The Late Positive Complex (LPC) is an Event-Related Potential (ERP) consistently observed in recognition-memory paradigms. In the present study, we investigated whether the LPC tracks the strength of multiple types of memory signals, and whether it does so in a decision dependent manner. For this purpose, we employed judgements of cumulative lifetime exposure to object concepts, and judgements of cumulative recent exposure (i.e., frequency judgements) in a study-test paradigm. A comparison of ERP signatures in relation to degree of prior exposure across the two memory tasks and the study phase revealed that the LPC tracks both types of memory signals, but only when they are relevant to the decision at hand. Another ERP component previously implicated in recognition memory, the FN400, showed a distinct pattern of activity across conditions that differed from the LPC; it tracked only recent exposure in a decision-dependent manner. Another similar ERP component typically linked to conceptual processing in past work, the N400, was sensitive to degree of recent and lifetime exposure, but it did not track them in a decision dependent manner. Finally, source localization analyses pointed to a potential source of the LPC in left ventral lateral parietal cortex, which also showed the decision-dependent effect. The current findings highlight the role of decision making in ERP markers of prior exposure in tasks other than those typically used in studies of recognition memory, and provides an initial link between the LPC and the previously suggested role of ventral lateral parietal cortex in memory judgements.
Feeling-of-knowing experiences breed curiosity A central tenet in theoretical work on metacognition is that retrieval experiences during memory search can exert control over behaviour. States of curiosity, which reflect motivational tendencies to seek out information, may play a critical role in this control function. We conducted two experiments to address this idea, focusing on links between feeling-of knowing (FOK) experiences, memory-search duration, and subsequent information-seeking behaviour. We administered an episodic FOK paradigm that probed memory for previously studied face-name pairs and subsequently provided an opportunity to select limited pairs for restudy. This setup allowed us to test whether current search duration and subsequent restudy choices are biased towards information with high FOK ratings. Results revealed a positive relationship between FOK ratings and the response times of these judgements. We observed a similar positive relationship between FOK ratings and subsequent item selection for restudy. Moreover, experimental manipulations of FOK ratings based on familiarity of the face cues also had parallel effects. Our findings suggest that metacognitive experiences during unsuccessful retrieval from episodic memory can induce states of curiosity that shape behaviour beyond the immediate retrieval context. Curiosity may act as a bond to ensure that memory gaps identified through unsuccessful retrieval adaptively guide future learning.
A central tenet in theoretical work on metacognition is that retrieval experiences during memory search can exert control over behaviour. States of curiosity, which reflect motivational tendencies to seek out information, may play a critical role in this control function. We conducted two experiments to address this idea, focusing on links between feeling-of knowing (FOK) experiences, memory-search duration, and subsequent information-seeking behaviour. We administered an episodic FOK paradigm that probed memory for previously studied face-name pairs and subsequently provided an opportunity to select limited pairs for restudy. This set-up allowed us to test whether current search duration and subsequent restudy choices are biased towards information with high FOK ratings. Results revealed a positive relationship between FOK ratings and the response times of these judgements. We observed a similar positive relationship between FOK ratings and subsequent item selection for restudy. Moreover, experimental manipulations of FOK ratings based on familiarity of the face cues also had parallel effects. Our findings suggest that metacognitive experiences during unsuccessful retrieval from episodic memory can induce states of curiosity that shape behaviour beyond the immediate retrieval context. Curiosity may act as a bond to ensure that memory gaps identified through unsuccessful retrieval adaptively guide future learning.
Perirhinal cortex (PrC) has long been implicated in familiarity assessment for objects and concepts. However, extant studies have mostly focused on changes in familiarity induced by recent exposure in laboratory settings. There is an increasing appreciation of other types of familiarity signals, in particular graded familiarity of object concepts accumulated throughout one’s lifetime. In prior work (Duke et al., 2017, Cortex, 89, 61–70) that investigated neural correlates of lifetime familiarity, PrC has been shown to track familiarity ratings when participants make related judgements. A theoretically important characteristic of familiarity is its automaticity. Support for this idea comes from documented modulation of behavioural performance, and of PrC signals, by recent exposure under conditions in which this exposure is not task relevant. In the current fMRI study, we aimed to determine whether PrC also tracks lifetime familiarity of object concepts automatically, and whether this type of familiarity also influences behavior when it is not task relevant. During scanning, neurotypical participants (N=30, age range 18-40, 7 males) provided animacy judgement about concrete object concepts presented at differing frequencies in an initial study phase. In a subsequent test phase, they made graded judgements of recent or lifetime familiarity. Behavioural performance showed sensitivity to both types of familiarity even when it was not relevant for the task at hand. Across five sets of fMRI analyses, we found that PrC consistently tracks recent and lifetime familiarity of object concepts regardless of the task at hand. Critically, while several other temporal-lobe regions also showed isolated familiarity effects, none of them tracked familiarity with the same consistency. These findings demonstrate that PrC automatically tracks multiple types of familiarity. They support models that assign a broad role in the representation of information about object concepts to this structure.
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