Brain imaging techniques involve various methods to either directly or indirectly visualize the structure
and function of the nervous system. One such technique is the PET scan, which creates a dynamic
image of the brain. This process involves injecting fluorodeoxyglucose (a man-made substance) into
the carotid artery. The substance then travels through the bloodstream into the brain, where it
accumulates in neurons, as fluorodeoxyglucose does not metabolize. The activity of the brain is
indicated by three colours: red for high activity, yellow for medium activity, and green for low activity.
There is also a 30-second delay, meaning the PET scan does not produce a live image. This essay
will provide a brief overview of the PET scan, using the study by Salmon et al. as an example.
The goal of the research by Salmon et al. was to replicate previous findings concerning the brain
areas activated by a verbal working memory task. The research method employed was a laboratory
experiment with a sample of 10 male European right-handed volunteers. A PET scan was used to
observe the cerebral blood flow of each participant. The participants performed two tasks: the Visual
Short-Term Memory (STM) task and the Phonological STM task. In the Visual STM task, participants
were randomly shown six Korean letters on a computer screen at a rate of one per second. They were
asked to remember the stimuli using a visual code. Then, a probe Korean letter was shown two
seconds after each sequence, and participants were asked to judge if the probe letter was present in
that sequence, pressing ‘yes’ or ‘no’ on a control pad. In the Phonological STM task, a randomized
sequence of six phonologically dissimilar consonants was displayed on a monitor. Participants were
asked to silently rehearse the stimuli and remember them in order. After each sequence, a target
consonant was displayed, and participants were asked to judge whether the target consonant was
present in the list. The results showed that for the phonological loop, cerebral blood flow was
observed in the premotor region, while for the visuospatial sketchpad, it was in the superior occipital
gyrus.
Salmon et al.'s study demonstrates the use of PET scans to investigate regional brain activity during
working memory tasks. For instance, visual and phonological memories are active in different parts of
the brain, as evidenced by the cerebral blood flow in the premotor region for the phonological loop
and in the superior occipital gyrus for the visuospatial sketchpad. This distinction is significant
because PET scans can observe activity and create a dynamic image of the brain. The PET scan was
necessary in this case because it was essential to visualize regional brain activity. Therefore, PET
scans can be instrumental in investigating the relationship between the brain and behaviour.
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