Low-imageability Words Research Articles

Medial temporal lobe amnesia impairs performance on a free association task

A growing body of evidence suggests that the hippocampus contributes to performance (or is implicated) in non-memory domains from perception to problem solving. In a previous study we found that hippocampal contribution to exemplar generation in a fluency task was determined jointly by the open-endedness of the task and its ability to elicit episodic memories (Sheldon and Moscovitch (2012) Hippocampus 22:1451-1466). In the current study, we extend these observations by exploring the role of the hippocampus in generative, goal-directed open-ended thought in patients with medial temporal lobe (MTL) amnesia on a free association task (think of words as they come to mind). Patients and control participants were asked to associate freely for one minute to cue words that varied in the open-endedness of the responses they elicited (greater for low- than high-frequency words), and in the ease with which episodic memories were evoked (greater for high imageable than low imageable words). As predicted, MTL amnesia patients generated fewer words than control participants when cues were highly imageable and low in frequency, but performed equivalently to them in the other conditions. These results support our prediction that the hippocampus contributes to free association, and possibly more generally to other generative tasks that are open-ended, creative, or that elicit the use of contextual and likely episodic memories in order to derive relevant information.

Neural networks underlying contributions from semantics in reading aloud

Reading is an essential part of contemporary society, yet much is still unknown about the physiological underpinnings of its information processing components. Two influential cognitive models of reading, the connectionist and dual-route cascaded models, offer very different accounts, yet evidence for one or the other remains equivocal. These models differ in several ways, including the role of semantics (word meaning) in mapping spelling to sound. We used a new effective connectivity algorithm, IMaGES, to provide a network-level perspective on these network-level models. Left hemisphere regions of interest were defined based on main effects in functional magnetic resonance imaging and included two regions linked with semantic processing—angular gyrus (AG) and inferior temporal sulcus (ITS)—and two regions linked with phonological processing—posterior superior temporal gyrus (pSTG) and posterior middle temporal gyrus (pMTG). Participants read aloud words of high or low spelling-sound consistency, word frequency, and imageability. Only the connectionist model predicted increased contributions from semantic areas with those computing phonology for low-consistency words. Effective connectivity analyses revealed that areas supporting semantic processing (e.g., the ITS) interacted with phonological areas (e.g., the pSTG), with the pattern changing as a function of word properties. Connectivity from semantic to phonological areas emerged for high- compared to low-imageability words, and a similar pattern emerged for low-consistency words, though only under certain conditions. Analyses of individual differences also showed that variation in the strength of modulation of ITS by AG was associated with reading aloud performance. Overall, these results suggest that connections with semantic processing areas are not only associated with reading aloud, but that these connections are also associated with optimal reading performance.

In search of meaning: Semantic effects on past-tense inflection

Within single-mechanism connectionist models of inflectional morphology, generating the past-tense form of a verb depends upon the interaction of semantic and phonological representations, with semantic information being particularly important for irregular or exception verbs. We assessed this hypothesis in two experiments requiring normal speakers to produce the past tense from a verb stem that takes a regular or exceptional past tense. Experiment 1 revealed significant latency advantages for high- over low-imageability words for both regular verbs (e.g., "lunged" faster than "loved") and exception items (e.g., "drank" faster than "dealt"); but critically, this effect was significantly larger for exceptions than for regulars. Experiment 2 employed a semantic priming paradigm where participants inflected verb stems (e.g., sit) preceded by related (e.g., chair) or unrelated primes (e.g., jug) and revealed a priming effect in accuracy that was confined to the exception items. Our results are consistent with predictions from single-mechanism connectionist models of inflectional morphology and converge with findings from neurological patients and studies of reading aloud.

Encoding of physics concepts: concreteness and presentation modality reflected by human brain dynamics.

Previous research into working memory has focused on activations in different brain areas accompanying either different presentation modalities (verbal vs. non-verbal) or concreteness (abstract vs. concrete) of non-science concepts. Less research has been conducted investigating how scientific concepts are learned and further processed in working memory. To bridge this gap, the present study investigated human brain dynamics associated with encoding of physics concepts, taking both presentation modality and concreteness into account. Results of this study revealed greater theta and low-beta synchronization in the anterior cingulate cortex (ACC) during encoding of concrete pictures as compared to the encoding of both high and low imageable words. In visual brain areas, greater theta activity accompanying stimulus onsets was observed for words as compared to pictures while stronger alpha suppression was observed in responses to pictures as compared to words. In general, the EEG oscillation patterns for encoding words of different levels of abstractness were comparable but differed significantly from encoding of pictures. These results provide insights into the effects of modality of presentation on human encoding of scientific concepts and thus might help in developing new ways to better teach scientific concepts in class.

The Interaction of Lexical Semantics and Cohort Competition in Spoken Word Recognition: An fMRI Study

Spoken word recognition involves the activation of multiple word candidates on the basis of the initial speech input--the "cohort"--and selection among these competitors. Selection may be driven primarily by bottom-up acoustic-phonetic inputs or it may be modulated by other aspects of lexical representation, such as a word's meaning [Marslen-Wilson, W. D. Functional parallelism in spoken word-recognition. Cognition, 25, 71-102, 1987]. We examined these potential interactions in an fMRI study by presenting participants with words and pseudowords for lexical decision. In a factorial design, we manipulated (a) cohort competition (high/low competitive cohorts which vary the number of competing word candidates) and (b) the word's semantic properties (high/low imageability). A previous behavioral study [Tyler, L. K., Voice, J. K., & Moss, H. E. The interaction of meaning and sound in spoken word recognition. Psychonomic Bulletin & Review, 7, 320-326, 2000] showed that imageability facilitated word recognition but only for words in high competition cohorts. Here we found greater activity in the left inferior frontal gyrus (BA 45, 47) and the right inferior frontal gyrus (BA 47) with increased cohort competition, an imageability effect in the left posterior middle temporal gyrus/angular gyrus (BA 39), and a significant interaction between imageability and cohort competition in the left posterior superior temporal gyrus/middle temporal gyrus (BA 21, 22). In words with high competition cohorts, high imageability words generated stronger activity than low imageability words, indicating a facilitatory role of imageability in a highly competitive cohort context. For words in low competition cohorts, there was no effect of imageability. These results support the behavioral data in showing that selection processes do not rely solely on bottom-up acoustic-phonetic cues but rather that the semantic properties of candidate words facilitate discrimination between competitors.

Imageability estimates for 3,000 disyllabic words

We provide imageability estimates for 3,000 disyllabic words (as supplementary materials that may be downloaded with the article from www.springerlink.com ). Imageability is a widely studied lexical variable believed to influence semantic and memory processes (see, e.g., Paivio, 1971). In addition, imageability influences basic word recognition processes (Plaut, McClelland, Seidenberg, & Patterson, 1996). In fact, neuroimaging studies have suggested that reading high- and low-imageable words elicits distinct neural activation patterns for the two types e.g., Bedny & Thompson-Schill (Brain and Language 98:127-139, 2006; Graves, Binder, Desai, Conant, & Seidenberg NeuroImage 53:638-646, 2010). Despite the usefulness of this variable, imageability estimates have not been available for large sets of words. Furthermore, recent megastudies of word processing e.g., Balota et al. (Behavior Research Methods 39:445-459, 2007) have expanded the number of words that interested researchers can select according to other lexical characteristics (e.g., average naming latencies, lexical decision times, etc.). However, the dearth of imageability estimates (as well as those of other lexical characteristics) limits the items that researchers can include in their experiments. Thus, these imageability estimates for disyllabic words expand the number of words available for investigations of word processing, which should be useful for researchers interested in the influences of imageability both as an input and as an outcome variable.

Impaired semantic knowledge underlies the reduced verbal short-term storage capacity in Alzheimer's disease

A decrease in verbal short-term memory (STM) capacity is consistently observed in patients with Alzheimer's disease (AD). Although this impairment has been mainly attributed to attentional deficits during encoding and maintenance, the progressive deterioration of semantic knowledge in early stages of AD may also be an important determinant of poor STM performance. The aim of this study was to examine the influence of semantic knowledge on verbal short-term memory storage capacity in normal aging and in AD by exploring the impact of word imageability on STM performance. Sixteen patients suffering from mild AD, 16 healthy elderly subjects and 16 young subjects performed an immediate serial recall task using word lists containing high or low imageability words. All participant groups recalled more high imageability words than low imageability words, but the effect of word imageability on verbal STM was greater in AD patients than in both the young and the elderly control groups. More precisely, AD patients showed a marked decrease in STM performance when presented with lists of low imageability words, whereas recall of high imageability words was relatively well preserved. Furthermore, AD patients displayed an abnormal proportion of phonological errors in the low imageability condition. Overall, these results indicate that the support of semantic knowledge on STM performance was impaired for lists of low imageability words in AD patients. More generally, these findings suggest that the deterioration of semantic knowledge is partly responsible for the poor verbal short-term storage capacity observed in AD.

Testing the associative-link hypothesis in immediate serial recall: Evidence from word frequency and word imageability effects

Two immediate serial recall experiments were conducted to test the associative-link hypothesis (Stuart & Hulme, 2000). We manipulated interitem association by varying the intralist latent semantic analysis (LSA) cosines in our 7-item study word lists, each of which consists of high- or low-frequency words in Experiment 1 and high- or low-imageability words in Experiment 2. Whether item recall performance was scored by a serial-recall or free-recall criterion, we found main effects of interitem association, word imageability, and word frequency. The effect of interitem association also interacted with the word frequency effect, but not with the word imageability effect. The LSA-cosine×word frequency interaction occurred in the recency, but not primacy, portion of the serial position curve. The present findings set explanatory boundaries for the associative-link hypothesis and we argue that both item- and associative-based mechanisms are necessary to account for the word frequency effect in immediate serial recall.

A multiple case study of verbal short‐term memory in velo‐cardio‐facial syndrome

Velo-cardio-facial syndrome (VCFS, 22q11.2 deletion) is characterized by severely delayed language development. The current study explored the integrity of verbal short-term memory (STM), a cognitive function critically involved in language development, in eight children with VCFS. Using a multiple case study design, we presented a series of STM tasks exploring immediate serial recall for word and non-word lists to eight children with VCFS (aged 8-12 years) and to chronological-age-matched control groups. A first task assessed the integrity of phonological coding in verbal STM by comparing recall for phonologically similar and dissimilar words. Subsequently, the interaction between verbal knowledge and STM capacity was investigated by comparing recall for high- and low-imageability words, for high- and low-frequency words, and for words and non-words. A final task assessed short-term serial order recognition for digit sequences. When computing the number of items recalled in the word recall tasks, independently of their serial position, only one child presented consistent difficulties. Short-term recall of non-words was normal in each child. Phonological similarity and verbal knowledge influenced STM performance to a similar extent in children with VCFS and controls. On the other hand, when applying a strict serial recall criterion, difficulties with the word and non-word recall tasks were observed in most children. Half of the patients were also impaired in the serial order recognition task. Despite mild intellectual disability, it is possible for short-term retention capacities for verbal item information to be at an age-appropriate level in VCFS. However, STM for serial order information could be impaired more specifically.

Word imageability affects the hippocampus in recognition memory

Concrete words, whose meanings are readily imagined, are better remembered than abstract words. However, the neural correlates of this effect are poorly understood. Here, we investigated the effect of imageability on brain activity in the medial temporal lobe (MTL) processes underlying recognition memory. We recorded event-related potentials (ERPs) via depth electrodes from within the MTL in 14 patients with drug-resistant epilepsy. Patients performed a continuous word recognition task with words of high and low imageability (controlled for word frequency). Behaviorally, recognition performance was better for high, compared to low, imageable words. Two ERP components associated with recognition memory, the AMTL-N400 and the hippocampal late negative component, showed an old/new effect, but only the hippocampal P600 showed a main effect of imageability. We suggest that the hippocampal effect of imageability in recognition memory may be associated with conceptual or pictorial information processing of concrete words.

Confounds in the distinction between high- and low-imageability words: Phonological, etymological, and morphological differences

Confounds in the distinction between high- and low-imageability words: Phonological, etymological, and morphological differences

Deep dysphasia in Turkish

Deep dysphasia is a language impairment that is defined by impaired repetition. In this study we report a bilingual Turkish-English patient BRB who shows many of the features of deep dysphasia in both languages. BRB was given lexical and non-lexical processing tasks including oral reading, repetition and writing to dictation manipulating several variables (AoA, regularity, imageability, grammatical class) in Turkish (L1) and English (L2). BRB was also asked to translate orally and in writing both high and low frequency and high and low imageability words from L1 to L2 and from L2 to L1. Significant main effects of language and task as well as interactions between language and task were observed e.g., BRB’s repetition, reading and writing was better in L1 than L2 object naming was better in L2 than L1 but only with high imageability words. We argue that impaired language processing in deep dysphasia arises from the under-activation of phonological representations. We propose that current models of deep dysphasia require modification to explain bilingual deep dysphasia and also interpret BRB’s performance using a model of bilingual lexical processing.

Separable effects of priming and imageability on word processing: an ERP study

Concrete, highly imageable words (e.g. banana) are easier to understand than abstract words for which it is difficult to generate an image (e.g. justice). This effect of concreteness or imageability has been taken by some as evidence for the existence of separable verbal- and image-based semantic systems. Instead, however, effects of concreteness may result from better associations to relevant contextual representations for concrete than for abstract words within a single semantic system. In this study, target words of high and low imageability were preceded by supportive (related) or non-supportive (unrelated) context words. The influence of contextual support on the imageability effect was measured by recording event-related brain potentials (ERPs) to the high and low imageable target words in both context conditions. The topographic distributions of the ERPs elicited by the high versus low imageable target words were found to be different, and this effect was independent of contextual support. These data are consistent with the idea that distinct verbal- and image-based semantic codes exist for word representations, and that as a result, concrete words that are highly imageable can be understood more easily.

The contribution of the right cerebral hemisphere to the recovery from aphasia: a single longitudinal case study

We examined the role of the right cerebral hemisphere in the recovery from aphasia of HJ, a 50-year-old right-handed and unilingual man who suffered from severe aphasia caused by an extensive left hemisphere (LH) lesion. He was followed-up over 10 months at 4-month intervals, with a lateralized lexical decision task (LDT), an attentional task, and a language battery. Testing started when HJ was 2 months poststroke. In the LDT, words were presented to central vision or lateralized to the left or right visual hemifield. At each test period, we examined the effect of the degree of imageability (high vs. low), and the grammatical class (noun vs. verb) of the targets on HJ's response times and error rates, with left visual field, right visual field, and central vision presentations. The results of the experiment showed that the pattern obtained with the LDT could not be accounted for by fluctuations in attention. There was an interaction of grammatical class with degree of imageability with left visual field displays only. The right hemisphere (RH) was faster with high-imageability words than with low-imageability words, regardless of their grammatical class. There was also an overall RH advantage on response times at 2 and 6 months after onset. This RH predominance coincided with a major recovery of language comprehension and the observation of semantic paralexias, while no major change in language expression was observed at that point. Ten months after onset, the pattern of lateralization changed, and response times for the LDT with either presentation site were equivalent. This LH improvement coincided with some recovery of language expression at the single-word level. The results of this study suggest that, in cases of severe aphasia caused by extensive LH lesions, the RH may play an important role in the recovery process. Furthermore, these results show that the contribution of the two cerebral hemispheres to recovery may vary overtime and affect specific aspects of language.

Imageability effects, phonological errors, and the relationship between auditory repetition and picture naming: Implications for models of auditory repetition

Hanley and Kay (1997) reported the case of a patient (PS) who showed effects of imageability on tests of auditory repetition, but whose errors were phonological rather than semantic. They argued that this pattern of performance could be explained in terms of a partial impairment to both lexical and nonlexical repetition routes so long as some interaction between the two routes was allowed, consistent with Hillis and Caramazza's (1991) "summation" hypothesis. The present paper investigates the performance of a new patient (MF) who also makes a large number of phonological errors when repeating words of low imageability. MF performs at a similar level to PS on tests of picture naming, but is less impaired than PS when repeating words and nonwords. It is argued that the pattern of performance that MF demonstrates on these and on a wide range of other tests of word production and comprehension can be readily accommodated in terms of the dual-route account of impaired auditory repetition that Hanley and Kay (1997) put forward. However, we argue that it is difficult to explain these patients' performance in terms of models of auditory word repetition that do not incorporate a separate nonlexical repetition route (Dell, Schwartz, Martin, Saffran, & Gagnon, 1997; Foygel & Dell, 2000).

Initial right hemisphere take-over and subsequent bilateral participation during recovery from aphasia

Background: In 1887, Gowers proposed that supplemental action by the right frontal cortex could sustain language following aphasia. Since then, many studies using a wide variety of experimental paradigms have examined the role of the right hemisphere in the recovery from aphasia. Aims: This study examines the right hemisphere's participation in the recovery from aphasia between four and sixteen months following brain damage. Methods & Procedures: RJ, a young woman with severe Broca's aphasia resulting from a left fronto-temporal hematoma, was followed up at four-month intervals with a divided visual field presentation lexical decision task (LDT). At each time of measurement, we examined her performance with high- and low-imageability nouns and verbs, directed to either cerebral hemisphere and in central vision. A language test was used to examine the pattern of language recovery over time, and a non-verbal version of the Stroop test (NVST) served to follow up changes in attention. The results obtained with the LDT and the NVST were analyzed with ANOVAs; the changes in the pattern of language recovery and the results on the attentional task were also considered in the analysis. Outcomes & Results: There was a left visual field advantage with high-imageability words, regardless of their grammatical class, at four months post stroke. The right hemisphere advantage extended to low-imageability words at eight months after aphasia onset. Concurrently, language comprehension tasks made a significant recovery, whereas language expression tasks recovered only slightly. Furthermore, there was no significant improvement on the attentional task within the same time period. One year after the stroke, RJ's pattern of lateralization changed; there was a marginally significant central vision advantage on word processing, and no significant difference in her performance on lateralized presentations. There was a remarkable recovery on oral expression tasks, and some improvement on the attentional task within the same period. Conclusions: The results of the present study indicate that recovery from aphasia may be sustained by both cerebral hemispheres. The participation of either hemisphere may vary with time elapsed. Our results suggest that high-imageability nouns and verbs may constitute a good target for speech therapy during the first months post stroke, in order to benefit from right hemisphere takeover capacities. Furthermore, low imageability nouns and verbs are candidates for right hemisphere takeover as well, if enough time is allowed. Finally, the results of this study suggest that right hemisphere involvement in language recovery may occur in the absence of a concurrent improvement of attention. In line with previous studies, our results indicate that the recovery of oral expression coincides with the improvement of left hemisphere function. Hence, the fact that language expression started to improve one year after the stroke suggests that recovery from a severe language expression deficit is a long process, and may require long-term follow-up.

Recollective experience in individuals with a visual impairment: the role of sensory and conceptual processing

A series of studies was carried out designed to investigate the proposal that visually impaired people tend to encode auditory input primarily in terms of sensory features at the expense of non-sensory semantic features. The first two studies investigated recollective experience in blind adolescents of words that differed in terms of imageability. In Experiment 1 participants were presented with high and low visual imageability words. During the subsequent recognition test they were asked to indicate whether their recognition judgements were based on recollection ("remember" responses) or familiarity ("know" responses). The results indicated that, while the number of remember responses was greater than know responses overall, recollective experience did not interact with imageability. Experiment 2 found the same pattern of performance using words that differed in terms of auditory imageability. Experiment 3 investigated memory for one aspect of sensory input, i.e. voice pitch, by testing recall for whether items had been presented by a male or a female. The results indicated superior performance on the part of individuals with visual impairment relative to sighted controls. Experiment 4 provided evidence that recall in individuals with visual impairment did not differ for semantically related and semantically unrelated words. The overall findings, therefore, were consistent with the view that individuals with visual impairment place more reliance on data-driven than conceptual processing, although the role of introspections of memories needs to be explored further.

Semantic effects as a function of reading skill in word naming of a transparent orthography

The highly transparent Turkish orthography was employed to examine imageability in relation to level of skill in two experiments. In experiment 1, previously skilled readers (n = 24) named 40 high frequency and 40 low frequency words manipulated factorially with imageability. A significant main effect was only found for frequency. In experiment 2, a total of 44 adult Turkish readers (16 very skilled and 28 skilled) named the same stimuli as in experiment 1. The results showed an expected main effect for skill and frequency. However, whilst the main effect for imageability was nonsignificant, a 2-way interaction of skill by imageability and a 3-way interaction of skill by imageability by frequency were found to be significant. Very skilled readers named high imageable low frequency words significantly faster than matched low imageable low frequency words. Insofar as poor readers are concerned the results are contradictory to previous findings in English whilst data from highly skilled participants are in line with those reported for skilled readers for English. Implications of these findings on the existing literature are discussed.

The interaction of meaning and sound in spoken word recognition.

Models of spoken word recognition vary in the ways in which they capture the relationship between speech input and meaning. Modular accounts prohibit a word's meaning from affecting the computation of its form-based representation, whereas interactive models allow activation at the semantic level to affect phonological processing. We tested these competing hypotheses by manipulating word familiarity and imageability, using lexical decision and repetition tasks. Responses to high-imageability words were significantly faster than those to low-imageability words. Repetition latencies were also analyzed as a function of cohort variables, revealing a significant imageability effect only for words that were members of large cohorts, suggesting that when the mapping from phonology to semantics is difficult, semantic information can help the discrimination process. Thus, these data support interactive models of spoken word recognition.

How is your B-A-B-Y? Dissociated oral and written production

We report a case study of a patient (HR) with a large left temporal lesion who inserted spelled words, particularly nouns, into his fluent but otherwise empty spoken production. Although he generated neologisms in picture-naming and oral reading tasks, they did not appear in his spontaneous speech. Characteristics of his written production included the following: semantic errors; misspellings; frequency and word-length effects; and better performance for concrete nouns than for low-imageability nouns, verbs, function words, adjectives and adverbs. HR's attempts at writing sentences were agrammatic and notably lacking in verbs; he also performed poorly in generating sentences from printed sentence fragments. Although impaired in auditory rhyming tasks, his performance was superior to the detection of rhymes presented visually. HR's writing performance and the striking differences between his spoken and written output are similar to those of a number of patients previously reported. We note parallels between these patterns and the characteristics of cases where the processing and/or production of written words can be assigned to the right hemisphere.