In this case, if specific attention is given these expressions, often some words can begin to be found. What comes to mind for me on this topic, is the notion of the developing infant and a mother who is unable to hold her infant's distress in mind adequately, so that the infant's capacity for the development of a space for thought may be impeded. I agree with Vivien here. Sometimes, very large parts of the person may not be able to be articulated. But sometimes it is very specific.
Patients become silent.
I think this is quite likely to represent an aspect of the person's being where caretakers have not been able to hold the emotional experience, so that the subsequent articulation and expression of it hasn't developed. I've come to believe that it is sometimes useful to actively work with creative media. Words are easier, to be sure. Also, I think this connects with some of the work of neurophysiologists and traumatologists. Thought isn't really involved at that level.