Neural circuitry is typically modulated via invasive brain implants and tethered optical fibres in restrained animals. Here we show that wide-field illumination in the second near-infrared spectral window (NIR-II) enables implant-and-tether-free deep-brain stimulation in freely behaving mice with stereotactically injected macromolecular photothermal transducers activating neurons ectopically expressing the temperature-sensitive transient receptor potential cation channel subfamily V member 1 (TRPV1). The macromolecular transducers, ~40 nm in size and consisting of a semiconducting polymer core and an amphiphilic polymer shell, have a photothermal conversion efficiency of 71% at 1,064 nm, the wavelength at which light attenuation by brain tissue is minimized (within the 400–1,800 nm spectral window). TRPV1-expressing neurons in the hippocampus, motor cortex and ventral tegmental area of mice can be activated with minimal thermal damage on wide-field NIR-II illumination from a light source placed at distances higher than 50 cm above the animal’s head and at an incident power density of 10 mW mm^–2. Deep-brain stimulation via wide-field NIR-II illumination may open up opportunities for social behavioural studies in small animals.

神经回路通常通过侵入性大脑植入物和束缚动物的系绳光纤进行调制。在这里，我们展示了第二个近红外光谱窗口 (NIR-II) 中的广域照明能够在自由行为的小鼠中实现无植入物和无系绳的深部脑刺激，其中立体定向注射大分子光热换能器激活异位表达温度的神经元 -敏感瞬时受体电位阳离子通道亚家族 V 成员 1 (TRPV1)。大分子换能器，大小约为 40 nm，由半导体聚合物核和两亲聚合物壳组成，在 1,064 nm 处的光热转换效率为 71%，脑组织的光衰减最小的波长（在 400– 1,800 nm 光谱窗口）。海马体中表达 TRPV1 的神经元，^–2。通过宽视场 NIR-II 照明进行深部脑刺激可能为小动物的社会行为研究开辟了机会。