You know what an annotated bibliography is - your students do not. In addition to setting clear goals and expectations for this assignment, refer to these resources to help you elucidate the process:
The Online Writing Center at Purdue University provides a useful guide for understanding how to create an annotated bibliography.
The annotation should address the following questions:
Summarize: What are the main arguments or research findings presented in the article? What topics are covered in the article? If someone asked what this article is about, what would you say?
Evaluate: Why did you choose this source? How does it compare with the other sources in your bibliography? How does it relate to the connection between neuroscience and environmental beliefs?