Final answer:
The study done by Friston in 2008 focused on the role of the prefrontal cortex in cognition and affect. PET scans showed that the left inferior prefrontal cortex was more activated during a semantic task. The study provided insight into cognitive flexibility and memory recall.
Step-by-step explanation:
The study done by Friston in 2008 focused on the prefrontal cortex and its role in cognition and affect. Friston's study, along with other research, used brain imaging techniques such as positron emission tomography (PET) scans to examine brain activation during different tasks. Results suggested that the prefrontal cortex is involved in cognitive flexibility and memory recall. For example, a study using PET scans found that the left inferior prefrontal cortex was more activated during a semantic task compared to a perceptual task.