Processing Of Word Meaning Research Articles

Access to perceptual and conceptual information in the left and right hemispheres.

It is assumed that there are hemispheric differences in the type of information available for the processing of word meanings, e.g., categorical or associative information. In the present experiment, we used a semantic priming paradigm to examine whether perceptual or conceptual properties of word meanings would be associated with the left or right hemisphere. The present experiment also examined time-course activation of these properties across the hemispheres, using short and long stimulus onset asynchronies. The results indicated that perceptual information is available only in the right hemisphere at an early rather than a late stage of target processing, while conceptual information is available in both hemispheres at both early and later stages of target processing. It is suggested that the imagery system in the right hemisphere may contribute to the perceptual priming observed in this hemisphere.

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.

ACCESS TO PERCEPTUAL AND CONCEPTUAL INFORMATION IN THE LEFT AND RIGHT HEMISPHERES

It is assumed that there are hemispheric differences in the type of information available for the processing of word meanings, e.g., categorical or associative information. In the present experiment, we used a semantic priming paradigm to examine whether perceptual or conceptual properties of word meanings would be associated with the left or right hemisphere. The present experiment also examined time-course activation of these properties across the hemispheres, using short and long stimulus onset asynchronies. The results indicated that perceptual information is available only in the right hemisphere at an early rather than a late stage of target processing, while conceptual information is available in both hemispheres at both early and later stages of target processing. It is suggested that the imagery system in the right hemisphere may contribute to the perceptual priming observed in this hemisphere.

An ERP study of the temporal course of the Stroop color-word interference effect

The electrophysiological correlates of the Stroop color-word interference effect were studied in eight healthy subjects using high-density Event-Related Potentials (ERPs). Three response modalities were compared: Overt Verbal, Covert Verbal, and Manual. Both Overt Verbal and Manual versions of the Stroop yielded robust Stroop color-word interference as indexed by longer RT for incongruent than congruent color words. The Incongruent vs Congruent ERP difference wave presented two effects. A first effect was a medial dorsal negativity between 350–500 ms post-stimulus (peak at 410 ms). This effect had a significantly different scalp distribution in the Verbal and Manual Stroop versions, with an anterior–medial focus for overt or covert speech, and a broader medial–dorsal distribution for the manual task. Dipole source analysis suggested two independent generators in anterior cingulate cortex. Later on in time, a prolonged positivity developed between 500–800 ms post-stimulus over left superior temporo-parietal scalp. This effect was present for all the three response modalities. A possible interpretation of these results is that Stroop color-word interference first activates anterior cingulate cortex (350–500 ms post-stimulus), followed by activation of the left temporo-parietal cortex, possibly related to the need of additional processing of word meaning.

Conceptual relationships between spoken words and environmental sounds: Event-related brain potential measures

Identifiable nonspeech sounds were paired with spoken words. In Experiment 1, words preceded by related sounds yielded faster lexical decision times than those preceded by unrelated sounds. In Experiment 2, subjects were presented with sound/word and word/sound pairs while event-related potentials were recorded. Words preceded by related sounds elicited smaller N400 components than those preceded by unrelated sounds; this N400 context effect was slightly larger at electrode sites over the right hemisphere. A context effect similar in latency and morphology was observed for sounds—a smaller negative wave for related than unrelated sounds. The context effect for sounds was significantly larger at left than right recording sites, suggesting differential hemispheric involvement in the processing of word meanings than the “meanings” of environmental sounds.

Semantic and associative priming in the cerebral hemispheres: Some words do, some words don't … sometimes, some places

This study investigated spreading activation for words presented to the left and right hemispheres using an automatic semantic priming paradigm. Three types of semantic relations were used: similar-only (Deer-Pony), associated-only (Bee-Honey), and similar + associated (Doctor-Nurse). Priming of lexical decisions was symmetrical over visual fields for all semantic relations when prime words were centrally presented. However, when primes and targets were lateralized to the same visual field, similar-only priming was greater in the LVF than in the RVF, no priming was obtained for associated-only words, and priming was equivalent over visual fields for similar + associated words. Similar results were found using a naming task. These findings suggest that it is important to lateralize both prime and target information to assess hemisphere-specific spreading activation processes. Further, while spreading activation occurs in either hemisphere for the most highly related words (those related by category membership and association), our findings suggest that automatic access to semantic category relatedness occurs primarily in the right cerebral hemisphere. These results imply a unique role for the right hemisphere in the processing of word meanings. We relate our results to our previous proposal ( Burgess & Simpson, 1988a; Chiarello, 1988c) that there is rapid selection of one meaning and suppression of other candidates in the left hemisphere, while activation spreads more diffusely in the right hemisphere. We also outline a new proposal that activation spreads in a different manner for associated words than for words related by semantic similarity.

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 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.

The effects of effort on Stroop interference

Stroop interference was defined as the difference in time needed to name the ink colors of printed color and color-related words versus control plus signs. The effect of effort on Stroop interference was studied using an inter-subject competition procedure designed to manipulate effort. In experiment 1, subjects in the competition group were successful at inhibiting Stroop interference when compared to the performance of subjects in the no-competition group. This result is consistent with theories that postulate attentional effects on Stroop interference. In experiment 2, the significant decrease in Stroop interference was accompanied by a significant reduction in recognition memory for Stroop list items. Therefore, Stroop interference was reduced at a stage during the processing of word meaning. This result is consistent with theories that locate Stroop interference before response output.

Mental models of word meaning

Four experiments compared five alternative mental models of word meaning: a defining-attributes model, two characteristic-attribute models, and two mixed models. The two characteristic-attribute models (and the two mixed models) differed from each other in terms of whether weights of attributes were summed or averaged. In Experiment 1, 11 subjects provided lists of attributes for 24 different nouns. Subjects also rated the necessity, sufficiency, and importance of each attribute to a given word's definition. Results showed that both defining (necessary and sufficient) and characteristic attributes could be identified from subjects' ratings for most nouns, but that the role of defining attributes was especially pronounced for proper names. In Experiment 2, the same subjects later rated the extent to which given lists of attributes successfully described referents of each given word. Mathematical modeling of results supported a mixed model of reference based on defining attributes plus the weighted sum of all attributes (defining and characteristic). Experiment 3 replicated the results of Experiment 1 with 25 new subjects and slightly modified procedures. In Experiment 4, 32 subjects were presented with two alternative attribute lists for each given word, and were to select the better referent of the word as quickly as possible. The preferred mixed model from Experiment 2 was shown best to account for both the mental representation and real-time processing of word meanings.