Here is a great short little video from a scientific standpiont about how ayahuasca effects the brain and can help create new pathways to allow for healing from past events and traumas.
In the video, they explain how as the brain develops, it creates pathways that are associated with certain events. The example they use is if as a child you were attacked by a dog, this event causes trama and emotional distress. These emotions and memories create a pathway that stored and triggered each time you see a dog in the future; or perhaps even just hear a dog barking. Even if the dog is comepletely unfamiliar, there is an automatic fear response as seeing the animal reignites the brain pathway that was formed during the original traumatic event. Ayahuasca activates activity in the brain, allowing new pathways to form and view past events from a different perpective, releasing fear and allowing for healing.