[There is a strong pathological association of déjà vu with temporal lobe epilepsy. This correlation has led some researchers to speculate that the experience of déjà vu is possibly a neurological anomaly related to improper electrical discharge in the brain. As most people suffer a mild (i.e. non-pathological) epileptic episode regularly (e.g. the sudden “jolt”, a hypnagogic jerk, that frequently occurs just prior to falling asleep), it is conjectured that a similar (mild) neurological aberration occurs in the experience of déjà vu, resulting in an erroneous sensation of memory.]
Sentience is perhaps the opposite of Déjà vu combined with “our” ability to sense the future using the prefrontal cortex which ultimately gives “us” the ability to feel the present, feel our existence. (It is interesting to note how the purpose of language breaks down here. There is no “me”, “I” … it is just an illusion created by the temporary constructs of “our” minds.)
In other words, the non-fallacious memory that “we were there” or “we have been through this” combined with the simulated feeling of “what it would be like if” gives us sentience. The more accurate those feelings are w.r.t the reality; i.e. the more similar the consciousness arrow of time is to the thermodynamic arrow of time, the more sentient we are.
From evolutionary point of view, a life-form with a consciousness arrow of time (i.e. a record of events that has happened and will happen) which is very similar to the thermodynamic arrow of time (i.e. events that really happened and will happen as the entropy increases); is the best thing that the environment would like to have because such an entity would not only preserve its existence but also the existence of the entire ecosystem.
Animals of today that has evolved through time has an excellent mechanisms to have non-fallacious memories but, if I paraphrase Daniel Gilbert right: Human beings are the one & only latest models of evolutionary improvement that are capable of planning and simulating the future because of our larger prefrontal cortex.
That makes us more sentient than Orangutans. But there is still a long way to go. Recent research conducted by Daniel Gilbert (a professor of psychology at Harvard) shows us that we are still terrible at predicting & planning. We are awful at predicting what will give us happiness. Do you expect that a new car or home will give you happiness? Certainly it will, just not as much as you expect. The same is true in the opposite. Do you think that getting rejected by your crush or losing a game will make you unhappy? It will, just not as much as you expect.