Wiltrud Fassbinder

Coarse coding and discourse comprehension in adults with right hemisphere brain damage

Background: Various investigators suggest that some discourse‐level comprehension difficulties in adults with right hemisphere brain damage (RHD) have a lexical‐semantic basis. As words are processed, the intact right hemisphere arouses and sustains activation of a wide‐ranging network of secondary or peripheral meanings and features—a phenomenon dubbed “coarse coding”. Coarse coding impairment has been postulated to underpin some prototypical RHD comprehension deficits, such as difficulties with nonliteral language interpretation, discourse integration, some kinds of inference generation, and recovery when a reinterpretation is needed. To date, however, no studies have addressed the hypothesised link between coarse coding deficit and discourse comprehension in RHD. Aims: The current investigation examined whether coarse coding was related to performance on two measures of narrative comprehension in adults with RHD. Methods & Procedures: Participants were 32 adults with unilateral RHD from cerebrovascular accident, and 38 adults without brain damage. Coarse coding was operationalised as poor activation of peripheral/weakly related semantic features of words. For the coarse coding assessment, participants listened to spoken sentences that ended in a concrete noun. Each sentence was followed by a spoken target phoneme string. Targets were subordinate semantic features of the sentence‐final nouns that were incompatible with their dominant mental representations (e.g., “rotten” for apple). Targets were presented at two post‐noun intervals. A lexical decision task was used to gauge both early activation and maintenance of activation of these weakly related semantic features. One of the narrative tasks assessed comprehension of implied main ideas and details, while the other indexed high‐level inferencing and integration. Both comprehension tasks were presented auditorily. For all tasks, accuracy of performance was the dependent measure. Correlations were computed within the RHD group between both the early and late coarse coding measures and the two discourse measures. Additionally, ANCOVA and independent t‐tests were used to compare both early and sustained coarse coding in subgroups of good and poor RHD comprehenders. Outcomes & Results: The group with RHD was less accurate than the control group on all measures. The finding of coarse coding impairment (difficulty activating/sustaining activation of a words peripheral features) may appear to contradict prior evidence of RHD suppression deficit (prolonged activation for context‐inappropriate meanings of words). However, the sentence contexts in this study were unbiased and thus did not provide an appropriate test of suppression function. Correlations between coarse coding and the discourse measures were small and nonsignificant. There were no differences in coarse coding between RHD comprehension subgroups on the high‐level inferencing task. There was also no distinction in early coarse coding for subgroups based on comprehension of implied main ideas and details. But for these same subgroups, there was a difference in sustained coarse coding. Poorer RHD comprehenders of implied information from discourse were also poorer at maintaining activation for semantically distant features of concrete nouns. Conclusions: This study provides evidence of a variant of the postulated link between coarse coding and discourse comprehension in RHD. Specifically, adults with RHD who were particularly poor at sustaining activation for peripheral semantic features of nouns were also relatively poor comprehenders of implied information from narratives.

A different story on “Theory of Mind” deficit in adults with right hemisphere brain damage

Background: Difficulties in social cognition and interaction can characterise adults with unilateral right hemisphere brain damage (RHD). Some pertinent evidence involves their apparently poor reasoning from a “Theory of Mind” perspective, which requires a capacity to attribute thoughts, beliefs, and intentions in order to understand other peoples behaviour. Theory of Mind is typically assessed with tasks that induce conflicting mental representations. Prior research with a commonly used text task reported that adults with RHD were less accurate in drawing causal inferences about mental states than at making non‐mental‐state causal inferences from control texts. However, the Theory of Mind and control texts differed in the number and nature of competing discourse entity representations. This stimulus discrepancy, together with the explicit measure of causal inferencing, likely put the adults with RHD at a disadvantage on the Theory of Mind texts. This project was supported in part by grant # DC01820 from the National Institute on Deafness and Other Communicative Disorders. The authors are indebted to Denise Balason, Meghan Capellini, Bethany Peters, Anita Lewis, Sara Byers, and Annie Palaika for their assistance. Aims: This study revisited the question of Theory of Mind deficit in adults with RHD. The aforementioned Theory of Mind texts were used but new control texts were written to address stimulus discrepancies, and causal inferencing was assessed relatively implicitly. Adults with RHD were hypothesised not to display a Theory of Mind deficit under these conditions. Methods & Procedures: The participants were 22 adults with unilateral RHD from cerebrovascular accident, and 38 adults without brain damage. Participants listened to spoken texts that targeted either mental‐state or non‐mental‐state causal inferences. Each text was followed by spoken True/False probe sentences, to gauge target inference comprehension. Both accuracy and RT data were recorded. Data were analysed with mixed, two‐way Analyses of Variance (Group by Text Type). Outcomes & Results: There was a main effect of Text Type in both accuracy and RT analyses, with a performance advantage for the Theory of Mind/mental‐state inference stimuli. The control group was faster at responding, and primed more for the target inferences, than the RHD group. The overall advantage for Theory of Mind texts was traceable to one highly conventional inference: someone tells a white lie to be polite. Particularly poor performance in mental‐state causal inferencing was not related to neglect or lesion site for the group with RHD. Conclusions: With appropriate stimulus controls and a relatively implicit measure of causal inferencing, this study found no “Theory of Mind” deficit for adults with RHD. The utility of the “Theory of Mind” construct is questioned. A better understanding of the social communication difficulties of adults with RHD will enhance clinical management in the future.

Activation and maintenance of peripheral semantic features of unambiguous words after right hemisphere brain damage in adults

Background: The right cerebral hemisphere (RH) sustains activation of subordinate, secondary, less common, and/or distantly related meanings of words. Much of the pertinent data come from studies of homonyms, but some evidence also suggests that the RH has a unique maintenance function in relation to unambiguous nouns. In a divided visual field priming study, Atchley, Burgess, and Keeney (1999) reported that only left visual field/RH presentation yielded evidence of continuing activation of peripheral semantic features that were incompatible with the most common image or representation of their corresponding nouns (e.g., rotten for “apple”). Activation for weakly related features that were compatible with the dominant representation (e.g., crunchy) was sustained over time regardless of the visual field/hemisphere of initial stimulus input. Several studies report that unilateral right hemisphere brain damage (RHD) in adults affects the RHs meaning maintenance function, but this work also has centred on homonyms, and/or more recently metonymic and metaphoric polysemous words. Aims: The current investigation examined whether RHD deficits in processing secondary and/or distantly related meanings of words, typically observed in studies of homonyms, would extend to peripheral, weakly related semantic features of unambiguous nouns. Methods & Procedures: Participants were 28 adults with unilateral RHD from cerebrovascular accident, and 38 adults without brain damage. Participants listened to spoken sentences that ended with an unambiguous noun. Each sentence was followed by a spoken target phoneme string. Targets included peripheral semantic features of the sentence‐final noun that were either compatible or incompatible with the dominant mental images of the noun, and were presented at two intervals after that noun. A lexical decision task was used to gauge both the early activation and maintenance of activation for these weakly related semantic features. Outcomes & Results: Accuracy data demonstrated activation (priming) for both types of peripheral features, in both groups, shortly after presentation of the corresponding noun. Neither group evidenced continuing activation for either type of feature at a longer interval. These results are interpreted as reflecting rapid decay/poor maintenance of activation for distantly related features for both groups. The lack of a biasing context, however, did not provide an appropriate test for previously reported suppression deficits after RHD. Fast decay of activation of compatible semantic features was unexpected for the control group. Adults with RHD were less accurate than the control group at both test intervals for the features that are semantically more distant from their associated nouns (Related‐incompatible features). Accordingly, it is argued that the RHD groups poor maintenance of activation for these features reflects a deficit, rather than normal performance. The interpretation of results from this study is complicated by the lack of RT priming for either type of semantic feature, and for either participant group. Conclusions: The right cerebral hemisphere appears to be necessary for activating semantic features that are particularly distantly related to their corresponding lexical items, and for sustaining activation of these features in the absence of a biasing context. Because lexical processing has been linked with discourse comprehension for adults with RHD, more work in this area should enhance clinical management in the future.

Reliability and Validity of the Computerized Revised Token Test: Comparison of Reading and Listening Versions in Persons With and Without Aphasia

PURPOSE This study assessed the reliability and validity of intermodality associations and differences in persons with aphasia (PWA) and healthy controls (HC) on a computerized listening and 3 reading versions of the Revised Token Test (RTT; McNeil & Prescott, 1978). METHOD Thirty PWA and 30 HC completed the test versions, including a complete replication. Reading versions varied according to stimulus presentation method: (a) full-sentence presentation, (b) self-paced word-by-word full-sentence construction, and (c) self-paced word-by-word presentation with each word removed with the onset of the next word. Participants also received tests of aphasia and reading severity. RESULTS The listening version produced higher overall mean scores than each of the reading versions. Differences were small and within 1 standard error of measurement of each version. Overall score test-retest reliability among versions for PWA ranged from r=.89 to r=.97. Correlations between the listening and reading versions ranged from r=.79 to r=.85. All versions correlated highly with aphasia and reading severity. Correlations were generally low for the HC due to restricted variability. Factor analysis yielded a 2-factor solution for PWA and a single-factor for HC. CONCLUSIONS Intermodality differences were small, and all 4 versions were reliable, concurrently valid, and sensitive to similar linguistic processing difficulties in PWA.

Characterising comprehension difficulties after right brain damage: Attentional demands of suppression function

Background: Comprehension deficits that typify adults with right brain damage (RBD) have been linked to considerations of processing capacity and processing demands, as well as to ineffective suppression of mental activation that is incompatible with a contextually intended interpretation. Aims: As a first step in investigating how processing resource factors and more specific difficulties like suppression deficits interact to yield characteristic RBD comprehension patterns, the current study was designed to assess whether suppression function consumes attention. Methods & Procedures: A total of 28 RBD and 22 non-brain-damaged adults listened to sentence stimuli that biased the meaning of a sentence-final lexical ambiguity (e.g., “spade”). The suppression task involved speeded judgements of whether a subsequent spoken probe word fitted the overall sentence meaning. In experimental stimuli, the probe word (e.g., “cards”) was unrelated to the biased meaning of the ambiguity. Comparison stimuli ended in an unambiguous word (e.g., “shovel”) that was clearly unrelated to the spoken probe. Thus, slowness after an experimental sentence, relative to its comparison sentence, indicated that the contextually inappropriate meaning of the experimental ambiguity interfered with the probesentence relatedness judgement (i.e., had not been suppressed). In two dual-task conditions, participants allocated 20% or 50% of their “brain power” to a concurrent secondary task, reporting orally whether the probe word consisted of one or two syllables. Outcomes & Results: For both groups, suppression of contextually unintended meanings of lexical ambiguities was more effective in a single-task condition than when attention was shared with a secondary task. The secondary syllable-counting task also suffered when allocated less attention. Conclusions: Effective suppression consumes finite processing capacity. As elaborated in the paper, several combinations of these variables could underlie relatively good and poor comprehension after RBD. Researchers and clinicians need to keep in mind such potential interactions of ineffective comprehension mechanisms, stimulus/task processing demands, and processing capacity.

Hemispheric differences in word meaning processing: Alternative interpretations of current evidence

Background: Drawing heavily on results from studies with divided visual field (dvf) presentation, current models of hemispheric differences in word semantic processing converge on a proposal (henceforth, “the standard model”) that is increasingly being applied in studies of individuals with brain damage. According to this model, left hemisphere processes focus word meanings to their core, whereas right hemisphere processes keep wider representations active. Aims: This paper has three aims: (a) to raise concerns about methodological aspects of the dvf studies that are usually cited in support for the standard model, specifically assumptions about interpretation of lateral dvf prime presentation and priming measures; (b) to highlight areas of further research and theoretical clarification, with reference to studies with central presentation and general models of word‐meaning processing; and (c) to discuss the implications of these concerns for deriving a model of hemispheric differences in word‐meaning processing, using evidence from paired word priming studies as an example. Main Contribution: The paper discusses problematic assumptions about paired word priming studies of hemispheric contributions to word semantic processing and proposes further research to clarify these assumptions. Furthermore, it introduces an alternative interpretation of the available data, which provides a more parsimonious account of hemispheric engagement in the paired word semantic priming task. Conclusions: Current evidence about hemispheric differences in word‐meaning processing is far from conclusive. It is important to consider alternative interpretations of the available evidence when applying models based on this evidence to the study of language disorders. The alternative account proposed in this paper suggests that LH processing, rather than generally reducing activated word meanings to their core, is important for maintaining meanings that are unambiguous and consistent.

Real-time Processing in Reading Sentence Comprehension for Normal Adult Individuals and Persons with Aphasia

Background: Persons with aphasia (PWA) have shown difficulties in integrating linguistic materials over time and distance in sentence processing. However, few studies have investigated sentence-processing difficulties among PWA as reflected in online processing measures. Furthermore, relatively few studies have examined the online processing of syntactically simple but computationally demanding sentences among PWA. Such sentences are important from the perspective of resource-related theories of aphasic language deficits, which predict that such sentences should be challenging for PWA even if the syntactic structures involved are not. Aims: The purpose of the study was to investigate the sentence-level online reading times of normal adult individuals (NAI) and PWA by word category and as a function of adjective padding. It was assumed that head nouns entail greater processing costs than determiners because they represent the point at which integration of material within a noun phrase must take place. It was also assumed that increasing adjectival padding within a noun phrase requires more integration and creates greater processing costs. Methods & Procedures: A total of 30 NAI and 30 PWA participated in the current study. Sentence stimuli were obtained from the Computerised Revised Token Test (CRTT) (McNeil et al., 2008). Sentences were presented using a non-cumulative (Word Fade = WF) self-paced word-by-word reading method (CRTT-R-WF). Reading times for the determiners and the correct nouns were analysed. Outcomes & Results: Both groups showed significantly longer reading times for the nouns than for determiners and in two-adjective than in one-adjective conditions. Furthermore, the reading times for the two-adjective condition were significantly longer than the one-adjective condition for nouns but not determiners across the groups. The PWA exhibited significantly longer overall reading times, as well as significantly longer reading times on the nouns than the NAI. Conclusions: Increased linguistic integration costs—imposed by greater amounts of material to be integrated, and appearing at the point where integration must take place—differentiated reading-time performance between the NAI and PWA participant groups. The PWA showed differentially longer online processing times for elements that imposed high integration costs. This difference appeared most dramatically when two adjectives intervened between the determiner and the head noun. The current results are consistent with resource-related hypotheses regarding aphasic language deficits, which suggest that PWA with limited control of processing resources should show differentially greater impairments in sentence processing as compared to NAI.

Slowed lexical-semantic activation in individuals with right hemisphere brain damage?

This study investigated whether prolonged interference from contextually inappropriate semantic activation after right hemisphere damage (RHD) could be related to a slowing of lexical-semantic activation. A total of 9 adults with RHD and 8 non-brain-damaged adults judged whether auditory probe words fit the overall meaning of sentence stimuli that were biased to one interpretation of a sentence-final lexical ambiguity. Probes, presented at 0 and 1000 ms interstimulus intervals (ISI), represented the contextually inappropriate meanings of the ambiguities. At 0 ms ISI, the control group was predicted to show interference from these contextually inappropriate meanings, but if lexical activation was slowed for RHD participants, no interference would be expected. Although the previous finding of prolonged interference at 1000 ms ISI (Tompkins, Baumgaertner, Lehman, & Fassbinder, 2000) was replicated for the RHD group, neither group showed interference at 0 ms ISI. Potential accounts for these results relate to the possibility of slowed activation in normal ageing, and/ or the effects of strategic processing.