Lin, W-J; (2017) The function of medial prefrontal cortex in mental imagery and autobiographical memory. Doctoral thesis , UCL (University College London).

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Abstract

The medial prefrontal cortex (mPFC) is consistently implicated in the network supporting autobiographical memory and episodic simulation, but its functional contribution to these cognitive abilities remains unclear. Given its involvement in value processing in decision-making processes, mPFC might be important in contributing in a similar way during memory and imagery. Two fMRI experiments were carried out in order to examine if the mPFC plays a role in representing the subjective value of elements in autobiographical memory and, separately, in mental imagery. In Experiment 1, a paradigm was designed in which participants imagined scenarios involving details about spatial context, a physiological state of need (e.g. thirst), and two items which could be congruent (e.g. drink) or incongruent (e.g. food) with the imagined state. Results confirmed that the imagined-value paradigm is able to manipulate the participants’ subjective values of imagined items. Therefore, the same paradigm was performed while the participants were in the scanner in Experiment 2. The fMRI signal in the mPFC reflected the modulation of an item’s subjective value by the imagined physiological state, suggesting that the mPFC selectively tracks subjective value during mental imagery. In Experiment 3, the participants recalled autobiographical episodes and items (liked and disliked items) from each episode in the scanner. The blood oxygen level dependent (BOLD) signal in the ventromedial prefrontal cortex (vmPFC) was parametrically modulated by the affective values of the items in the participants’ memories when they were recalling and evaluating these items. An unrelated modulation by the participants’ familiarity with the items was also observed. During the retrieval of an event, the BOLD signal in the same region was modulated by the personal significance and emotional intensity of the memory, which was correlated with the values of the items within them. These results support the idea that vmPFC processes self-relevant information and suggest that it is involved in representing the personal emotional values of the elements comprising autobiographical memories. In conclusion, the experiments in this thesis provided evidence to support the hypothesis that mPFC represents the subjective values of elements in our mental imagery and autobiographical memories.

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