Neural Correlates of Memory

December 7th, 2011

This line of research has addressed a wide range of questions related to the neural representation of explicit and implicit memory.   For example, how do we form and recall memories for consciously recollectable forms of memory- such as words (Putnam et al., 2008, Journal of Neuroscience), unfamiliar faces (Kelley et al., 1998; Wig et al., 2004), or a song that is stuck in our heads (Kraemer et al., 2005, Nature), and how do we represent more implicit forms of memory such as occurs during observational learning (Cross et al., 2009, Cerebral Cortex; Cross et al., 2009, European Journal of Neuroscience; Wagner et al., 2011, Journal of Neuroscience) or repetition priming (Wig et al., 2005, Nature Neuroscience)?

However, the recent focus of this line of research has centered on social influences on memory.  For example, we have shown that resting-state activity in medial temporal lobe predicts individual differences in the ability to remember other people (Wig et al., 2008, PNAS).  Indeed, this initial finding of a relationship between resting-state activity and individual differences laid the groundwork for exploring the relationship between rs-fcMRI and other long-term measures of behavior (e.g., self-regulation) and stable measures of personality (e.g., self-esteem).

A second focus of our work on memory has centered on how social and affective cues shape subsequent memory. The ability of humans to encode and represent knowledge about others is a critical component of social interaction. Often, our impressions of individuals are shaped by subtle emotional acts (e.g., witnessing a person opening a door for an elderly man). How social and emotional content is integrated and represented in memory has been a topic of considerable neuroscientific interest (e.g., Adolphs, Tranel, Hamann, et al., 1999; Ochsner, 2000; Canli, Zhao, Brewer, Gabrieli, & Cahill, 2000; Phelps, 2004; Sharot, Delgado, & Phelps, 2004; Dolcos, LaBar, & Cabeza, 2004, 2005), and our recent work (Somerville et al., 2006, JCN) has complemented and extended these findings to social learning situations by demonstrating dissociable medial temporal lobe contributions to social memory.  Specifically, a functional dissociation was observed between the hippocampus and amygdala, with greater hippocampal activity during recognition of faces previously presented with contextual information (e.g., “Karen teaches piano lessons”) and more focused activity in the amygdala during recognition of faces that had been learned in the presence of an emotional context (e.g., “Eric is a mentor to a young child.”). Importantly, activity in the hippocampus was dependent on subjects’ ability to consciously recollect the associated contextual information, whereas activity in the amygdala was not, suggesting a role for the amygdala in providing a nonspecific arousal indicator in response to viewing individuals with emotionally colored pasts.

Current and future studies from this line of research focus on elucidating the relationship between reward and explicit and implicit memory.  For example, how does the reward value of material influence its subsequent memorability (e.g., alcohol advertising or fast-food marketing) and how does reward train and maintain unconscious habits (e.g., smoking, drinking, overeating, and excessive use of online digital environments) through repetition or observational learning (e.g., Wagner et al., 2011, Journal of Neuroscience).

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