What are the Sinosphere and the Indosphere in the study of Tibeto-Burman languages?

In the study of Tibeto-Burman languages, the terms Sinosphere and Indosphere refer to the distinct spheres of cultural and linguistic influence exerted by China and India, respectively. These influences have significantly contributed to the typological diversity observed across the Tibeto-Burman family.1

• The Sinosphere: This sphere encompasses languages and cultures shaped by Chinese influence. Examples include the Loloish branch of Tibeto-Burman, the Hmong-Mien family, the Kam-Sui branch of Kadai, and the Viet-Muong branch of Mon-Khmer.1
• The Indosphere: This sphere includes languages and cultures influenced by Indian traditions, such as social hierarchies like varna, religions like Hinduism and Buddhism, and Devanagari writing systems. The Tibeto-Burman languages of Nepal and much of the Kamarupan branch are considered Indospheric.1

Some linguistic communities, such as Tibetan and Thai, have been influenced by both cultural traditions, while others remain geographically remote enough to have escaped significant influence from either.1