Brushwork, mark making, strokes, etc. woven into an otherwise representational painting/drawing can serve as a reminder to the viewer that a living human being truly looked at and rendered the subject shown in the piece – that this painting/drawing is not merely a photographic snapshot or mechanical reproduction. Expressive strokes can maintain a liveliness and help to move the eye across the rendered forms and create a flow of energy. The direction of the strokes can help to indicate three-dimensional shapes.
The presence of expressive rendering throughout a piece can also keep the viewer from entirely losing him or herself in the illusion portrayed. More blatant and stronger strokes throughout a representational painting/drawing can strike a balance between the artist's emotional expression and the depiction of reality. Some strokes might go against the true indication of what the artist is objectively seeing, while other strokes serve to show the scene.
One might choose to push representation in this direction because of a strong emotional reaction to the characters or objects being rendered, or this approach might be used to express the strong emotions being felt by the characters themselves.
A painting/drawing might be done all in one session, alla prima, and the balance between depiction and movement can evoke the spontaneous and energetic experience of working this way... a moment is captured, and we sense the artist in action there with the subject, in time.
In works that strongly emphasize the emotional/energetic expression of the artist more so than the depiction of a scene, the artist can convey an overwhelming feeling that dominates and nearly replaces the experience of objective reality. Blinding anger, blissful rapture, and profound sadness might all be best portrayed this way. Particularly emotional artists might have periods in which any attempt at representation inevitably leads to this way of seeing... the emotions override the sense perceptions and only a minimal indication of the physical world can be managed. Or, in a painting/drawing that is meant to primarily emphasize expressive action, an artist might consciously choose this way of seeing in order to ground the viewer with a hint at reality... the eye follows the dance of the brush and the movement of colors but repeatedly finds a connection to reality, so the viewer is not lost entirely in the emotions.
Featured: The Starry Night by Vincent Van Gogh.