The period from 2002 to 2008 was defined by rapid maturation of bidirectional neural interfaces capable of both recording and stimulating across dense electrode arrays with real-time, closed-loop control. Advances in high-density sensing were driven by CMOS sensor arrays and on-chip electronics, paired with wireless power and data links to scale in-vivo neural recording and imaging. Long-term chronic implantation studies examined durability, yield, and stability of silicon-substrate microelectrodes across species and behavioral contexts, while methodological efforts emphasized real-time spike detection, data reduction, and variability in spike sorting workflows. Historical Significance: Foundational demonstrations of direct cortical control of three-dimensional neuroprosthetic movement with feedback established the core brain-computer interface paradigm for real-time decoding. Durable multisite recordings in awake primates and the chronic viability of silicon-substrate intracortical microelectrodes informed long-term implant strategies. Analyses of electrical parameter settings in neuromodulation highlighted how stimulation strategies shape therapeutic outcomes, guiding clinical optimization. The integration of low-power wireless neural recording systems with scalable electrode counts provided a blueprint for compact, implantable brain-machine interfaces that influenced subsequent hardware and software architectures.