Reduction of dopamine in basal ganglia and its effects on syllable sequencing in speech: A computer simulation study

Basal Ganglia, 2015

Valentin Senft, Terry Stewart, Trevor Bekolay, Chris Eliasmith, Bernd J. Kr{ö}ger


Abstract Background: Reduction of dopamine in basal ganglia is a common cause of Parkinson's Disease (PD). If dopamine-producing cells die in the substantia nigra, as seen in PD, a typical symptom is freezing of articulatory movements during speech production. Goal: It is the goal of this study to simulate syllable sequencing tasks by computer modelling of the cortico-basal ganglia-thalamus-cortical action selection loop using different levels of dopamine in order to investigate the freezing effect in more detail. Method: This simulation was done using the Neural Engineering Object (Nengo) software tool. In the simulation, two dopamine level parameters (lg and le), representing the effect of \{D1\} and \{D2\} receptors, and therefore the level of dopamine in striatum respectively, can be differentiated and modified. Results: By a decrease of the dopamine level parameters lg and le to 50% we replicated a freezing effect after less than 5 syllable productions. Furthermore freezing of action selection in speech was greater for dopamine level reduction in \{D1\} than \{D2\} receptors. Conclusions: In this study using a neuro-functional brain model, the speech freezing effect results from simulating a reduction of dopamine level in striatum.

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