Given her endearing but flaky responses to the world, your cat’s brain may appear to work in a quirky manner at best. Still, cat and human brains have the same structures that serve the same functions. An advanced prefrontal cortex helps humans respond rationally without relying on kitty “logic.”
The Amygdala: Emotion Processing Center
Two almond-shaped regions in the human brain control emotional responses based on input from other areas of the brain. The most common function of the amygdalae involves synthesizing fear responses from the environment, such as when you teeter at the top of the first big hill on a roller coaster.
Cats also have amygdalae that initiate emotional responses such as fear. For a kitty, a fear reaction may result when she is carried into the veterinary office and can surmise by the sights, smells and sounds that she's probably in for an unpleasant poking and prodding by the vet.
The Thalamus and Sensory Cortexes: Sources of Emotional Stimulation
The sensory cortexes via the thalamus send information to the amygdala gathered from your sensory organs. Your amygdala then initiates an emotional reaction based on these stimuli. For example, your eyes see that your best friend is walking toward you and smiling. This stimulus is perceived in the visual cortex, then the thalamus decides to pass on this information to the other parts of the brain, including the amygdala. The amygdala then says, "Hurray, my best friend!" and you have a positive emotional reaction to what you saw.
In a cat, a good example would be when she sees you walk through the door at the end of a long day. This sensory stimulation is interpreted by her amygdala, which sends endorphins (happy hormones) throughout her system, resulting in purring and a welcoming rub on your leg.
The Hippocampus: Memories Trigger Emotions
The hippocampus stores long-term memories, such as how you felt when you walked on the stage on graduation day. The hippocampus also feeds directly to the amygdala. Scientists believe that this is why a flood of strong emotions can follow when we recall a vivid memory.
Your kitty also has a hippocampus, although her stored memories are not quite the same as yours. Kitty will probably remember that the last time your neighbor's dog came to visit, the dog chased her and she hid under the couch. So, if Kitty sees the dog again, the information from her sensory cortex triggers the memory in her hippocampus, which communicates with her amygdala, which floods her with fear.
The Prefrontal Cortex: Choosing Reason Over Fear
The prefrontal cortex has a dialogue with the amygdala when a fear response is elicited. The amygdala says, "Be afraid!" Then, the prefrontal cortex considers, "Is this really something to be scared of?" If not, the prefrontal cortex sends this information to the amygdala, which ceases the fear reaction so you no longer feel scared. If this process happens several times from the same stimulus -- for example, your sibling jumps out of a closet and shouts "BOO!" -- eventually your prefrontal cortex "teaches" your amygdala that it should not have a fear reaction to that stimulus.
A cat's prefrontal cortex is not nearly as developed as a human's -- that's why she can't reason in the same way you can. Still, a cat's brain will eventually teach itself not to have emotional reactions to things that it can determine are irrational. For instance if your kitty is at first scared by the sound of your garbage disposal, eventually after hearing it every day she'll learn that nothing bad happens to her when you flip that switch. If cats were able to reason and diminish their fear reactions to the level humans do, they'd finally learn that the vacuum cleaner is nothing to be scared of.
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