OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

Which type of imaging uses oxygen levels to show brain activity?

1. CT scan

2. MRI scan

3. X-ray

4. Ultrasound

The correct answer is: MRI scan

The type of imaging that uses oxygen levels to demonstrate brain activity is an MRI scan, specifically functional Magnetic Resonance Imaging (fMRI). This advanced technique measures changes in blood flow associated with brain activity; when a specific area of the brain becomes more active, it requires more oxygen, leading to increased blood flow to that region. The fMRI detects these variations in blood oxygen levels, allowing for the visualization of which areas of the brain are involved in particular tasks or functions. Other imaging techniques do not focus on oxygen levels to assess brain activity. A CT scan utilizes X-rays to create detailed images of the brain's structure but does not provide functional information about brain activity. An X-ray primarily examines bones or structures, while an ultrasound uses sound waves for imaging soft tissues, neither of which provides insights related to brain activity or oxygen consumption. Therefore, the correct answer relates to how fMRI is uniquely capable of reflecting the dynamic changes in oxygen use in the brain during various cognitive processes.