neuronal activity related to a larger spectrum of events and consequently a large overlap of movement-related activation patterns between different neurons. We review the existing evidence for LOS in BG-related movement disorders, the possible neural mechanisms underlying LOS, its effects on frequently used measures of neuronal activity and its relation to theoretical models of the BG. The prevalence of LOS in a many BG-related disorders suggests that neuronal specificity may represent a key feature of normal information processing in the BG system. Thus, the concept of neuronal specificity may underlie a unifying conceptual framework for the BG role in normal and abnormal motor control.

No MeSH data available.


Related in: MedlinePlus

Theoretical models of the basal-ganglia. In all panels blue and red arrows indicate inhibitory and excitatory effects, respectively. (A) Schematic representation of the BG circuitry, according to the “box and arrow” model. (Based on: Albin et al., 1989; DeLong, 1990). (B) Illustration of BG “action selection process”: integration of excitatory and inhibitory pathways through the BG lead to focused excitation and diffused “surround” inhibition of thalamic neurons, thereby selecting the desired motor pattern while inhibiting potentially competing motor patterns (Based on: Mink, 1996). (C) Structure of the cortico-BG neural network according to the “reinforcement driven dimensionality reduction” model. Information from multiple cortical regions is integrated by lateral inhibitory connections within the striatum and feed-forward projections from the striatum to the GPi. A reward signal is provided via dopaminergic (DA) projections, and used to modulate the relative significance of different input dimensions (Based on: Bar-Gad et al., 2000).
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Figure 5: Theoretical models of the basal-ganglia. In all panels blue and red arrows indicate inhibitory and excitatory effects, respectively. (A) Schematic representation of the BG circuitry, according to the “box and arrow” model. (Based on: Albin et al., 1989; DeLong, 1990). (B) Illustration of BG “action selection process”: integration of excitatory and inhibitory pathways through the BG lead to focused excitation and diffused “surround” inhibition of thalamic neurons, thereby selecting the desired motor pattern while inhibiting potentially competing motor patterns (Based on: Mink, 1996). (C) Structure of the cortico-BG neural network according to the “reinforcement driven dimensionality reduction” model. Information from multiple cortical regions is integrated by lateral inhibitory connections within the striatum and feed-forward projections from the striatum to the GPi. A reward signal is provided via dopaminergic (DA) projections, and used to modulate the relative significance of different input dimensions (Based on: Bar-Gad et al., 2000).

Mentions: Theoretical models have tried to conceptualize the accumulating data of the BG system into a unified model explaining its role in normal behavior and in different pathological states (Figure 5). The early “box and arrow” model relied primarily on the anatomical connectivity of the BG, and described different normal and pathological states as deriving from global changes in the overall firing rate in different nuclei within the pathway. Later models addressed more detailed spatial and temporal patterns of the BG output, and how changes in these patterns may lead to abnormal states. This section reviews these models and the extent to which they address the phenomena of LOS in different BG-related disorders.


Loss of specificity in Basal Ganglia related movement disorders.

Bronfeld M, Bar-Gad I - Front Syst Neurosci (2011)

Theoretical models of the basal-ganglia. In all panels blue and red arrows indicate inhibitory and excitatory effects, respectively. (A) Schematic representation of the BG circuitry, according to the “box and arrow” model. (Based on: Albin et al., 1989; DeLong, 1990). (B) Illustration of BG “action selection process”: integration of excitatory and inhibitory pathways through the BG lead to focused excitation and diffused “surround” inhibition of thalamic neurons, thereby selecting the desired motor pattern while inhibiting potentially competing motor patterns (Based on: Mink, 1996). (C) Structure of the cortico-BG neural network according to the “reinforcement driven dimensionality reduction” model. Information from multiple cortical regions is integrated by lateral inhibitory connections within the striatum and feed-forward projections from the striatum to the GPi. A reward signal is provided via dopaminergic (DA) projections, and used to modulate the relative significance of different input dimensions (Based on: Bar-Gad et al., 2000).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3108383&req=5

Figure 5: Theoretical models of the basal-ganglia. In all panels blue and red arrows indicate inhibitory and excitatory effects, respectively. (A) Schematic representation of the BG circuitry, according to the “box and arrow” model. (Based on: Albin et al., 1989; DeLong, 1990). (B) Illustration of BG “action selection process”: integration of excitatory and inhibitory pathways through the BG lead to focused excitation and diffused “surround” inhibition of thalamic neurons, thereby selecting the desired motor pattern while inhibiting potentially competing motor patterns (Based on: Mink, 1996). (C) Structure of the cortico-BG neural network according to the “reinforcement driven dimensionality reduction” model. Information from multiple cortical regions is integrated by lateral inhibitory connections within the striatum and feed-forward projections from the striatum to the GPi. A reward signal is provided via dopaminergic (DA) projections, and used to modulate the relative significance of different input dimensions (Based on: Bar-Gad et al., 2000).
Mentions: Theoretical models have tried to conceptualize the accumulating data of the BG system into a unified model explaining its role in normal behavior and in different pathological states (Figure 5). The early “box and arrow” model relied primarily on the anatomical connectivity of the BG, and described different normal and pathological states as deriving from global changes in the overall firing rate in different nuclei within the pathway. Later models addressed more detailed spatial and temporal patterns of the BG output, and how changes in these patterns may lead to abnormal states. This section reviews these models and the extent to which they address the phenomena of LOS in different BG-related disorders.

Bottom Line: Studies of normal behavior have found that BG neurons tend to phasically modulate their activity in relation to different behavioral events.We review the existing evidence for LOS in BG-related movement disorders, the possible neural mechanisms underlying LOS, its effects on frequently used measures of neuronal activity and its relation to theoretical models of the BG.Thus, the concept of neuronal specificity may underlie a unifying conceptual framework for the BG role in normal and abnormal motor control.

View Article: PubMed Central - PubMed

Affiliation: The Leslie and Susan Gonda (Goldschmied) Multidisciplinary Brain Research Center, Bar-Ilan University Ramat-Gan, Israel.

ABSTRACT
The basal ganglia (BG) are a group of interconnected nuclei which play a pivotal part in limbic, associative, and motor functions. This role is mirrored by the wide range of motor and behavioral abnormalities directly resulting from dysfunction of the BG. Studies of normal behavior have found that BG neurons tend to phasically modulate their activity in relation to different behavioral events. In the normal BG, this modulation is highly specific, with each neuron related only to a small subset of behavioral events depending on specific combinations of movement parameters and context. In many pathological conditions involving BG dysfunction and motor abnormalities, this neuronal specificity is lost. Loss of specificity (LOS) manifests in neuronal activity related to a larger spectrum of events and consequently a large overlap of movement-related activation patterns between different neurons. We review the existing evidence for LOS in BG-related movement disorders, the possible neural mechanisms underlying LOS, its effects on frequently used measures of neuronal activity and its relation to theoretical models of the BG. The prevalence of LOS in a many BG-related disorders suggests that neuronal specificity may represent a key feature of normal information processing in the BG system. Thus, the concept of neuronal specificity may underlie a unifying conceptual framework for the BG role in normal and abnormal motor control.

No MeSH data available.


Related in: MedlinePlus