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Distinct roles for lateral and medial rostral prefrontal cortex in source monitoring of perceived and imagined events.

Turner MS, Simons JS, Gilbert SJ, Frith CD, Burgess PW - Neuropsychologia (2008)

Bottom Line: Lateral regions of rostral PFC were activated in both tasks.However medial regions of rostral PFC were activated only when participants were required to recollect source information for self-generated, "imagined" stimuli, indicating a specific role in self-referential processing.These results suggest that whilst the processing resources supported by some regions of lateral rostral PFC play a general role in source recollection, those supported by medial rostral PFC structures may be more specialised in their contributions.

View Article: PubMed Central - PubMed

Affiliation: Institute of Cognitive Neuroscience and Department of Psychology, University College London, 17 Queen Square, London WC1N 3AR, UK. martha.turner@ucl.ac.uk

ABSTRACT
Rostral prefrontal cortex (PFC) is known to be involved in source memory, the ability to recollect contextual information about an event. However it is unclear whether subregions of rostral PFC may be differentially engaged during the recollection of different kinds of source detail. We used event related functional MRI to contrast two forms of source recollection: (1) recollection of whether stimuli had previously been perceived or imagined, and (2) recollection of which of two temporally distinct lists those stimuli had been presented in. Lateral regions of rostral PFC were activated in both tasks. However medial regions of rostral PFC were activated only when participants were required to recollect source information for self-generated, "imagined" stimuli, indicating a specific role in self-referential processing. In addition, reduced activity in a region of medial ventro-caudal PFC/basal forebrain was associated with making "imagined-to-perceived" confabulation errors. These results suggest that whilst the processing resources supported by some regions of lateral rostral PFC play a general role in source recollection, those supported by medial rostral PFC structures may be more specialised in their contributions.

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Related in: MedlinePlus

Examples of the stimuli used during study and test phases. In the study phase two temporally distinct lists of items were presented. In each list participants viewed either a clue and target word, or a clue and a question mark, prompting them to imagine the target word. In both cases they were instructed to count the number of letters in the target word. In the subsequent test phase they either viewed or were prompted to imagine target words embedded in sentences, and carried out one of two source tasks: either to recollect whether the word had been presented in the first or second list of the study phase (temporal source task), or whether the word had been seen or imagined in the study phase (perceived/imagined source task).
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fig1: Examples of the stimuli used during study and test phases. In the study phase two temporally distinct lists of items were presented. In each list participants viewed either a clue and target word, or a clue and a question mark, prompting them to imagine the target word. In both cases they were instructed to count the number of letters in the target word. In the subsequent test phase they either viewed or were prompted to imagine target words embedded in sentences, and carried out one of two source tasks: either to recollect whether the word had been presented in the first or second list of the study phase (temporal source task), or whether the word had been seen or imagined in the study phase (perceived/imagined source task).

Mentions: There were 16 blocks in the experiment, which alternated between study and test blocks (Fig. 1). Each study phase comprised two lists of 8 words each. Within each list half of the words were presented on the screen, while participants were prompted to imagine the other half. Each test phase comprised 32 trials, of which 8 assessed memory for whether the item had previously been perceived or imagined (P/I source), 8 assessed memory for which of the two study lists items had appeared in (temporal source), 8 were “new” trials involving presentation of non-studied items, and 8 were fixation trials. Again half of the target words were presented, and half were imagined by participants. This manipulation was introduced to control for potential priming effects arising when previously perceived items were perceived again at test. Thus there were three experimental factors: study condition (perceive or imagine), test condition (perceive or imagine), and source task (P/I or temporal).


Distinct roles for lateral and medial rostral prefrontal cortex in source monitoring of perceived and imagined events.

Turner MS, Simons JS, Gilbert SJ, Frith CD, Burgess PW - Neuropsychologia (2008)

Examples of the stimuli used during study and test phases. In the study phase two temporally distinct lists of items were presented. In each list participants viewed either a clue and target word, or a clue and a question mark, prompting them to imagine the target word. In both cases they were instructed to count the number of letters in the target word. In the subsequent test phase they either viewed or were prompted to imagine target words embedded in sentences, and carried out one of two source tasks: either to recollect whether the word had been presented in the first or second list of the study phase (temporal source task), or whether the word had been seen or imagined in the study phase (perceived/imagined source task).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2697314&req=5

fig1: Examples of the stimuli used during study and test phases. In the study phase two temporally distinct lists of items were presented. In each list participants viewed either a clue and target word, or a clue and a question mark, prompting them to imagine the target word. In both cases they were instructed to count the number of letters in the target word. In the subsequent test phase they either viewed or were prompted to imagine target words embedded in sentences, and carried out one of two source tasks: either to recollect whether the word had been presented in the first or second list of the study phase (temporal source task), or whether the word had been seen or imagined in the study phase (perceived/imagined source task).
Mentions: There were 16 blocks in the experiment, which alternated between study and test blocks (Fig. 1). Each study phase comprised two lists of 8 words each. Within each list half of the words were presented on the screen, while participants were prompted to imagine the other half. Each test phase comprised 32 trials, of which 8 assessed memory for whether the item had previously been perceived or imagined (P/I source), 8 assessed memory for which of the two study lists items had appeared in (temporal source), 8 were “new” trials involving presentation of non-studied items, and 8 were fixation trials. Again half of the target words were presented, and half were imagined by participants. This manipulation was introduced to control for potential priming effects arising when previously perceived items were perceived again at test. Thus there were three experimental factors: study condition (perceive or imagine), test condition (perceive or imagine), and source task (P/I or temporal).

Bottom Line: Lateral regions of rostral PFC were activated in both tasks.However medial regions of rostral PFC were activated only when participants were required to recollect source information for self-generated, "imagined" stimuli, indicating a specific role in self-referential processing.These results suggest that whilst the processing resources supported by some regions of lateral rostral PFC play a general role in source recollection, those supported by medial rostral PFC structures may be more specialised in their contributions.

View Article: PubMed Central - PubMed

Affiliation: Institute of Cognitive Neuroscience and Department of Psychology, University College London, 17 Queen Square, London WC1N 3AR, UK. martha.turner@ucl.ac.uk

ABSTRACT
Rostral prefrontal cortex (PFC) is known to be involved in source memory, the ability to recollect contextual information about an event. However it is unclear whether subregions of rostral PFC may be differentially engaged during the recollection of different kinds of source detail. We used event related functional MRI to contrast two forms of source recollection: (1) recollection of whether stimuli had previously been perceived or imagined, and (2) recollection of which of two temporally distinct lists those stimuli had been presented in. Lateral regions of rostral PFC were activated in both tasks. However medial regions of rostral PFC were activated only when participants were required to recollect source information for self-generated, "imagined" stimuli, indicating a specific role in self-referential processing. In addition, reduced activity in a region of medial ventro-caudal PFC/basal forebrain was associated with making "imagined-to-perceived" confabulation errors. These results suggest that whilst the processing resources supported by some regions of lateral rostral PFC play a general role in source recollection, those supported by medial rostral PFC structures may be more specialised in their contributions.

Show MeSH
Related in: MedlinePlus