UNASSIGNED: This study aimed to analyze the spiking patterns of subthalamic nucleus and globus pallidus coupling in hyperdirect pathway in healthy primates and in Parkinson\'s disease using a conductance-based model. The effect of calcium membrane potential has also been investigated.
UNASSIGNED: System of coupled differential equation arising from the conductance-based model has been simulated using ODE45 in MATLAB 7.14 to analyze the spiking patterns.
UNASSIGNED: Analysis of spiking patterns suggests that subthalamic nucleus with synaptic input from globus pallidus in hyperdirect pathways is capable of showing two types of spiking pattern - irregular and rhythmic. Characterization of spiking patterns in healthy and Parkinson condition has been done based on their frequency, trend, and spiking rate. Results indicate that rhythmic patterns does not account for Parkinson\'s disease. Further, calcium membrane potential is an important parameter to target for identifying the cause of this disease.
UNASSIGNED: This work demonstrates that subthalamic nucleus and globus pallidus coupling in hyperdirect pathway can account for Parkinson\'s symptoms. However, the entire process of excitations and inhibition caused by glutamate and GABA receptors is limited by the timing of depolarization of the model. There is improvement in the correlation between healthy and Parkinson\'s patterns by increase in calcium membrane potential, however, for a limited time.

Uncertainties concerning anatomy and function of cortico-subcortical projections have arisen during the recent years. A clear distinction between cortico-subthalamic (hyperdirect) and cortico-tegmental projections (superolateral medial forebrain bundle, slMFB) so far is elusive. Deep Brain Stimulation (DBS) of the slMFB (for major depression, MD and obsessive compulsive disorders, OCD) has on the one hand been interpreted as actually involving limbic (prefrontal) hyperdirect pathways. On the other hand slMFB\'s stimulation region in the mesencephalic ventral tegmentum is said to impact on other structures too, going beyond the antidepressant (or anti OCD) efficacy of sole modulation of the cortico-tegmental reward-associated pathways. We have here used a normative diffusion MRT template (HCP, n = 80) for long-range tractography and augmented this dataset with ex-vivo high resolution data (n = 1) in a stochastic brain space. We compared this data with histological information and used the high resolution ex-vivo data set to scrutinize the mesencephalic tegmentum for small fiber pathways present. Our work resolves an existing ambiguity between slMFB and prefrontal hyperdirect pathways which-for the first time-are described as co-existent. DBS of the slMFB does not appear to modulate prefrontal hyperdirect cortico-subthalamic but rather cortico-tegmental projections. Smaller fiber structures in the target region-as far as they can be discerned-appear not to be involved in slMFB DBS. Our work enfeebles previous anatomical criticism and strengthens the position of the slMFB DBS target for its use in MD and OCD.