Answer:
left side of his brain
Step-by-step explanation:
The left hemisphere of the brain is also called the digital brain, and it is known to be controlling the right side of the body.
The left side of the brain is known to be performing some important functions such as logic, language, reasoning, numbers and skills, analytical thoughts and right hand control.
It should be understood that a damage to this side of the brain will definitely affect those functions mentioned above.
In this case, the damage to the left side of isaac's brain affects his abilities to speak and process language.