Compensatory coupling between leak and HCN conductances defines a low dimensional solution manifold in GPe neuron...

The external segment of the globus pallidus contains distinct neuronal subtypes, primarily classified as prototypical and arkypallidal neurons, which exhibit different anatomical, electrophysiological, and functional properties. This cellular heterogeneity plays a central role in shaping basal ganglia activity under both physiological and pathological conditions, including neurodegenerative disorders such as Parkinson's disease. Alterations in intrinsic membrane conductances, particularly leak and hyperpolarization activated cyclic nucleotide-gated (HCN) currents, have been implicated in abnormal neuronal excitability and dysfunctional circuit dynamics. In this study, we used a Hodgkin-Huxley-like computational model to investigate how variations in leak ([Formula: see text]) and HCN ([Formula: see text]) conductances shape the intrinsic dynamics of these pacemaker neuronal subtypes. By systematically exploring the [Formula: see text] parameter space, we characterized key electrophysiological features, including firing rate, sag ratio, and trough potential, and constrained these responses using experimental benchmarks. We then introduced an intersection-based methodology to identify subsets of conductance values that simultaneously satisfy multiple physiological constraints. Within this constrained space, we uncovered a robust inverse relationship between [Formula: see text] and [Formula: see text], defining a low-dimensional solution manifold that captures coordinated interactions between these conductances. This manifold preserves physiological excitability through balanced adjustments in ion channel properties, consistent with experimental observations and the principle of ion channel degeneracy. Importantly, deviations from this regime provide a mechanistic framework to understand how imbalances in [Formula: see text] and [Formula: see text] may drive to abnormal excitability and pathological dynamics in basal ganglia circuits. Overall, this work establishes a quantitative link between intrinsic conductance regulation and neuronal function, offering a framework to investigate how disruptions in these mechanisms may contribute to neurodegenerative conditions.