The role of intra-thalamic nuclei in motor pattern expression by the basal ganglia: a formal model

I. JOURDAN; P. BARTTFELD; L. RIQUELME, B.S. ZANUTTO

EEUU

Congreso; Neuroscience 2006; 2006

Society for Neuroscience

The main topic analyzed in this study is how the Basal Ganglia (BG) allows a base-state of non-cortical correlation in pattern expression. The model was developed using an “integrate-and-fire” neural network. The BG nuclei were connected according to neuro-physiological data (Wichmann & DeLong 1996; Koch, 1999). In rats and monkeys, it was found that, when there is cortical activation, it exists synchronization between the BG and the cortex, i.e. when a task is being executed or in Parkinson´s disease. If we consider the internal segment at the Globus Pallidus (GPi), synchronism GPi-cortex from 3Hz to 85Hz can be found). On the other hand, in delta sleep or in anaesthetized animals, there is a very low frequency correlation (1-10 Hz), but there is no high frequency correlation between GPi-cortex. (Boraud et al. 2005, Foffani et al. 2005,Magill et al. 2000, Magill et al 2004, Levy et al. 2002). At high frequency, with cortical activation, the correlation between the BG output and the cortex could be relevant for the motor pattern expression (Mink, 1996). Considering high frequency only, the BG network would maintain the GPi and the cortex decorrelated when there is no pattern to select, like in delta sleep or with an anaesthetized model.Many thalamus-BG and thalamus-BG-cortex loops are BG modulators. Particularly, there exists an anatomic thalamus-BG loop, between GPi - intralaminar thalamic nuclei (IL) and Subthalamic nucleus (STN). (Castle et al. 2005). We analyzed the different BG nuclei synaptic strengths, including the IL-BG path. Our model shows that, in anaesthetized animals, the thalamic path could be relevant to allow a high frequency decorrelated state between the GPi and the cortex.