Fig. 4

Heat map based on walking distance and identified clusters. a Based on the values of the \({s}^{\text{PPN}}\) and \({s}^{\text{CnF}}\) parameters, walking distances over 15 s are indicated by color changes. b FOG instances were determined using the FOG-identifying algorithm [17] followed by hierarchical cluster analysis. Clusters 1–4 are shown in green, red, purple, and yellow, respectively. Gray indicates parameter combinations, whose results were not identified as FOGs. PPN, pedunculopontine nucleus; CnF, cuneiform nucleus