- Email: [email protected]
Introduction to the special issue on functional neuroimaging of episodic memory
Neuropsychologia 51 (2013) 2319–2321
Contents lists available at ScienceDirect
Neuropsychologia journal homepage: www.elsevier.com/locate/neuropsychologia
Editorial
Introduction to the special issue on functional neuroimaging of episodic memory
In 1998, Dr. Nobuo Ohta of the University of Tsukuba organized the first Tsukuba International Conference on Memory (TIC-1). This conference, which focused on memory and consciousness, was so successful that it led to nine TIC meetings. In 1999, Dr. Ohta and Peter Graf organized TIC-2, which focused on memory development across the lifespan. Between 2002 and 2004, Dr. Ohta and Lars-Goran Nilsson organized TIC-3 on memory and society, Ohta and Izawa organized TIC-4 on human learning and memory, and Ohta, Uttl, and Siegenthaler organized TIC-5 on memory and emotion. Between 2008 and 2011, the topics were visual memory (TIC-7: Ohta, Utll, & Itoh), memory and aging (TIC-8: Ohta & Naveh-Benjamin), and dementia and memory (TIC-9: Ohta & Goran-Nilsson). From March 4 to 6, 2012, Dr. Ohta and me organized the last TIC meeting, which took place in Tokyo. The meeting, which was sponsored by Gakushuin University, focused on functional neuroimaging of episodic memory and included talks by Donna Rose Addis, Emrah Duzel, Simona Ghetti, Guillen Fernandez, Elizabeth Kensinger, Kenneth Norman, Lars Nyberg, Ken Paler, Charan Ranganath, Michael Rugg, Craig Stark, and myself. Their talks were fantastic and inspired lively theoretical discussions, which continued into the night at izakayas of Shinjuku. To have a record of this wonderful meeting, a special issue was arranged with the editor of Neuropsychologia, Dr. Michael Rugg. Invitations to participate in the special issue were also sent to researchers who were invited to but could not attend the Tokyo meeting. As a result, the special issue includes additional papers from the laboratories of Lila Davachi, Ian Dobbins, Kelly Giovanello, Marcia Johnson, and Anthony Wagner. The special issue consists of 14 articles, which cover the gamut of episodic memory processes and associated memory functions and can be roughly divided into six groups. The first group of articles investigated the memory contributions of various medial temporal lobe (MTL) subregions, which is, of course, a core issue in cognitive neuroscience of episodic memory. Hannula, Libby, Yonelinas, and Ranganath (this issue) tested predictions of the three-process theory that perirhinal cortex mediates memory for objects, the parahippocampal cortex, memory for contexts, and the hippocampus, memory for object– context associations (Davachi, 2006; Eichenbaum, Yonelinas, & Ranganath, 2007). Consistent with this theory, successful retrieval activity was found in the parahippocampal cortex for scenes and in the hippocampus for both objects and scenes. However, inconsistent with the theory, successful retrieval activity in perirhinal cortex was found not only for objects but also for scenes. The study by Heusser, Awipi, and Davachi (this issue) investigated 0028-3932/$ - see front matter & 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.neuropsychologia.2013.08.001
perirhinal contributions to conceptual priming and explicit memory. Although the perirhinal cortex is strongly linked to processing of visual objects (Bussey, Saksida, & Murray, 2005), there is also evidence linking this region to processing of conceptual representations (Taylor, Moss, Stamatakis, & Tyler, 2006). Consistent with the latter, Heuser and collaborators found several perirhinal regions that showed priming-related repetition suppression across modalities. Interestingly, repetition enhancement in some of these regions predicted subsequent episodic memory. Finally, the study by Chen, Dastjerdi, Foster, LaRocque, Rauschecker, Parvizi, et al. (this issue) investigated the memory functions of MTL subregions using intracranial electroencephalography. They found that the hippocampus, but not the perirhinal cortex, responded to stimuli that violated expectations based on previous stimuli sequences. The fact that this response (an increase in slow-theta power) occurred very fast suggests it reflects a hippocampal mechanism rather than a re-entrant process. In sum, the results of the first group of studies suggest that the memory contributions of the perirhinal cortex are broader than expected and shed light on the neurophysiological mechanism of associative memory in the hippocampus. The second group of articles focused on the neural mechanisms of processes that increase or decrease the probability that a piece of information is later remembered. For example, a piece of information is more likely to be remembered later if it fits well with preexistent knowledge. The study by van Kestern, Beul, Takashima, Henson, Ruiter, and Fernandez (this issue) tested the hypothesis that the encoding of information congruent with preexistent schemas is partly supported by the medial prefrontal cortex (PFC) whereas the encoding of incongruent information relies more primarily on MTL. Consistent with the hypothesis, subsequent memory effects (SMEs¼ subsequently remembered forgotten) in medial PFC increased with congruency, whereas SMEs in MTL decreased with congruency. The study by Wing, Marsh, and Cabeza (this issue) investigated another variable known to enhance encoding: retrieval practice. They found that, compared to word pairs that were merely restudied, pairs that were practiced through retrieval elicited larger SMEs in anterior hippocampus, lateral temporal cortex, and medial PFC. Testing also enhanced hippocampal connectivity with ventrolateral PFC and midline regions. Lastly, the study by Detre, Natarajan, Gershman, and Norman (this issue) tested the neurobiologyinspired hypothesis that the effects of activating a memory representation on later representation strength conform to a U-shaped function: very low activation does not affect strength, moderate activation reduces strength, and high activation increases strength (nonmonotonic plasticity hypothesis). Detre and collaborators covertly
2320
Editorial / Neuropsychologia 51 (2013) 2319–2321
measured the activation of stimulus-specific information during a word–picture version of the think/no-think paradigm. As predicted, moderate activation of the no-think item led to diminished performance in a final memory test, whereas higher levels of activation led to enhanced memory performance. In conclusion, the second group of studies revealed mechanisms whereby subsequent remembering is enhanced by preexistent schemas or retrieval practice and can be disrupted by partial activation of stored representations. The third group of articles investigated the interaction between episodic memory retrieval and other mental processes. The study by Holland and Kensinger (this issue) examined how retrievalrelated activity is affected by emotional regulation. Participants encoded negative and neutral images and one week later they recalled each picture (from a verbal cue) after an instruction to upregulate, down-regulate, or maintain the emotional experience elicited by the recalled picture. Interestingly, they found a dissociation in temporal dynamics: up-regulation engaged PFC early during the instruction period whereas down-regulation recruited PFC during the memory search process. The study by De Brigard, Addis, Ford, Schacter, and Giovanello (this issue) investigated episodic counterfactual thinking, which refers to the process of thinking about what could have happened in our past, yet did not occur. Participants recalled autobiographical events with either positive or negative outcomes, and later in the scanner, they recalled the original version or imagined a version with the alternative outcome. Counterfactual thinking recruited many of the same brain regions as episodic memory retrieval (MTL, PFC, posterior cingulate, etc.), particularly when the subjective likelihood of the alternative outcome was greater. To sum up, the results of the third group of studies show how the episodic retrieval network is modulated by emotional goals and can be used for conceiving alternative outcomes of past events. The fourth group of articles focused on the neural mechanisms of source memories at both ends of the developmental continuum. The study by DeMaster, Pathman, and Ghetti (this issue) investigated childhood development of spatial memory retrieval. Different developmental trends were observed in various components of the retrieval network. Challenging the assumption that hippocampal memory functions develop early during childhood, the hippocampus contributed to source memory success in young adults but not in children (8–9 and 10–11 years). The study by Mitchell, Ankudowich, Durbin, Greene, and Johnson (this issue) investigated the effects of old age on the neural mechanisms of source memory. Different tasks measured source memory for stimulus format (word vs. picture) or encoding task (self- vs. other-referential). Activation differences in regions associated with stimulus format (e.g., visual cortex) and encoding task (e.g., medial PFC) were relatively spared in older adults, whereas activation differences in regions associated with retrieval orientation (lateral PFC and parietal regions) were reduced by aging. These results suggest an age-related deficit in selective attention to internal representations. In sum, the fourth group of studies found significant developmental differences in source memory mechanisms in the hippocampus during childhood and frontoparietal regions during old age. The fifth group of articles investigated episodic memory processes that differ between healthy and pathological aging. The study by Stark, Yassa, Lacy, and Stark (this issue) examined pattern separation, which refers to the ability to orthogonalize overlapping inputs into distinct memory representations, a process linked to the dentate gyrus of the hippocampus. They used an object recognition memory task that included not only studied and nonstudied objects also very similar versions of studied objects. In this test, low performing older adults were impaired in rejecting similar lures but not in overall recognition, whereas individuals with mild cognitive impairments (MCI) were impaired in both
measures. The study by Westerberg, Mayes, Florczak, Chen, Creery, Parrish, et al. (this issue) tested amnestic MCI, Alzheimer's disease (AD), and control participants in a silhouette forced-choice recognition task, assumed to be more dependent on familiarity, and a silhouette yes/no recognition task, assumed to involve additional memory and decision processes. MCI participants were impaired in the yes/no recognition performance, which correlated with hippocampal volume, but not in forced-choice recognition performance, which correlated with perirhinal volume. AD participants were impaired in both tests. These results support the idea that perirhinal-related familiarity processes are relatively spared in MCI but not in AD. In sum, the fifth group of studies reported memory dissociations as a function of the pathology progression from normal aging to MCI to AD, and hence, they have potential implications for the diagnosis of AD. Finally, the sixth group of studies used a genetic imaging approach. The study by Kauppi, Nilsson, Adolfsson, Lundquist, Eriksson, and Nyberg (this issue) examined the effects of BDNF Val66Met polymorphism in a large sample of participants. BDNF Met allele carriers showed a subtle impairment in memory performance and a significant reduction in MTL activity during encoding (but not during retrieval). Interestingly, the effect was not modulated by age. The study by Wittmann, Tan, Lisman, Dolan, and Düzel (this issue) investigated the effects of the dopamine transporter (DAT) gene on motivated memory. In 10repeat homozygotes, but not in 9/10 repeat heterozygotes, memory encoding was enhanced by both reward and punishment anticipation. Compared to heterozygotes, homozygotes showed increased striatal activity during reward/punishment anticipation and hippocampal SMEs. These results are consistent with the idea that motivational memory encoding depends on dopaminergic effects on the hippocampus. To sum up, the results of the sixth group highlight the importance of investigating the gene-related variations in the neural mechanisms of memory. In conclusion, the 14 studies in this special issue provide the reader with a snapshot of the state-of-the-art of functional neuroimaging of episodic memory and related functions in 2012–2013. The studies covered a large variety of encoding and retrieval processes and examined many different variables, including the nature of the stimuli (objects vs. scenes, words vs. pictures), the role of preexistent schemas, the effects of retrieval practice, and the impact of partial access to memory representations. They also investigated emotion regulation, counterfactual thinking, childhood and old-age development, the distinction between healthy and pathological aging, and genetic effects. The 14 studies yielded important results about the main components of the episodic memory network, including MTL subregions, lateral and medial PFC and parietal regions, ventral occipitotemporal areas, and various subcortical regions. These results have important implications not only for memory theory but also for a variety of clinical and educational domains. I would like to thank Dr. Ohta for inviting me to organize TIC-10 with him, Gakushuin University for sponsoring this event, and Dr. Rugg for inviting me to edit the special issue. I am also indebted to the contributing authors for submitting some of their best work to the special issue and to the all the reviewers who donated their time. Last but not least, I thank the National Institutes of Health for supporting my research, as well as most of the studies reported in this special issue.
References Bussey, T. J., Saksida, L. M., & Murray, E. A. (2005). The perceptual-mnemonic/ feature conjunction model of perirhinal cortex function. Quarterly Journal of Experimental Psychology B, 58, 269–282.
Editorial / Neuropsychologia 51 (2013) 2319–2321
Chen, J., Dastjerdi, M., Foster, B. L., LaRocque, K. F., Rauschecker, A. M., Parvizi, J., et al., (2013). Human hippocampal increases in low-frequency power during associative prediction violations. Neuropsychologia. /http://dx.doi.org/10.1016/ j.neuropsychologia.2013.03.019S, (in this issue). Davachi, L. (2006). Item, context and relational episodic encoding in humans. Current Opinion in Neurobiology, 16, 693–700. De Brigard, F., Addis, D. R., Ford, J. H., Schacter, D. L., & Giovanello, K. S. (2013). Remembering what could have happened: Neural correlates of episodic counterfactual thinking. Neuropsychologia. /http://dx.doi.org/10.1016/j.neurop sychologia.2013.01.015S, (in this issue). De Master, D., Pathman, T., & Ghetti, S. (2013). Development of memory for spatial context: Hippocampal and cortical contributions. Neuropsychologia. /http://dx. doi.org/10.1016/j.neuropsychologia.2013.05.026S, (in this issue). Detre, G. J., Natarajan, A., Gershman, S. J., & Norman, K. A. (2013). Moderate levels of activation lead to forgetting in the think/no-think paradigm. Neuropsychologia. /http://dx.doi.org/10.1016/j.neuropsychologia.2013.02.017S, (in this issue). Eichenbaum, H., Yonelinas, A. P., & Ranganath, C. (2007). The medial temporal lobe and recognition memory. Annual Reviews of Neuroscience, 30, 123–152. Hannula, D. E., Libby, L. A., Yonelinas, A. P., & Ranganath, C. Medial temporal lobe contributions to cued retrieval of items and contexts. Neuropsychologia. /http://dx.doi.org/10.1016/j.neuropsychologia.2013.02.011S, (in this issue). Heusser, A. C., Awipi, T., & Davachi, L. (2013). The ups and downs of repetition: Modulation of the perirhinal cortex by conceptual repetition predicts priming and long-term memory. Neuropsychologia. /http://dx.doi.org/10.1016/j.neurop sychologia.2013.04.018S, (in this issue). Holland, A. C., & Kensinger, E. A. (2013). An fMRI investigation of the cognitive reappraisal of negative memories. Neuropsychologia. /http://dx.doi.org/10. 1016/j.neuropsychologia.2013.02.012S, (in this issue). Kauppi, K., Nilsson, L.-G., Adolfsson, R., Lundquist, A., Eriksson, E., & Nyberg, L. Decreased medial temporal lobe activation in BDNF 66Met allele carriers during memory encoding. Neuropsychologia. /http://dx.doi.org/10.1016/j.neu ropsychologia.2012.11.028S, (in this issue). Mitchell, K. J., Ankudowich, E., Durbin, K. A., Greene, E. J., & Johnson, M. K. Agerelated differences in agenda-driven monitoring of format and task information. Neuropsychologia. /http://dx.doi.org/10.1016/j.neuropsychologia.2013.01. 012S, (in this issue).
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Stark, S. M., Yassa, M. A., Lacy, J. W., & Stark, C. E. L. A task to assess behavioral pattern separation (BPS) in humans: Data from healthy aging and mild cognitive impairment. Neuropsychologia. /http://dx.doi.org/10.1016/j.neuropsy chologia.2012.12.014S, (in this issue). Taylor, K. I., Moss, H. E., Stamatakis, E. A., & Tyler, L. K. (2006). Binding crossmodal object features in perirhinal cortex. Proceedings of the National Academy of Sciences of the United States of America, 103, 8239–8244. van Kesteren, M. T. R., Beul, S. F., Takashima, A., Henson, R. N., Ruiter, D. J., & Fernández, G. Differential roles for medial prefrontal and medial temporal cortices in schema-dependent encoding: From congruent to incongruent. Neuropsychologia. /http://dx.doi.org/10.1016/j.neuropsychologia.2013.05.027S, (in this issue). Westerberg, C., Mayes, A., Florczak, S. M., Chen, Y., Creery, J., Parrish, T., et al. Distinct medial temporal contributions to different forms of recognition in amnestic mild cognitive impairment and Alzheimer's disease. Neuropsychologia. /http://dx.doi.org/10.1016/j.neuropsychologia.2013.06.025S, (in this issue). Wing, E. A., Marsh, E. J., & Cabeza, R. Neural correlates of retrieval-based memory enhancement: An fMRI study of the testing effect. Neuropsychologia. /http://dx. doi.org/10.1016/j.neuropsychologia.2013.04.004S, (in this issue). Wittmann, B. C., Tan, G. C., Lisman, J. E., Dolan, R. J., & Düzel, E. DAT genotype modulates striatal processing and long-term memory for items associated with reward and punishment. Neuropsychologia. /http://dx.doi.org/10.1016/j.neurop sychologia.2013.07.018S, (in this issue).
Roberto Cabeza Center for Cognitive Neuroscience, Duke University, United States E-mail address: [email protected]
Available online 3 August 2013
Contents lists available at ScienceDirect
Neuropsychologia journal homepage: www.elsevier.com/locate/neuropsychologia
Editorial
Introduction to the special issue on functional neuroimaging of episodic memory
In 1998, Dr. Nobuo Ohta of the University of Tsukuba organized the first Tsukuba International Conference on Memory (TIC-1). This conference, which focused on memory and consciousness, was so successful that it led to nine TIC meetings. In 1999, Dr. Ohta and Peter Graf organized TIC-2, which focused on memory development across the lifespan. Between 2002 and 2004, Dr. Ohta and Lars-Goran Nilsson organized TIC-3 on memory and society, Ohta and Izawa organized TIC-4 on human learning and memory, and Ohta, Uttl, and Siegenthaler organized TIC-5 on memory and emotion. Between 2008 and 2011, the topics were visual memory (TIC-7: Ohta, Utll, & Itoh), memory and aging (TIC-8: Ohta & Naveh-Benjamin), and dementia and memory (TIC-9: Ohta & Goran-Nilsson). From March 4 to 6, 2012, Dr. Ohta and me organized the last TIC meeting, which took place in Tokyo. The meeting, which was sponsored by Gakushuin University, focused on functional neuroimaging of episodic memory and included talks by Donna Rose Addis, Emrah Duzel, Simona Ghetti, Guillen Fernandez, Elizabeth Kensinger, Kenneth Norman, Lars Nyberg, Ken Paler, Charan Ranganath, Michael Rugg, Craig Stark, and myself. Their talks were fantastic and inspired lively theoretical discussions, which continued into the night at izakayas of Shinjuku. To have a record of this wonderful meeting, a special issue was arranged with the editor of Neuropsychologia, Dr. Michael Rugg. Invitations to participate in the special issue were also sent to researchers who were invited to but could not attend the Tokyo meeting. As a result, the special issue includes additional papers from the laboratories of Lila Davachi, Ian Dobbins, Kelly Giovanello, Marcia Johnson, and Anthony Wagner. The special issue consists of 14 articles, which cover the gamut of episodic memory processes and associated memory functions and can be roughly divided into six groups. The first group of articles investigated the memory contributions of various medial temporal lobe (MTL) subregions, which is, of course, a core issue in cognitive neuroscience of episodic memory. Hannula, Libby, Yonelinas, and Ranganath (this issue) tested predictions of the three-process theory that perirhinal cortex mediates memory for objects, the parahippocampal cortex, memory for contexts, and the hippocampus, memory for object– context associations (Davachi, 2006; Eichenbaum, Yonelinas, & Ranganath, 2007). Consistent with this theory, successful retrieval activity was found in the parahippocampal cortex for scenes and in the hippocampus for both objects and scenes. However, inconsistent with the theory, successful retrieval activity in perirhinal cortex was found not only for objects but also for scenes. The study by Heusser, Awipi, and Davachi (this issue) investigated 0028-3932/$ - see front matter & 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.neuropsychologia.2013.08.001
perirhinal contributions to conceptual priming and explicit memory. Although the perirhinal cortex is strongly linked to processing of visual objects (Bussey, Saksida, & Murray, 2005), there is also evidence linking this region to processing of conceptual representations (Taylor, Moss, Stamatakis, & Tyler, 2006). Consistent with the latter, Heuser and collaborators found several perirhinal regions that showed priming-related repetition suppression across modalities. Interestingly, repetition enhancement in some of these regions predicted subsequent episodic memory. Finally, the study by Chen, Dastjerdi, Foster, LaRocque, Rauschecker, Parvizi, et al. (this issue) investigated the memory functions of MTL subregions using intracranial electroencephalography. They found that the hippocampus, but not the perirhinal cortex, responded to stimuli that violated expectations based on previous stimuli sequences. The fact that this response (an increase in slow-theta power) occurred very fast suggests it reflects a hippocampal mechanism rather than a re-entrant process. In sum, the results of the first group of studies suggest that the memory contributions of the perirhinal cortex are broader than expected and shed light on the neurophysiological mechanism of associative memory in the hippocampus. The second group of articles focused on the neural mechanisms of processes that increase or decrease the probability that a piece of information is later remembered. For example, a piece of information is more likely to be remembered later if it fits well with preexistent knowledge. The study by van Kestern, Beul, Takashima, Henson, Ruiter, and Fernandez (this issue) tested the hypothesis that the encoding of information congruent with preexistent schemas is partly supported by the medial prefrontal cortex (PFC) whereas the encoding of incongruent information relies more primarily on MTL. Consistent with the hypothesis, subsequent memory effects (SMEs¼ subsequently remembered forgotten) in medial PFC increased with congruency, whereas SMEs in MTL decreased with congruency. The study by Wing, Marsh, and Cabeza (this issue) investigated another variable known to enhance encoding: retrieval practice. They found that, compared to word pairs that were merely restudied, pairs that were practiced through retrieval elicited larger SMEs in anterior hippocampus, lateral temporal cortex, and medial PFC. Testing also enhanced hippocampal connectivity with ventrolateral PFC and midline regions. Lastly, the study by Detre, Natarajan, Gershman, and Norman (this issue) tested the neurobiologyinspired hypothesis that the effects of activating a memory representation on later representation strength conform to a U-shaped function: very low activation does not affect strength, moderate activation reduces strength, and high activation increases strength (nonmonotonic plasticity hypothesis). Detre and collaborators covertly
2320
Editorial / Neuropsychologia 51 (2013) 2319–2321
measured the activation of stimulus-specific information during a word–picture version of the think/no-think paradigm. As predicted, moderate activation of the no-think item led to diminished performance in a final memory test, whereas higher levels of activation led to enhanced memory performance. In conclusion, the second group of studies revealed mechanisms whereby subsequent remembering is enhanced by preexistent schemas or retrieval practice and can be disrupted by partial activation of stored representations. The third group of articles investigated the interaction between episodic memory retrieval and other mental processes. The study by Holland and Kensinger (this issue) examined how retrievalrelated activity is affected by emotional regulation. Participants encoded negative and neutral images and one week later they recalled each picture (from a verbal cue) after an instruction to upregulate, down-regulate, or maintain the emotional experience elicited by the recalled picture. Interestingly, they found a dissociation in temporal dynamics: up-regulation engaged PFC early during the instruction period whereas down-regulation recruited PFC during the memory search process. The study by De Brigard, Addis, Ford, Schacter, and Giovanello (this issue) investigated episodic counterfactual thinking, which refers to the process of thinking about what could have happened in our past, yet did not occur. Participants recalled autobiographical events with either positive or negative outcomes, and later in the scanner, they recalled the original version or imagined a version with the alternative outcome. Counterfactual thinking recruited many of the same brain regions as episodic memory retrieval (MTL, PFC, posterior cingulate, etc.), particularly when the subjective likelihood of the alternative outcome was greater. To sum up, the results of the third group of studies show how the episodic retrieval network is modulated by emotional goals and can be used for conceiving alternative outcomes of past events. The fourth group of articles focused on the neural mechanisms of source memories at both ends of the developmental continuum. The study by DeMaster, Pathman, and Ghetti (this issue) investigated childhood development of spatial memory retrieval. Different developmental trends were observed in various components of the retrieval network. Challenging the assumption that hippocampal memory functions develop early during childhood, the hippocampus contributed to source memory success in young adults but not in children (8–9 and 10–11 years). The study by Mitchell, Ankudowich, Durbin, Greene, and Johnson (this issue) investigated the effects of old age on the neural mechanisms of source memory. Different tasks measured source memory for stimulus format (word vs. picture) or encoding task (self- vs. other-referential). Activation differences in regions associated with stimulus format (e.g., visual cortex) and encoding task (e.g., medial PFC) were relatively spared in older adults, whereas activation differences in regions associated with retrieval orientation (lateral PFC and parietal regions) were reduced by aging. These results suggest an age-related deficit in selective attention to internal representations. In sum, the fourth group of studies found significant developmental differences in source memory mechanisms in the hippocampus during childhood and frontoparietal regions during old age. The fifth group of articles investigated episodic memory processes that differ between healthy and pathological aging. The study by Stark, Yassa, Lacy, and Stark (this issue) examined pattern separation, which refers to the ability to orthogonalize overlapping inputs into distinct memory representations, a process linked to the dentate gyrus of the hippocampus. They used an object recognition memory task that included not only studied and nonstudied objects also very similar versions of studied objects. In this test, low performing older adults were impaired in rejecting similar lures but not in overall recognition, whereas individuals with mild cognitive impairments (MCI) were impaired in both
measures. The study by Westerberg, Mayes, Florczak, Chen, Creery, Parrish, et al. (this issue) tested amnestic MCI, Alzheimer's disease (AD), and control participants in a silhouette forced-choice recognition task, assumed to be more dependent on familiarity, and a silhouette yes/no recognition task, assumed to involve additional memory and decision processes. MCI participants were impaired in the yes/no recognition performance, which correlated with hippocampal volume, but not in forced-choice recognition performance, which correlated with perirhinal volume. AD participants were impaired in both tests. These results support the idea that perirhinal-related familiarity processes are relatively spared in MCI but not in AD. In sum, the fifth group of studies reported memory dissociations as a function of the pathology progression from normal aging to MCI to AD, and hence, they have potential implications for the diagnosis of AD. Finally, the sixth group of studies used a genetic imaging approach. The study by Kauppi, Nilsson, Adolfsson, Lundquist, Eriksson, and Nyberg (this issue) examined the effects of BDNF Val66Met polymorphism in a large sample of participants. BDNF Met allele carriers showed a subtle impairment in memory performance and a significant reduction in MTL activity during encoding (but not during retrieval). Interestingly, the effect was not modulated by age. The study by Wittmann, Tan, Lisman, Dolan, and Düzel (this issue) investigated the effects of the dopamine transporter (DAT) gene on motivated memory. In 10repeat homozygotes, but not in 9/10 repeat heterozygotes, memory encoding was enhanced by both reward and punishment anticipation. Compared to heterozygotes, homozygotes showed increased striatal activity during reward/punishment anticipation and hippocampal SMEs. These results are consistent with the idea that motivational memory encoding depends on dopaminergic effects on the hippocampus. To sum up, the results of the sixth group highlight the importance of investigating the gene-related variations in the neural mechanisms of memory. In conclusion, the 14 studies in this special issue provide the reader with a snapshot of the state-of-the-art of functional neuroimaging of episodic memory and related functions in 2012–2013. The studies covered a large variety of encoding and retrieval processes and examined many different variables, including the nature of the stimuli (objects vs. scenes, words vs. pictures), the role of preexistent schemas, the effects of retrieval practice, and the impact of partial access to memory representations. They also investigated emotion regulation, counterfactual thinking, childhood and old-age development, the distinction between healthy and pathological aging, and genetic effects. The 14 studies yielded important results about the main components of the episodic memory network, including MTL subregions, lateral and medial PFC and parietal regions, ventral occipitotemporal areas, and various subcortical regions. These results have important implications not only for memory theory but also for a variety of clinical and educational domains. I would like to thank Dr. Ohta for inviting me to organize TIC-10 with him, Gakushuin University for sponsoring this event, and Dr. Rugg for inviting me to edit the special issue. I am also indebted to the contributing authors for submitting some of their best work to the special issue and to the all the reviewers who donated their time. Last but not least, I thank the National Institutes of Health for supporting my research, as well as most of the studies reported in this special issue.
References Bussey, T. J., Saksida, L. M., & Murray, E. A. (2005). The perceptual-mnemonic/ feature conjunction model of perirhinal cortex function. Quarterly Journal of Experimental Psychology B, 58, 269–282.
Editorial / Neuropsychologia 51 (2013) 2319–2321
Chen, J., Dastjerdi, M., Foster, B. L., LaRocque, K. F., Rauschecker, A. M., Parvizi, J., et al., (2013). Human hippocampal increases in low-frequency power during associative prediction violations. Neuropsychologia. /http://dx.doi.org/10.1016/ j.neuropsychologia.2013.03.019S, (in this issue). Davachi, L. (2006). Item, context and relational episodic encoding in humans. Current Opinion in Neurobiology, 16, 693–700. De Brigard, F., Addis, D. R., Ford, J. H., Schacter, D. L., & Giovanello, K. S. (2013). Remembering what could have happened: Neural correlates of episodic counterfactual thinking. Neuropsychologia. /http://dx.doi.org/10.1016/j.neurop sychologia.2013.01.015S, (in this issue). De Master, D., Pathman, T., & Ghetti, S. (2013). Development of memory for spatial context: Hippocampal and cortical contributions. Neuropsychologia. /http://dx. doi.org/10.1016/j.neuropsychologia.2013.05.026S, (in this issue). Detre, G. J., Natarajan, A., Gershman, S. J., & Norman, K. A. (2013). Moderate levels of activation lead to forgetting in the think/no-think paradigm. Neuropsychologia. /http://dx.doi.org/10.1016/j.neuropsychologia.2013.02.017S, (in this issue). Eichenbaum, H., Yonelinas, A. P., & Ranganath, C. (2007). The medial temporal lobe and recognition memory. Annual Reviews of Neuroscience, 30, 123–152. Hannula, D. E., Libby, L. A., Yonelinas, A. P., & Ranganath, C. Medial temporal lobe contributions to cued retrieval of items and contexts. Neuropsychologia. /http://dx.doi.org/10.1016/j.neuropsychologia.2013.02.011S, (in this issue). Heusser, A. C., Awipi, T., & Davachi, L. (2013). The ups and downs of repetition: Modulation of the perirhinal cortex by conceptual repetition predicts priming and long-term memory. Neuropsychologia. /http://dx.doi.org/10.1016/j.neurop sychologia.2013.04.018S, (in this issue). Holland, A. C., & Kensinger, E. A. (2013). An fMRI investigation of the cognitive reappraisal of negative memories. Neuropsychologia. /http://dx.doi.org/10. 1016/j.neuropsychologia.2013.02.012S, (in this issue). Kauppi, K., Nilsson, L.-G., Adolfsson, R., Lundquist, A., Eriksson, E., & Nyberg, L. Decreased medial temporal lobe activation in BDNF 66Met allele carriers during memory encoding. Neuropsychologia. /http://dx.doi.org/10.1016/j.neu ropsychologia.2012.11.028S, (in this issue). Mitchell, K. J., Ankudowich, E., Durbin, K. A., Greene, E. J., & Johnson, M. K. Agerelated differences in agenda-driven monitoring of format and task information. Neuropsychologia. /http://dx.doi.org/10.1016/j.neuropsychologia.2013.01. 012S, (in this issue).
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Roberto Cabeza Center for Cognitive Neuroscience, Duke University, United States E-mail address: [email protected]
Available online 3 August 2013