Continue to the right until a glowing brain slug attaches itself to your head. This will be your first encounter with the brain slugs and you'll be seeing a few more of these before the game is done! These things will force you to move continuously in the same direction until they are exposed to light. Light will make them change direction and force you to walk in the opposite way. To get rid of them we need to solve a puzzle and lead them to a small group of demonic plants that live on the roof that will grab it from you.
The brain slug will force you to the left at first until you hit the light beam, at which point you will turn around and start cruising in the opposite direction. Continue down the hill and jump across the gap. Jump over the box here and continue until you reach a second beam of light. The direction will change once again. As you head back the other way push the box.
When you are underneath the demonic growth on the ceiling, jump on the box and then jump again - the growth should snatch the brain slug from your head. This will return your controls to normal.
Continue to the right.