North American Veterinary Licensing Examination (NAVLE) Practice Test

In a cat that is circling to the left, the most likely affected part of the brain is the left cerebrum. This is because circling behavior typically occurs toward the side of the brain that is affected. This phenomenon is known as "circling toward the lesion," and it is due to the fact that the brain functions are contralateral when it comes to motor control.

The left side of the cerebrum controls the right side of the body and vice versa. Therefore, if the left cerebrum is compromised due to a brain tumor, the cat would exhibit signs of impaired proprioception and coordination on the right side, which often results in circling towards the left side where the lesion is located.

This type of behavior provides a clear indication of where the disruption in normal brain activity is occurring, making the left cerebrum the most likely location of the tumor in this scenario. Understanding this basic neuroanatomy principle is crucial for interpreting signs of neurological disease in animals.