Hollywood zombies Vs The actual possibility

For years Hollywood has been portraying zombies as corpses that have been brought back to life and for the most part people are expecting that's what the zombie apocalypse will be. Perhaps we are looking in the wrong place.  The thought of dead bodies rising from the ground and corpses walking around seems a little far fetched to me but maybe there is another cause of zombie-like behavior.  Take Toxoplasmosis for instance.  This particular infection is caused by the parasite Toxoplasma gondii. Normally it only infects rats and causes them to act in a manner that would lead to death, usually by cats, which is how their life cycle is completed. This parasite has also been known to inhabit pigs and cows and the CDC has reported that "More than 60 million men, women and children in the U.S. carry the Toxoplasma parasite".  If this parasite can make rats act strangely than who is to say it couldn't effect humans? Dr. E. Fyller Torrey at the Stanely Research Institute made a connection between this parasite and and schizophrenia.  

Toxoplasmosis isn't only thing that can alter behavior.  Take for instance the epidemic in Uganda they call the "nodding disease".  It usually only effects children between 5 and 15.  This disease is very debilitating. It causes seizures and most of the children effected wander around aimlessly. Most have to be tied down to keep them from just wandering off. The CDC has no known cure but they believe it is transmitted by a parasite from the black fly.  While this disease is serious and nothing to joke about it can make you wonder. How long is it until an epidemic that can effect humans enough to act "zombie-like" spreads across the country with no known cure?

Can zombies learn?

Are zombies capable of grasping knowledge or just walk around aimlessly feeding?  In The Zombie Autopsies by Dr. Steven Scholoman, the virus deteriorates the the brain down to the amygdala which controls the fight-or-flight response. Zombies just happen to always choose the fight response because ventromidial hypothalamus (the part that tells you when your stomach is full) is destroyed so they are always hungry.  The part of the brain responsible for problem solving, the frontal lobe, is also destroyed as well as the cerebellum which control motor skills. All in all you get an individual who can't move very well, can't communicate, doesn't recognize anyone and is hungry all the time.
The T-virus from the movie Resident Evil destroys pretty much all of the brain except for the cerebellum and brain stem. Basically this reverts a person back to the most primal state with poor motor skills. I guess when you break a person down, the only thing they really know is that they have to eat to survive. I suppose the point I'm trying to make is that you can't really learn anything without a brain. However if you can remember the instinct to feed then is there a possibility that you can remember other things.
In the 1985 film, Day of the Dead, Dr Logan believe that zombies can become domesticated and achieves this with a zombie he calls Bub. Bub seems to remember parts of its former life and certain objects. One of the soldiers becomes outraged and kills one of the doctors, Bub sees this and appears to become upset and even sheds a tear.
They touch base on this again in The Land of the Dead, 2005. The zombies in town seem to remember their former lives. They can be seen playing instruments and operating gas pumps, although not very well. A particular zombie named "Big Daddy" is seen getting upset at the sight of his fellow zombies getting killed (or rekilled I guess you could say) and eventually learns to use firearms.  He teaches his fellow undead to use weapons and eventually the go for revenge.

I can't say I like the thought of zombies being able to learn, it kinda takes away from the whole primal and basic nature of them however it would definitely be a game changer for survival.

Zombie Genesis

Exactly how did the zombie outbreak occur?  Well that depends on who's telling the story but generally it has to do with a reanimation virus.  In the 1968 Night of the Living Dead, it was speculated that a space probe entering earths atmosphere exploded and released radioactive contamination, thus reanimating recently deceased human beings.

Now if we are talking Resident Evil zombies, they were the result of an accident at an Umbrella research facility.  A sample known as the T-virus broke and was release into the air.  Long story short, everyone in the facility ended up dead and the T-virus reanimated their corpses.  The same principals apply, dead body walking around trying to eat you.

In the 2002 British flick 28 Days Later, some animal rights activist decide to free some chimps from a research facility against the warning of the chief scientist who warns them that they are infected with a "Rage" virus.  Monkey attack...people get infected...  In most every zombie flick there is a delay from the time you are bitten to when you actually turn into a zombie however , not with the "Rage" virus.  The turn around time is almost instantaneous and these aren't your average zombies that just wander around aimlessly tripping over themselves like a new baby deer, these bastards are quick.
In the 2007 film, Flight of the Living Dead: Outbreak on a Plane, a scientist infected with a genetically engineered virus is smuggled on to a 747 in a container. The virus he is infect with was designed to make soldiers able to continue to fight after being mortally wounded and also gives them superhuman strength. The outbreak starts when the plane goes through some turbulence and the container get damaged releasing the infected scientist. As you can imagine he starts chewing on passengers.
In the 2009 comedy, Zombieland, the plague is started by a mutated strain of mad cow disease.
In the current TV series The Walking Dead, it would appear that the virus is spread fairly easily like the flu or a common cold since everyone is infected.  You don't have to be bitten in order to turn into a zombie, you simply just have to die and you become reanimated within minutes to hours later.  I won't go into further detail on how this outbreak got started since this is still an ongoing show and it hasn't been revealed yet.
I could go on about how the zombie infections start in every movie I've seen but you get the point. It starts either by radiation or most commonly by some virus. Regardless of how it starts all outbreaks have one thing in common, if you become one there is no cure.

Origins of life undeath

The original concept of the zombie started with the Haitian Voodoo culture where a priest or Bokor would administer a powder referred to as coup padre to an individual and he would start his transformation into zombiism. Their heart rate would slow down and their breathing would become shallow so they would have the appearance of being dead. Their soul would become possessed by the Bokor and the zombie would do nothing except perform the will of the Bokor.
There have been many movies based on these zombies from the 1930s all the way to the 1960s. So how did we get from these mindless drones to the zombies of today? Que Mr. George A. Romero.

Romero's 1968 cult classic,  Night of the Living Dead, brought the zombie from a mindless vegetable under the control of some spiritual being to the flesh craving undead horde that everyone knows and loves. Just about every book, movie, and tv show that has had anything to do with zombies since the late 60s has been based on Romero's version of the zombie.