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PubMed2001

Task-dependent modulation of regions in the left inferior frontal cortex during semantic processing.

To distinguish areas involved in the processing of word meaning (semantics) from other regions involved in lexical processing more generally, subjects were scanned with positron emission tomography (PET) while performing lexical tasks, three of which required varying degrees of semantic analysis and one that required phonological analysis. Three closely apposed regions in the left inferior frontal cortex and one in the right cerebellum were significantly active above baseline in the semantic tasks, but not in the nonsemantic task. The activity in two of the frontal regions was modulated by the difficulty of the semantic judgment. Other regions, including some in the left temporal cortex and the cerebellum, were active across all four language tasks. Thus, in addition to a number of regions known to be active during language processing, regions in the left inferior frontal cortex were specifically recruited during semantic processing in a task-dependent manner. A region in the right cerebellum may be functionally related to those in the left inferior frontal cortex. Discussion focuses on the implications of these results for current views regarding neural substrates of semantic processing.

Acoustic Stimulation↗
PubMed2002

Implicit memory for words played during isoflurane- or propofol-based anesthesia: the lexical decision task.

BACKGROUND: Unconscious processing of words during general anesthesia has been suggested after surgery with several tests of implicit memory. Patients can neither recall those words nor do they have explicit memories of other intraoperative events. It is unclear to what degree information is processed during general anesthesia and which tests are best suited to detect implicit memory. In the current study, a lexical decision paradigm not previously used to demonstrate implicit memory during anesthesia was used. METHODS: Sixty patients undergoing lumbar disc surgery were assigned to receive isoflurane infusion- or propofol infusion-based anesthesia combined with alfentanil infusions and a nitrous oxide-oxygen mixture. A control group of 10 medical students listened to tapes without receiving anesthesia. Two tapes, each containing a list of 30 low-frequency German nouns repeated for 15 min, were prepared, with half of the patients listening to tape A and the other half listening to tape B during the operation. Exposure time was 15 min from the time of skin incision onward. In the test phase, approximately 7 h later, words from lists A and B plus 60 nonwords were presented in random order by a computer program. Subjects were asked to indicate, by pressing one of two response buttons, whether the spoken word was or was not a legal German word (lexical decision). RESULTS: A recognition test revealed chance recognition for words presented during anesthesia. Lexical decision responses, however, were slightly faster to primed (previously presented) words than to unprimed (not previously presented) words when the entire group of patients was tested, suggesting a small implicit memory effect, which barely failed to reach the significance level. When the two medication groups were tested separately, no significant implicit memory effect could be ascertained statistically. The effects of previous exposure were much more pronounced in the control group. CONCLUSIONS: Balanced anesthesia techniques with isoflurane or propofol lead to only a minimal, statistically borderline implicit memory effect in the lexical decision paradigm.

Acoustic Stimulation↗
PubMed2005

Parafoveal-on-foveal effects on eye movements in text reading: does an extra space make a difference?

Schiepers proposed that in text reading, the currently fixated word and the next word are processed in parallel but with a time delay of 90 ms per degree of eccentricity. In his model, the benefit of seeing the upcoming word is due to the fact that the parafoveal information from fixation n is combined with the foveal information from fixation n+1 to boost word recognition, at least when the fixation on word n is of an optimal duration (between 210 and 270 ms). We tested this assumption by adding an extra blank space between the foveal and the parafoveal word. According to the model, this should result in a 30 ms longer processing time for the foveal word. However, reading time was shorter for a word followed by a double space than for a word followed by a single space. An effect of parafoveal word length was also observed with a longer word in the parafoveal leading to shorter fixation times on the foveal word. Implications of these low-level parafoveal-on-foveal effects are discussed.

Eye Movements↗
PubMed2003

Processing fat-related information in individuals at risk for developing an eating disorder.

The authors examined the effect that being at risk for developing an eating disorder has on the lexical processing of words related to fat and words not related to fat. Individuals (n = 17) at risk for developing an eating disorder were compared with controls (n = 31) using a lexical decision task in which fat-related words (e.g., large), unrelated words (e.g., fair), neutral words (e.g., post), and pseudowords (e.g., flirp) were given. The results revealed an expected Group x Stimuli interaction for reaction times indicating that at-risk individuals were significantly faster at processing fat-related words than words unrelated to fat. The authors discuss these results within the context of how fat-related stimuli are processed in at-risk individuals and how models of information processing can aid in the interpretation and understanding of eating disorders.

Adult↗
PubMed2004

Magnetic brain activity elicited by visually presented symbols and Japanese characters.

A standard model of word reading postulates that the posterior inferior temporal cortex is involved in the processing of written words. This processing probably occurs within 200 ms after stimulus presentation. In order to characterize this process more precisely, we conducted a MEG study during a reading task in nine right-handed normal Japanese subjects. The subjects were required to respond to a word pertaining to the human body so that all stimuli would be subject to the same semantic processing. The trials for non-target conditions, such as kanji words, meaningful kana words, kana pseudowords and symbols were analysed to avoid possible P300 effect. The magnetic response peak of around 200 ms for symbols was smaller than any of the other three letter conditions. This result may suggest that M200 reflects the word-specific process such as visual word form recognition.

Adult↗
PubMed2005

Semantic and phonological processing in reading Korean Hangul and Hanja words.

The Korean orthography uses both alphabetic Hangul and logographic Hanja. Two experiments investigated semantic and phonological processing of words written in the two scripts. In the experiments, Korean readers had to respond to words either in a pure context with words from one single script or in a mixed context with words from the two scripts. The task was naming in Experiment 1 and semantic categorization in Experiment 2. The results showed that for Hangul words, there were significant word frequency effects in categorization, but not in naming, and that there were reliable script-switching effects in naming, but not in categorization. For Hanja words, however, there were clear and strong effects of words frequency, regardless of the task used, but significant effects of script-switching were only observed in categorization. These results suggest that the strategies adopted in processing Hangul and Hanja words are determined both by task demand and nature of the script.

Humans↗
PubMed1981

On the relationship between autobiographical memory and perceptual learning.

Although the majority of research on human memory has concentrated on a person's ability to recall or recognize items as having been presented in a particular situation, the effects of memory are also revealed in a person's performance of a perceptual task. Prior experience with material can make that material more easily identified or comprehended in perceptually difficult situations. Unlike with standard retention tests, effects of prior experience on a perceptual task do not logically require that a person be aware that he or she is remembering. Indeed, amnesic patients purportedly show effects of practice in their subsequent performance of a perceptual or motor task even though they profess that they do not remember having engaged in that prior experience. The experiments that are reported were designed to explore the relationship between the more aware autobiographical form of memory that is measured by a recognition memory test and the less aware form of memory that is expressed in perceptual learning. Comparisons of effects on perceptual learning and recognition memory reveal two classes of variables. Variables such as the level of processing of words during study influenced recognition memory, although they had no effect on subsequent perceptual recognition. A study presentation of a word had as large an effect on its later perceptual recognition when recognition memory performance was very poor as it did when recognition memory performance was near perfect. In contrast, variables such as the number and the spacing of repetitions produced parallel effects on perceptual recognition and recognition memory. Following Mandler and others, it is suggested that there are two bases for recognition memory. If an item is readily perceived so that it seems to "jump out" from the page, a person is likely to judge that he or she has previously seen the item in the experimental situation. Variables that influence ease of perceptual recognition, then, can also have an effect on recognition memory, so parallel effects are found. The second basis for recognition memory involves elaboration of a word's study context and depends on such factors as level of processing during study--factors that are not important for perceptual recognition of isolated words. Comparisons of perceptual recognition and recognition memory are shown to be useful for determining how a variable has its effect. Effects of study on perceptual recognition appear to be totally due to memory for physical or graphemic information. Results reported are also relevant to theories of perceptual learning. A single presentation of an item is shown to have large and long-lasting effects on its later perceptual recognition. At least partially, effects of study on perceptual recognition depend on the same variables as do effects on more standard memory tests.

Discrimination Learning↗
PubMed1999

Semantic or lexico-syntactic factors: what determines word-class specific activity in the human brain?

Words from different classes have been found to activate different brain areas. However, it is unclear whether grammatical word properties, for example their being part of different lexical categories (e.g. nouns vs. verbs) or semantic features of the words (e.g. that they refer to visually perceived entities or to actions) are relevant for eliciting differential brain responses. We tested this by comparing brain potentials elicited by nouns and verbs that varied in their action and visual associations. Naturally spoken word stimuli were from three categories: (1) nouns with strong visual associations; (2) action verbs with strong associations of actions, and (3) nouns with strong action associations. Word-category specific differences became apparent around 500 ms after stimulus onset, approximately 150-200 ms after the average recognition point of the words involved. Brain responses to visual nouns and action verbs differed at central and occipital recording sites. A very similar topographical difference emerged from the comparison of visual vs. action nouns, whereas no significant difference was found between action-related nouns and verbs. These results indicate that grammatical differences alone, e.g. between two lexical classes such as action verbs and action-related nouns, are not sufficient for eliciting differential brain responses. In contrast, semantic differences between items from the same lexical category can be sufficient for changing the topography of cortical processes induced by word stimuli. This is support for associative theories of word processing.

Adult↗
PubMed1993

A model for conceptual processing of naturalistic scenes.

Are there fundamental differences in the way in which a list of pictures and a list of words are processed? We report three experiments that examine serial position effects for rapidly-presented naturalistic scenes. The experiments provide a basis for comparison with the U-shaped serial position curve and list-length effect which typically result from verbal learning experiments. In contrast to the U-shaped verbal serial position function, our results show a flat function at the beginning serial positions and a recency effect which is small and limited to the last serial position. There is a set-size effect. Results suggest that the processing leading to a memory representation for visual stimuli such as pictures and linguistic stimuli such as words is qualitatively dissimilar. The findings can be accounted for by a serial processing model whose main parameter is the probability that the subject will switch attention from one picture to the next.

Attention↗
PubMed2001

Specificity of Stroop interference in patients with pain and PTSD.

The authors investigated processing of threat words in motor vehicle accident survivors using a modified Stroop procedure. Three samples were included: 28 participants with comorbid posttraumatic stress disorder (PTSD) and pain, 26 participants with pain without PTSD, and 21 participants without pain or any psychiatric conditions. Four word categories were used: (a) accident words, (b) pain words, (c) positive words, and (d) neutral words. This study examined whether processing biases would occur to accident words only in participants with PTSD or if these biases would also be noted in the No PTSD/Pain sample. Additionally, this study examined whether processing biases would be noted to pain words in the 2 pain samples, irrespective of PTSD. Overall, color naming was significantly slower in the PTSD/Pain group in comparison with the other groups. As well, the PTSD/Pain sample showed significant response delays to both accident and pain-related words, whereas patients with No PTSD/Pain showed delays to pain stimuli only.

Adult↗
PubMed2002

A case study of pure word deafness: modularity in auditory processing?

AL, a woman with an acquired disturbance of auditory processing beginning in the second decade, was originally diagnosed as having pure word deafness. Recent analysis with a wide range of stimuli suggests that her comprehension deficit also extends to a subset of musical and non-verbal environmental sounds. The perceptual demands of the different auditory stimuli appear to account for part of the apparent material specificity. Additionally, over the years, the presumed temporal lobe cortical pathology has been supplemented by a mild to moderate, peripheral low-frequency hearing loss and evidence of dysfunction in lower level auditory processing pathways. The current peripheral dysfunction closely resembles cases recently labeled as auditory neuropathy. The diagnosis of pure word deafness should not be based on a limited set of auditory stimuli; additionally, a careful assessment using modern audiological techniques should be performed to evaluate peripheral auditory functions.

Achievement↗
PubMed2004

Limitations of the dual-process-theory regarding the writing of words and non-words to dictation.

It is generally assumed that the lexical and phonological systems are involved in writing to dictation. In an experiment concerned with the writing of words and non-words to dictation, the handwriting of female students was registered using a digitising tablet. The data contradict the assumption that the phonological system represents an alexical process. Both words and non-words which were acoustically presented to the subjects were lexically parsed. The analysis of kinematic data revealed significant differences between the subjects' writing of words and non-words. The findings reveal gross disturbances of handwriting fluency during the writing of non-words. The findings of the experiment cannot be explained by the dual-process-theory.

Adult↗
PubMed1998

Modulation of human extrastriate visual processing by selective attention to colours and words.

The present study investigated the effect of visual selective attention upon neural processing within functionally specialized regions of the human extrastriate visual cortex. Field potentials were recorded directly from the inferior surface of the temporal lobes in subjects with epilepsy. The experimental task required subjects to focus attention on words from one of two competing texts. Words were presented individually and foveally. Texts were interleaved randomly and were distinguishable on the basis of word colour. Focal field potentials were evoked by words in the posterior part of the fusiform gyrus. Selective attention strongly modulated long-latency potentials evoked by words. The attention effect co-localized with word-related potentials in the posterior fusiform gyrus, and was independent of stimulus colour. The results demonstrated that stimuli receive differential processing within specialized regions of the extrastriate cortex as a function of attention. The late onset of the attention effect and its co-localization with letter string-related potentials but not with colour-related potentials recorded from nearby regions of the fusiform gyrus suggest that the attention effect is due to top-down influences from downstream regions involved in word processing.

Action Potentials↗
PubMed2003

Hemispheric asymmetry in the processing of emotional content in word meanings: the effect of current and past depression.

We examined hemispheric lateralization of emotion processing by comparing the performance of clinically depressed, previously depressed, and control individuals on a divided visual field task. Participants were asked to make affective valence judgments for each in a series of laterally presented person-descriptive adjectives. Study results suggest that the right cerebral hemisphere (RH) is preferentially sensitive to the affective context of language. Among targets presented to the RH, depressed and previously depressed participants were significantly faster and more accurate in their judgments of negative target words, while controls responded more quickly and accurately to positive target words. No such effects were observed for targets presented to the left hemisphere. It is hypothesized that affective sensitivity may result in differences in semantic network organization across individuals who vary in affective experience.

Adolescent↗
PubMed1991

Automatic processes in lexical access and spreading activation.

The semantic priming effect can be reduced or eliminated depending on how the prime word is processed. The experiments reported here investigate this prime task effect. Two experiments used identity and semantic priming tasks to determine whether the prime word is encoded at a lexical level under letter-search conditions. When the prime task was naming, both identity and semantic priming occurred; however, when a letter-search task was performed on the prime word, only identity priming occurred, thus supporting the argument that the search task affects activation of semantic associates rather than lexical access of the prime word. Another experiment demonstrated that this identity priming was the result of lexical processes rather than of letter-by-letter priming. A cross-modal priming technique demonstrated that the letter-search prime task does not actively suppress activation of semantic associates. The implications of these results for automaticity and for proposed mechanisms of priming are discussed.

Adult↗
PubMed2001

Differential cognitive processing of Kanji and Kana words: do orthographic and semantic codes function in parallel in word matching task.

Relative engagements of the orthographic and semantic codes in Kanji and Hiragana word recognition were investigated. In Exp. 1, subjects judged whether the pairs of Kanji words (prime and target) presented sequentially were physically identical to each other in the word condition. In the sentence condition, subjects decided whether the target word was valid for the prime sentence presented in advance. The results showed that the response times to the target swords orthographically similar (to the prime) were significantly slower than to semantically related target words in the word condition and that this was also the case in the sentence condition. In Exp. 2, subjects judged whether the target word written in Hiragana was physically identical to the prime word in the word condition. In the sentence condition, subjects decided if the target word was valid for the previously presented prime sentence. Analysis indicated that response times to orthographically similar words were slower than to semantically related words in the word condition but not in the sentence condition wherein the response times to the semantically and orthographically similar words were largely the same. Based on these results, differential contributions of orthographic and semantic codes in cognitive processing of Japanese Kanji and Hiragana words was discussed.

Adult↗
PubMed1988

Apparent shift in visual field preference after unilateral stroke.

Patients with either a left- or a right-hemisphere stroke lesion scored higher in tasks of word-picture matching and of nonverbal shape matching when information was presented tachistoscopically (120 msec) to the visual field (VF) projecting to their undamaged hemisphere. Left-hemisphere stroke patients (n = 13) were dissociated from right-hemisphere stroke patients (n = 15) by low word recognition from memory and by low right VF but nearly normal left VF accuracy in word-picture matching or shape matching; the former appeared to rely upon processing of word meaning by the right hemisphere. In contrast, right-stroke patients had higher right than left VF scores in both tasks, and their discrimination of nonverbal shapes via the right VF was not different from that of controls (n = 15). Preferred processing by the VF projecting to the undamaged hemisphere appeared as a shift in perceptual asymmetry but may indicate, in support of a "direct access" model, that each hemisphere responds more or less efficiently to word and to nonverbal shape discriminations.

Aged↗
PubMed2005

Are semantic and syntactic cues inducing the same processes in the identification of word order?

The purpose of this study was to find a common pattern of event-related potential (ERP) fluctuations regardless of the type of information (either semantic or syntactic) determining the presence of a reversed word order. ERPs were recorded while subjects read Spanish transitive sentences in which either semantic or syntactic information determined the actual word order. On the one hand (semantic condition), the order could be reversed by using an inanimate noun in the first noun phrase (NP), together with a verb representing an action that cannot correspond to an inanimate entity. On the other hand (syntactic condition), word order could be manipulated depending on the presence of a preposition preceding the second NP, which confirms the preferred word order, or a determiner, conveying a reversed word order. Interestingly, the inanimate first noun elicited a frontal negativity, which could be interpreted as the detection of an initial difficulty for using that noun as the subject of the sentence. At the point of disambiguation in either condition, a late posterior positivity was observed. The P600/SPS might, therefore, be an indicator of the syntactic processing costs incurred by the variation of word order, reflecting phrase structure reallocation processes common to this operation regardless of the cue used.

Adult↗