This symptom is commonly found along with the loss of satisfaction however is more associated with the persons emotional attachment to things and people.
A loss of satisfaction is a bit more broad and touches the feelings resulting from contact with things and people whereas in the loss of emotional attachments, it is the connection in itself, instead of the result of being around those things, in this case, people and the sentimental things in our lives.
That is, imagine losing affection for all the people and animals and things in your life that you love; mom, dad, dog, etc.
Not all symptoms associated with depression seem to carry enough weight to pressure the person to want to seek treatment however, with some, this one included, even to a person that is unaware of their illness would be alarmed to note that the love and affection for others now ceases to exist.
Further, this is one symptom that contributes to the desires of escape which many of us do. In fact, me personally, this was one of the driving factors behind my reasoning not to stay here.
There is a decline in the connection to activities. The person may also notice a decline in feelings towards those they love.
The loss of interest in activity progresses to indifference. A mother may begin to care less about her children well being or care if anything would happen to them. A dedicated worker loses interest in working anymore. It is the beginning of a state in which you feel disconnected, from everything.
Eventually apathy fully develops. Apathy, is a state that we presume and feel, that we are not connected to anyone or anything. Which is eerie as some of these people our biologically related to us and we have been around them all of our lives. Imagine being dropped into a body in another world around things and people you have never seen. This is that but in out life now.