Support for anterior temporal involvement in semantic error production in aphasia: new evidence from VLSM

Semantic errors in aphasia (e.g., naming a horse as “dog”) frequently arise from faulty mapping of concepts onto lexical items. A recent study by our group used voxel-based lesion-symptom mapping (VLSM) methods with 64 patients with chronic aphasia to identify voxels that carry an association with semantic errors. The strongest associations were found in the left anterior temporal lobe (L-ATL), in the mid- to anterior MTG region. The absence of findings in Wernicke’s area was surprising, as were indications that ATL voxels made an essential contribution to the post-semantic stage of lexical access. In this follow-up study, we sought to validate these results by re-defining semantic errors in a manner that was less theory dependent and more consistent with prior lesion studies. As this change also increased the robustness of the dependent variable, it made it possible to perform additional statistical analyses that further refined the interpretation. The results strengthen the evidence for a causal relationship between ATL damage and lexically-based semantic errors in naming and lend confidence to the conclusion that chronic lesions in Wernicke’s area are not causally implicated in semantic error production.     

Hemispheric asymmetries in auditory distraction

Serial-verbal short-term memory is impaired by irrelevant sound, particularly when the sound changes acoustically (the changing-state effect). In contrast, short-term recall of semantic information is impaired only by the semanticity of irrelevant speech, particularly when it is semantically related to the target memory items (the between-sequence semantic similarity effect). Previous research indicates that the changing-state effect is larger when the sound is presented to the left ear in comparison to the right ear, the left ear disadvantage. In this paper, we report a novel finding whereby the between-sequence semantic similarity effect is larger when the irrelevant speech is presented to the right ear in comparison to the left ear, but this right ear disadvantage is found only when meaning is the basis of recall (Experiments 1 and 3), not when order is the basis of recall (Experiment 2). Our results complement previous research on hemispheric asymmetry effects in cross-modal auditory distraction by demonstrating a role for the left hemisphere in semantic auditory distraction.     

Lexicality, morphological structure, and semantic transparency in the processing of German ver-verbs: The complementarity of on-line and off-line evidence

Two types of experiments investigate the visual on-line and off-line processing of German ver-verbs (e.g., verbittern ‘to embitter'). In Experiments 1 and 2 (morphological priming), latency patterns revealed the existence of facilitation effects for the morphological conditions (BITTER-VERBITTERN and BITTERN-VERBITTERN) as compared to the neutral conditions (SAUBER-VERBITTERN and SÄUBERN-VERBITTERN). In Experiments 3 and 4 (rating tasks) participants had to judge whether the target (VERBITTERN) “comes from,” “contains a form of,” or “contains the meaning of” the root (BITTER) or the root+en substring (BITTERN). Taken together, these studies revealed the combined influence of the three factors of lexicality (real word status), morphological structure, and semantic transparency.     

The effects of perceived competence and sociability on electoral outcomes

Previous research demonstrated that inferences of competence from the face are good predictors of electoral outcomes [Todorov, A., Mandisoza, A. N., Gore, A., & Hall, C. C. (2005). Inferences of competence from faces predict election outcomes. Science, 308, 1623-1626]. In the current work we examined the role of another key dimension in social perception, namely perceived sociability. Results showed that people considered both competence and sociability, as inferred from the face, as related to higher chances of winning the elections. A different pattern emerged in relation to the actual electoral outcomes. Indeed, perceived competence was related to higher chances of winning, whereas perceived sociability was negatively related to electoral success. It is thus shown that these two fundamental dimensions in social perception exert opposite effects on voting behaviors.     

The semantic red effect: Processing the word red undermines intellectual performance

Recent research has shown that a two second glimpse of color can have an important influence on affect, cognition, and behavior. The present research examined whether perceiving color is necessary to produce an effect on psychological functioning or whether the mere act of processing a color word might be sufficient. Specifically, four experiments tested the hypothesis that processing the word red undermines intellectual performance, much like actually perceiving the color red. Supportive data were obtained with three different types of subtle manipulation, with three different types of control words, and on two different types of IQ test performance. Worry, but not mood or general arousal, was shown to mediate the semantic red effect, which appears to take place outside of individuals’ awareness. The theoretical and practical implications of the results are discussed.     

Semantics and truth relative to a world

This paper argues that relativity of truth to a world plays no significant role in empirical semantic theory, even as it is done in the model-theoretic tradition relying on intensional type theory. Some philosophical views of content provide an important notion of truth at a world, but they do not constrain the empirical domain of semantic theory in a way that makes this notion empirically significant. As an application of this conclusion, this paper shows that a potential motivation for relativism based on the relativity of truth to a world fails.     

The question shapes the answer: the neural correlates of task differences reveal dynamic semantic processing

Task effects in semantic processing were investigated by contrasting the neural activation associated with two semantic categorization tasks (SCT) using event-related fMRI. The two SCTs involved different decision categories: is it an animal? vs. is it a concrete thing? Participants completed both tasks and, across participants, the same core set of items were presented in both tasks. Results showed task differences in the neural activation associated with these items: in the animal SCT there was greater activation in a number of frontal and temporal regions, including left superior and middle temporal gyri, while in the concrete SCT there was greater activation in left medial frontal gyrus and bilaterally in the precentral gyri. These results are interpreted as evidence of top-down modulation of semantic processing; participants make adjustments to optimize performance in a given task and these adjustments have consequences for the activation observed.     

Semantic interference during object naming in agrammatic and logopenic primary progressive aphasia (PPA)

This study examined the time course of object naming in 21 individuals with primary progressive aphasia (PPA) (8 agrammatic (PPA-G); 13 logopenic (PPA-L)) and healthy age-matched speakers (n = 17) using a semantic interference paradigm with related and unrelated interfering stimuli presented at stimulus onset asynchronies (SOAs) of −1000, −500, −100 and 0 ms. Results showed semantic interference (SI) (i.e. significantly slower RTs in related compared to unrelated conditions) for all groups at −500, −100 and 0 ms, indicating timely spreading activation to semantic competitors. However, both PPA groups showed a greater magnitude of SI than normal across SOAs. The PPA-L group and six PPA-G participants also evinced SI at −1000 ms, suggesting an abnormal time course of semantic interference resolution, and concomitant left hemisphere cortical atrophy in brain regions associated with semantic processing. These subtle semantic mapping impairments in non-semantic variants of PPA may contribute to the anomia of these patients.     

When phonology fails: orthographic neighbourhood effects in dyslexia

Both cerebral hemispheres contain phonological, orthographic and semantic representations of words, however there are between-hemisphere differences in the relative engagement and specialization of the different representations. Taking orthographic processing for example, previous studies suggest that orthographic neighbourhood size (N) has facilitatory effects in the right but not the left hemispheres. To pursue the nature of this asymmetric N effect, in particular whether there are individual differences in such specialisation, we examined N in a case of developmental dyslexia, FM. We first describe the nature of his difficulties, which are mainly severe phonological deficits. Employing the divided visual field paradigm with FM revealed a greater sensitivity in the right than in the left hemisphere to orthographic variables, with a significant inhibitory N effect in the left, but not right hemisphere. Such inhibition, to a lesser degree, was found among a group of adults with dyslexia but not among age-matched normal readers. We argue that enhanced sensitivity to orthographic cues is developed in some cases of dyslexia when a normal, phonology-based left hemisphere word recognition processing is not achieved. The interpretation presented here is cast in terms of differences between people with dyslexia and typical readers that originate in the atypical way in which orthographic representations are initially set up.