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ISSN : 1226-9654
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Vol.25 No.1
Abstract
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 the previous behavioral findings by demonstrating that loading WM with face images can reduce task-irrelevant face processing in the face-selective cortical region, the fusiform face are (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 contents of WM shares limited-capacity processing with distractors.
Abstract
The present study investigated perception of biological motion (BM) focusing on two issues. Although it has been reported that the right posterior region of the superior temporal sulcus (pSTS) is more strongly activated than the left pSTS when viewing BM, the reason is not well understood. Second, most previous studies have focused on the accuracy of BM perception while reaction time (RT) to BM compared with other motion signals remains relatively unknown. BM and non-BM stimuli were briefly presented in each (left and right) visual field in Task 1. In Task 2, the same stimuli were displayed at the center. RT and accuracy were measured in both tasks. To explore a possible perceptual correlate of the neural anisotropy in the pSTS, RT and accuracy between the two visual fields were compared (Task 1). To examine the efficiency of BM processing, RT and accuracy differences between BM and non-BM were examined (Task 1 and Task 2). The result from Task 1 demonstrated that RT was faster and accuracy was higher when BM was presented in the left visual field. This suggests a perceptual correlate of greater right pSTS activation associated with BM perception. The results from Task 1 and Task 2 revealed that BM was detected more quickly and accurately than non-BM, suggesting that BM processing is more efficient than other global motion processing when information is limited by brief exposure. Analysis of error trials from the two tasks also suggests a perceptual bias of judging ambiguous motion signals as BM.
Abstract
Retrieval-induced forgetting implies that repeatedly retrieving a subset of previously studied items can cause forgetting of related non-retrieved material. The present study was designed to investigate the effect of negative emotion on retrieval-induced forgetting(RIF). Two experiments were conducted with 189 volunteers. The emotional valence within lists was manipulated as attaching emotional adjectives on neutral words in each category. Participants studied words from total 6 categories and it consisted of neutral and emotional stimuli in each category. And then they repeatedly retrieved a subset of the neutral material. Later, a recall test was conducted for all previously studied items. When participants studied neutral and negative stimuli in one category and then only repeatedly retrieved a subset of the neutral material (RP+), retrieval practice on the neutral items caused effect of the retrieval-induced forgetting on the emotional stimuli (RP-). Namely, the emotional valence had a different effect on retrieval-induced forgetting across RP+ and RP- conditions. And the effect systemically varied with the intensity of emotionality in the lists.
Abstract
Tests show hand movement and hand touch influence the perception of visual motion. However, previous studies tested these two factors independently. This study examined how differently participants might disambiguate ambiguity in visual motion with simultaneous manipulation of hand movement and touch. While participants observed a streaming/bouncing ambiguous motion display, consisting of two disks that moved horizontally, they moved both hands toward each other, along with the two disks, and either returned from the middle or continued, crossing each other, either with or without the hands touching in the middle. The results supported previous studies showing hand crossing induced greater visual streaming perception, while hand touching induced greater visual bouncing perception. However, when both cues conflicted, their effects decreased significantly, suggesting kinesthetic information and cutaneous touch information additionally influence vision. In addition, the results showed hand returning, alone, did not induce visual bouncing perception, suggesting that kinesthetic information may be effective only for motions in which an object moves along a straight or smooth trajectory or only during initiation of the object's motion.
Abstract
We compared detection accuracies of P300-based guilty knowledge test based on 2 bootstrap approaches: bootstrapped correlation difference (BCD) and bootstrapped amplitude difference (BAD). Event-related potential data of the guilty group (n=12) and the innocent group (n=12) in Kang and Kim(2010)'s study were subjected to bootstrap analysis. P300 amplitude from all single sweeps of each of target, probe, and irrelevant stimulus at the parietal midline (Pz) or the frontal midline (Fz) electrode site was collected for each participant. Target stimulus is relevant to the experimental task, but not related to the crime. Participants were asked to discriminate the target stimulus from other stimuli. Probe stimulus includes the critical information of the crime, the guilty knowledge, thus guilty participants are supposed to pay attention to it compared to irrelevant stimulus. Irrelevant stimulus is not relevant to the crime and the task. Two different bootstrap analysis were applied to determine individual's guilt or innocence. BCD method estimated double-centered correlation coefficients between the average of target and probe sweeps, and between the average of probe and irrelevant sweeps for a participant. If the former are greater than the latter in 600 trials out of 1,000 bootstrap iterations, the participant is regarded as guilty. BAD method estimated amplitude difference between probe and irrelevant sweeps, and if the difference is positive, the participant is found to be guilty. As a result, BCD method outperformed BAD method. The detection accuracies, without indeterminacy, of BCD and BAD were up to 80.0%, 56.5%, respectively. It seems that BCD method is more appropriate to determine individual's guilt or innocence, and to get high detection accuracy of the guilty knowledge test using event-related potentials.
Abstract
What kind of information do people use to make predictions? The principle that causal Bayes nets suggest is that people follow structural constraints like the Markov principle. Previous studies have cast doubt on the psychological validity of the screening-off principle. I tested three hypotheses about how people used causal information to make predictions. Experiment 1 revealed that people violated the screening-off rule even when a causal structure was causally sufficient supporting the contradiction hypothesis (Walsh and Sloman, 2004). Experiment 2 controlled possible compounding in Experiment 1 but still reported the violation. Possible implications to the causal Bayes net formalism were discussed.
Abstract
Fear conditioning, in which a neutral conditioned stimulus (CS) is contingently paired with an aversive unconditioned stimulus (US) and acquires capacity to elicit conditioned response (CR), has been studied extensively to elucidate neural substrate of associative memory. It has been shown that the critical change for the fear memory is stored as a form of modified synaptic response in the lateral nucleus (LA) of the amygdala. On the other hand, extinction, in which the fear CR is reduced as a result of repeated exposure to the CS without the US, has been known to depend on the infralimbic cortex (IL) of the medial prefrontal cortex. However, little is known about the interaction between the IL and LA over the course of extinction process. In the current study, we investigated the synaptic changes in the IL-LA pathway by measuring evoked field potentials (EFPs) before and after fear extinction. Following fear conditioning in which the rats were presented with five parings of the CS and footshock US, they were subjected to two extinction sessions composed of 10 CS-only trials each. In addition, they received a retention test composed of three CS-only presentations. To measure synaptic plasticity, evoked field potentials (EFPs) were recorded in the lateral nucleus of the amygdala (LA) by stimulating the IL, six hours after every session. The recorded EFP was significantly increased after the first extinction but not after the subsequent sessions. These data indicate that dynamic regulation of IL-LA synaptic efficacy underlies the suppression of conditioned fear response following extinction and suggest that consolidation of memory extinction involves changes in other synapses than IL-LA pathway.