Re: is your brain analog or digital(binary)

Here's the short answer:  the brain is analog in time, but digital in the
signals it conveys.

The brain is made up of neurons (nerve cells).  Each one receives input 
from many other neurons, sometimes tens of thousands.  (Input neurons,
such as photoreceptors in the retina and hair cells in the ear, can also
be activated by external stimuli like light and vibration.)

Each input changes the neuron's voltage.  When it reaches a certain 
threshold, the neuron "fires" a nerve impulse or "action potential";  it 
sends a signal down its axon to other neurons (or to muscle cells).  This 
process is analog in time, because a neuron can fire an action potential at 
any time;  there is no global clock, as in a modern digital computer, which 
makes everything happen in synchronized steps.  On the other hand, an 
action potential is an all-or-nothing, digital event;  they don't come in 
different strengths or sizes.

At a smaller scale, the signal passes from one neuron to another across a 
gap called a synapse.  This happens as neurotransmitter chemicals diffuse 
across the gap and then attach to the receiving neuron.  This is not 
all-or-nothing, but it is digital at an even lower level:  the chemicals 
are released in standard-sized bundles.  (Several bundles may be released 
as a result of a single action potential.)  How strongly the action 
potential affects the receiving neuron depends on the amount of 
neurotransmitter released, the number and type of receptors on the 
receiving neuron, and the other impulses reaching that neuron.  This is 
effectively analog, but the threshold converts it into a digital action 
potential.

For completeness, I should point out that there are a few neurons which 
operate in a slightly different fashion, passing an analog signal directly 
from one neuron to the next.  The above description holds for the vast 
majority of them, though.