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163
Dissociating Reading Processes on the Basis of Neuronal Interactions
, 2005
"... Previous studies of patients with phonological and surface alexia have demonstrated a double dissociation between the reading of pseudo words and words with atypical spelling-tosound relationships. A corresponding double dissociation in the neuronal activation patterns for pseudo words and exceptio ..."
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Cited by 43 (3 self)
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Previous studies of patients with phonological and surface alexia have demonstrated a double dissociation between the reading of pseudo words and words with atypical spelling-tosound relationships. A corresponding double dissociation in the neuronal activation patterns for pseudo words and exception words has not, however, been consistently demonstrated in normal subjects. Motivated by the literature on acquired alexia, the present study contrasted pseudo words to exception words and explored how neuronal interactions within the reading system are influenced by word type. Functional magnetic resonance imaging was used to measure neuronal responses during reading in 22 healthy volunteers. The direct comparison of reading pseudo words and exception words revealed a double dissociation within the left frontal cortex. Pseudo words preferentially increased left
Source monitoring 15 years later: What have we learned from fMRI about the neural mechanisms of source memory
- Psychological Bulletin
, 2009
"... Focusing primarily on functional magnetic resonance imaging (fMRI), this article reviews evidence regarding the roles of subregions of the medial temporal lobes, prefrontal cortex, posterior representational areas, and parietal cortex in source memory. In addition to evidence from standard episodic ..."
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Cited by 36 (3 self)
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Focusing primarily on functional magnetic resonance imaging (fMRI), this article reviews evidence regarding the roles of subregions of the medial temporal lobes, prefrontal cortex, posterior representational areas, and parietal cortex in source memory. In addition to evidence from standard episodic memory tasks assessing accuracy for neutral information, the article considers studies assessing the qualitative characteristics of memories, the encoding and remembering of emotional information, and false memories, as well as evidence from populations that show disrupted source memory (older adults, individuals with depression, posttraumatic stress disorder, or schizophrenia). Although there is still substantial work to be done, fMRI is advancing understanding of source memory and highlighting unresolved issues. A continued 2-way interaction between cognitive theory, as illustrated by the source monitoring framework (M. K. Johnson, S. Hashtroudi, & D. S. Lindsay, 1993), and evidence from cognitive neuroimaging studies should clarify conceptualization of cognitive processes (e.g., feature binding, retrieval, monitoring), prior knowledge (e.g., semantics, schemas), and specific features (e.g., perceptual and emotional information) and of how they combine to create true and false memories.
Feature detection and letter identification
, 2006
"... Seeking to understand how people recognize objects, we have examined how they identify letters. We expected this 26-way classification of familiar forms to challenge the popular notion of independent feature detection (‘‘probability summation’’), but find instead that this theory parsimoniously acco ..."
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Cited by 35 (3 self)
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Seeking to understand how people recognize objects, we have examined how they identify letters. We expected this 26-way classification of familiar forms to challenge the popular notion of independent feature detection (‘‘probability summation’’), but find instead that this theory parsimoniously accounts for our results. We measured the contrast required for identification of a letter briefly presented in visual noise. We tested a wide range of alphabets and scripts (English, Arabic, Armenian, Chinese, Devanagari, Hebrew, and several artificial ones), three- and five-letter words, and various type styles, sizes, contrasts, durations, and eccentricities, with observers ranging widely in age (3 to 68) and experience (none to fluent). Foreign alphabets are learned quickly. In just three thousand trials, new observers attain the same proficiency in letter identification as fluent readers. Surprisingly, despite this training, the observers—like clinical letterby-letter readers—have the same meager memory span for random strings of these characters as observers seeing them for the first time. We compare performance across tasks and stimuli that vary in difficulty by pitting the human against the ideal observer, and expressing the results as efficiency. We find that efficiency for letter identification is independent of duration, overall contrast, and eccentricity, and only weakly dependent on size, suggesting that letters are identified by a similar computation across this wide range of viewing conditions. Efficiency is also independent of age and years of reading. However, efficiency does vary across alphabets and type styles, with more complex forms yielding lower efficiencies, as one might expect from Gestalt theories of perception. In fact, we find that efficiency is inversely proportional to perimetric complexity (perimeter squared over ‘‘ink’ ’ area) and nearly independent of everything else. This, and the surprisingly
Presemantic” cognition in semantic dementia: Six deficits in search of an explanation
- Journal of Cognitive Neuroscience
, 2006
"... ‘‘Oh, sir, you must be well aware that life is full of endless absurdities which do not even have to appear plausible, since they are true.’’ —From Six Characters in Search of an Author, by Luigi Pirandello (1921) & On the basis of a theory about the role of semantic knowl-edge in the recognitio ..."
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Cited by 34 (10 self)
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‘‘Oh, sir, you must be well aware that life is full of endless absurdities which do not even have to appear plausible, since they are true.’’ —From Six Characters in Search of an Author, by Luigi Pirandello (1921) & On the basis of a theory about the role of semantic knowl-edge in the recognition and production of familiar words and objects, we predicted that patients with semantic dementia would reveal a specific pattern of impairment on six different tasks typically considered ‘‘pre-’ ’ or ‘‘non-’ ’ semantic: reading aloud, writing to dictation, inflecting verbs, lexical decision, object decision, and delayed copy drawing. The prediction was that all tasks would reveal a frequency-by-typicality interaction, with patients performing especially poorly on lower-frequency items with atypical structure (e.g., words with an atypical spelling-to-sound relationship; objects with an atypical feature for their class, such as the hump on a camel, etc). Of 84 critical observations (14 patients performing 6 tasks), this prediction was correct in 84/84 cases; and a single component in a factor analysis accounted for 87 % of the variance across seven mea-sures: each patient’s degree of impairment on atypical items in the six experimental tasks and a separate composite score re-f lecting his or her degree of semantic impairment. Errors also consistently conformed to the predicted pattern for both ex-pressive and receptive tasks, with responses reflecting residual knowledge about the typical surface structure of each domain. We argue that these results cannot be explained as associated but unrelated deficits but instead are a principled consequence of a primary semantic impairment. &
Hidden cognitive states revealed in choice reaching tasks.
- Trends in Cognitive Sciences,
, 2009
"... Perceptual and cognitive processes have largely been inferred based on reaction times and accuracies obtained from discrete responses. However, discrete responses are unlikely to capture dynamic internal processes, occurring in parallel, and unfolding over time. Recent studies measuring continuous ..."
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Cited by 34 (4 self)
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Perceptual and cognitive processes have largely been inferred based on reaction times and accuracies obtained from discrete responses. However, discrete responses are unlikely to capture dynamic internal processes, occurring in parallel, and unfolding over time. Recent studies measuring continuous hand movements during target choice reaching tasks reveal the temporal evolution of hidden internal events. For instance, the direction of curved reaching trajectories reflects attention, language representations and the spatial number line, in addition to interactions between the ventral and dorsal visual streams. This elucidates the flow of earlier cognitive states into motor outputs. Thus, this line of research provides new opportunities to integrate information across different disciplines such as perception, cognition and action, which have usually been studied in isolation. Introduction Progress in understanding how human cognition operates owes much to the information processing approach, which has adopted the computer metaphor of distinct processing units. The theoretical assumption of discrete intermediate stages has inspired cleverly designed experiments to identify sequential stages of perception, cognition, decision-making and motor output. Reaction times and accuracies obtained from discrete responses such as button presses have been viewed as useful and effective behavioral measurements to individuate sub-components, each adding its own processing times For decades, however, an alternative view of brain processing has also persisted, reappearing under various guises including connectionism and non-linear systems analysis: multiple internal states can be activated in parallel, and coexist We shed light on ongoing endeavors to capture the dynamics of multiple cognitive states unfolding over time
I: How the brain constructs cognition
- Mareschal, D and Johnson, MH
, 2003
"... Below is the unedited précis of a book that is being accorded BBS multiple book review. This preprint has been prepared for potential commentators who wish to nominate themselves for formal commentary invitation. Please do not write a commentary unless you receive a formal invitation. Invited commen ..."
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Cited by 32 (18 self)
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Below is the unedited précis of a book that is being accorded BBS multiple book review. This preprint has been prepared for potential commentators who wish to nominate themselves for formal commentary invitation. Please do not write a commentary unless you receive a formal invitation. Invited commentators will receive full instructions. Commentary must be based on the book.*
A ventral visual stream reading center independent of visual experience
- Current Biology
, 2011
"... The visual word form area (VWFA) is a ventral stream visual area that develops expertise for visual reading [1–3]. It is activated across writing systems and scripts [4, 5] and encodes letter strings irrespective of case, font, or location in the visual field [1] with striking anatomical reproducibi ..."
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Cited by 28 (5 self)
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The visual word form area (VWFA) is a ventral stream visual area that develops expertise for visual reading [1–3]. It is activated across writing systems and scripts [4, 5] and encodes letter strings irrespective of case, font, or location in the visual field [1] with striking anatomical reproducibility across individuals [6]. In the blind, comparable reading expertise can be achieved using Braille. This study investigated which area plays the role of the VWFA in the blind. One would expect this area to be at either parietal or bilateral occipital cortex, reflecting the tactile nature of the task and crossmodal plasticity, respectively [7, 8]. However, according to the metamodal theory [9], which suggests that brain areas are responsive to a specific representation or computation regardless of their input sensory modality, we predicted recruitment of the left-hemispheric VWFA, identically
Evidence for early morphological decomposition in visual word recognition
- Journal of Cognitive Neuroscience
, 2010
"... ■ We employ a single-trial correlational MEG analysis technique to investigate early processing in the visual recognition of mor-phologically complex words. Three classes of affixed words were presented in a lexical decision task: free stems (e.g., taxable), bound roots (e.g., tolerable), and unique ..."
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Cited by 26 (2 self)
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■ We employ a single-trial correlational MEG analysis technique to investigate early processing in the visual recognition of mor-phologically complex words. Three classes of affixed words were presented in a lexical decision task: free stems (e.g., taxable), bound roots (e.g., tolerable), and unique root words (e.g., vul-nerable, the root of which does not appear elsewhere). Analysis was focused on brain responses within 100–200 msec poststim-ulus onset in the previously identified letter string and visual word-form areas. MEG data were analyzed using cortically con-strainedminimum-norm estimation. Correlations were computed between activity at functionally defined ROIs and continuous measures of the words ʼ morphological properties. ROIs were identified across subjects on a reference brain and then morphed back onto each individual subjectʼs brain (n = 9). We find evi-dence of decomposition for both free stems and bound roots at the M170 stage in processing. The M170 response is shown to be sensitive to morphological properties such as affix frequency and the conditional probability of encountering each word given its stem. These morphological properties are contrasted with ortho-graphic form features (letter string frequency, transition probabil-ity from one string to the next), which exert effects on earlier stages in processing (∼130 msec). We find that effects of decom-position at the M170 can, in fact, be attributed to morphological properties of complex words, rather than to purely orthographic and form-related properties. Our data support a model of word recognition in which decomposition is attempted, and possibly utilized, for complex words containing bound roots as well as free word-stems. ■
Information-processing modules and their relative modality specificity
, 2007
"... This research uses fMRI to understand the role of eight cortical regions in a relatively complex information-processing task. Modality of input (visual versus auditory) and modality of output (manual versus vocal) are manipulated. Two perceptual regions (auditory cortex and fusiform gyrus) only refl ..."
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Cited by 25 (6 self)
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This research uses fMRI to understand the role of eight cortical regions in a relatively complex information-processing task. Modality of input (visual versus auditory) and modality of output (manual versus vocal) are manipulated. Two perceptual regions (auditory cortex and fusiform gyrus) only reflected perceptual encoding. Two motor regions were involved in information rehearsal as well as programming of overt actions. Two cortical regions (parietal and prefrontal) performed processing (retrieval and representational change) independent of input and output modality. The final two regions (anterior cingulate and caudate) were involved in control of cognition independent of modality of input or output and content of the material. An information-processing model, based on the ACT-R theory, is described that predicts the BOLD response in these regions. Different modules in the theory vary in the degree to which they are modality-specific and the degree to which they are involved in central versus peripheral cognitive processes.
When would you prefer a SOSSAGE to a SAUSAGE? At about 100 msec. ERP correlates of orthographic typicality and lexicality in written word recognition
- Journal of Cognitive Neuroscience
, 2006
"... & Using a speeded lexical decision task, event-related potentials (ERPs), and minimum norm current source esti-mates, we investigated early spatiotemporal aspects of cortical activation elicited by words and pseudowords that varied in their orthographic typicality, that is, in the frequency of t ..."
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Cited by 24 (2 self)
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& Using a speeded lexical decision task, event-related potentials (ERPs), and minimum norm current source esti-mates, we investigated early spatiotemporal aspects of cortical activation elicited by words and pseudowords that varied in their orthographic typicality, that is, in the frequency of their component letter pairs (bigrams) and triplets (trigrams). At around 100 msec after stimulus onset, the ERP pattern revealed a significant typicality effect, where words and pseudowords with atypical orthography (e.g., yacht, cacht) elicited stronger brain activation than items characterized by typical spelling patterns (cart, yart). At 200 msec, the ERP pattern revealed a significant lexicality effect, with pseudo-words eliciting stronger brain activity than words. The two main factors interacted significantly at around 160 msec, where words showed a typicality effect but pseudowords did not. The principal cortical sources of the effects of both typicality and lexicality were localized in the inferior temporal cortex. Around 160 msec, atypical words elicited the stronger source currents in the left anterior inferior temporal cortex, whereas the left perisylvian cortex was the site of greater activation to typical words. Our data support distinct but interactive processing stages in word recognition, with surface features of the stimulus being processed before the word as a meaningful lexical entry. The interaction of typicality and lexicality can be explained by integration of information from the early form-based system and lexicosemantic processes. &
