Unformatted text preview: ack task. See a sequence of the same letters, and have to response
every time you see a letter repeat 1-trial back. Can vary the delay between when the letters
are shown (2 sec, 5 sec) and basically have to keep in mind what occurred on the last
trials. Easy task to do, and if you scan humans while they are doing it you ﬁnd the PFC is
active during the task delay period. The 2-back is just a step up in difﬁculty -- now have to
response if the letter occurred 2 trials back. in the 1-back simply maintaining what just
occurred, in the 2-back you must maintain things in your mind, but also manipulate them.
Researchers have used this task and fMRI, to show that this distinction between
maintaining, and maintaining/manipulating, is what distinguishes whether the dlpfc is
involved or not. Working Memory!
Functional Specialization within the Lateral Prefrontal Cortex! Meta-analysis of neuroimaging studies of working memory! Schematic of how they separate. Meta-analysis of neuroimaging studies of working memory. They are looking at the sites of activation of whether they are spatial or non spatial material in PFC. No
difference between the two -- nonspatial tends to happen in the right & left PFC, both VL and DL. Spatial which appears to happen mostly in the right hemisphere, happens in the VL, DL cortexes as
well. But if you separate working memory component by maintenence only (like the 1-back task) vs maintenence plus manipulation, start to see a distinction.. So when you only have to maintain info
in the vlpfc, but when you have to add the manipulation as well, you start to get these DL areas as well. It appears for very simple keeping info online but not doing anything with it, the VLPFC is just
ﬁne and all that is needed, but as soon as you start to play with it, and manipulating it, the DLPFC comes into play. D’Esposito et al., 1998! Mechanisms of Cognitive Control!
Selection of Task-Relevant Information!
Monitoring and Error Detection!
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- Fall '11
- Task Switching, PFC