Denise H. Wu

Method Matters: An Empirical Study of Impact in Cognitive Neuroscience

A major thrust of cognitive neuroscience is the elucidation of structure-function relationships in the human brain. Over the last several years, functional neuroimaging has risen in prominence relative to the lesion studies that formed the historical core of work in this field. These two methods have different strengths and weaknesses. Among these is a crucial difference in the nature of evidence each can provide. Lesion studies can provide evidence for necessity claims, whereas functional neuroimaging studies do not. We hypothesized that lesion studies will continue to have greater scientific impact even as the relative proportion of such studies in the cognitive neuroscience literature declines. Using methods drawn from systematic literature review, we identified a set of original cognitive neuroscience articles that employed either functional imaging or lesion techniques, published at one of two time points in the 1990s, and assessed the effect of the method used on each articles impact across the decade. Functional neuro-imaging studies were cited three times more often than lesion studies throughout the time span we examined. This effect was in large part due to differences in the influence of the journals publishing the two methods; functional neuroimaging studies appeared disproportionately more often in higher impact journals. There were also differences in the degree to which articles using one method cited articles using the other method. Functional neuroimaging articles were less likely to include such cross-method citations.

The Functional Neuroanatomy of Thematic Role and Locative Relational Knowledge

Lexical-semantic investigations in cognitive neuroscience have focused on conceptual knowledge of concrete objects. By contrast, relational concepts have been largely ignored. We examined thematic role and locative knowledge in 14 left-hemisphere-damage patients. Relational concepts shift cognitive focus away from the object to the relationship between objects, calling into question the relevance of traditional sensory-functional accounts of semantics. If extraction of a relational structure is the critical cognitive process common to both thematic and locative knowledge, then damage to neural structures involved in such an extraction would impair both kinds of knowledge. If the nature of the relationship itself is critical, then functional neuroanatomical dissociations should occur. Using a new lesion analysis method, we found that damage to the lateral temporal cortex produced deficits in thematic role knowledge and damage to inferior fronto-parietal regions produced deficits in locative knowledge. In addition, we found that conceptual knowledge of thematic roles dissociates from its mapping onto language. These relational knowledge deficits were not accounted for by deficits in processing nouns or verbs or by a general deficit in making inferences. Our results are consistent with the hypothesis that manners of visual motion serve as a point of entry for thematic role knowledge and networks dedicated to eye gaze, whereas reaching and grasping serve as a point of entry for locative knowledge. Intermediary convergence zones that are topographically guided by these sensory-motor points of entry play a critical role in the semantics of relational concepts.

An event-related fMRI investigation of phonological versus semantic short-term memory

Abstract Studies with normal and brain damaged subjects have indicated that there are semantic as well as phonological contributions to verbal short-term memory. An event-related functional MRI study was carried out to determine if different brain regions would be activated during the delay period in a phonological vs. a semantic retention task. A recognition probe procedure was used in which memory load and task (i.e. rhyme judgment vs. synonym judgment) were manipulated. A left inferior parietal region overlapping the supramarginal gyrus was more activated in the phonological than the semantic task. A large left inferior and mid-frontal region and another left parietal region showed a load effect that was common to the phonological and semantic tasks. No region showed significantly greater activation in the semantic than the phonological task, though there was a trend towards a more anterior localization of the frontal load effect in the semantic task compared to the phonological task.

Big Time Is Not Always Long: Numerical Magnitude Automatically Affects Time Reproduction

To reproduce the duration of an event precisely, one needs to represent the temporal information without being influenced by other magnitude attributes (e.g., size) of the event. In the present study, however, task-irrelevant numerical magnitude automatically affected participants’ reproduction of the duration of a stimulus. In Experiment 1, participants made key-press responses to reproduce the duration of numbers. Reproduced durations were shorter for small numbers (e.g., 1) than for large numbers (e.g., 9). In contrast, in Experiment 2, participants’ reproductions of a standard duration were longer when their key-press response was accompanied by visual presentation of a small number than when it was accompanied by presentation of a large number. These results clearly demonstrate that number-time interference extends beyond simple mapping between stimulus categories and response alternatives. The findings support the notion that either a common magnitude representation or closely connected magnitude representations underlie numerical and temporal processing.

Universal brain signature of proficient reading: Evidence from four contrasting languages

Significance Using functional MRI, we examined reading and speech perception in four highly contrasting languages: Spanish, English, Hebrew, and Chinese. With three complementary analytic approaches, we demonstrate that in spite of striking dissimilarities among writing systems, successful literacy acquisition results in a convergence of the speech and orthographic processing systems onto a common network of neural structures. These findings have the major theoretical implication that the reading network has evolved to be universally constrained by the organization of the brain network underlying speech. We propose and test a theoretical perspective in which a universal hallmark of successful literacy acquisition is the convergence of the speech and orthographic processing systems onto a common network of neural structures, regardless of how spoken words are represented orthographically in a writing system. During functional MRI, skilled adult readers of four distinct and highly contrasting languages, Spanish, English, Hebrew, and Chinese, performed an identical semantic categorization task to spoken and written words. Results from three complementary analytic approaches demonstrate limited language variation, with speech–print convergence emerging as a common brain signature of reading proficiency across the wide spectrum of selected languages, whether their writing system is alphabetic or logographic, whether it is opaque or transparent, and regardless of the phonological and morphological structure it represents.

The common magnitude code underlying numerical and size processing for action but not for perception

The interaction between numbers and action-related process has received increasing attention in the literature of numerical cognition. In the current study, two dual-task experiments were conducted to explore the interaction among numerical, prehension, and perceptual color/size judgments. The results revealed the commonality and distinctness of the magnitude representations that are involved in these tasks. Specifically, a photograph of a graspable object with a superimposed Arabic digit was presented in each trial. Participants were required to first judge the parity of the digit with a manual response while simultaneously planning a subsequent vocal response pertaining to the depicted object. When parity and action judgments were performed close in time, the compatibility effect between the numerical magnitude of the digit and the appropriate action (pinch vs. clutch) for the object was demonstrated in both manual and vocal responses. In contrast, such compatibility effect was absent when parity judgment was coupled with color-related or perceptual size judgment. The findings of the current study support the existence of a common magnitude code underlying numerical and non-numerical dimensions for action-related purposes, as proposed by the ATOM model (Walsh in Trends Cogn Sci 7:483–488, 2003). Furthermore, based on the selective presence of the compatibility effect, we argue that the interaction among different quantity dimensions conforms to the “dorsal-action and ventral-perception” organizational principle of the human brain.

An event-related potential study of the concreteness effect between Chinese nouns and verbs

The effect of concreteness has been heavily studied on nouns. However, there are scant reports on the effect for verbs. The present research independently manipulated concreteness and word class of Chinese disyllabic words in tasks that required different depths of semantic processing: a lexical decision task and a semantic relatedness judgment task. The results replicated the concreteness effect for nouns, indicating that concrete nouns elicited larger N400 responses than abstract nouns with a broad distribution over the scalp, irrespective of the task demands. Similar to the findings from English unambiguous verbs, the concreteness effect for Chinese verbs was also robustly observed from fontal to posterior electrodes in both tasks. These results suggest that when Chinese nouns and verbs are typical and unambiguous in both meanings and word classes, the similar topographic distributions of the N400 components reflect the same underlying cause(s) of the concreteness effect for these two word classes.

Dynamic allocation of attention to metrical and grouping accents in rhythmic sequences

Most people find it easy to perform rhythmic movements in synchrony with music, which reflects their ability to perceive the temporal periodicity and to allocate attention in time accordingly. Musicians and non-musicians were tested in a click localization paradigm in order to investigate how grouping and metrical accents in metrical rhythms influence attention allocation, and to reveal the effect of musical expertise on such processing. We performed two experiments in which the participants were required to listen to isochronous metrical rhythms containing superimposed clicks and then to localize the click on graphical and ruler-like representations with and without grouping structure information, respectively. Both experiments revealed metrical and grouping influences on click localization. Musical expertise improved the precision of click localization, especially when the click coincided with a metrically strong beat. Critically, although all participants located the click accurately at the beginning of an intensity group, only musicians located it precisely when it coincided with a strong beat at the end of the group. Removal of the visual cue of grouping structures enhanced these effects in musicians and reduced them in non-musicians. These results indicate that musical expertise not only enhances attention to metrical accents but also heightens sensitivity to perceptual grouping.

Adaptation of the human visual system to the statistics of letters and line configurations

By adulthood, literate humans have been exposed to millions of visual scenes and pages of text. Does the human visual system become attuned to the statistics of its inputs? Using functional magnetic resonance imaging, we examined whether the brain responses to line configurations are proportional to their natural-scene frequency. To further distinguish prior cortical competence from adaptation induced by learning to read, we manipulated whether the selected configurations formed letters and whether they were presented on the horizontal meridian, the familiar location where words usually appear, or on the vertical meridian. While no natural-scene frequency effect was observed, we observed letter-status and letter frequency effects on bilateral occipital activation, mainly for horizontal stimuli. The findings suggest a reorganization of the visual pathway resulting from reading acquisition under genetic and connectional constraints. Even early retinotopic areas showed a stronger response to letters than to rotated versions of the same shapes, suggesting an early visual tuning to large visual features such as letters.

A third route for reading? Implications from a case of phonological dyslexia.

Models of reading in the neuropsychological literature sometimes only include two routes from print to sound, a lexical semantic route and a sublexical phonological route. Other researchers hypothesize an additional route that involves a direct connection between lexical orthographic representations and lexical phonological representations. This so-called ‘third route’ has been invoked to account for the preserved oral reading of some patients who show severe semantic impairments and a disruption of the sublexical phonological route. In their summation hypothesis, Hillis and Caramazza proposed that reading in these cases could result from a combination of partial lexical semantic information and partial sublexical phonological information, thus obviating the need for the third route. The present study examined the case of a phonological dyslexic patient (ML) who exhibited preserved word reading, even for items he could not name, along with a non-word reading impairment. The relationship between ML’s naming and reading, and the influence of semantic variables on his reading were examined. The results of this examination are interpreted as supporting the existence of the third route.