The role of attention and study time in explicit and implicit memory for unfamiliar visual stimuli

The effects of limited attentional resources and study time on explicit and implicit memory were studied using Schacter and Cooper’s possible and impossible objects in their recognition and object decision paradigm. In one experiment, when attention at study was limited by a flanking digits procedure, object recognition was diminished but object decision priming for possible objects was unaffected; in another experiment, limiting attention plus reducing stimulus study time impaired object recognition and eliminated object priming. Recognition memory and perceptual priming for previously unfamiliar visual stimuli were both influenced by attention, although to different degrees. The intervening variable of study time determined the degree to which priming was affected by attentional resources. These results support a limited capacity attentional model for both recognition and perceptual priming of unfamiliar visual stimuli, and they highlight the need for assessing the interaction of attentional resources and study time in explicit and implicit memory tasks.     

提取干扰对知觉和概念启动的影响

通过学习—测验范式,分别以词汇判断、语义分类任务为测验,探讨提取干扰对不同识别式记忆的影响差异。结果发现,实验1验证了识别式知觉内隐记忆的提取干扰效应,实验2发现识别式概念内隐记忆在提取干扰下也明显降低;两个实验启动量联合分析发现,相比无干扰条件,概念启动比知觉启动受到提取干扰的破坏更大。上述结果说明识别式内隐记忆的提取干扰具有普遍性,提取干扰产生了不同识别式内隐记忆之间的分离,识别式概念内隐记忆更容易受到提取干扰的影响。     

Electrophysiological correlates of exemplar-specific processes in implicit and explicit memory

The present ERP study investigated the retrieval of task-irrelevant exemplar-specific information under implicit and explicit memory conditions. Subjects completed either an indirect memory test (a natural/artificial judgment) or a direct recognition memory test. Both test groups were presented with new items, identical repetitions, and perceptually different but conceptually similar exemplars of previously seen study objects. Implicit and explicit memory retrieval elicited clearly dissociable ERP components that were differentially affected by exemplar changes from study to test. In the indirect test, identical repetitions, but not different exemplars, elicited a significant ERP repetition priming effect. In contrast, both types of repeated objects gave rise to a reliable old/new effect in the direct test. The results corroborate that implicit and explicit memory fall back on distinct cognitive representation and, more importantly, indicate that these representations differ in the type of stimulus information stored. Implicit retrieval entailed obligatory access to exemplar-specific perceptual information, despite its being task irrelevant. In contrast, explicit retrieval proved to be more flexible with conceptual and perceptual information accessed according to task demands.     

内隐与外显记忆编码阶段脑机制的重叠与分离

记忆包括编码和提取两个重要阶段, 以往研究多关注内隐和外显记忆在提取阶段的脑机制分离, 那二者在编码阶段的脑机制是否不同？为探讨这个问题, 该实验采用两阶段的迫选再认方式, 把学习项目区分成三类：随后被选择且告知为见过的项目(记住), 随后被选择但告知为猜测的项目 (启动)以及随后未被选择的项目(忘记)。结果表明, 从200 ms开始的颞区负走向Dm效应为内隐记忆(启动vs忘记)所特有, 反映了对刺激的知觉加工过程, 400~500 ms前额区正走向的Dm效应为外显记忆(记住vs忘记)所特有, 反映了对刺激的精细加工过程, 而200~300 ms中央区及600 ms开始的顶区负走向的Dm效应为两种记忆类型所共有, 它们分别反映了对刺激的注意状态以及把编码后的刺激信息登记进相应记忆系统的过程。因此, 内隐记忆与外显记忆在编码阶段的脑机制既存在着分离, 也存在着重叠的现象。     

The influence of task requirements on priming in object decision and matching

We argue that task requirements can be the determinant in generating different results in studies on visual object recognition. We investigated priming for novel visual objects in three implicit memory tasks. A study-test design was employed in which participants first viewed line drawings of unfamiliar objects and later made different decisions about structural aspects of the objects. Priming for both symmetric and asymmetric possible objects was observed in a task requiring a judgment of structural possibility. However, when the task was changed to one requiring a judgment of structural symmetry, only symmetric possible objects showed priming. Finally, in a matching task in which participants made a same-different judgment, only symmetric possible objects exhibited priming. These results suggest that an understanding of object representation will be most fruitful if it is based on careful analyses of both the task demands and their interaction(s) with encoding and retrieval processes.     

Understanding or feeling? Motor and sensory processes in recall of haptic experiences

Effects of learning can show in a direct, i.e., explicit way, or they can be expressed indirectly, i.e., in an implicit way. It is investigated whether hepatic information shows implicit effect, and whether implicit haptic memory effects are based primarily on motor or on sensory memory components. In the first phase blindfolded subjects had to palpate objects in order to answer questions about the objects' distinct properties as fast as possible. In the following phase this task was repeated with the same objects and additional control items. Additionally, recognition judgements were required. Results demonstrate reliable effects of implicit memory for haptic information in terms of reaction times to old vs. new objects. Subjects who had to wear plastic gloves in the first stage showed comparable effects of repetition priming. Changing the questions--and, thus, hand movements--during the palpitation of objects known from the first stage, however, abolishes implicit memory expression. It is concluded, therefore, that implicit memory for haptic information is based on motor processes. On the other hand, explicit memory is hampered in subjects wearing gloves during the first phase, as revealed in terms of recognition performance while changing the questions about objects' properties has no effect on recognition judgements. Thus, explicit memory for haptic information seems to be based on the sensory processes when touching objects.     

Modulation of recognition and temporal order memory retrieval by dopamine D1 receptor in rats

The present study examines the effects of SKF 81297, a selective D1 agonist, on information retrieval in recognition and temporal order memory for objects, using three different tasks. Separate groups of rats were trained in each task and then given an intraperitoneal injection of saline or the D1 agonist (0.03, 0.3 mg/kg), before the memory testing trial in an object recognition, object location, and object temporal order memory tasks. We show that SKF 81297, at high dose (0.3 mg/kg), facilitates information retrieval after a long delay (4 h) in the three memory tasks whereas both high and low doses of D1 agonist impair recognition memory after a short delay (15 min). These results indicate a significant role of dopamine D1 receptors in recognition memory for both familiarity and place of objects in addition to object temporal order memory.     

The role of chronic physical exercise and selective attention at encoding on implicit and explicit memory

Despite the evidence revealing benefits of chronic cardiovascular exercise on executive functions, little research has been conducted on long-term memory. We aimed to investigate the effect of physical exercise on implicit and explicit memory when attention was modulated at encoding in two groups of active and sedentary participants. With this purpose, attention was manipulated in a similar way in the implicit and explicit memory tasks by presenting picture outlines of two familiar objects, one in blue and the other in green, and participants were asked to pay attention only to one of them. Implicit memory was assessed through conceptual priming and explicit memory through a free recall task followed by recognition. The results did not reveal significant differences between groups in conceptual priming or free recall. However, in recognition, while both groups had similar discrimination for attended stimuli, active participants showed lower discrimination between unattended and new stimuli. These results suggested that exercise may have effects on specific cognitive processes, that is, that active participants may suppress non-relevant information better than sedentary participants, making the discrimination between unattended and new items more difficult.     

Electromyographic evidence for response conflict in the exclude recognition task

How do memory retrieval processes lead to overt responses in strategic recognition tasks (responding “old” to one class of familiar stimulus and “new” to another)? Many current theories of memory retrieval ignore the response requirements in such memory tasks, instead modeling them using memory processes (e.g., familiarity and recollection) alone (see Yonelinas, 2002). We argue that strategic recognition involves conflict in response processing similar to canonical conflict tasks (e.g., the Stroop task). The parallel task set (PTS) model (Seymour, 2001) accounts for performance in strategic recognition tasks (e.g., the exclude recognition task) by suggesting that motor response conflict occurs when one responds “new” to familiar stimuli. We tested this prediction using surface electromyography, a measure incontrovertibly related to motor execution. Overall, results are consistent with the PTS model’s assumption that recognition, motor, and control processes interact in strategic retrieval tasks. The implications of these data for models of memory retrieval and response conflict are discussed.     

Aging affects word-stem completion and recognition but not category generation

In this study, we investigated the effect of aging on two implicit memory tasks, word-stem completion and category generation, and on explicit recognition. We compared the performance of young and older adults on these implicit memory tasks with those of explicit recognition. We expected better performance of young than older adults in the explicit memory task and similar priming in both implicit memory tasks. The results showed that young adults performed better than older adults in the recognition task. Moreover, both age groups showed priming in the implicit memory tasks, although priming was greater in young adults compared to older adults in the word-stem completion memory task, whereas both age groups showed similar levels of priming in the category generation task. The present results showed dissociations as a function of age not only between the explicit and the implicit tasks but also between the implicit tasks.     

Influence of object size on baseline identification, priming, and explicit memory

We investigated the influence of size on identification, priming, and explicit memory for color photos of common objects. Participants studied objects displayed in small, medium, and large sizes and memory was assessed with both implicit identification and explicit recognition tests. Overall, large objects were easier to identify than small objects and study-to-test changes in object size impeded performance on explicit but not implicit memory tests. In contrast to previous findings with line-drawings of objects but consistent with predictions from the distance-as-filtering hypothesis, we found that study-test size manipulations had large effects on old/new recognition memory test for objects displayed in large size at test but not for objects displayed small or medium at test. Our findings add to the growing body of literature showing that the findings obtained using line-drawings of objects do not necessarily generalize to color photos of common objects. We discuss implications of our findings for theories of object perception, memory, and eyewitness identification accuracy for objects.     

The consolidation of object and context recognition memory involve different regions of the temporal lobe

These experiments investigated the involvement of several temporal lobe regions in consolidation of recognition memory. Anisomycin, a protein synthesis inhibitor, was infused into the hippocampus, perirhinal cortex, insular cortex, or basolateral amygdala of rats immediately after the sample phase of object or object-in-context recognition memory training. Anisomycin infused into perirhinal or insular cortices blocked long-term (24 h), but not short-term (90 min) object recognition memory. Infusions into the hippocampus or amygdala did not impair object recognition memory. Anisomycin infused into the hippocampus blocked long-term, but not short-term object-in-context recognition memory, whereas infusions administered into the perirhinal cortex, insular cortex, or amygdala did not affect object-in-context recognition memory. These results clearly indicate that distinct regions of the temporal lobe are differentially involved in long-term object and object-in-context recognition memory. Whereas perirhinal and insular cortices are required for consolidation of familiar objects, the hippocampus is necessary for consolidation of contextual information of recognition memory. Altogether, these results suggest that temporal lobe structures are differentially involved in recognition memory consolidation.     

Decreased parahippocampal activity in associative priming: evidence from an event-related fMRI study

In recent years, there has been intense debate on the neural basis of associative priming, particularly on the role of the medial temporal lobe (MTL) in retrieving associative information without awareness. In this study, event-related fMRI was used while healthy subjects performed a perceptual identification task on briefly presented unrelated word pairs and an associative recognition memory task. Contamination of priming by explicit memory was successfully controlled, as associative priming and explicit memory were dissociated on the behavioral level. The fMRI results showed a functional dissociation within the MTL with respect to associative priming effects. The right parahippocampal cortex, but not the hippocampus, showed decreased activation for old vs. new pairs and old vs. recombined pairs (associative priming). The bilateral hippocampus and the right parahippocampal cortex were involved in explicit associative memory. These data provide evidence that subregions of the MTL participate in associative priming even when explicit involvement was controlled. Thus, different regions within the MTL play distinct roles in explicit and implicit associative memory.     

编码与提取干扰对内隐和外显记忆的非对称性影响

以往研究表明在外显记忆中,编码与提取加工存在着非对称性,但在内隐记忆中,二者的关系并不明确,因此实验采用“学习-再认”范式,考察在编码或提取中分别附加的干扰任务对词汇判断或再认产生的影响。结果证实编码与提取干扰对内隐或外显记忆都具有非对称性的影响,但又存在着差异,即编码干扰会导致随后外显记忆成绩显著减少,而提取干扰对其影响较小,相反,编码干扰对随后内隐测验中启动效应的影响较小,但提取干扰会破坏启动效应,从而为内隐记忆和外显记忆的分离提供了进一步的证据     

Exposure effects on music preference and recognition

In three experiments, the effects of exposure to melodies on their subsequent liking and recognition were explored. In each experiment, the subjects first listened to a set of familiar and unfamiliar melodies in a study phase. In the subsequent test phase, the melodies were repeated, along with a set of distractors matched in familiarity. Half the subjects were required to rate their liking of each melody, and half had to identify the melodies they had heard earlier in the study phase. Repetition of the studied melodies was found to increase liking of the unfamiliar melodies in the affect task and to be best for detection of familiar melodies in the recognition task (Experiments 1, 2, and 3). These memory effects were found to fade at different time delays between study and test in the affect and recognition tasks, with the latter leading to the most persistent effects (Experiment 2). Both study-to-test changes in melody timbre and manipulation of study tasks had a marked impact on recognition and little influence on liking judgments (Experiment 3). Thus, all manipulated variables were found to dissociate the memory effects in the two tasks. The results are consistent with the view that memory effects in the affect and recognition tasks pertain to the implicit and explicit forms of memory, respectively. Part of the results are, however, at variance with the literature on implicit and explicit memory in the auditory domain. Attribution of these differences to the use of musical material is discussed.