As discussed in your text, henry molaison (h. m.) lost extensive tissue in the inner part of both temporal lobes, including the hippocampus and amygdala in both hemispheres. in her research, brenda milner found that molaison could learn a new procedural task, mirror tracing, as well as typical control participants did. however, he could not remember the details of the task. this outcome suggests that

His procedural memory was not affected but his declarative memory was.

Explanation:

Procedural memory is part of the long-time-memory and is responsible for knowing how to do things. Therefore, this memory stores the procedure to perform certain actions.

In this example, Molaison could learn a new procedural task the same way as the rest of the control participants did. So, we can conclude that his procedural memory was not affected.

Declarative memory has to do with the fact of being able to recall facts or events, therefore it has to do with the ability of "declaring" facts.

For example, procedural memory would be responsible for remembering how to ride a bike (but if someone asks you to explain it you really can't put it into words) while declarative memory is easier to verbalize.

In this example, Molaison could not remember the details of the task (he wasn't able to verbalize them), thus we can conclude that his declarative memory was affected.