Topicalization is a process of establishing a topic at the beginning of a sentence. This topic-comment structure familiarly as OSV (object-subject-verb) is a very common use in American Sign Language.
In an OSV sentence, the non-manual signal is raised eyebrows and tilt head forward at the beginning of the sentence when signing the object (O), then proceeding with the rest of the sentence (SV).
See a few examples below. The gloss /\ depicts raised eyebrows. I'll start with a few simple sentences before giving a more complex sentence.
The sentence above, /\book/\, ix-me give-hir (where "hir" is a non-gendered pronoun for "her/him"). The signer raises her eyebrows and slightly tilted her head forward when signing "book" and then produces the rest of the sentence.
Another example of a basic sentence is /\paper/\, please you-give-me.. In SVO (subject-verb-object), this would be please you-give-me paper. No raised eyebrows would be visible in this SVO sentence.
Below is a couple of more examples with a little more complex sentences.
fruit/\, left-it-too-long, spoiled
Fruits spoils when it is kept too long.
The signer begins with the signed word fruit (topic) and establishes this referent in its spatial location, in which fruit becomes it; then, she signs keep-it-too-long (or left-it-for-long-time). This movement (temporal aspect) repeats a few times which suggests "for a long time." When she signs spoils in the same space as the previous (verb). The use of the specific space/location is similar to "it" in English.
/\speaker/\ [L]classifier-1 audience (hs)heckle+
Observe how this sentence is grammatically constructed. The Ameslan begins with the ASL word speaker (topicalization) and then establishes the classifier for person in reference to the speaker in a spatial location (which becomes a "pronoun"). Then she signs audience and heckle (verb inflection) towards the spatial referent (the speaker).
You may be also interested in syntax in sign language.
OSV sentence structure (Object-Subject-Verb).