Presentations

Abstract

Theories of reading propose that the quality of word form representations affects reading comprehension. One claim is that synchronous retrieval of orthographic and phonological representations leads to better performance than asynchronous retrieval. Based on this account, one may hypothesize that synchronous rather than asynchronous presentation of orthographic and phonological forms should be beneficial when establishing the mapping between both, as it should lead to tighter couplings. We tested this hypothesis in two multi-session experiments, where participants studied isolated words of a tonal language unknown to them, Chinese. During study, written (using Pinyin transcription) and spoken word forms were presented simultaneously or in asynchronous fashion (audio-first, written-first). In both experiments, we observed an advantage for asynchronous over synchronous presentation at test, with audio-first presentation being most beneficial. These results suggest that the timing of written and spoken word forms has profound effects on the ease of learning a new tonal language.

Abstract

Reading functions beyond early visual precessing are known to be lateralized to the left hemisphere, but how left-lateralization arises during literacy acquisition is an open question. Bilateral processing or rightward asymmetries have previously been associated with developmental dyslexia. However, it is unclear at present to what extent this lack of left-lateralization reflects differences in reading ability. In this study, a group of illiterate adults in rural India (N=29) participated in a literacy training program over the course of six months. fMRI measures were obtained before and after training on a number of different visual stimulus categories, including written sentences, false fonts, and object categories such as houses and faces. This training group was matched on demographic and socioeconomic variables to an illiterate no-training group and to low- and highly-literate control groups, who were also scanned twice but received no training (total N=90). In a cross-sectional analysis before training, reading ability was positively correlated with increased BOLD responses in a left-lateralized network including the dorsal and ventral visual streams for text and false fonts, but not for other types of visual stimuli. A longitudinal analysis of learning effects in the training group showed that beginning readers engage bilateral networks more than proficient readers. Lateralization of BOLD responses was further examined by calculating laterality indices in specific regions. We observed training-related changes in lateralization for processing written stimuli in a number of subregions in the dorsal and ventral visual streams, as well as in the cerebellum. Together with the cross-sectional results, these data suggest a causal relationship between reading ability and the degree of hemispheric asymmetry in processing written materials.

Abstract

INTRODUCTION fMRI findings have revealed the important insight that literacy-related learning triggers cognitive adaptation mechanisms manifesting themselves in increased BOLD responses during print processing tasks (Brem et al., 2010; Carreiras et al., 2009; Dehaene et al., 2010). It remains elusive, however, if the cortical plasticity effects of reading acquisition also lead to an intrinsic functional reorganization of neural circuits. METHODS Here, we used resting-state fMRI as a measure of domain-specific spontaneous neuronal activity to capture the impact of reading acquisition on the functional connectome (Honey et al., 2007; Lohmann et al., 2010; Raichle et al., 2001). In a controlled longitudinal intervention study, we taught 21 illiterate adults from Northern India for 6 months how to read Hindi scripts and compared their resting-state fMRI data with those acquired from a sample of 9 illiterates, matched for demographic and socioeconomic variables, that did not undergo such instruction. RESULTS Initially, we investigated at the whole-brain level, if the experience of becoming literate modifies network nodes of spontaneous hemodynamic activity. Therefore, we compared training-related differences in the degree centrality of BOLD signals between the groups (Zuo et al., 2012). A significant group by time interaction (tmax = 4.17, p < 0.005, corrected for cluster size) was found in a cluster extending from the right superior colliculus of the brainstem (+6, -30, -3) to the bilateral pulvinar nuclei of the thalamus (+6, -18, -3; -6, -21, -3). This interaction was characterized by a significant mean degree centrality increase in the trained group (t(1,20) = 8.55, p < 0.001) that did not appear in the untrained group which remained at its base level (t(1,8) = 0.14, p = 0.893). The cluster obtained from the degree centrality analysis was then used as a seed region in a voxel-wise functional connectivity analysis (Biswal et al., 1995). A significant group by time interaction (tmax = 4.45, p < 0.005, corrected for cluster size) emerged in the right occipital cortex (+24, -81, +15; +24, -93, +12; +33, -90, +3). The cortico-subcortical mean functional connectivity got significantly stronger in the group that took part in the reading program (z = 3.77, p < 0.001) but not in the group that remained illiterate (z = 0.77, p = 0.441). Individual slopes of cortico-subcortical connectivity were significantly associated with the improvement in letter knowledge (r = 0.40, p = 0.014) and with the improvement word reading ability (r = 0.38, p = 0.018). CONCLUSION Intrinsic hemodynamic activity changes driven by literacy occurred in subcortical low-level relay stations of the visual pathway and their functional connections to the occipital cortex. Accordingly, the visual system of beginning readers appears to go through fundamental modulations at earlier processing stages than suggested by previous event-related fMRI experiments. Our results add a new dimension to current concepts of the brain basis of reading and raise novel questions regarding the neural origin of developmental dyslexia.

Abstract

The notion that processing spoken (object) words involves activation of category-specific representations in visual cortex is a key prediction of modality-specific theories of representation that contrasts with theories assuming dedicated conceptual representational systems abstracted away from sensorimotor systems. Although some neuroimaging evidence is consistent with such a prediction (Desai et al., 2009; Hwang et al., 2009; Lewis & Poeppel, 2014), these findings do not tell us much about the nature of the representations that were accessed. In the present study, we directly tested whether low-level visual cortex is involved in spoken word processing. Using continuous flash suppression we show that spoken words activate behaviorally relevant low-level visual representations and pin down the time-course of this effect to the first hundreds of milliseconds after word onset. We investigated whether participants (N=24) can detect otherwise invisible objects (presented for 400ms) when they are presented with the corresponding spoken word 200ms before the picture appears. We implemented a design in which all cue words appeared equally often in picture-present (50%) and picture-absent trials (50%). In half of the picture-present trials, the spoken word was congruent with the target picture ("bottle" -> picture of a bottle), while on the other half it was incongruent ("bottle" -> picture of a banana). All picture stimuli were evenly distributed over the experimental conditions to rule out low-level differences that can affect detectability regardless of the prime words. Our results showed facilitated detection for congruent vs. incongruent pictures in terms of hit rates (z=-2.33, p=0.02) and d'-scores (t=3.01, p<0.01). A second experiment (N=33) investigated the time-course of the effect by manipulating the timing of picture presentation relative to word onset and revealed that it arises as soon as 200-400ms after word onset and decays at around word offset. Together, these data strongly suggest that spoken words can rapidly activate low-level category-specific visual representations that affect the mere detection of a stimulus, i.e. what we see. More generally our findings fit best with the notion that spoken words activate modality-specific visual representations that are low-level enough to provide information related to a given token and at the same time abstract enough to be relevant not only for previously seen tokens (a signature of episodic memory) but also for generalizing to novel exemplars one has never seen before.

Abstract

The notion that processing spoken (object) words involves activation of category-specific representations in visual cortex is a key prediction of modality-specific theories of representation that contrasts with theories assuming dedicated conceptual representational systems abstracted away from sensorimotor systems. Although some neuroimaging evidence is consistent with such a prediction (Desai et al., 2009; Hwang et al., 2009; Lewis & Poeppel, 2014), these findings do not tell us much about the nature of the representations that were accessed. In the present study, we directly tested whether low-level visual cortex is involved in spoken word processing. Using continuous flash suppression we show that spoken words activate behaviorally relevant low-level visual representations and pin down the time-course of this effect to the first hundreds of milliseconds after word onset. We investigated whether participants (N=24) can detect otherwise invisible objects (presented for 400ms) when they are presented with the corresponding spoken word 200ms before the picture appears. We implemented a design in which all cue words appeared equally often in picture-present (50%) and picture-absent trials (50%). In half of the picture-present trials, the spoken word was congruent with the target picture ("bottle" -> picture of a bottle), while on the other half it was incongruent ("bottle" -> picture of a banana). All picture stimuli were evenly distributed over the experimental conditions to rule out low-level differences that can affect detectability regardless of the prime words. Our results showed facilitated detection for congruent vs. incongruent pictures in terms of hit rates (z=-2.33, p=0.02) and d'-scores (t=3.01, p<0.01). A second experiment (N=33) investigated the time-course of the effect by manipulating the timing of picture presentation relative to word onset and revealed that it arises as soon as 200-400ms after word onset and decays at around word offset. Together, these data strongly suggest that spoken words can rapidly activate low-level category-specific visual representations that affect the mere detection of a stimulus, i.e. what we see. More generally our findings fit best with the notion that spoken words activate modality-specific visual representations that are low-level enough to provide information related to a given token and at the same time abstract enough to be relevant not only for previously seen tokens (a signature of episodic memory) but also for generalizing to novel exemplars one has never seen before.

Abstract

Current cognitive models of spoken word recognition and comprehension are underspecified with respect to when and how multimodal information interacts. We compare two computational models both of which permit the integration of concurrent information within linguistic and non-linguistic processing streams, however their architectures differ critically in the level at which multimodal information interacts. We compare the predictions of the Multimodal Integration Model (MIM) of language processing (Smith, Monaghan & Huettig, 2014), which implements full interactivity between modalities, to a model in which interaction between modalities is restricted to lexical representations which we represent by an extended multimodal version of the TRACE model of spoken word recognition (McClelland & Elman, 1986). Our results demonstrate that previous visual world data sets involving phonological onset similarity are compatible with both models, whereas our novel experimental data on rhyme similarity is able to distinguish between competing architectures. The fully interactive MIM system correctly predicts a greater influence of visual and semantic information relative to phonological rhyme information on gaze behaviour, while by contrast a system that restricts multimodal interaction to the lexical level overestimates the influence of phonological rhyme, thereby providing an upper limit for when information interacts in multimodal tasks

Abstract

Current cognitive models of spoken word recognition and comprehension are underspecified with respect to when and how multimodal information interacts. We compare two computational models both of which permit the integration of concurrent information within linguistic and non-linguistic processing streams, however their architectures differ critically in the level at which multimodal information interacts. We compare the predictions of the Multimodal Integration Model (MIM) of language processing (Smith, Monaghan & Huettig, 2014), which implements full interactivity between modalities, to a model in which interaction between modalities is restricted to lexical representations which we represent by an extended multimodal version of the TRACE model of spoken word recognition (McClelland & Elman, 1986). Our results demonstrate that previous visual world data sets involving phonological onset similarity are compatible with both models, whereas our novel experimental data on rhyme similarity is able to distinguish between competing architectures. The fully interactive MIM system correctly predicts a greater influence of visual and semantic information relative to phonological rhyme information on gaze behaviour, while by contrast a system that restricts multimodal interaction to the lexical level overestimates the influence of phonological rhyme, thereby providing an upper limit for when information interacts in multimodal tasks.

Abstract

Prominent theories of predictive language processing assume that language production processes are used to anticipate upcoming linguistic input during comprehension (Dell & Chang, 2014; Pickering & Garrod, 2013). Here, we explored the converse case: Does a task set including production in addition to comprehension encourage prediction, compared to a task only including comprehension? To test this hypothesis, participants carried out a cross-modal naming task (Exp 1a), a self-paced reading task (Exp1 b) that did not include overt production, and a task (Exp 1c) in which naming and reading trials were evenly interleaved. We used the same predictable (N = 40) and non-predictable (N = 40) sentences in all three tasks. The sentences consisted of a fixed agent, a transitive verb and a predictable or non-predictable target word (The man breaks a glass vs. The man borrows a glass). The mean cloze probability in the predictable sentences was .39 (ranging from .06 to .8; zero in the non-predictable sentences). A total of 162 volunteers took part in the experiment which was run in a between-participants design. In Exp 1a, fifty-four participants listened to recordings of the sentences which ended right before the spoken target word. Coinciding with the end of the playback, a picture of the target word was shown which the participants were asked to name as fast as possible. Analyses of their naming latencies revealed a statistically significant naming advantage of 108 ms on predictable over non-predictable trials. Moreover, we found that the objects’ naming advantage was predicted by the target words’ cloze probability in the sentences (r = .347, p = .038). In Exp 1b, 54 participants were asked to read the same sentences in a self-paced fashion. To allow for testing of potential spillover effects, we added a neutral prepositional phrase (breaks a glass from the collection/borrows a glass from the neighbor) to each sentence. The sentences were read word-by-word, advancing by pushing the space bar. On 30% of the trials, comprehension questions were used to keep up participants' focus on comprehending the sentences. Analyses of their spillover region reading times revealed a numerical advantage (8 ms; tspillover = -1.1, n.s.) in the predictable as compared to the non-predictable condition. Importantly, the analysis of participants' responses to the comprehension questions, showed that they understood the sentences (mean accuracy = 93%). In Exp 1c, the task comprised 50% naming trials and 50% reading trials which appeared in random order. Fifty-four participants named and read the same objects and sentences as in the previous versions. The results showed a naming advantage on predictable over non-predictable items (99 ms) and a positive correlation between the items’ cloze probability and their naming advantage (r = .322, p = .055). Crucially, the post-target reading time analysis showed that with naming trials and reading trials interleaved, there was also a statistically reliable prediction effect on reading trials. Participants were 19 ms faster at reading the spillover region on predictable relative to non-predictable items (tspillover = -2.624). To summarize, although we used the same sentences in all sub-experiments, we observed effects of prediction only when the task set involved production. In the reading only experiment (Exp 1b), no evidence for anticipation was obtained although participants clearly understood the sentences and the same sentences yielded reading facilitation when interleaved with naming trials (Exp 1c). This suggests that predictive language processing can be modulated by the comprehenders’ task set. When the task set involves language production, as is often the case in natural conversation, comprehenders appear to engage in prediction to a stronger degree than in pure comprehension tasks. In our discussion, we will discuss the notion that language production may engage prediction, because being able to predict words another person is about to say might optimize the comprehension process and enable smooth turn-taking.

Abstract

A substantial body of literature has shown that readers and listeners often anticipate information. An open question concerns the mechanisms underlying predictive language processing. Multiple mechanisms have been suggested. One proposal is that comprehenders use event knowledge to predict upcoming words. Other theoretical frameworks propose that predictions are made based on simple word associations. In a recent EEG study, Metusalem and colleagues reported evidence for the modulating influence of event knowledge on prediction. They examined the degree to which event knowledge is activated during sentence comprehension. Their participants read two sentences, establishing an event scenario, which were followed by a final sentence containing one of three target words: a highly expected word, a semantically unexpected word that was related to the described event, or a semantically unexpected and event-unrelated word (see Figure, for an example). Analyses of participants’ ERPs elicited by the target words revealed a three-way split with regard to the amplitude of the N400 elicited by the different types of target: the expected targets elicited the smallest N400, the unexpected and event-unrelated targets elicited the largest N400. Importantly, the amplitude of the N400 elicited by the unexpected but event-related targets was significantly attenuated relative to the amplitude of the N400 elicited by the unexpected and event-unrelated targets. Metusalem et al. concluded that event knowledge is immediately available to constrain on-line language processing. Based on a post-hoc analysis, the authors rejected the possibility that the results could be explained by simple word associations. In the present study, we addressed the role of simple word associations in discourse comprehension more directly. Specifically, we explored the contribution of associative priming to the graded N400 pattern seen in Metusalem et al’s study. We conducted two EEG experiments. In Experiment 1, we reran Metusalem and colleagues’ context manipulation and closely replicated their results. In Experiment 2, we selected two words from the event-establishing sentences which were most strongly associated with the unexpected but event-related targets in the final sentences. Each of the two associates was then placed in a neutral carrier sentence. We controlled that none of the other words in these carrier sentences was associatively related to the target words. Importantly, the two carrier sentences did not build up a coherent event. We recorded EEG while participants read the carrier sentences followed by the same final sentences as in Experiment 1. The results showed that as in Experiment 1 the amplitude of the N400 elicited by both types of unexpected target words was larger than the N400 elicited by the highly expected target. Moreover, we found a global tendency towards the critical difference between event-related and event-unrelated unexpected targets which reached statistical significance only at parietal electrodes over the right hemisphere. Because the difference between event-related and event-unrelated conditions was larger when the sentences formed a coherent event compared to when they did not, our results suggest that associative priming alone cannot account for the N400 pattern observed in our Experiment 1 (and in the study by Metusalem et al.). However, because part of the effect remained, probably due to associative facilitation, the findings demonstrate that during discourse reading both event knowledge activation and simple word associations jointly contribute to the prediction process. The results highlight that multiple mechanisms underlie predictive language processing.