Question: What is the name of the geographical region that early Islamic usage often regarded everywhere east of western Persia and where Vistaham helped Khosrow regain his throne after the rebellion of Bahram Chobin?  

<P0-S0> Shirin (? <P0-S1>  – 628 AD) (Persian: شيرين‎ ‎ ) was a wife of the Sassanid Persian Shahanshah (king of kings), Khosrow Parviz. <P0-S2>  In the revolution after the death of Khosrow's father Hormizd IV, the General Bahram Chobin took power over the Persian empire. <P0-S3>  Shirin fled with Khosrow to Syria, where they lived under the protection of Byzantine emperor Maurice. <P0-S4>  In 591, Khosrow returned to Persia to take control of the empire and Shirin was made queen. <P0-S5>  She used her new influence to support the Christian minority in Iran, but the political situation demanded that she do so discreetly. <P0-S6>  Initially she belonged to the Church of the East, the so-called Nestorians, but later she joined the miaphysite church of Antioch, now known as the Syriac Orthodox Church. <P0-S7>  After conquering Jerusalem in 614, amidst the Byzantine–Sasanian War of 602–628, the Persians captured the True Cross of Jesus and brought it to their capital Ctesiphon, where Shirin took the cross in her palace. <SEP> <P1-S0> Taqlid or taqleed (Arabic تَقْليد "taqlīd") is an Islamic terminology denoting the conformity of one person to the teaching of another. <P1-S1>  The person who performs taqlid is termed "muqallid". <P1-S2>  The definite meaning of the term varies depending on context and age. <P1-S3>  Classical usage of the term differs between Sunni Islam and Shia Islam. <P1-S4>  Sunni Islamic usage designates the unjustified conformity of one person to the teaching of another, apart from justified conformity of layperson to the teaching of "mujtahid" (a person who is qualified for independent reasoning). <P1-S5>  Shia Islamic usage designates the general conformity of non-mujtahid to the teaching of mujitahid, and there is no negative connotation. <P1-S6>  In contemporary usage, especially in the context of Islamic reformism, it is often shed in a negative light, and translated as "blind imitation". <P1-S7>  This refers to the perceived stagnation of independent intellectual effort ("ijtihad") and uncritical imitation of traditional religious interpretation by the religious establishment in general. <SEP> <P2-S0> Khorasan (Middle Persian: , Persian: خراسان‎ ‎ "Xorâsân"    ) is a historical region lying in the northeast of Persia. <P2-S1>  However, in pre-Islamic and early Islamic times, the term "Khurassan" frequently had a much wider denotation, covering also parts of Central Asia and Afghanistan; early Islamic usage often regarded everywhere east of western Persia, so-called Jibal or what was subsequently termed 'Irak 'Adjami, as being included in a vast and ill-defined region of Khurasan, which might even extend to the Indus Valley and Sind. <SEP> <P3-S0>  Vistahm helped Khosrow regain his throne after the rebellion of Bahram Chobin, but later led a revolt himself, which encompassed the entire Iranian East before being suppressed. <P3-S1> Bistam or Vistahm (also transliterated Wistaxm, Persian: بیستام‎ ‎ ), was a Parthian dynast of the Ispahbudhan house, and maternal uncle of the Sasanian "shah" of Persia, Khosrow II (reigned 591–628).