The study investigates the concurrent activation of direct and indirect pathways in the striatum during action initiation. Using a novel in-vivo method that combines Cre-dependent viral expression of the genetically encoded calcium indicator GCAMP3 with time-correlated single-photon counting (TCSPC) fiber optics, researchers observed transient increases in neural activity in both direct- and indirect-pathway spiny projection neurons (SPNs) when mice initiated actions. These activations preceded the initiation of contraversive movements and predicted the occurrence of specific movements within 500 ms. The findings challenge the classical view of basal ganglia function, suggesting that coordinated activation of both pathways is critical for action selection and precise timing of basal ganglia output. The study also highlights the importance of further research to understand the motor symptoms associated with basal ganglia disorders.The study investigates the concurrent activation of direct and indirect pathways in the striatum during action initiation. Using a novel in-vivo method that combines Cre-dependent viral expression of the genetically encoded calcium indicator GCAMP3 with time-correlated single-photon counting (TCSPC) fiber optics, researchers observed transient increases in neural activity in both direct- and indirect-pathway spiny projection neurons (SPNs) when mice initiated actions. These activations preceded the initiation of contraversive movements and predicted the occurrence of specific movements within 500 ms. The findings challenge the classical view of basal ganglia function, suggesting that coordinated activation of both pathways is critical for action selection and precise timing of basal ganglia output. The study also highlights the importance of further research to understand the motor symptoms associated with basal ganglia disorders.