Bridge thoughts are the thoughts between the lines.
They are before a new speech or line, and bridge the ‘end’ to the ‘beginning’.
You first receive the impulse from something sent to you, and then you respond, and, as you inhale, different thoughts affect your mind and breath until you say words.
These different thoughts are bridge thoughts. It’s in the space before you speak.
It’s a detailed part of your work.
You may or may not say in words what you are thinking at the beginning of your breath, or what you are thinking in the middle of it. You may even switch completely by the time words leave your mouth: deflecting it, altering it, colouring it, twisting it, clarifying it, sharpening it, putting consciousness to it.
It being the words you speak.
The brain works at such speed - keep learning how yours works.
It is useful to explore and experience these minute, specific and rapid thoughts that flavour your speech. In your preparation you can write down, say out loud, or visualize these unwritten thoughts. That work can stimulate your imagination.
This ‘bridge thought’ work is tied to your inner monologue work. See if it assists you to be more specific.