Brain mechanisms of pain relief by transcutaneous electrical nerve stimulation: A functional magnetic resonance imaging study

Journal Article
J.C. Choi, J. Kim, E. Kang, J.-M. Lee, J. Cha, Y.J. Kim, H.G. Lee, J.-H. Choi, D.-J. Yi
(2016) European Journal of Pain, 20, 92-105

Background: Although the exact mechanism of TENS pain relief is unknown, it is believed that TENS impulses interrupt nociceptive signals at the dorsal horn of the spinal cord. Aims: To evaluate the hypotheses that during pain caused by noxious stimuli, brain responses, temporal summation and brain functional connectivity are modulated by TENS, and that mechanisms of pain relief by TENS differ between men and women. Methods: During fMRI scanning, the same noxious stimuli were delivered to each participant in pain-only and pain+TENS conditions. In the pain-only condition, noxious stimuli were presented without TENS. In the pain+TENS condition, participants received noxious stimuli and TENS concurrently. Participants were initially presented with TENS at an intensity that was just below that causing discomfort. TENS intensity was presented in a step-wise fashion to prevent temporal summation from repetitive noxious stimuli. Results: Pain and unpleasantness ratings were significantly higher in the pain-only than the pain+TENS condition. With non-painful TENS, primary and secondary somatosensory and parietal cortices were activated, and temporal summation from repetitive noxious stimuli was prevented. Periaqueductal gray (PAG) and lateral prefrontal cortex functional connectivity was increased by TENS, and modulated by testosterone and cortisol. Women reported greater pain during TENS than men, and showed greater activation in the temporoparietal junction cortex and increased PAG functional connectivity with the orbitofrontal cortex. Conclusion: TENS led to pain reduction, probably due to activation of the descending pain-inhibitory pathway, indicating that this TENS method may be applied in clinical practice.

중복 간섭: 단어-사진 스트룹 과제를 통한 공동 활성화 모형 검증 (Redundant interference: Evidence for the coactivation model in a word-picture Stroop task)

Journal Article
안석환, 이윤정, 이도준
(2015) 한국심리학회지: 인지 및 생물, 27(2), 313-319.

관찰자는 하나의 자극이 제시되었을 때보다 두 개의 똑같은 자극이 제시되었을 때 자극을 더 빨리 탐지하고 더 정확히 기억할 수 있는데, 이러한 현상을 중복 효과(redundancy effect)라고 한다. 본 실험은 방해자극의 중복 효과가 표적 반응에 미치는 영향을 관찰함으로써 시각 체계가 중복된 자극을 처리하는 방식을 이해하고자 하였다. 단어-사진 스트룹 과제에서 자극 간 출현 시간 간격이 변화할 때 단일 방해자극과 중복된 방해자극에 의한 반응 간섭량을 측정하였다. 그 결과, 중복된 두 개의 방해자극은 단일 방해자극에 비해 전반적인 표적 반응 시간에는 영향을 끼치지 않았음에도 불구하고 유의미하게 큰 스트룹 간섭을 유발하였다. 본 실험의 결과는 중복된 자극이 개별적으로 처리된다고 보는 경주 모형보다, 중복된 자극이 단일한 지각 표상을 구성한다고 가정하는 공동 활성화 모형을 지지한다.

Observers more rapidly detect and more accurately remember two identical targets than a single target, a phenomenon called the redundancy effect. To understand how the visual system deals with redundant information, the current experiment investigated the effect of redundant distractors on target responses. In a word-picture Stroop task, we measured response interference by a single or redundant distractors when the stimulus onset asynchrony varies between a target and the distrator(s). As results, two redundant distractors produced greater Stroop interference than a single distractor although overall response times remained constant. These findings are not compatible with a race model, which assumes separate processing of redundant stimuli, but support a coactivation model, which assumes that redundant stimuli form a single perceptual representation.

행위 가능성에 의한 개인외 공간의 시각 민감도 향상 (Action capability enhances visual sensitivity in the extrapersonal space)

Journal Article
박정호, 김효정, 백종수, 이도준
(2015) 한국심리학회지: 인지 및 생물, 27(3), 543-560.

관찰자를 둘러싼 공간 중 손이나 발이 닿을 수 있는 공간과 그 바깥 공간을 각각 개인주변 공간과 개인외 공간이라 한다. 관찰자의 행위가 집중되는 개인주변 공간에서는 신체 감각과 통합된 시각 정보처리가 물체에 관한 시각 표상을 향상시킨다. 최근 여러 연구들은 개인외 공간에서도 관찰자가 도구를 사용하여 행위를 취할 수 있으면 개인주변 공간과 유사한 다중 감각적 통합이 발생할 수 있다고 보고하였다. 이에 본 연구는 개인외 공간의 시각 표상이 행위 가능성에 의해 향상될 수 있는지 검증하였다. 참가자들은 손이 닿을 수 없는 거리에 위치한 컴퓨터 화면 속의 과제를 자판을 사용하여 수행하였다. 실험 전, 후에 대비역을 측정함으로써 시각 민감도에 미치는 행위 가능성의 효과를 측정하였다. 실험 1에서는 화면에 제시된 공의 움직임을 직접 조작했던 행위 집단과 조작할 수 없었던 관찰 집단의 시각 민감도 변화를 측정하였다. 그 결과, 행위 집단의 시각 민감도가 관찰 집단에 비해 더 향상되었다. 실험 2에서는 행위 가능성을 참가자 내 설계로 조작하였다. 각 참가자는 공을 한쪽 화면에서는 움직일 수 있었지만 다른 쪽에서는 움직일 수 없었다. 그 결과, 공을 조작할 수 있었던 위치의 시각 민감도가 다른 위치의 시각 민감도보다 더 향상되었다. 이러한 결과는 행위 가능성에 의해 활성화된 두정엽의 행위자-중심 좌표 체계가 개인외 공간의 시각 표상을 향상시켰기 때문인 것으로 추정된다.

The physical space around an observer can be divided into the peripersonal space that immediately surrounds the observer and the peripersonal space that cannot be reached by the observer’s hands and other body parts. Actions are mostly executed in the peripersonal space, in which visual processing integrates with somatic perception and enhances visual representations of objects. Recent studies have provided evidence that similar multimodal integration takes place in the extrapersonal space as well if tool-use enables an observer to act towards objects there. Here, we tested if action capability can improve visual sensitivity in the extrapersonal space. Participants performed a task in a distant screen of a computer by using a keyboard. The effect of action capability on visual sensitivity was measured in terms of contrast threshold. Experiment 1 compared threshold changes in one group of participants, who manipulated the movement of a target ball with those in the other group of participants, who did not have a chance to manipulate the ball movement. The improvement in visual sensitivity was greater in the action group than in the observation group. Experiment 2 allowed individual participants to manipulate the movement of a target ball in a part of the screen but not in another part of the screen. Participants showed greater improvement in visual sensitivity only in the screen area in which they were capable of moving the ball. These findings suggest that action capability activates actor-centered coordinate systems in parietal cortex, which in turn enhance visual representations of the extrapersonal space.

디폴트 모드 연결망의 기억 부호화 및 공고화 신호 분석 (Memory encoding and consolidation in the default mode networks)

Journal Article
탁경진, 이홍미, 이도준
(2014) 한국심리학회지: 인지 및 생물, 26(4), 343-367.

본 연구는 후속 기억 패러다임과 휴지기 기능적 연결성 분석을 통해 기억 생성에 관여하는 디폴트 모드 연결망의 신호를 분석하였다. 참가자들은 기능적 자기 공명 영상(functional magnetic resonance imaging, fMRI)을 촬영하는 동안 다수의 장면과 얼굴 사진들을 학습하였고 뇌 영상 촬영이 종료된 후에는 재인 검사를 수행하였다. 디폴트 모드 연결망(default mode networks, DMN)을 정의하고 휴지기 기능적 연결성의 변화를 추적하기 위해 학습 단계 전후에는 휴지기 영상을 촬영하였다. 재인 검사 결과를 바탕으로 학습 단계의 기능 영상을 사진이 기억된 시행과 망각된 시행으로 분류하여 비교하였다. 이를 통해 두 가지 주요 결과를 얻었다. 첫째, DMN의 하위 영역들은 나중에 기억된 자극보다 망각된 자극을 학습하는 동안 더 많이 활성화되었다. 특히 이러한 후속 망각(subsequent forgetting, SF) 효과는 우반구 각회(angular gyrus)에서 가장 두드러지게 나타났다. 둘째, 학습후 휴지기 영상에서 해마와 해마방 장소 영역의 기능적 연결성이 증가한 참가자일수록 후속 재인 검사에서 장면 사진을 더 정확하게 기억하였다. 본 연구의 결과는 디폴트 모드 연결망의 기억 부호화 및 공고화 기능을 하위 영역별로 상세화하고, 동시에 기억의 생성 과정을 이해하기 위해 연결망 수준의 접근이 필요하다는 점을 시사한다.

The current study analyzed the neural signals from the default mode networks (DMN) using the subsequent memory paradigm and a resting-state functional connectivity (rsFC) analysis. Participants learned a number of scenes and faces during functional magnetic resonance imaging (fMRI) in the scanner and later performed a recognition test. To define the DMN and track the changes in rsFC, resting scans were acquired before and after the learning phase. Based on subsequent recognition performance, trials in the learning phase were categorized into either subsequently remembered or subsequently forgotten trials. Here are two main findings: First, DMN subregions showed greater activation for subsequently forgotten than remembered trials. Such subsequent forgetting (SF) effects were most reliable in the right angular gyrus. Second, greater functional connectivity between the hippocampus and the parahippocampal place area (PPA) during the post-learning resting scan predicted better memory for the scenes in the subsequent recognition test. These findings provide information about memory encoding and consolidation functions in the DMN and support the necessity of network-level approaches to understand human memory.

친숙감이 심리적 거리에 미치는 영향 (Effects of familiarity on the construction of psychological distance)

Journal Article
배희경, 김경미, 이도준
(2014) 인지과학, 25(2), 109-133.

관찰자가 대상이나 상황에 관해 느끼는 주관적인 간극을 심리적 거리라고 한다. 심리적 거리는 개인이 그 대상과 상황에 대해 취하는 의사결정과 행위에 영향을 끼친다. 본 연구는 친숙감의 수준이 심리적 거리의 형성에 끼치는 효과를 탐색하였다. 친숙한 자극이 덜 친숙한 자극에 비해 심리적으로 더 가깝게 느껴진다면, 자극이 유발하는 친숙감 수준이 자극의 지각된 공간적 거리와 상호작용할 것으로 예상하였다. 각 실험에서 참가자들은 먼저 사전 노출 단계에서 세 개의 무의미 단어를 경험하였다. 선행 연구들에 따르면 친숙감은 자극의 노출 횟수와 지각적 유창성(perceptual fluency)의 영향을 받는다. 따라서 참가자들이 단어 판단 과제를 수행하는 동안, 무의미 단어들은 각기 다른 수준의 빈도(실험 1)와 선명도(실험 2)로 제시되었다. 그 다음 단계에서 참가자들은 가장 친숙한 무의미 단어와 가장 덜 친숙한 무의미 단어를 가지고 거리 스트룹 과제를 수행하였다. 각각의 단어들은 깊이 단서가 분명한 장면 사진들 속에서 지각적으로 가깝거나 먼 장소에 출현하였다. 그 결과, 두 실험 모두에서 단어의 친숙감과 공간적 거리 간 상호작용이 유의미하였다. 친숙한 단어는 가까운 위치에서 제시되었을 때 빠른 판단 반응을 유발하였고 상대적으로 덜 친숙한 단어는 먼 위치에서 제시되었을 때 빠른 판단 반응을 유발하였다. 이러한 결과는 친숙감에 대한 상위인지적 평가(metacognitive evaluation)가 심리적 거리의 형성을 뒷받침하는 주요 요인임을 의미한다.

Psychological distance refers to the perceived gap between a stimulus and a person’s direct experience and its activation influences the decisions and actions that the person makes towards the stimulus. We investigated whether the level of familiarity affects the construction of psychological distance. Specifically, we hypothesized that a familiar stimulus, relative to an unfamiliar stimulus, is perceived to be psychologically closer to the observer and so its perception might be modulated by the perceived spatial distance. The familiarity of stimuli was manipulated in terms of preexposure frequency and preexposure perceptual fluency. In experiments, participants were first exposed with three nonsense words in a lexical decision task. The nonsense words were presented in nonword trials with different levels of frequency (frequent vs. rare, Experiment 1) or with different levels of visibility (less blurred vs. more blurred, Experiment 2). Participants then performed a distance Stroop task with the most familiar and the least familiar nonwords. Each of them appeared in either proximal or distant spatial locations in scenes with clear depth cues. The results showed a significant interaction between the word familiarity and the spatial distance: the familiar word was judged faster in proximal locations but slower in distant locations relative to the unfamiliar word. The current findings suggest that metacognitive evaluation of familiarity could be one of the critical factors that underlie the construction of psychological distance.

선조외 신체 영역에서 도구 행동유도성과 행위 주체감의 상호작용 (The interaction between tool affordance and the sense of agency in the Extrastriate Body Area)

Journal Article
김효정, 박정호, 이도준
(2013) 인지과학, 24(1), 49-69.

우리가 타인과 상호작용하거나 물체를 사용하는 동안 뇌에서는 신체 이미지를 추적하고 행위의 주체를 파악하려는 신경 정보처리가 끊임없이 이루어진다. 선조외 시각 피질(Extrastriate Body Area, EBA)은 신체에 관한 시각 입력과 우리 자신의 움직임에 관한 내적 신호들을 통합하여 행위 주체감(sense of agency) 생성을 위한 초기 신경 표상을 제공한다. 그러나 이러한 과정에서 물체의 기능적 특성이 행위 주체에 따라서 어떻게 반영되는지 알려진 바는 거의 없다. 이에 본 연구는 기능성 자기공명 영상 기법을 활용하여 자신 또는 타인이 도구를 사용하는 장면을 참가자들이 상상할 때 도구의 행동유도성(affordance)이 EBA의 신경 반응에 끼치는 영향을 관찰하였다. 각 시행에서 참가자들은 신체를 향해 사용하는 도구(예, 망원경)나 신체 바깥 방향으로 사용하는 도구(예, 주사위)를 제시받았다. 이 때, 도구를 둘러싼 사각형 테두리의 색깔에 따라서 참가자들은 자신 혹은 타인이 그 도구를 사용한다고 상상하였다. 실험 결과, 우반구 EBA는 참가자가 ‘자신’의 행위를 상상할 때 바깥 방향 도구 조건보다 신체 방향 도구 조건에서 더 많이 활성화되었으나, 참가자가 ‘타인’의 행위를 상상할 때는 도구의 사용 방향으로부터 영향을 받지 않았다. 후속 검사에 따르면 자신 조건과 타인 조건에서 각각 상상하는 동안 참가자가 느낀 생동감의 차이는 없었다. 이러한 결과는 EBA가 도구의 행동유도성 정보를 신체 도식에 반영함으로써 행위 주체감을 향상시키고 우리 자신의 행동을 안내하는 데 기여하고 있음을 시사한다.

While we interact with other people or objects, the brain continuously updates our own body schema to recognize the agent of observed actions. The Extrastriate Body Area (EBA) provides an initial interface for the sense of agency by integrating visual inputs of body parts with internal signals related to self-generated body movements. Less is known, however, about how the functional use of tools contributes to such processes. Here, we investigated whether tool-specific affordance would differentially affect the neural responses in the EBA depending on the agency of imaginary actions. In each trial we presented a picture of an object in a rectangular frame. Objects were either the tools typically brought towards the body (body tools; e.g., telescope, earphones) or away from the body (world tools; e.g., pen, dice; Rueschemeyer, Pfeiffer, & Bekkering, 2010). Depending on the color of the frame, participants imagined either themselves or the other person using the tool (self vs. other conditions). These four types of trials were randomly intermixed with blank trials. As results, independently localized right EBA regions of interest showed greater activation when participants imagined themselves using body tools than using world tools whereas no such differential activations were found when they imagined the other person using the tools. The postscan test revealed no significant difference in vividness of imagery between the self and other conditions. Our results suggest that the EBA incorporates functional affordance of tools into the body schema in order to enhance the sense of agency and to guide our own actions.

Working memory load can reduce task-irrelevant processing in human fusiform gyrus

Journal Article
민수정, 김가민, 이도준, 김민식
(2013) 한국심리학회지: 인지 및 생물, 25(1), 1-24.

How does working memory (WM) load affect concurrent visual selection? A previous study has shown that high WM load increases functional magnetic resonance imaging (fMRI) signals for task-irrelevant information, suggesting that visual selection is impaired with a WM load. In contrast, recent behavioral experiments demonstrated that visual selection can be enhanced if the type of WM load overlaps with distractor processing. Using fMRI, the current experiment extends this behavioral finding by demonstrating that loading WM with face images can reduce task-irrelevant face processing in the face-selective cortical region, the fusiform face area (FFA). In Experiment 1, while remembering a famous (low load) or novel (high load) face, participants performed a politician-athlete classification for names overlaid on distractor faces. In Experiment 2, participants remembered one novel face (low load) or three different novel faces (high load) for the WM task. In both experiments, high WM load enhanced target selection. The FFA responses were reduced to face distractors when WM was demanded.  We further demonstrated that these results were not driven by load-dependent baseline shifts in the FFA activity in Experiment 3. In conjunction with previous studies,  the current findings suggest that WM load can attenuate distractor interference and improve target selection when the content of WM shares limited-capacity processing with distractors.

The effect of attention on repetition suppression and multivoxel pattern similarity

Journal Article
Moore, K. S., Yi, D. -J., & Chun, M. M.
(2013) Journal of Cognitive Neuroscience, 25(8), 1305-1328.

Fundamental to our understanding of learning is the role of attention. We investigated how attention affects two fMRI measures of stimulus-specific memory: repetition suppression (RS) and pattern similarity (PS). RS refers to the decreased fMRI signal when a stimulus is repeated, and it is sensitive to manipulations of attention and task demands. In PS, region-wide voxel-level patterns of responses are evaluated for their similarity across repeated presentations of a stimulus. More similarity across presentations is related to better learning, but the role of attention on PS is not known. Here, we directly compared these measures during the visual repetition of scenes while manipulating attention. Consistent with previous findings, we observed RS in the scene-sensitive parahippocampal place area only when a scene was attended both at initial presentation and upon repetition in subsequent trials, indicating that attention is important for RS. Likewise, we observed greater PS in response to repeated pairs of scenes when both instances of the scene were attended than when either or both were ignored. However, RS and PS did not correlate on either a scene-by-scene or subject-by-subject basis, and PS measures revealed above-chance similarity even when stimuli were ignored. Thus, attention has different effects on RS and PS measures of perceptual repetition.

Out of Mind, Out of Sight: Perceptual Consequences of Memory Suppression

Journal Article
Kim, K., & Yi, D.-J.
(2013) Psychological Science, 24(4), 569-574

In the present study, the effect of memory suppression on subsequent perceptual processing of visual objects was examined within a modified think/no-think paradigm. Suppressing memories of visual objects significantly impaired subsequent perceptual identification of those objects when they were briefly encountered (Experiment 1) and when they were presented in noise (Experiment 2), relative to performance on baseline items for which participants did not undergo suppression training. However, in Experiment 3, when perceptual identification was performed on mirror-reversed images of to-be-suppressed objects, no impairment was observed. These findings, analogous to those showing forgetting of suppressed words in long-term memory, suggest that suppressing memories of visual objects might be mediated by direct inhibition of perceptual representations, which, in turn, impairs later perception of them. This study provides strong support for the role of inhibitory mechanisms in memory control and suggests a tight link between higher-order cognitive operations and perceptual processing.

Social distance decreases responders’ sensitivity to fairness in the ultimatum game

Journal Article
Kim, H., Schnall, S., Yi, D. -J., & White, M. P.
(2013) Judgment and Decision Making, 8(5), 632-638.

Studies using the Ultimatum Game have shown that participants reject unfair offers extended by another person although this incurs a financial cost. Previous research suggests that one possible explanation for this apparently self- defeating response is that unfair offers involve strong negative responses that decrease the chances of responders accept- ing offers that would objectively constitute a net profit. We tested the hypothesis that one way of reducing responders’ rejections of unfair offers is through increased psychological distance, so that participants move away from the concrete feeling of being unfairly treated. Social distance was manipulated by having participants play the Ultimatum Game either for themselves, or for another person. Compared to deciding for one’s self or a close social contact, participants showed less sensitivity to fairness when deciding for a stranger, as indicated by fewer rejected unfair offers. We suggest that social distance helps people move beyond immediate fairness concerns in the Ultimatum Game.

생각회피 훈련을 통한 의도적 망각에서 항목 강도와 연합 강도의 효과 (Effects of Item vs. Associative Strength on Intentional Forgetting in the Think/No-think Paradigm)

Journal Article
홍유림, 이도준
(2012) 한국심리학회지: 인지 및 생물, 24(3), 231-250.

본 연구는 원하지 않는 기억의 인출을 인지적으로 억제할 수 있다는 사실을 실험적으로 증명한 생각/생각회피 패러다임(think/no-think paradigm)을 사용하여 1) 표적 항목의 기억 강도가 높을수록 인지적 억제가 촉진되어 망각이 잘 발생하고 2) 반면에 단서와 표적의 연합 강도가 높으면 간섭이 약화되어 망각이 덜 발생할 가능성을 검증하였다. 실험 1에서는 표적 항목의 기억 강도를 조작하기 위해 부정적이거나 중립적인 정서가를 가진 단어들을 사용하고, 사전 연합 학습 단계의 훈련 수준에 따라 단서와 표적 간 연합 강도의 세기를 구분하였다. 그 결과, 중성적인 표적에 비해 부정적인 표적에 대한 망각이 회피 조건에서 더 크게 발생하였다. 또한 표적이 사전 학습 단계에서 학습이 잘 되었을수록 망각이 덜 발생하였다. 실험 2에서는 표적 대신 단서의 정서가를 조작함으로써 단어쌍의 연합 강도를 실험 1과 같게 유지한 채 표적 항목의 기억 강도는 조건별 차이가 나지 않도록 하였다. 그 결과, 사전 학습의 효과는 재현되었지만 단서의 정서가는 표적의 망각에 영향을 끼치지 않았다. 이러한 결과는 항목 자체가 가지는 기억 강도와 항목들 간의 연합 강도가 각각 억제와 간섭을 통해 독립적으로 의도적 망각에 상반된 효과를 유발할 수 있음을 증명한다.

The present study hypothesized 1) that the forgetting effects would be greater for targets with strong item memory strength because the item to be forgotten is clear and easily accessed by cognitive control process, 2) the forgetting effects would be lesser for the cue-target pairs with strong associative memory strength because the effect of interference from other competitive stimuli associated with the cue is relatively smaller using think/no-think (TNT) paradigm demonstrated the facts that unwanted memory can be forgotten intentionally. In Experiment 1, target stimuli had either emotional or neutral content to adjust item memory strength of the target while cue-target pairs were distinguished based on the associative memory strength between cue and target words during a training phase. Results indicated an enhancing effect on the think condition and suppressing effect on the no-think condition following repeated practice given the target contained negative valence rather than neutral valence. In addition, greater suppression was observed when cue-target pairs contained weak associative memory strength. In Experiment 2, instead of targets, the valence of cues was changed to adjust the item memory strength of cue stimuli while maintaining the level of associative memory strength between cue-target pairs. The associative memory strength effect depending on the training level in the learning phase was almost the same as in Experiment 1, but there was no significant difference between valences of cues. The finding indicates that the item memory strength and the associative memory strength have opposite effects on intentional forgetting by the inhibition and interference mechanism respectively.

장기 기억 과제에서 연합 항목의 범주 관계가 해마 활동에 미치는 영향 (The Effects of Categorical Relationship Between Memory Items on Hippocampal Activation in a Long-term Associative Memory Task)

Journal Article
정주연, 민수정, 한상훈, 이도준
(2012) 한국심리학회지: 인지 및 생물, 24(4), 453-470.

장기 기억 과제에서 연합쌍을 부호화하거나 인출할 때 항목들의 범주 관계가 해마의 신경 활동에 미치는 영향을 관찰하기 위해 기능성 자기공명영상(fMRI) 연구를 수행하였다. 뇌영상을 촬영하는 동안 학습 단계와 검사 단계로 구성된 실험 절차를 총 여덟 차례 반복 실시하였다. 각 단계마다 12개의 연합쌍이 화면에 출현하였다. 학습 단계의 연합쌍 중 절반은 검사 단계에서 그대로 제시되었고 나머지 절반은 재조합되어 제시되었다. 참가자들은 학습 단계에서 연합쌍을 외웠고 검사 단계에서 연합 재인 과제를 수행하였다. 범주 간 연합 조건의 연합쌍은 얼굴과 건물로 구성되었고 범주 내 연합 조건의 연합쌍은 얼굴과 얼굴, 또는 건물과 건물로 구성되었다. 실험 결과, 얼굴-건물 연합쌍에 대한 재인율은 얼굴-얼굴 연합쌍과 건물-건물 연합쌍에 대한 재인율과 다르지 않았다. 그러나 학습 및 검사 단계에서 범주 간 연합 조건에 대해 더 많이 활성화된 덩이소들이 해마를 비롯한 여러 뇌 영역에서 발견되었다. 학습 단계와 검사 단계에서 발견된 해마 덩이소들의 위치는 대체로 겹치지 않았지만, 학습 단계에서 발견된 우반구 해마의 덩이소들은 검사 단계에서도 비슷한 패턴으로 활성화되었다. 이러한 결과는 기억 항목의 지각적, 개념적 유사성이 해마 신경 활동에 영향을 끼친다는 점을 의미하며, 해마의 연합 기능을 규명하기 위해 범주에 대한 이해가 선행되어야 함을 시사한다.

An event-related functional magnetic resonance imaging (fMRI) experiment was conducted to test the effects of categorical relationship between memory items on hippocampal activation during encoding and retrieval of long-term associative memory. The experiment alternated a learning and a test phase eight times in the scanner. Each phase presented 12 associative pairs. During a test phase, a half of the learned pairs were repeated and the other half were rearranged. Participants determined if each pair was intact or rearranged. The between-domain association condition presented face-building pairs and the within-domain association condition presented either face-face or building-building pairs. As results, although behavioral performance of associative recognition was not different between the two conditions, many clusters in the hippocampus and the other brain areas showed greater activation in the between-domain association condition both during learning and test phases, confirming and extending a previous observation (Piekema et al., 2009). In the hippocampus, while such clusters were not spatially overlapped between learning and test phases, the clusters defined in the learning phase produced patterns of activation similar to the test phase. Overall, the current study demonstrates that perceptual and conceptual similarity of memory items affects hippocampal activity and suggests that theoretical and empirical understanding about domain is useful to investigate binding functions in the hippocampus.

의사결정과 자아

특집 원고
김현지, 이도준
(2012) 정보과학, 30(12), 35-42.

 

최근 인지신경과학의 연구 범위는 지각 및 인지 기능 위주의 ‘차가운’ 정보 처리에서 사회 및 정서적 의사결정에 관여하는 ‘뜨거운’ 정보 처리로 넓게 확대되고 있다. 구체적으로는 대인 지각, 이타 행동, 선입관과 편견을 반영하는 신경 표상을 포함하여 소비와 신용거래 등과 같은 경제 상황에서 효용(utility)의 변화를 추적하는 신경 메커니즘 등이 주목을 끌고 있다. 이는 심리학과 경제학을 비롯한 행동과학이 뇌신경의 기능과 구조를 이해하는 새로운 관점을 제공하기 때문인데, 특히 이들 학문 분야에서 발전되어온 의사결정 모형들은 뇌신경 활성화 패턴을 체계적으로 관찰할 수 있는 프로토콜로서 유용하게 활용되고 있다. 이와 동시에 인지신경과학은 행동과학의 발전에도 기여하고 있다. 행동 관찰을 통해 얻은 자료들을 인간이 아닌 동물에서 얻은 신경생리학적 자료들과 연계하여 해석하거나 신경해부학적 지식에서 행동과학적 가설을 도출하는 것이 전보다 수월해졌다. 그리고 무엇보다도, 다양한 행동의 뇌신경 자료가 비교 분석되면서 서로 달라 보였던 행동들 간의 관련성이 드러나고 이를 통해 넓은 범위의 인간 행동에 적용 가능한 통합적인 관점들이 등장하고 있다.

이 중 한 가지 관점으로서 본 논문은 의사결정자의 자아(self)를 중심으로 다양한 인지적, 사회적 상황에서의 행동 및 신경영상학적 연구 결과들을 종합하고자 한다. 기본적으로 의사결정은 예상되는 결과를 근거로 현재의 선택 옵션을 평가하는 행위이므로 의사결정의 성공 여부는 미래의 사건을 상상하는 능력에 달려있다. 그러나 미래에 관한 정보는 늘 부족하기 마련이므로 미래를 마음 속으로 정확히 시뮬레이션 하기는 쉽지 않다. 또한 의사결정을 내리는 지금의 자아와 그 결과를 경험하게 될 미래의 자아는 다를 수 있다. 자아는 기억과 경험의 결합체로서 새로운 경험을 통해 끊임없이 재조직되기 때문에 의사결정의 결과에 대한 주관적 가치도 시간이 흐르면 변하게 된다. 이를 감안할 때, 의사결정은 미래의 자아가 가질 생각과 감정을 읽는 행동으로 볼 수 있으며 ‘지금 여기의 나’를 초월하는 정신작용이라는 면에서 회상, 상상력, 공감 등 다른 고차원적 행동과 관련성을 가진다. 본 논문은 이러한 관점을 바탕으로 다양한 사회-정서적 의사결정 상황이 자아를 중심으로 표상되는 방식을 자아의 특성과 함께 논의하고 그에 근거하여 새로운 연구 방향을 제시하고자 한다.

Negative effects of item repetition on source memory

Journal Article
Kim, K., Yi, D.-J., Raye, C. L., & Johnson, M. K.
(2012) Memory and Cognition, 40(6), 889-901

In the present study, we explored how item repetition affects source memory for new item-feature associations (picture-location or picture-color). We presented line drawings varying numbers of times in Phase 1. In Phase 2, each drawing was presented once with a critical new feature. In Phase 3, we tested memory for the new source feature of each item from Phase 2. Experiments 1 and 2 demonstrated and replicated the negative effects of item repetition on incidental source memory. Prior item repetition also had a negative effect on source memory when different source dimensions were used in Phases 1 and 2 (Experiment 3) and when participants were explicitly instructed to learn source information in Phase 2 (Experiments 4 and 5). Importantly, when the order between Phases 1 and 2 was reversed, such that item repetition occurred after the encoding of critical item- source combinations, item repetition no longer affected source memory (Experiment 6). Overall, our findings did not support predictions based on item predifferentiation, within-dimension source interference, or general interference from multiple traces of an item. Rather, the findings were consistent with the idea that prior item repetition reduces attention to subsequent presentations of the item, decreasing the likelihood that critical item-source associations will be encoded.

스트룹 간섭의 희석 및 중복 효과 (Dilution and redundancy effects on Stroop interference)

Journal Article
이지영, 민수정, 이도준
(2011) 인지과학, 22(4), 469-494.

동일한 지각 범주에 속하는 물체들은 범주 별로 특성화된, 제한된 용량의 주의 자원을 차지하기 위해 서로 경쟁한다. 그러나 지각적으로 동일한 두 개의 물체가 시각 분석 과정에서 상호작용하는 방식에 대해서는 잘 알려져 있지 않다. 지각적으로 같은 물체들은 동일한 범주의 물체들이 경쟁하듯이 서로의 정보처리를 억제할 가능성도 있지만, 오히려 서로 협력을 통해 잡음에 강하고 지속력 있는 지각 표상을 생성할 가능성도 있다. 본 연구는 이러한 가능성들을 검증하기 위해 그림-이름 스트룹 과제를 사용한 세 건의 행동 실험을 실시하였다. 그 결과, 같은 범주에 속하는 두 개의 방해자극들은 서로의 간섭 효과를 희석시켰지만, 두 개의 중복된 방해자극들은 서로의 간섭 효과를 강화하였다(실험 1). 중복 효과는 동일한 반응과 연합된, 지각적으로 다른 방해자극들을 제시했을 때는 사라졌고(실험 2), 대뇌 반구 별 자극 제시 방법의 영향을 받지 않았다(실험 3). 이러한 결과는 방해자극의 중복 효과가 반구 간 상호 독립적인 주의 자원에 기초한 지각적 표상 수준의 처리 과정에서 발생하고 있음을 의미한다. 본 연구의 결과는 스트룹 간섭이 지각적 범주 수준의 주의 자원의 제약을 받는다는 가설을 지지하고, 더 나아가 자극의 중복이 지각 정보처리를 촉진함으로써 이러한 제약을 극복할 수 있음을 시사한다.

It is well known that visual objects belonging to the same perceptual category compete for category-specific, limited-capacity attentional resource. However, it remains to be seen how perceptually identical objects interact with each other during visual analyses. Perceptually identical objects might suppress each other as much as categorically identical objects do. Alternatively, they might cooperate to generate a perceptual representation which is long lasting and robust to noise. Such possibilities were tested in the current research with three behavioral experiments using the Stroop task. As results, relative to a single distractor, Stroop interference was diluted by two different distractors of a category while it was enhanced by two perceptually identical distractors (Experiment 1). This redundancy effect disappeared when two different distractors associated with the same response were presented (Experiment 2), and it was not affected by the between- vs. within-hemisphere distractor presentations (Experiment 3). These findings indicate that the redundancy effect of distractors may be mediated by perceptual representations based on hemisphere-independent attentional resources. Overall, the current study supports the hypothesis that Stroop interference is constrained by category-specific attentional resources and further suggests that redundant presentations of a stimulus overcome such attentional constraints by facilitating perceptual processing.

상하 반전된 장면의 테두리 확장(Boundary Extension of Inverted Scenes)

Journal Article
공진기, 이도준
(2011) 인지과학, 22(2), 173-192.

시각 체계는 장면을 지각할 때 주어진 감각 정보에만 의존하지 않는다. 맥락 정보를 적극 활용함으로써 주변 환경과의 시공간적 연속선상에서 장면을 파악한다. 그러나 부족한 감각정보를 맥락 정보로 채워 넣는 과정에서 실제 본 장면보다 더 넓은 영역을 봤다고 잘못 기억하는 경우가 있는데, 이를 테두리 확장(boundary extension) 효과라고 한다. 본 연구는 상하반전(inversion)의 효과를 통해 테두리 확장 현상에 관한 가설들을 검증하였다. 상하반전된 장면에서 맥락 정보를 추출하기 어렵다는 기존 연구 결과들에 근거하여 학습 단계 또는 검사 단계에서 장면 사진을 거꾸로 제시하였다. 세 가지 실험의 결과, 테두리 확장 효과는 장면이 학습 단계에서 상하반전 되었을 때 감소하였는데, 장면을 구성하는 물체의 방향성이 분명할수록 더 감소하였다. 이러한 결과는 적절한 맥락이 활성화됨으로써 장면이 외연될 수 있다는 것과 테두리 확장 효과가 장면이 기억으로 부호화되는 과정에서 발생한다는 것을 시사한다.

The visual system applies previously learned contextual knowledge to facilitate the perception and encoding of scenes. When extrapolation following the employment of contextual information occurs, it sometimes leads to scene memory distortion: people report as if they saw more than they actually had seen. This phenomenon is called the “boundary extension” effect (Intraub & Richardson, 1989). The present study aimed to clarify the effects of contextual information on boundary extension in a more systematic way. Based on the assumption that it is harder to extract contextual information from inverted scenes compared to intact scenes, we presented inverted scenes either during encoding or retrieval to manipulate the level of contextual information and compared the magnitude of boundary extension effect for upright versus inverted scenes. In a series of experiments, we found that scene inversion during encoding, but not during retrieval, significantly reduced boundary extension. Showing reduced memory distortion for inverted scenes, the current study directly demonstrated that access to contextual information is a critical component of scene extrapolation process.

Placebo effects on analgesia related to testosterone and premotor activation

Journal Article
Choi, J. C., Yi, D.-J., Han, B. S., Lee, P. H., Kim, J. H., & Kim, B. -H.
(2011) Neuroreport, 22(9), 419-423.

Using functional magnetic resonance imaging, we tested whether graded placebo conditions could modulate the degree of placebo effect and brain activation patterns in study participants and whether the placebo effect could be influenced by hormones. Each participant was investigated under three conditions: the control (no placebo) condition, the low-placebo condition, and the high-placebo condition (HPC). Activations of the premotor areas, anterior cingulate cortex, and prefrontal cortex were stronger in the HPC compared with those in the control and low placebo conditions. The premotor areas were activated by increased testosterone levels under the HPC. These results suggest that testosterone may affect the brain activation and response to pain during a high-placebo response, with the data supported by brain imaging.

지각적 부담과 범주 별 희석이 시각 탐색에 미치는 영향(The Effects of Perceptual Load and Category-Specific Dilution on Visual Search)

Journal Article
임지향, 이도준
(2010) 인지과학, 21(1),177-197.

선택적 정보처리에 관한 지각적 부담 가설과 희석 가설을 비교하기 위해 세 개의 실험을 실시하였다. 지각적 부담 가설은 행동 목표에 부합하는 과제의 지각적 부담이 적을수록 불필요한 정보가 더 깊이 처리될 수 있다고 보는 반면, 희석 가설은 지각적 부담에 관계없이 제한된 주의 자원에 대한 경쟁에 의해 정보 선택 여부가 결정된다고 본다. 두 가설을 비교하기 위하여 표적 탐색의 지각적 부담이 방해자극의 반응 간섭에 미치는 영향을 측정하였다. 실험 1과 2에서는 탐색 배열을 구성하는 비표적자극의 개수와 색깔을 각각 조절하여 시각탐색의 지각적 부담을 조작하였다. 그 결과 방해자극의 간섭은 지각적 부담에 상관없이 비표적자극이 많을수록 감소하였다. 실험 3에서는 비표적자극의 역할을 규명하기 위해 비표적자극과 방해자극의 지각적 범주를 같거나 다르게 제시하였다. 그 결과 지각적 범주가 같을 때에만 방해자극의 간섭이 감소하였다. 전반적으로 본 연구의 결과는 지각적 부담 가설보다는 희석 가설과 일치하며, 더 나아가 시각 정보의 선택이 지각적 범주 별로 특화된 주의 자원의 제약을 받는다는 증거를 제공한다.

Three experiments compared two hypotheses on visual selection; perceptual load hypothesis and dilution hypothesis. The perceptual load hypothesis predicts that perceptual load of task-relevant processing determines the level of task-irrelevant processing whereas the dilution hypothesis predicts that competition for limited-capacity attentional resource, not perceptual load, determines the locus of selection. To compare the two hypotheses, we investigated the influence of perceptual load in visual search on response interference by a distractor. Experiment 1 and 2 manipulated perceptual load by the set size of a search array and the colors of a target and non-targets, respectively. As a result, distractor interference decreased with a set size regardless of perceptual load. In order to further test the set size effect, Experiment 3 manipulated the perceptual categories of non-targets and a distractor. The results showed that distractor interference decreased only when non-targets belonged to the same category as a distractor. Overall, the current findings support the dilution hypothesis, but not the perceptual load hypothesis, and provide the evidence that visual selection is constrained by capacity-limited, category-specific attentional resources.

자기 참조적 출처 기억에서의 자기 긍정 편향

Journal Article
김경미, 이도준
(2010) 한국심리학회지: 사회 및 성격, 24(1), 47-61.

Spatiotemporal object continuity in human ventral visual cortex

Journal Article
Yi, D. -J., Turk-Browne, N. B., Flombaum, J. I., Scholl, B. J., Kim, M.-S., & Chun, M. M.
(2008) Proceedings of the National Academy of Sciences, USA, 105, 8840-8845.

Coherent visual experience requires that objects be represented as the same persisting individuals over time and motion. Cognitive science research has identified a powerful principle that guides such processing: Objects must trace continuous paths through space and time. Little is known, however, about how neural representations of objects, typically defined by visual features, are influenced by spatiotemporal continuity. Here, we report the consequences of spatiotemporally continuous vs. discontinuous motion on perceptual representations in human ventral visual cortex. In experiments using both dynamic occlusion and apparent motion, face-selective cortical regions exhibited significantly less activation when faces were repeated in continuous vs. discontinuous trajectories, suggesting that discontinuity caused featurally identical objects to be represented as different individuals. These results indicate that spatiotemporal continuity modulates neural representations of object identity, influencing judgments of object persistence even in the most staunchly “featural” areas of ventral visual cortex.

When a thought equals a look: Refreshing enhances perceptual memory

Journal Article
Yi, D. -J., Turk-Browne, N. B., Chun, M. M., & Johnson, M. K.
(2008) Journal of Cognitive Neuroscience, 20(8), 1371-1380.

Cognition constantly involves retrieving and maintaining information that is not perceptually available in the current environment. Studies on visual imagery and working memory suggest that such high-level cognition might, in part, be mediated by the revival of perceptual representations in the inferior temporal cortex. Here, we provide new support for this hypothesis, showing that reflectively accessed information can have similar consequences for subsequent perception as actual perceptual input. Participants were presented with pairs of frames in which a scene could appear, and were required to make a category judgment on the second frame. In the critical condition, a scene was presented in the first frame, but the second frame was blank. Thus, it was necessary to refresh the scene from the first frame in order to make the category judgment. Scenes were then repeated in subsequent trials to measure the effect of refreshing on functional magnetic resonance imaging repetition attenuation—a neural index of memory—in a scene-selective region of the visual cortex. Surprisingly, the refreshed scenes produced equal attenuation as scenes that had been presented twice during encoding, and more attenuation than scenes that had been presented once during encoding, but that were not refreshed. Thus, the top-down revival of a percept had a similar effect on memory as actually seeing the stimulus again. These findings indicate that high-level cognition can activate stimulus-specific representations in the ventral visual cortex, and that such top-down activation, like that from sensory stimulation, produces memorial changes that affect perceptual processing during a later encounter with the stimulus.

Neural dissociation of delay and uncertainty in inter-temporal choice.

Journal Article
Luhmann, C. C., Chun, M. M., Yi, D. -J., Lee, D., & Wang, X. -J
(2008) Journal of Neuroscience, 28(53), 14459-14466.

Decision makers often face choices whose consequences unfold over time. To explore the neural basis of such intertemporal choice behavior, we devised a novel two-alternative choice task with probabilistic reward delivery and contrasted two conditions that differed only in whether the outcome was revealed immediately or after some delay. In the immediate condition, we simply varied the reward probability of each option and the outcome was revealed immediately. In the delay condition, the outcome was revealed after a delay during which the reward probability was governed by a constant hazard rate. Functional imaging revealed a set of brain regions, such as the posterior cingulate cortex, parahippocampal gyri, and frontal pole, that exhibited activity uniquely associated with the temporal aspects of the task. This engagement of the so-called “default network” suggests that during intertemporal choice, decision makers simulate the impending delay via a process of prospection.

What makes repressors good suppressors?: The effect of trait anxiety

Journal Article
김경미, 이도준, 양은주, 이기학
(2007) 한국심리학회지: 일반, 26, 261-278.

Masked-target recovery requires focused attention on the target object

Journal Article
Woodman, G. F., & Yi, D. -J.
(2007) Visual Cognition, 15(4), 385-401.

Flashing a homogeneous light mask after the presentation of a masked target reduces the deleterious effects of the mask, a phenomenon often called target recovery. Target recovery has been studied using masking paradigms in which a target object is presented in isolation prior to the presentation of a mask, thus capturing attention. In the present study, we examined whether target recovery is possible when a target does not benefit from attentional capture. We hypothesized that target recovery would be eliminated when a target must compete with distractors for perceptual attention. Replicating classic studies, we observed target recovery when pattern and light masks followed an isolated target. However, target recovery was not observed when a light mask followed a masked visual search target. Furthermore, using an attentional-capture paradigm we found that sudden onset search targets were recoverable whereas nononset targets were not. The present findings indicate that attentional capture by a target prior to masking plays a critical role in the subsequent recovery of the target.

Visual quality determines the direction of neural repetition effects

Journal Article
Turk-Browne, N. B., Yi, D. -J., Leber, A. B. & Chun, M. M.
(2007) Cerebral Cortex, 17, 425-433.

One ubiquitous finding in functional magnetic resonance imaging studies is that repeated stimuli elicit lower responses than novel stimuli. In apparent contradiction, some studies have reported the exact opposite effect—greater responses to repeated than novel stimuli—in many of the same brain regions. Interestingly, these latter enhancement effects are typically obtained when stimuli have been degraded. To explore this observation, the present study examines the degree to which visual quality mediates repetition effects in a stimulus-selective ventral visual area. Subjects were presented with grayscale photographs of scenes that were either near or substantially above visual threshold, as determined by calibrating image contrast to behavioral performance. The presentation of 2 identical high-contrast scenes elicited lower blood oxygen level–dependent (BOLD) responses than the presentation of 2 different high-contrast scenes (repetition attenuation). Conversely, the presentation of 2 identical low-contrast scenes elicited greater BOLD responses than the presentation of 2 different low-contrast scenes (repetition enhancement). Neurophysiological studies suggest that repetition attenuation in ventral visual areas may reflect the reactivation of perceptual representations that have become sparse and selective as a result of prior experience, whereas repetition enhancement may reflect spared access to existing representations by severely degraded input.

Beyond the edges of a view: boundary extension in human scene-selective visual cortex

Journal Article
Park, S., Intraub, H., Yi, D. -J., Widders, D., Chun, M. M.
(2007) Neuron, 54, 335-342.

To allow perception of a continuous world, cortical mechanisms extrapolate missing information with highly constrained predictions about the environment just beyond the edges of a view. Here, we report functional magnetic resonance imaging evidence for extrapolation of scene layout information beyond what was physically presented, an illusion known as boundary extension. Consistent with behavioral reports, we observed boundary extension for scene-selective attenuation in the parahippocampal place area (PPA) and retrosplenial cortex (RSC), but no such extrapolation of object representations in the lateral occipital complex (LOC). These results demonstrate that scene layout representations are extrapolated beyond the confines of the perceptual input. Such extrapolation may facilitate perception of a continuous world from discontinuous views.

Attentional modulation of repetition attenuation is anatomically dissociable for scenes and faces

Journal Article
Yi, D. -J., Olson, I. R., & Chun, M. M.
(2006) Vision Research, 46, 914-924.

What does perceptual experience contribute to figure-ground segregation? To study this question, we trained observers to search for symmetric dot patterns embedded in random dot backgrounds. Training improved shape segmentation, but learning did not completely transfer either to untrained locations or to untrained shapes. Such partial specificity persisted for a month after training. Interestingly, training on shapes in empty backgrounds did not help segmentation of the trained shapes in noisy backgrounds. Our results suggest that perceptual training increases the involvement of early sensory neurons in the segmentation of trained shapes, and that successful segmentation requires perceptual skills beyond shape recognition alone.

Attentional modulation of repetition attenuation is anatomically dissociable for scenes and faces

Journal Article
Yi, D. -J., Kelley, T. A., Marois, R. & Chun, M. M.
(2006) Brain Research, 1080, 53-62.

Repeating a stimulus generally leads to a decreased response in neural activity compared to that for novel items. This neural attenuation provides a marker for stimulus-specific perceptual encoding and memory that can be detected using functional magnetic resonance imaging (fMRI). Although previously assumed to occur automatically whenever a stimulus is repeated, recent studies have begun to show that the repetition attenuation effect is task-specific and modulated by attention. Here, we demonstrate that attention is crucial for obtaining neural attenuation even after extensive stimulus repetitions. Furthermore, the effect of attention on attenuation is anatomically dissociable for stimuli that have relatively segregated neural representations in high-level perceptual cortex. To manipulate attention, we used overlapping scene and face images, and asked subjects to attend to either category. In a scene-sensitive cortical region known as the parahippocampal place area (PPA), significant attenuation in the fMRI BOLD signal was observed for the attended repeated scenes (relative to attended novel scenes), while no attenuation was observed for ignored repeated scenes or attended repeated faces against their respective novel image baselines. Conversely, in the face-sensitive region known as the fusiform face area (FFA), significant attenuation was observed for attended repeated faces, but not for ignored repeated faces or attended repeated scenes. An additional control experiment ruled out alternative explanations based on global signal level reductions due to inattention. Thus, attention actively governed when neuronal activity was attenuated to repeated perceptual input, and such attenuation was specific to the cortical regions that actively represent the attended category of stimuli.

Attentional Modulation of Learning-Related Repetition Attenuation Effects in Human Parahippocampal Cortex

Journal Article
Yi, D. -J., & Chun, M. M.
(2005) Journal of Neuroscience, 25(14), 3593-3600.

Two of the most fundamental processes in biological vision are attention and learning. Attention actively selects and enhances visual information that is most relevant to behavior. Learning enables the visual system to benefit from perceptual experience. The amount of visual information to learn is infinite; however, top-down control mechanisms must somehow regulate learning to achieve an adaptive balance between plasticity and stability in neural circuitry. Functional magnetic resonance imaging (fMRI) can measure learning-related changes in neural activity to previously viewed perceptual stimuli. Described variably as the repetition suppression or adaptation effect, the attenuation in neural activity to repeated stimuli versus novel stimuli provides a marker for stimuli-specific perceptual processing and memory. One important issue concerns whether repetition attenuation is automatic or not, and recent work has begun to show that it is sensitive to task demands. Accordingly, the present study further examined how attention controls the attenuated response to repeated stimuli, specifically testing whether attention is important for initial encoding, for the expression of memory traces, or for both encoding and expression. To manipulate attention, we used overlapping scene and face images and asked subjects to attend to either category. fMRI revealed significant attenuation in the parahippocampal place area for only the repeated scenes that were attended both during the initial presentation and during repetition. Thus, attention actively governs when neuronal activity is attenuated to repeated perceptual input, and such attention is important during both initial encoding and subsequent expression of the learned information.

The neural fate of consciously perceived and missed events in the attentional blink

Journal Article
Marois, R., Yi, D. -J., & Chun, M. M.
(2004) Neuron, 41, 465-472.

Cognitive models of attention propose that visual perception is a product of two stages of visual processing: early operations permit rapid initial categorization of the visual world, while later attention-demanding capacity-limited stages are necessary for the conscious report of the stimuli. Here we used the attentional blink paradigm and fMRI to neurally distinguish these two stages of vision. Subjects detected a face target and a scene target presented rapidly among distractors at fixation. Although the second, scene target frequently went undetected by the subjects, it nonetheless activated regions of the medial temporal cortex involved in high-level scene representations, the parahippocampal place area (PPA). This PPA activation was amplified when the stimulus was consciously perceived. By contrast, the frontal cortex was activated only when scenes were successfully reported. These results suggest that medial temporal cortex permits rapid categorization of the visual input, while the frontal cortex is part of a capacity-limited attentional bottleneck to conscious report.

Neural fate of ignored stimuli: dissociable effects of perceptual and working memory load

Journal Article
Yi, D. -J., Woodman, F. G., Widders, D., Marois, R., & Chun, M. M.
(2004) Nature Neuroscience

Observers commonly experience functional blindness to unattended visual events, and this problem has fuelled an intense debate concerning the fate of unattended visual information in neural processing. Here we used functional magnetic resonance imaging (fMRI) to demonstrate that the type of task that a human subject engages in determines the way in which ignored visual background stimuli are processed in parahippocampal cortex. Increasing the perceptual difficulty of a foveal target task attenuated processing of task-irrelevant background scenes, whereas increasing the number of objects held in working memory did not have this effect. These dissociable effects of perceptual and working memory load clarify how task-irrelevant, unattended stimuli are processed in category-selective areas in human ventral visual cortex.

Inhibition of return to occluded objects

Journal Article
Yi, D. -J., Kim, M. -S., & Chun, M. M.
(2003) Perception & Psychophysics, 65(8), 1222-1230.

Since many visual objects are vulnerable to occlusion, an active process that tracks objects behind occluders confers considerable ecological validity to the visual system. We studied this possibility by testing whether inhibition of return can be observed with occluded objects. In our experiments, two moving objects disappeared or reappeared behind occluders while a cue and a probe were presented. Contrary to the results of a previous study (Tipper, Weaver, Jerreat, & Burak, 1994), responses were consistently delayed for the cued object that was occluded when it was cued (Experiment 1), when it was probed (Experiment 2), or both (Experiment 3). These results suggest that attention can select occluded objects that are out of view. Our findings are in line with prior studies that have demonstrated similar perceptual/attentional effects for occluded objects, as well as for visible objects.

위치에 근거한 선택에서의 위치의 본질: 상징적 공간 탐사 과제로부터의 증거

Journal Article
김민식, 이도준
(2000) 한국심리학회지: 실험, 12 (1), 15-26.

시각 탐색에서의 선분 운동 착시

Journal Article
이도준, 김민식
(1999) 한국심리학회지: 실험, 11(2), 171-184.