So far I have noticed this in the areas of keeping in touch with people in the way I used to - ringing up, sending a letter or card at birthdays, Christmas or from holiday jaunts. Other Parkinson's symptons like a whispery breathy voice, small quavery handwriting, a blank facial expression all conspire to make communication harder that it used to be.
Just the other day somebody said I looked worried, but no, I wasn't feeling worried at all, just pleasantly relaxed, while doing my exercises at the gym. Maybe I just need to smile a bit more, exercise my facial muscles and practise doing so in the mirror, so these things become second nature once again.