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The myth of the visual word form area.

Recent functional imaging studies have referred to a posterior region of the left midfusiform gyrus as the "visual word form area" (VWFA). We review the evidence for this claim and argue that neither the neuropsychological nor neuroimaging data are consistent with a cortical region specialized for visual word form representations. Specifically, there are no reported cases of pure alexia who have deficits limited to visual word form processing and damage limited to the left midfusiform. In addition, we present functional imaging data to demonstrate that the so-called VWFA is activated by normal subjects during tasks that do not engage visual word form processing such as naming colors, naming pictures, reading Braille, repeating auditory words, and making manual action responses to pictures of meaningless objects. If the midfusiform region has a single function that underlies all these tasks, then it does not correspond to visual word form processing. On the other hand, if the region participates in several functions as defined by its interactions with other cortical areas, then identifying the neural system sustaining visual word form representations requires identification of the set of regions involved. We conclude that there is no evidence that visual word form representations are subtended by a single patch of neuronal cortex and it is misleading to label the left midfusiform region as the visual word form area.

Cognition↗

Functional anatomy of a common semantic system for words and pictures.

The relationship between the semantic processing of words and of pictures is a matter of debate among cognitive scientists. We studied the functional anatomy of such processing by using positron-emission tomography (PET). We contrasted activity during two semantic tasks (probing knowledge of associations between concepts, and knowledge of the visual attributes of these concepts) and a baseline task (discrimination of physical stimulus size), performed either with words or with pictures. Modality-specific activations unrelated to semantic processing occurred in the left inferior parietal lobule for words, and the right middle occipital gyrus for pictures. A semantic network common to both words and pictures extended from the left superior occipital gyrus through the middle and inferior temporal cortex to the inferior frontal gyrus. A picture-specific activation related to semantic tasks occurred in the left posterior inferior temporal sulcus, and word-specific activations related to semantic tasks were localized to the left superior temporal sulcus, left anterior middle temporal gyrus, and left inferior frontal sulcus. Thus semantic tasks activate a distributed semantic processing system shared by both words and pictures, with a few specific areas differentially active for either words or pictures.

Adult↗

Developmental changes in ERP correlates of spoken word recognition during early school years: a phonological priming study.

OBJECTIVE: We investigated event-related potential (ERP) correlates of developmental changes in spoken word recognition during early school years. We focused on implicit processing of word onsets as this may change considerably due to vocabulary growth and reading acquisition. METHODS: Subjects were pre-schoolers (5-6 years), beginning readers (7-8 years) and adults. Two experiments examined phonological onset priming effects on ERP measures in an auditory lexical decision task. Primes were words (Expt. 1) or non-words (Expt. 2). RESULTS: ERPs elicited by words showed clear developmental changes in ERP latency and morphology, especially with regard to early negativities like the N1. Prominent priming effects were an enhanced N400 amplitude due to alliterating word primes in beginning readers, and typical phonological N400 reductions due to alliterating non-word primes in all groups. Priming further led to opposite early effects with word primes (N1/N(200) reduction) vs. non-word primes (P1/N1 enhancement) in all groups. CONCLUSIONS: These changes in ERP morphology and priming effects suggest that the lexical system undergoes substantial restructuring at the level of phonological processing and representation. In particular, our results indicate distinct processing of word onsets in beginning readers, confirming that vocabulary growth and the acquisition of reading may critically contribute to the formation of a fully segmental lexical system.

Adult↗

Concurrent verbal and emotion laterality effects exhibited by normally achieving and learning disabled children.

This study assessed both left- and right-hemisphere functions simultaneously when two-syllable words differing only in the initial stop consonant and spoken in different emotional tones were paired dichotically. Seventy-two right-handed normally achieving children, 12 boys and 12 girls at each of grades 1, 3, and 5, were instructed to detect either the presence of a specific word or of a specific emotion. In addition, 30 right-handed learning disabled (LD) children (age-matched to the normal controls) were assessed to determine whether LD children distribute verbal and nonverbal functions to different hemispheres. Results indicated that although both control and LD children demonstrated an overall REA for word stimuli and an LEA for emotional stimuli, and that emotional stimuli were easier to process than word stimuli, LD children were less accurate in processing both types of stimuli than their control counterparts. 'Complementary specialization,' as assessed through distribution of laterality effects, was found to be greater for control children than for LD children. However, the lack of consistency in complementary specialization found among the three developmental grade levels may be indicative that independent brain mechanisms underlying verbal and emotional processing have yet to be fully established in children. Further, in contrast to adult findings, a larger LEA was obtained for the emotion 'happy' than for the emotion 'sad.' It was concluded that whereas independent hemisphere processing for words and emotions is somewhat prevalent for control children, LD children might not be as strongly lateralized for opposite hemisphere processing of these functions.

Analysis of Variance↗

Neural responses to morphological, syntactic, and semantic properties of single words: an fMRI study.

Dissociations in the recognition of specific classes of words have been documented in brain-injured populations. These include deficits in the recognition and production of morphologically complex words as well as impairments specific to particular syntactic classes such as verbs. However, functional imaging evidence for distinctions among the neural systems underlying these dissociations has been inconclusive. We explored the neural systems involved in processing different word classes in a functional Magnetic Resonance Imaging study, contrasting four groups of words co-varying morphological complexity (simple, monomorphemic words vs complex derived or inflected words) and syntactic class (verbs vs nouns/adjectives). Subtraction of word from letter string processing showed activation in left frontal and temporal lobe regions consistent with prior studies of visual word processing. No differences were observed for morphologically complex and simple words, despite adequate power to detect stimulus specific effects. A region of posterior left middle temporal gyrus showed significantly increased activation for verbs. Post hoc analyses showed that this elevated activation could also be related to semantic properties of the stimulus items (verbs have stronger action associations than nouns, and action association is correlated with activation). Results suggest that semantic as well as syntactic factors should be considered when assessing the neural systems involved in single word comprehension.

Adolescent↗

Semantic processing and memory for attended and unattended words in dichotic listening: behavioral and electrophysiological evidence.

Thirty-two Ss studied words presented to 1 ear, while ignoring a concurrent word list presented to the opposite ear. The N400 component of the event-related potentials elicited by attended words was modulated by semantic priming between successive words. The N400 elicited by unattended words was insensitive to semantic manipulation. Recognition memory was better for attended than for unattended words. However, the percentage of false positives was elevated equally for lures that were semantically related to "old" words, whether they had been attended or unattended. Words that were initially attended induced similar repetition effects in a lexical decision task as words that were initially unattended. Hence, both attended and unattended words are semantically processed and activate semantic representations. However, attended words from traces that are subsequently more available to conscious recollection than unattended words.

Adult↗

The use of source memory to identify one's own episodic confusion errors.

In 4 category cued recall experiments, participants falsely recalled nonlist common members, a semantic confusion error. Errors were more likely if critical nonlist words were presented on an incidental task, causing source memory failures called episodic confusion errors. Participants could better identify the source of falsely recalled words if they had deeply processed the words on the incidental task. For deep but not shallow processing, participants could reliably include or exclude incidentally shown category members in recall. The illusion that critical items actually appeared on categorized lists was diminished but not eradicated when participants identified episodic confusion errors post hoc among their own recalled responses; participants often believed that critical items had been on both the incidental task and the study list. Improved source monitoring can potentially mitigate episodic (but not semantic) confusion errors.

Adult↗

Electrophysiological studies of visual word perception, lexical organization, and semantic processing: a tutorial review.

Visual word recognition requires the matching of an orthographic unit to its meaning via a phonological unit in the mental lexicon. The nature and the speed of this process are affected by "bottom-up" factors (e.g., the manner in which the phonology is represented by the orthography) and by "top-down" factors (e.g., network connections between related words in the lexicon, and contextual semantic information). Event-related potentials (ERPs) provide a relatively new tool that complements behavioral measures of word recognition. ERP components recorded during word perception tasks have been found to be sensitive to orthographic, phonological, and semantic manipulations. They go beyond behavioral measures by providing continuous information about the activity of the cognitive system from stimulus onset to the occurrence of the response. In addition, ERPs enable the researcher to examine word perception and reading in more natural situations, without time constraints and overt responses. Finally, intra-cranial ERP recording in humans and modern analytical techniques may shed light on the relations between cognitive linguistic processes and brain structures. Collaboration between cognitive psychologists, linguists, and ERP researchers will be necessary to exploit the great potential of these electrophysiological techniques.

Cognition↗

Distinct cortical areas for names of numbers and body parts independent of language and input modality.

Some models of word comprehension postulate that the processing of words presented in different modalities and languages ultimately converges toward common cerebral systems associated with semantic-level processing and that the localization of these systems may vary with the category of semantic knowledge being accessed. We used functional magnetic resonance imaging to investigate this hypothesis with two categories of words, numerals, and body parts, for which the existence of distinct category-specific areas is debated in neuropsychology. Across two experiments, one with a blocked design and the other with an event-related design, a reproducible set of left-hemispheric parietal and prefrontal areas showed greater activation during the manipulation of topographical knowledge about body parts and a right-hemispheric parietal network during the manipulation of numerical quantities. These results complement the existing neuropsychological and brain-imaging literature by suggesting that within the extensive network of bilateral parietal regions active during both number and body-part processing, a subset shows category-specific responses independent of the language and modality of presentation.

Adult↗

[Recognition processes for Chinese and original words written in Hangul].

The purpose of this study is to examine recognition processes for Chinese and original words written in Hangul. It was tested whether or not the processing time for Chinese words is different from that for original words. In the first experiment, naming latencies for Chinese words were longer than those for original words. Also, the naming latencies for high-frequency-Chinese-words with final consonant (CVC + CVC) were shorter than those for high-frequency-Chinese-words without final consonant (CV + CV). The second experiment was conducted to clarify the lexical process by using the lexical decision task. The lexical decision times for Chinese words were not different from those for original words. The data suggest that the reading of Hangul words is mediated by lexical information as well as by phonological information.

Adult↗

Word order in sentence processing: an experimental study of verb placement in German.

We examine the question of whether the human comprehension device exhibits word-order preferences during on-line sentence comprehension. The focus is on the positioning of finite verbs and auxiliaries relative to subjects and objects in German. Results from three experiments (using self-paced reading and event-related brain potentials) show that native speakers of German prefer to process finite verbs in second position (i.e., immediately after the subject and before the object). We will account for this order preference in terms of the relative processing costs associated with SVfO and SOVf. Our finding that word-order preferences play an important role in the on-line comprehension of German sentences is compatible with results from previous studies on English and other languages.

Adult↗

Gender differences in brain activity generated by unpleasant word stimuli concerning body image: an fMRI study.

BACKGROUND: We have previously reported that the temporomesial area, including the amygdala, is activated in women when processing unpleasant words concerning body image. AIMS: To detect gender differences in brain activation during processing of these words. METHOD: Functional magnetic resonance imaging was used to investigate 13 men and 13 women during an emotional decision task consisting of unpleasant words concerning body image and neutral words. RESULTS: The left medial prefrontal cortex and hippocampus were activated only among men, and the left amygdala was activated only among women during the task; activation in the apical prefrontal region was significantly greater in men than in women. CONCLUSIONS: Our data suggest that the prefrontal region is responsible for the gender differences in the processing of words concerning body image, and may also be responsible for gender differences in susceptibility to eating disorders.

Adult↗

Effects of form familiarity on perception of words, pseudowords, and nonwords in the two cerebral hemispheres.

Previous investigations of hemispheric processes of word perception provide a mixed picture of the sensitivity of each hemisphere to the familiarity of the visual form of lateralized displays. We investigated this issue by presenting words, pseudowords, and nonwords briefly to either the left (LH) or right (RH) hemisphere in lowercase, uppercase, and a matched, unfamiliar mixed-case form, and used an eye tracker to ensure central fixation and the Reicher-Wheeler task to suppress influences of stimulus asymmetry. Familiarity of form exerted a substantial effect on perception. In particular, perception of LH and RH displays of words, pseudowords, and nonwords was least accurate for mixed case, intermediate for upper case, and most accurate for lowercase. However, form had no effect on the LH advantage observed for words, pseudowords, and nonwords, indicating that form affected processing in both hemispheres to a similar extent. Moreover, LH and RH displays both showed that mixed case disrupted performance most for words, and more for pseudowords than for nonwords, indicating the sensitivity to form shown by each hemisphere reflected more than a general perceptual process. Implications for the role of form familiarity in hemispheric processing of words are discussed.

Adolescent↗

The effects of case mixing on word recognition: evidence from a PET study.

The early stages of visual word recognition were investigated by scanning participants using PET as they took part in implicit and explicit reading tasks with visually disrupted stimuli. CaSe MiXiNg has been shown in behavioral studies to increase reaction times (RTs) in naming and other word recognition tasks. In this study, we found that during both an implicit (feature detection) task and an explicit word-naming task, mixed-case words compared to same-case words produced increased activation in an area of the right parietal cortex previously associated with visual attention. No effect of case was found in this area for pseudowords or consonant strings. Further, lowering the contrast of the stimuli slowed RTs as much as case mixing, but did not lead to the same increase in right parietal activation. No significant effect of case mixing was observed in left-hemisphere language areas. The results suggest that reading mixed-case words requires increased attentional processing. However, later word recognition processes may be relatively unaffected by the disruption in presentation.

Attention↗

Processing emotional pictures and words: effects of valence and arousal.

There is considerable debate regarding the extent to which limbic regions respond differentially to items with different valences (positive or negative) or to different stimulus types (pictures or words). In the present event-related fMRI study, 21 participants viewed words and pictures that were neutral, negative, or positive. Negative and positive items were equated on arousal. The participants rated each item for whether it depicted or described something animate or inanimate or something common or uncommon. For both pictures and words, the amygdala, dorsomedial prefrontal cortex (PFC), and ventromedial PFC responded equally to all high-arousal items, regardless of valence. Laterality effects in the amygdala were based on the stimulus type (word = left, picture = bilateral). Valence effects were most apparent when the individuals processed pictures, and the results revealed a lateral/medial distinction within the PFC: The lateral PFC responded differentially to negative items, whereas the medial PFC was more engaged during the processing of positive pictures.

Adolescent↗

The right hemisphere involvement in the processing of morphologically derived words.

It is widely documented that the left hemisphere is dominant in all complex linguistic tasks, including the processing of inflectional morphology. Both in Italian and in other languages, patients with brain damage with a selective deficit in derivational morphology have never been reported. Here we present the unusual case of two patients with very similar right-hemisphere lesions, who in the absence of aphasic disorders showed a selective inability in producing derivational morphology. Although both patients were unimpaired in producing verb infinitives, they both showed a selective deficit in producing nouns derived from verbs. This difficulty was not present in deriving nouns from other grammatical categories, such as adjectives. Interestingly, both patients mostly substituted the derived noun with the past participle of the verb. This pattern of results documents for the first time a right-hemisphere contribution in the domain of derivational morphology.

Aged↗

Cerebral organization of component processes in reading.

The cerebral organization of word identification processes in reading was examined using functional magnetic resonance imaging (fMRI). Changes in fMRI signal intensities were measured in 38 subjects (19 males and 19 females) during visual (line judgement), orthographic (letter case judgement), phonological (nonword rhyme judgement) and semantic (semantic category judgement) tasks. A strategy of multiple subtractions was employed in order to validate relationships between structure and function. Orthographic processing made maximum demands on extrastriate sites, phonological processing on a number of frontal and temporal sites, and lexical-semantic processing was most strongly associated with middle and superior temporal sites. Significant sex differences in the cerebral organization of reading-related processes were also observed.

Adult↗

Evaluating a split processing model of visual word recognition: effects of word length.

A new theory of visual word recognition is based on the fact that the fovea is split in humans. When a reader fixates the center of a written word, the initial letters of the word that are to the left of fixation are projected first to the right cerebral hemisphere (RH) while the final letters are projected to the left cerebral hemisphere (LH). This paper explores the possibility that this has consequences for the early processing of the beginning and ends of centrally fixated words: specifically that lexical decision RTs are affected by the number of letters to the left of fixation but not by the number of letters to the right of fixation. For centrally presented five- and eight-letter words, we manipulated number of letters presented to the right or to the left of a fixation point (Experiment 1). We found that longer latencies to longer letter strings characterised the processing of the initial letters of words while LH word recognition features characterised the ends of words. Experiment 2 was a lateralized version of Experiment 1, and revealed the well established visual field and word length interaction. The results supported the split fovea theory.

Adult↗