*(When Rahu's shadow is on the sky (Ascendant/Midheaven) and Ketu is in the underworld; his brain keeps running all the time, even if the person has gone to sleep.)*
This is a profound psychological description of the Rahu-Ketu axis, particularly when Rahu is elevated (in the 1st or 10th house) and Ketu is deep below (in the 7th or 4th house).
Rahu represents the head (obsessive thoughts), and Ketu represents the lower body (detachment). When this axis is highly active, the person's mind becomes a relentless, unstoppable machine.
Dr. Sharma explains that even when the physical body is exhausted and the person falls asleep ("banda chahe so geya"), their brain never shuts off ("dimaag hardam chalta"). They suffer from intense dreams, subconscious anxiety, and wake up feeling mentally drained.