Jeremy J. Tree

Word association norms for two cohorts of British adults

Abstract Word association data were obtained from two cohorts of British adults. Young adults (21–30 years of age) and older adults (66–81) responded to 90 words in a discrete word association task. An associative frequency measure was calculated by counting how many participants produced a particular word and then converting this number into a proportion. The degree of overlap between the cohorts in terms of dominant responses, the responses with the highest association frequencies, was moderate. Dominant responses were common to the two cohorts for only 36 of the 90 items. When the top three responses were considered the degree of overlap increased to approximately 60%. Four measures of response heterogeneity were calculated for each stimulus item. Comparison of the responses of the younger and older adults indicates that there was less response heterogeneity amongst the older cohort. These norms should be of use to investigators interested in developmental changes in the structure of semantic memory across the adult lifespan as well as to researchers interested in comparing results from neurologically impaired older adults to a normative sample from the same age cohort.

Computational Modeling of Reading in Semantic Dementia: Comment on Woollams, Lambon Ralph, Plaut, and Patterson (2007)

Woollams, Lambon Ralph, Plaut, and Patterson reported detailed data on reading in 51 cases of semantic dementia. They simulated some aspects of these data using a connectionist parallel distributed processing (PDP) triangle model of reading. We argue here that a different model of reading, the dual route cascaded (DRC) model of Coltheart, Rastle, Perry, Langdon, and Ziegler (2001), not only provides a more accurate simulation of these aspects of reading in semantic dementia than does the PDP model but also provides highly accurate simulations of other aspects of reading in this disorder that the PDP approach has not simulated. We conclude that our findings add to evidence both from simulations of normal skilled reading and from simulations of other kinds of acquired dyslexia that the nonconnectionist DRC model of reading offers a better account of normal and disordered reading than the connectionist PDP models of reading.

Sometimes faster, sometimes slower: associative and competitor priming in picture naming with young and elderly participants

Abstract There are reports on facilitatory and inhibitory priming effects with semantically related prime–target pairs in naming experiments conducted with both young and elderly participants. We would suggest that facilitatory priming effects in naming occur only with associatively, non-semantically related items, whereas inhibitory priming effects occur with semantically related, non-associated items. The current experiments examined the effects of both types of primes on picture naming with young (age range: 18–25) and elderly participants (age range: 66–87). We demonstrate that associative relatedness results in short-term facilitatory priming effects and semantic relatedness results in long-term inhibitory priming effects. Age had no impact on associative facilitatory priming, and there was only limited evidence that age had an impact on the pattern of semantic inhibitory priming. We argue that at best these results are consistent with a weak form of an inhibitory deficit in older adults.

Computational modelling of phonological dyslexia: How does the DRC model fare?

This paper investigates the patterns of reading impairment in phonological dyslexia using computational modelling with the dual-route cascaded model of reading (DRC, Coltheart, Rastle, Perry, Langdon, & Ziegler, 2001). Systematic lesioning of nonlexical and phonological processes in DRC demonstrates that different lesions and severity of those lesions can reproduce features of phonological dyslexia including impaired reading of nonwords, relatively spared reading of words, an advantage for reading pseudohomophones. Using the same stimuli for model and for patients, lesions to DRC were also used to simulate the reading accuracy shown by three individuals with acquired phonological dyslexia. No single lesion could replicate the reading performance of all three individuals. In order to simulate reading accuracy for one individual a phonological impairment was necessary (addition of noise to the phoneme units), and for the remaining two individuals an impairment to nonlexical reading procedures (increasing the time interval between each new letter being processed) was necessary. We argue that no single locus of impairment (neither phonological nor nonlexical) can account for the reading impairments of all individuals with phonological dyslexia. Instead, different individuals have different impairments (and combinations of impairments) that together provide the spectrum of patterns found in phonological dyslexia.

Deep Dysphasic Performance in Non-fluent Progressive Aphasia: a Case Study

We present a patient (PW) with non-fluent progressive aphasia, characterized by severe word finding difficulties and frequent phonemic paraphasias in spontaneous speech. It has been suggested that such patients have insufficient access to phonological information for output and cannot construct the appropriate sequence of selected phonemes for articulation. Consistent with such a proposal, we found that PW was impaired on a variety of verbal tasks that demand access to phonological representations (reading, repetition, confrontational naming and rhyme judgement); she also demonstrated poor performance on syntactic and grammatical processing tasks. However, examination of PW’s repetition performance also revealed that she made semantic paraphasias and that her performance was influenced by imageability and lexical status. Her auditory-verbal short-term memory was also severely compromised. These features are consistent with ‘deep dysphasia’, a disorder reported in patients suffering from stroke or cerebrovascular accident, and rarely reported in the context of non-fluent progressive aphasia. PW’s pattern of performance is evaluated in terms of current models of both non-fluent progressive aphasia and deep dysphasia.

Acquired prosopagnosia without word recognition deficits

It has long been suggested that face recognition relies on specialized mechanisms that are not involved in visual recognition of other object categories, including those that require expert, fine-grained discrimination at the exemplar level such as written words. But according to the recently proposed many-to-many theory of object recognition (MTMT), visual recognition of faces and words are carried out by common mechanisms [Behrmann, M., & Plaut, D. C. (2013). Distributed circuits, not circumscribed centers, mediate visual recognition. Trends in Cognitive Sciences, 17, 210–219]. MTMT acknowledges that face and word recognition are lateralized, but posits that the mechanisms that predominantly carry out face recognition still contribute to word recognition and vice versa. MTMT makes a key prediction, namely that acquired prosopagnosics should exhibit some measure of word recognition deficits. We tested this prediction by assessing written word recognition in five acquired prosopagnosic patients. Four patients had lesions limited to the right hemisphere while one had bilateral lesions with more pronounced lesions in the right hemisphere. The patients completed a total of seven word recognition tasks: two lexical decision tasks and five reading aloud tasks totalling more than 1200 trials. The performances of the four older patients (3 female, age range 50–64 years) were compared to those of 12 older controls (8 female, age range 56–66 years), while the performances of the younger prosopagnosic (male, 31 years) were compared to those of 14 younger controls (9 female, age range 20–33 years). We analysed all results at the single-patient level using Crawfords t-test. Across seven tasks, four prosopagnosics performed as quickly and accurately as controls. Our results demonstrate that acquired prosopagnosia can exist without word recognition deficits. These findings are inconsistent with a key prediction of MTMT. They instead support the hypothesis that face recognition is carried out by specialized mechanisms that do not contribute to recognition of written words.

Opportunities to say ‘yes’: Rare speech automatisms in a case of progressive nonfluent aphasia and apraxia

We describe the investigation of speech automatisms in a man with progressive nonfluent aphasia and apraxias. Occurrence of the automatisms yes and right, were analysed across a range of speech tasks varying in length, propositionality, lexical and articulatory complexity, whether tasks engaged internal generation or external triggering and articulatory distortions, and while completing pantomimes/gestures. No differences were found in occurrence across most tasks but there was a significant interaction between automatism production and apraxic speech errors and during limb praxic tasks, suggesting that production of the automatism was unrelated to linguistic or lexical variables, but was related to the presence of speech apraxia coupled with disinhibition.

The Definition and Diagnosis of Developmental Prosopagnosia

Over the last 20 years much attention in the field of face recognition has been directed towards the study of developmental prosopagnosia (DP), with some authors investigating the behavioural characteristics of the condition, and many others using these individuals to further our theoretical understanding of the typical face-processing system. It is broadly agreed that the term “DP” refers to people who have failed to develop the ability to recognize faces in the absence of neurological illness or injury, yet more precise terminology in relation to potential subtypes of the population are yet to be confirmed. Furthermore, specific diagnostic techniques and inclusion and exclusion criteria have yet to be uniformly accepted across the field, making cross-paper comparisons and meta-analyses very difficult. This paper presents an overview of the current challenges that face research into DP and introduces a series of papers that attempt to further our understanding of the conditions characteristics. It is hoped that this special issue will provide a springboard for further research addressing these issues, improving the current state of the art by ensuring the quality of theoretical investigations into DP, and by posing advances that will assist those who have the condition.

Longitudinal assessment of language and memory impairments in pathologically confirmed cortico-basal ganglionic degeneration

We report a longitudinal case study (patient EP) of histologically confirmed cortico-basal ganglionic degeneration (CBD) who presented with non-fluent progressive aphasia (NFPA). While NFPA has been documented in clinical descriptions of other reports of CBD, details are often limited and the majority of studies are cross-sectional in nature. The present study conducted detailed longitudinal assessment with EP over a period of two years that revealed substantial impairments of episodic memory, semantic memory, naming and particular aspects of reading and spelling. Our investigations identify key features of EPs pattern of impairment that warrant further examination with other cases of CBD. In particular, testing of EPs nonword reading and spelling found that both were impaired and declined over time. In addition, verbal recognition deteriorated faster than non-verbal recognition through the course of the disease. Our review of the literature suggests that poor nonword reading and spelling may be consistent features of CBD, but more studies are needed to confirm this suggestion, and to determine whether they warrant inclusion in profiling CBD.

Computational modelling of the effects of semantic dementia on visual word recognition

Rogers, Lambon Ralph, Hodges, and Patterson (2004) studied two-alternative forced-choice visual lexical decision performance in patients with semantic dementia. With item pairs where the target word was more “typical” (i.e., higher in bigram and trigram frequency) than the foil (all foils were pseudohomophones), lexical decision performance was good and was unaffected by word frequency. With item pairs where the target word was less “typical” (i.e., lower in bigram and trigram frequency) than the foil, lexical decision performance was worse and was affected by word frequency, being particularly inaccurate when the word targets were low in frequency. We show (using as materials all the monosyllabic items used by Rogers and colleagues) that the same pattern of results occurs in the lexical decision performance of the DRC (dual-route cascaded) computational model of reading when the model is lesioned by probabilistic deletion of low-frequency words from its orthographic lexicon. We consider that the PDP (parallel distributed processing) computational model of reading used by Woollams, Plaut, Lambon Ralph, and Patterson (2007) to simulate reading in semantic dementia is not capable of simulating this lexical decision result. We take this, in conjunction with previous work on computational modelling of reading aloud in surface dyslexia, phonological dyslexia, and semantic dementia using the DRC and PDP reading models, to indicate that the DRC model does a better job than the PDP model in accounting for what is known about the various forms of acquired dyslexia.