Understanding Behavior in HD.final.8-18-05 - Huntington's Disease ...

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UNDERSTANDING BRAIN COMMUNICATION AND CIRCUITRY
The caudate is a very important structure because it has multiple connections with, or circuits to, other
parts of the brain. A circuit is a pathway by which information travels in the brain. These circuits run through
the caudate carrying information from one part of the brain to another. Brain circuits operate much like other
circuits that we are familiar with in our daily lives. For example, a light bulb can fill a room with light with the
flick of a switch that allows the electrical current to travel through the circuit. The light bulb cannot give off
light if the circuit is disconnected or
blocked in any way.
The brain works in a similar manner
such that behavior occurs without difficulty
when the circuits are operating properly. As
the caudate deteriorates, however, some
circuits may “flicker” on and off and other
circuits will cease working, with the result
that the messages just don’t get through from one part of the brain to the other. Consider the circuits
operating in your home. The circuits that operate your lights are “one-way” circuits, light switch to light bulb.
There are also circuits that allow two-way communication, or feedback, to occur. A good example of a two-way
circuit is the heating and cooling system in your home. A thermostat is used to set the desired temperature in
your home. The furnace turns on and off to heat the home. The room temperature is recorded on a
thermometer, which is read by the thermostat. When the desired room temperature and the current room
temperature are consistent with
one another, no heating is
required. When the room
temperature is lower than the
desired temperature, however,
the heating system turns on.
This circuit, as pictured on the
left, requires that the heating
system (the furnace) receive
information from the
thermostat to complete the
circuit and produce the desired
behavior (heating).