Subject: How does THC affect the brain in relation to perception and focus?

I am trying to better understand how THC affects the brain in relation to
perception and focus. As I understand it, people react to the chemical
differently. Also, it seems that eating and smoking produce different effects. 

My main question essentially is, what about THC makes a person able to focus and
think so much "clearer" for lack of a better word? My best way of describing
what I mean by "clear" is to have the ability to not be distracted by memories,
and senses that one does not see as critical to the current task. For instance
one could focus on a song playing and actually listen to it acknowledging the
various sounds that they would not be conscious of otherwise.

On a slightly related note, Is there a way to currently see how neurons fire in
detail? Are there any theories about neurons firing in patterns and,
hypothetically speaking, if neurons do fire in patterns which lead to our
perceptions, could simulating the pattern trigger the same preceptions? 

Re: How does THC affect the brain in relation to perception and focus?