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Dissociating explicit and implicit category knowledge with fMRI
- Journal of Cognitive Neuroscience
, 2003
"... & Neuroimaging of healthy volunteers identified separate neural systems supporting the expression of category knowl-edge depending on whether the learning mode was intentional or incidental. The same visual category was learned either intentionally or implicitly by two separate groups of partici ..."
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Cited by 47 (2 self)
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& Neuroimaging of healthy volunteers identified separate neural systems supporting the expression of category knowl-edge depending on whether the learning mode was intentional or incidental. The same visual category was learned either intentionally or implicitly by two separate groups of participants. During a categorization test, functional magnetic resonance imaging (fMRI) was used to compare brain activity evoked by category members and nonmembers. After implicit learning, when participants had learned the category incidentally, decreased occipital activity was observed for novel categorical stimuli compared with noncategorical stimuli. In contrast, after intentional learning, novel categorical stimuli evoked increased activity in the hippocampus, right prefrontal cortex, left inferior temporal cortex, precuneus, and posterior cingulate. Even though the categorization test was identical in the two conditions, the differences in brain activity indicate differing representations of category knowledge depending on whether the category had been learned intentionally or implicitly. &
Aging and the neural correlates of successful picture encoding: Frontal activations compensate for decreased medial-temporal activity
- Journal of Cognitive Neuroscience
, 2005
"... & We investigated the hypothesis that increased prefrontal activations in older adults are compensatory for decreases in medial-temporal activations that occur with age. Because scene encoding engages both hippocampal and prefrontal sites, we examined incidental encoding of scenes by 14 young an ..."
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Cited by 45 (11 self)
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& We investigated the hypothesis that increased prefrontal activations in older adults are compensatory for decreases in medial-temporal activations that occur with age. Because scene encoding engages both hippocampal and prefrontal sites, we examined incidental encoding of scenes by 14 young and 13 older adults in a subsequent memory paradigm using functional magnetic resonance imaging (fMRI). Behavioral results indicated that there were equivalent numbers of remembered and forgotten items, which did not vary as a function of age. In an fMRI analysis subtracting forgotten items from remembered items, younger and older adults both activated inferior frontal and lateral occipital regions bilat-erally; however, older adults showed less activation than young adults in the left and right parahippocampus and more activation than young adults in the middle frontal cortex. Moreover, correlations between inferior frontal and para-hippocampal activity were significantly negative for old but not young, suggesting that those older adults who showed the least engagement of the parahippocampus activated inferior frontal areas the most. Because the analyses included only the unique activations associated with remembered items, these data suggest that prefrontal regions could serve a compensatory role for declines in medial-temporal activa-tions with age. &
Processing objects at different levels of specificity
- Journal of Cognitive Neuroscience
, 2004
"... & How objects are represented and processed in the brain is a central topic in cognitive neuroscience. Previous studies have shown that knowledge of objects is represented in a featurebased distributed neural system primarily involving occipital and temporal cortical regions. Research with nonhu ..."
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Cited by 33 (6 self)
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& How objects are represented and processed in the brain is a central topic in cognitive neuroscience. Previous studies have shown that knowledge of objects is represented in a featurebased distributed neural system primarily involving occipital and temporal cortical regions. Research with nonhuman primates suggest that these features are structured in a hierarchical system with posterior neurons in the inferior temporal cortex representing simple features and anterior neurons in the perirhinal cortex representing complex conjunctions of features (Bussey & Saksida, 2002; Murray & Bussey, 1999). On this account, the perirhinal cortex plays a crucial role in object identification by integrating information from different sensory systems into more complex polymodal feature conjunctions. We tested the implications of these claims for human object processing in an event-related fMRI study in which we presented colored pictures of common objects for 19 subjects to name at two levels of specificity—basic and domain. We reasoned that domain-level naming requires access to a coarsergrained representation of objects, thus involving only posterior regions of the inferior temporal cortex. In contrast, basic-level naming requires finer-grained discrimination to differentiate between similar objects, and thus should involve anterior temporal regions, including the perirhinal cortex. We found that object processing always activated the fusiform gyrus bilaterally, irrespective of the task, whereas the perirhinal cortex was only activated when the task required finer-grained discriminations. These results suggest that the same kind of hierarchical structure, which has been proposed for object processing in the monkey temporal cortex, functions in the human. &
The cortical underpinnings of contextbased memory distortion
- J Cogn
"... & Everyday contextual settings create associations that later afford generating predictions about what objects to expect in our environment. The cortical network that takes advantage of such contextual information is proposed to connect the representation of associated objects such that seeing o ..."
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Cited by 11 (4 self)
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& Everyday contextual settings create associations that later afford generating predictions about what objects to expect in our environment. The cortical network that takes advantage of such contextual information is proposed to connect the representation of associated objects such that seeing one object (bed) will activate the visual representations of other objects sharing the same context (pillow). Given this proposal, we hypothesized that the cortical activity elicited by seeing a strong contextual object would predict the occurrence of false memories whereby one erroneously ‘‘remembers’ ’ having seen a new object that is related to a previously presented object. To test this hypothesis, we used functional magnetic resonance imaging during encoding of contextually related objects, and later tested recognition memory. New objects that were contextually related to previously presented objects were more often falsely judged as ‘‘old’ ’ compared with new objects that were contextually unrelated to old objects. This phenomenon was reflected by activity in the cortical network mediating contextual processing, which provides a better understanding of how the brain represents and processes context. &
Neuropsychologia Neural correlates of contextual cueing are modulated by explicit learning
"... a b s t r a c t Contextual cueing refers to the facilitated ability to locate a particular visual element in a scene due to prior exposure to the same scene. This facilitation is thought to reflect implicit learning, as it typically occurs without the observer's knowledge that scenes repeat. U ..."
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a b s t r a c t Contextual cueing refers to the facilitated ability to locate a particular visual element in a scene due to prior exposure to the same scene. This facilitation is thought to reflect implicit learning, as it typically occurs without the observer's knowledge that scenes repeat. Unlike most other implicit learning effects, contextual cueing can be impaired following damage to the medial temporal lobe. Here we investigated neural correlates of contextual cueing and explicit scene memory in two participant groups. Only one group was explicitly instructed about scene repetition. Participants viewed a sequence of complex scenes that depicted a landscape with five abstract geometric objects. Superimposed on each object was a letter T or L rotated left or right by 90 • . Participants responded according to the target letter (T) orientation. Responses were highly accurate for all scenes. Response speeds were faster for repeated versus novel scenes. The magnitude of this contextual cueing did not differ between the two groups. Also, in both groups repeated scenes yielded reduced hemodynamic activation compared with novel scenes in several regions involved in visual perception and attention, and reductions in some of these areas were correlated with response-time facilitation. In the group given instructions about scene repetition, recognition memory for scenes was superior and was accompanied by medial temporal and more anterior activation. Thus, strategic factors can promote explicit memorization of visual scene information, which appears to engage additional neural processing beyond what is required for implicit learning of object configurations and target locations in a scene.
Retrieval Contrast
"... Paller et al. the initial phase of the experiment, participants learned the faces of 20 previously unfamiliar individuals along with associations between each face and a distinct name, voice, and biographical fact. Next, in the test phase, fMRI or ERP brain responses were monitored while participant ..."
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Paller et al. the initial phase of the experiment, participants learned the faces of 20 previously unfamiliar individuals along with associations between each face and a distinct name, voice, and biographical fact. Next, in the test phase, fMRI or ERP brain responses were monitored while participants performed a recognition memory task for the learned faces, as well as a gender-classification task that placed minimal demands on memory retrieval processing. The memory task was performed with different proportions of learned and new faces in the heavy-retrieval and light-retrieval conditions, as shown in Figure 1. The gender-classification task was performed with new faces. All new faces were unique (i.e., each new face used in the experiment was presented in the memory task or in the gender task on only one occasion). Subsequently, a face/nonface discrimination task was used to identify face-responsive brain regions. The contrast between memory and gender conditions was used to identify neural correlates of face-cued retrieval during a recognition test versus face processing in the absence of memorial requirements, whereas the contrast between heavy-retrieval and light-retrieval conditions was used to isolate neural correlates of successfully remembering person-specific information.
Access the most recent version at doi: 10.1101/lm.251906
, 2006
"... Distinct roles for medial temporal lobe structures in memory for objects and their locations ..."
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Distinct roles for medial temporal lobe structures in memory for objects and their locations
Article Combining Computational Modeling and Neuroimaging to Examine Multiple Category Learning Systems in the Brain
, 2012
"... www.mdpi.com/journal/brainsci/ ..."
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RESEARCH ARTICLE Associative Processing Is Inherent in Scene Perception
, 1371
"... How are complex visual entities such as scenes represented in the human brain? More con-cretely, along what visual and semantic dimensions are scenes encoded in memory? One hypothesis is that global spatial properties provide a basis for categorizing the neural re-sponse patterns arising from scenes ..."
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How are complex visual entities such as scenes represented in the human brain? More con-cretely, along what visual and semantic dimensions are scenes encoded in memory? One hypothesis is that global spatial properties provide a basis for categorizing the neural re-sponse patterns arising from scenes. In contrast, non-spatial properties, such as single ob-jects, also account for variance in neural responses. The list of critical scene dimensions has continued to grow—sometimes in a contradictory manner—coming to encompass prop-erties such as geometric layout, big/small, crowded/sparse, and three-dimensionality. We demonstrate that these dimensions may be better understood within the more general framework of associative properties. That is, across both the perceptual and semantic do-mains, features of scene representations are related to one another through learned associ-ations. Critically, the components of such associations are consistent with the dimensions that are typically invoked to account for scene understanding and its neural bases. Using fMRI, we show that non-scene stimuli displaying novel associations across identities or lo-cations recruit putatively scene-selective regions of the human brain (the parahippocampal/
