How does the brain mediate interpretation of incongruent auditory emotions? The neural response to prosody in the presence of conflicting lexico‐semantic cues

We frequently encounter conflicting emotion cues. This study examined how the neural response to emotional prosody differed in the presence of congruent and incongruent lexico-semantic cues. Two hypotheses were assessed: (i) decoding emotional prosody with conflicting lexico-semantic cues would activate brain regions associated with cognitive conflict (anterior cingulate and dorsolateral prefrontal cortex) or (ii) the increased attentional load of incongruent cues would modulate the activity of regions that decode emotional prosody (right lateral temporal cortex). While the participants indicated the emotion conveyed by prosody, functional magnetic resonance imaging data were acquired on a 3T scanner using blood oxygenation level-dependent contrast. Using SPM5, the response to congruent cues was contrasted with that to emotional prosody alone, as was the response to incongruent lexico-semantic cues (for the 'cognitive conflict' hypothesis). The right lateral temporal lobe region of interest analyses examined modulation of activity in this brain region between these two contrasts (for the 'prosody cortex' hypothesis). Dorsolateral prefrontal and anterior cingulate cortex activity was not observed, and neither was attentional modulation of activity in right lateral temporal cortex activity. However, decoding emotional prosody with incongruent lexico-semantic cues was strongly associated with left inferior frontal gyrus activity. This specialist form of conflict is therefore not processed by the brain using the same neural resources as non-affective cognitive conflict and neither can it be handled by associated sensory cortex alone. The recruitment of inferior frontal cortex may indicate increased semantic processing demands but other contributory functions of this region should be explored.     

Comprehension of emotional prosody following unilateral hemispheric lesions: processing defect versus distraction defect

Two studies were conducted in order to determine whether the poor performance of RHD patients on emotional prosody tasks could be attributed to a defect in perceiving/categorizing emotional prosody (processing defect) or to a problem in being distracted by the semantic content of affectively intoned sentences (distraction defect). In one study, patients with RHD, LHD or NHD listened to affectively intoned sentences in which the semantic content was congruent or incongruent with the emotional prosody. In a second study, the patients listened to affectively intoned sentences that had been speech filtered or unfiltered. Findings from these studies indicate that both processing and distraction defects are present in RHD patients.     

Impaired processing of affective prosody in Korsakoff's syndrome

In order to further characterize reported deficits in affect perception in alcoholic Korsakoff patients, selected prosody subtests from the Tübingen Affect Battery were administered to seven Korsakoff patients and seven normal control participants. Results indicated that both linguistic and affective prosody discrimination were intact in Korsakoff patients. As well, affective prosody identification was unimpaired when the semantic content of the sentence was emotionally congruent with affective prosody. In contrast, affective prosody identification was significantly impaired when the semantic content was either neutral or incongruent with prosody. These results suggest that Korsakoff patients are impaired in interpreting the meaning of affective prosody in the absence of semantic cues as to the emotional content of sentences.     

ERP evidence for a sex-specific Stroop effect in emotional speech

The present study investigated the interaction of emotional prosody and word valence during emotional comprehension in men and women. In a prosody-word interference task, participants listened to positive, neutral, and negative words that were spoken with a happy, neutral, and angry prosody. Participants were asked to rate word valence while ignoring emotional prosody, or vice versa. Congruent stimuli were responded faster and more accurately as compared to incongruent emotional stimuli. This behavioral effect was more salient for the word valence task than for the prosodic task and was comparable between men and women. The event-related potentials (ERPs) revealed a smaller N400 amplitude for congruent as compared to emotionally incongruent stimuli. This ERP effect, however, was significant only for the word valence judgment and only for female listeners. The present data suggest that the word valence judgment was more difficult and more easily influenced by task-irrelevant emotional information than the prosodic task in both men and women. Furthermore, although emotional prosody and word valence may have a similar influence on an emotional judgment in both sexes, ERPs indicate sex differences in the underlying processing. Women, but not men, show an interaction between prosody and word valence during a semantic processing stage.     

The determiner congruency effect in language production investigated with functional MRI

In language production, naming a picture with a gender-marked determiner phrase is faster in the presence of a distractor noun with the same grammatical gender (congruent condition) as compared with a different grammatical gender (incongruent condition). We investigated the neural correlates of this determiner congruency effect in German with functional magnetic resonance imaging (fMRI). Participants named pictures of real objects with determiner phrases (e.g. "der Tisch"-the table) in the presence of a gender-congruent or gender-incongruent distractor noun. Different comparisons allow the following functional segregation within the prefrontal cortex. First, the comparison between picture naming versus rest revealed a steeper slope of the haemodynamic response function (HRF) in the gender-congruent than the gender-incongruent condition in the left BA 44, suggesting the involvement of BA 44 in determiner selection. HRF amplitude differences between the congruent and the incongruent condition were observed outside the language network in the right fronto-median wall (congruent > incongruent), and in the left premotor cortex, middle frontal gyrus, cerebellum, and inferior parietal lobe (incongruent > congruent). The latter regions are known to be involved in the processing of incongruence and conflict in general. The data thus reveal the involvement of the left BA 44 in the selection of determiners for language production.     

Mediotemporal contributions to semantic processing: fMRI evidence from ambiguity processing during semantic context verification

The medial temporal lobe (MTL) is well known to be crucial for various types of memory; however, controversy remains as to which of its substructures contribute to semantic processing and, if so, to what extent. The current study addresses the issue of MTL contributions to semantic processing during lexico-semantic ambiguity processing by using functional magnetic resonance imaging (fMRI) in combination with a context verification task (CVT). The CVT required decisions on the semantic fit of congruent and incongruent target words to the overall meaning of preceding sentential contexts with and without semantic ambiguity. In two of the four experimental conditions (congruent homographic, incongruent homographic), target decisions were critically dependent on the successful processing of prior sentence-final lexico-semantic ambiguity. Semantic context verification per se evidenced bilateral activations of the hippocampus that were part of a functional network including inferior prefrontal and superior parietal cortices. Commonalities in activation differences pertaining to the specific cognitive component of lexico-semantic ambiguity processing were found in a left temporal lobe network that comprised activation foci in the temporal pole, the parahippocampal and fusiform gyri. The present results suggest that the hippocampus may well contribute to semantic processing, namely by a mnemonic function that serves to link the target meaning representation with the meaning of a prior sentence context. Contrary to previous reports from human lesion studies, the present findings further suggest, that the specific cognitive component of lexico-semantic ambiguity processing is neither dependent on the hippocampus nor exclusively subserved by the temporal pole, but also recruits an associative semantic memory function from the parahippocampal gyrus as well as a more general (bottom-up) semantic function from the fusiform gyrus.     

Hemispheric specialisation in processing prosodic structures: Revisited

Background : Research addressing prosodic deficits in brain-damaged populations has concentrated on the specialised capabilities of the right and the left cerebral hemispheres in processing the global characteristics of prosody. This focus has been of interest in that the fundamental frequency (F0), duration and intensity acoustic characteristics within a prosodic structure can convey different linguistic and nonlinguistic information. Much of the research investigating this interesting phenomenon has produced conflicting results. As such, different theories have been proposed in an attempt to provide plausible explanations of the conflicting findings regarding hemispheric specialisation in processing prosodic structures. Aims : The purpose of this study was to examine one of the theories, the functional lateralisation theory, through four experiments that altered the linguistic and nonlinguistic functions across a range of prosodic structures. Methods & Procedures : Three groups of subjects participated in each of the four experiments: (1) eight subjects with LHD, (2) eight subjects with RHD, and (3) eight control subjects. The first experiment addressed the extent to which the processing of lexical stress differences would be lateralised to the left or right hemisphere by requiring listeners to determine the meanings and grammatical assignments of two-syllable words conveyed through stressed or unstressed syllables. In another linguistic condition, the second experiment placed demands on syntactic parsing operations by requiring listeners to parse syntactically ambiguous sentences which were disambiguated through the perception of prosodic boundaries located at syntactic junctures. A third linguistic condition required listeners to determine the categorical assignment of a speaker's intention of making a statement or asking a question conveyed through the prosodic structures. The fourth experiment was designed to determine hemispheric lateralisation in processing nonlinguistic prosodic structures. In this experiment, listeners were required to determine the emotional state of a speaker conveyed through the prosodic structures in sentences that contained semantic information which was either congruent or incongruent with the emotional content of the prosodic structures. Results : When subjects were asked to identify lexical stress differences (Experiment 1), syntactically ambiguous sentences (Experiment 2), and questions and statements (Experiment 3) conveyed through prosody, the LHD group demonstrated a significantly poorer performance than the control and RHD groups. When asked to identify emotions conveyed through prosody (Experiment 4), the RHD group demonstrated a significantly poorer performance than the control and LHD groups. Conclusion : These findings support the functional lateralisation theory that proposes a left hemisphere dominance for processing linguistic prosodic structures and a right hemisphere dominance for processing nonlinguistic prosodic structures.     

Syntactic and semantic modulation of neural activity during auditory sentence comprehension

In previous functional neuroimaging studies, left anterior temporal and temporal-parietal areas responded more strongly to sentences than to randomly ordered lists of words. The smaller response for word lists could be explained by either (1) less activation of syntactic processes due to the absence of syntactic structure in the random word lists or (2) less activation of semantic processes resulting from failure to combine the content words into a global meaning. To test these two explanations, we conducted a functional magnetic resonance imaging study in which word order and combinatorial word meaning were independently manipulated during auditory comprehension. Subjects heard six different stimuli: normal sentences, semantically incongruent sentences in which content words were randomly replaced with other content words, pseudoword sentences, and versions of these three sentence types in which word order was randomized to remove syntactic structure. Effects of syntactic structure (greater activation to sentences than to word lists) were observed in the left anterior superior temporal sulcus and left angular gyrus. Semantic effects (greater activation to semantically congruent stimuli than either incongruent or pseudoword stimuli) were seen in widespread, bilateral temporal lobe areas and the angular gyrus. Of the two regions that responded to syntactic structure, the angular gyrus showed a greater response to semantic structure, suggesting that reduced activation for word lists in this area is related to a disruption in semantic processing. The anterior temporal lobe, on the other hand, was relatively insensitive to manipulations of semantic structure, suggesting that syntactic information plays a greater role in driving activation in this area.     

Effects of Prosodic and Semantic Cues on Facial Emotion Recognition in Relation to Autism-Like Traits

The current study investigated whether those with higher levels of autism-like traits process emotional information from speech differently to those with lower levels of autism-like traits. Neurotypical adults completed the autism-spectrum quotient and an emotional priming task. Vocal primes with varied emotional prosody, semantics, or a combination, preceded emotional target faces. Prime-target pairs were congruent or incongruent in their emotional content. Overall, congruency effects were found for combined prosody-semantic primes, however no congruency effects were found for semantic or prosodic primes alone. Further, those with higher levels of autism-like traits were not influenced by the prime stimuli. These results suggest that failure to integrate emotional information across modalities may be characteristic of the broader autism phenotype.     

The contribution of semantic memory to the recognition of basic emotions and emotional valence: Evidence from the semantic variant of primary progressive aphasia

ABSTRACT

There is compelling evidence that semantic memory is involved in emotion recognition. However, its contribution to the recognition of emotional valence and basic emotions remains unclear. We compared the performance of 10 participants with the semantic variant of primary progressive aphasia (svPPA), a clinical model of semantic memory impairment, to that of 33 healthy participants using three experimental tasks assessing the recognition of: 1) emotional valence conveyed by photographic scenes, 2) basic emotions conveyed by facial expressions, and 3) basic emotions conveyed by prosody sounds. Individuals with svPPA showed significant deficits in the recognition of emotional valence and basic emotions (except happiness and surprise conveyed by facial expressions). However, the performance of the two groups was comparable when the performance on tests assessing semantic memory was added as a covariate in the analyses. Altogether, these results suggest that semantic memory contributes to the recognition of emotional valence and basic emotions. By examining the recognition of emotional valence and basic emotions in individuals with selective semantic memory loss, our results contribute to the refinement of current theories on the role of semantic memory in emotion recognition.