Defining pure alexia.

Core questions in current pure alexia research

Randi Starrfelt

Dan Bub

Dejerine and the history of pure alexia

Joseph Jules Dejerine (1849-1917)

Bub, D. N., Arguin, M., & Lecours, A. R. (1993). Jules Dejerine and his interpretation of pure alexia. Brain and Language, 45, 531-559.

Min egen historie om Dejerine og hans patient Oscar C

(Introduktion til bogen "Hjerneprocesser", 1997 _ Hvis jeg må prale lidt: Jeg omtalte også Oscar C's serielle tal-for-tal læsning (112 -> 1-1-2) - men så havde jeg også læst både Dejerines egen oprindelige beskrivelse fra 1892 i uddrag og Dans 1993-artikel)

Bub introduced some of the lesser known aspects of Oscar C’s disorder, and hinted that his deficit may have been less ’pure’ than commonly believed. He asked whether Oscar C perhaps did have subtle writing difficulties following his first stroke. He also noted that there were contradictions in the original reports as to whether Oscar could read numbers normally or not. The suggested normal reading of numbers in pure alexic patients has been at the core of the debate about the ‘purity’ of pure alexia. The literature was recently reviewed by Randi Starrfelt & Marlene Behrmann, who found no clear evidence for such a dissociation in performance. (Starrfelt & Behrmann (2011). Number reading in pure alexia: A review. Neuropsychologia, 49; 2283 – 2298_ pdf)

Matthew Lambon-Ralph

Differences in severity or in kind?

Are there different forms of pure alexia?

Matt Lambon-Ralph

Elizabeth Warrington

UCL Institute of Neurology, University College London, London, UK

Evidence from two patients with posterior cortical atrophy and profound visual impairment - and good reading (Yong et al., in press, see below)

During more than 50 years, Elizabeth has contributed greatly to the study of alexias - as she has to so many other areas. Selected references.

A classic in the pure alexia literature: Warrington, E. K. & Shallice, T. (1980). Word-form dyslexia. Brain, 103, 99-112.

Yong, K. X., Warren, J. D., Warrington, E. K., & Crutch, S. J. (2013). Intact reading in patients with profound early visual dysfunction. Cortex.
Notes: Despite substantial neuroscientific evidence for a region of visual cortex dedicated to the processing of written words, many studies continue to reject explanations of letter-by-letter (LBL) reading in terms of impaired word form representations or parallel letter processing in favour of more general deficits of visual function. In the current paper, we demonstrate that whilst LBL reading is often associated with general visual deficits, these deficits are not necessarily sufficient to cause reading impairment and have led to accounts of LBL reading which are based largely on evidence of association rather than causation. We describe two patients with posterior cortical atrophy (PCA) who exhibit remarkably preserved whole word and letter reading despite profound visual dysfunction. Relative to controls, both patients demonstrated impaired performance on tests of early visual, visuoperceptual and visuospatial processing; visual acuity was the only skill preserved in both individuals. By contrast, both patients were able to read aloud words with perfect to near-perfect accuracy. Reading performance was also rapid with no overall significant difference in response latencies relative to age- and education-matched controls. Furthermore, the patients violated a key prediction of general visual accounts of LBL reading - that pre-lexical impairments should result in prominent word length effects; in the two reported patients, evidence for abnormal word length effects was equivocal or absent, and certainly an order of magnitude different to that reported for LBL readers. We argue that general visual accounts cannot explain the pattern of reading data reported, and attribute the preserved reading performance to preserved direct access to intact word form representations and/or parallel letter processing mechanisms. The current data emphasise the need for much clearer evidence of causality when attempting to draw connections between specific aspects of visual processing and different types of acquired peripheral dyslexia (in press).
Dementia Research Centre, Department of Neurodegeneration, UCL Institute of Neurology, University College London, UK.

Daniel Fiset

Université du Quebec

On letter-by-letter reading, letter confusability effect from visual similarity in letters, and spatial frequency

Fiset, D., Gosselin, F., Blais, C., & Arguin, M. (2006). Inducing letter-by-letter dyslexia in normal readers. Journal of Cognitive Neuroscience, 18, 1466-1476.

Anna Woollams

Neuroscience and Aphasia Research Unit, School of Psychological Sciences, University of Manchester, Manchester, UK

Case series of patients
with lesions of the left ventral occipito-temporal cortex

Roberts, D. J., Woollams, A. M., Kim, E., Beeson, P. M., Rapcsak, S. Z., & Lambon Ralph, M. A. (2012). Efficient Visual Object and Word Recognition Relies on High Spatial Frequency Coding in the Left Posterior Fusiform Gyrus: Evidence from a Case-Series of Patients with Ventral Occipito-Temporal Cortex Damage. Cerebral Cortex.
Recent visual neuroscience investigations suggest that ventral occipito-temporal cortex is retinotopically organized, with high acuity foveal input projecting primarily to the posterior fusiform gyrus (pFG), making this region crucial for coding high spatial frequency information. Because high spatial frequencies are critical for fine-grained visual discrimination, we hypothesized that damage to the left pFG should have an adverse effect not only on efficient reading, as observed in pure alexia, but also on the processing of complex non-orthographic visual stimuli. Consistent with this hypothesis, we obtained evidence that a large case series (n = 20) of patients with lesions centered on left pFG: 1) Exhibited reduced sensitivity to high spatial frequencies; 2) demonstrated prolonged response latencies both in reading (pure alexia) and object naming; and 3) were especially sensitive to visual complexity and similarity when discriminating between novel visual patterns. These results suggest that the patients' dual reading and non-orthographic recognition impairments have a common underlying mechanism and reflect the loss of high spatial frequency visual information normally coded in the left pFG

Thomas Habekost & Randi Starrfelt

Dept. of Psychology, Copenhagen University

Thomas and Randi have previously published on the importance of subtle low level visual deficits for pure alexia:

Starrfelt, R., Habekost, T., & Gerlach, C. (2010). Visual processing in pure alexia: a case study. Cortex, 46, 242-255. pdf

Here they presented new data with gabor gratings used with case LK: Starrfelt, Nielsen, Habekost & Andersen (in press). How low can you go: Spatial frequency sensitivity in pure alexia. Brain & Language.

abstract

Randi Starrfelt

Randi and Thomas have previously investigated the subtle visual deficits in pure alexia using methods based on a Theory of Visual Attention (TVA, see http://cvc.psy.ku.dk/), and suggested that the patients perceive “Too little – too late” to read fast and fluently. They are now working on extending their paradigm to investigate the speed of visual word processing in pure alexia, and presented data from this project.

Starrfelt, R., Habekost, T., & Leff, A. P. (2009). Too little, too late: reduced visual span and speed characterize pure alexia. Cerebral Cortex, 19, 2880-2890 pdf

Thomas Habekost
and
Christian Gerlach

Copenhagen

Thomas and Christian have collaborated with Randi Starrfelt on much of her work on pure alexia and visual word processing, e.g.

Starrfelt, R. & Gerlach, C. (2007). The visual what for area: words and pictures in the left fusiform gyrus. NeuroImage,
35, 334-342.

Behrmann, M. & Plaut, D. C. (2013). Bilateral Hemispheric Processing of Words and Faces: Evidence from Word Impairments in Prosopagnosia and Face Impairments in Pure Alexia. Cerebral Cortex.
Considerable research has supported the view that faces and words are subserved by independent neural mechanisms located in the ventral visual cortex in opposite hemispheres. On this view, right hemisphere ventral lesions that impair face recognition (prosopagnosia) should leave word recognition unaffected, and left hemisphere ventral lesions that impair word recognition (pure alexia) should leave face recognition unaffected. The current study shows that neither of these predictions was upheld. A series of experiments characterizing speed and accuracy of word and face recognition were conducted in 7 patients (4 pure alexic, 3 prosopagnosic) and matched controls. Prosopagnosic patients revealed mild but reliable word recognition deficits, and pure alexic patients demonstrated mild but reliable face recognition deficits. The apparent comingling of face and word mechanisms is unexpected from a domain-specific perspective, but follows naturally as a consequence of an interactive, learning-based account in which neural processes for both faces and words are the result of an optimization procedure embodying specific computational principles and constraints

Richard J. Wise

London

With Zoe Woodhead and others, Richard has with fMRI explored how the two hemispheres respond to sine-wave gratings varying in spatial frequency

Woodhead, Z. V., Wise, R. J., Sereno, M., & Leech, R. (2011). Dissociation of sensitivity to spatial frequency in word and face preferential areas of the fusiform gyrus. Cerebral Cortex, 21, 2307-2312.

Zoe Woodhead and Richard Wise

Tobias Pflugshaupt

Luzern, Schwitzerland

Introduction

Pflugshaupt, T., Gutbrod, K., Wurtz, P., von Wartburg, R., Nyffeler, T., De Haan, B. et al. (2009). About the role of visual field defects in pure alexia. Brain, 132, 1907-1917.

Jason Barton

University of British Columbia, Vancouver, Canada

Sheldon, C. A., Abegg, M., Sekunova, A., & Barton, J. J. (2012). The word-length effect in acquired alexia, and real and virtual hemianopia. Neuropsychologia, 50, 841-851.

Brenda Rapp

Department of Cognitive Science, Johns Hopkins University, Baltimore

Argye Hillis

Department of Neurology, Johns Hopkins University School of Medicine, Johns Hopkins Hospital, 600 N. Wolfe Street, Baltimore, MD

Hillis, A. E., Newhart, M., Heidler, J., Barker, P., Herskovits, E., & Degaonkar, M. (2005). The roles of the "visual word form area" in reading. NeuroImage, 24, 548-559.

-- and much more

H. Branch Coslett

Department of Neurology, University of Pennsylvania, Philadelphia

Case report :

Turkeltaub, P. E., et al. (2013). Alexia due to ischemic stroke of the visual word form area. Neurocase, in press
(abstract included in link below)

... Branch Coslett has published a great number of papers on reading and alexia, including chapters on alexia in some of the most authoritative textbooks

Laurent Cohen

Department of Neurology, Hopital de la Salpetriere, Paris

discussant

Dehaene, S. & Cohen, L. (2011). The unique role of the visual word form area in reading. Trends in Cognitive Sciences, 15, 254-262.

Stan Dehaene & Laurent Cohen
have had a productive cooperation over many years

Introduction by

Tim Shallice

Institute of Cognitive Neuroscience, University College, London, UK

How does the compensatory mechanism in pure alexia (LBL-reading) work ?

selected references

Jonathan Grainger

Laboratoire de Psychologie Cognitive,
Aix Marseille University,
Marseille , France

... evidence from experiments, many of which used event-related potentials (ERPs) to examine the time course of visual word recognition using masked repetition priming paradigms

Michael McCloskey

Department of Cognitive Sciences,
Johns Hopkins University,
Baltimore, MD

.. evidence from letter position in spelling

more ..

The afternoon session: "What can "implicit reading" tell us about pure alexia?" was introduced by Karalyn Patterson,

Karalyn Patterson

MRC Cognition and Brain Sciences Unit,
Cambridge, UK

Karalyn contributed one of the 'classics' in the pure alexia literature:
Patterson, K. & Kay, J. (1982). Letter-by-letter reading: psychological descriptions of a neurological syndrome. Quarterly Journal of Experimental Psychology A,Human Experimental Psychology, 34, 411-441.

She is an expert on semantic dementia, which is also characterized by surface alexia. This condition is suitable for testing notions about top-down influences on reading (see below)

In her talk, she also presented data from Lambon-Ralph, M. A., Hesketh, A., & Sage, K. (2004). Implicit recognition in pure alexia: The Saffran effect - A tale of two systems or two procedures? Cognitive Neuropsychology, 21, 401-421. abstract

	Woollams, A. M., Ralph, M. A., Plaut, D. C., & Patterson, K. (2007). SD-squared: on the association between semantic dementia and surface dyslexia. Psychological Review, 114, 316-339. Within the connectionist triangle model of reading aloud, interaction between semantic and phonological representations occurs for all words but is particularly important for correct pronunciation of lower frequency exception words. This framework therefore predicts that (a) semantic dementia, which compromises semantic knowledge, should be accompanied by surface dyslexia, a frequency-modulated deficit in exception word reading, and (b) there should be a significant relationship between the severity of semantic degradation and the severity of surface dyslexia. The authors evaluated these claims with reference to 100 observations of reading data from 51 cases of semantic dementia. Surface dyslexia was rampant, and a simple composite semantic measure accounted for half of the variance in low-frequency exception word reading. Although in 3 cases initial testing revealed a moderate semantic impairment but normal exception word reading, all of these became surface dyslexic as their semantic knowledge deteriorated further. The connectionist account attributes such cases to premorbid individual variation in semantic reliance for accurate exception word reading. These results provide a striking demonstration of the association between semantic dementia and surface dyslexia, a phenomenon that the authors have dubbed SD-squared
Anna Woollams. Medical Research Council (MRC) Cognition and Brain Sciences Unit, Cambridge, United Kingdom. anna.woollams@mrc-cbu.cam.ac.uk

Woodhead, Z. V., Brownsett, S. L., Dhanjal, N. S., Beckmann, C., & Wise, R. J. (2011). The visual word form system in context. Journal of Neuroscience, 31, 193-199.
According to the "modular" hypothesis, reading is a serial feedforward process, with part of left ventral occipitotemporal cortex the earliest component tuned to familiar orthographic stimuli. Beyond this region, the model predicts no response to arrays of false font in reading-related neural pathways. An alternative "connectionist" hypothesis proposes that reading depends on interactions between feedforward projections from visual cortex and feedback projections from phonological and semantic systems, with no visual component exclusive to orthographic stimuli. This is compatible with automatic processing of false font throughout visual and heteromodal sensory pathways that support reading, in which responses to words may be greater than, but not exclusive of, responses to false font. This functional imaging study investigated these alternative hypotheses by using narrative texts and equivalent arrays of false font and varying the hemifield of presentation using rapid serial visual presentation. The "null" baseline comprised a decision on visually presented numbers. Preferential activity for narratives relative to false font, insensitive to hemifield of presentation, was distributed along the ventral left temporal lobe and along the extent of both superior temporal sulci. Throughout this system, activity during the false font conditions was significantly greater than during the number task, with activity specific to the number task confined to the intraparietal sulci. Therefore, both words and false font are extensively processed along the same temporal neocortical pathways, separate from the more dorsal pathways that process numbers. These results are incompatible with a serial, feedforward model of reading

Behrmann, M. & Plaut, D. C. (2013). Distributed circuits, not circumscribed centers, mediate visual recognition. Trends in Cognitive Sciences, 17, 210-219.
Notes: Increasingly, the neural mechanisms that support visual cognition are being conceptualized as a distributed but integrated system, as opposed to a set of individual, specialized regions that each subserve a particular visual behavior. Consequently, there is an emerging emphasis on characterizing the functional, structural, and computa tional properties of these broad networks. We present a novel theoretical perspective, which elucidates the developmental emergence, computational properties, and vulnerabilities of integrated circuits using face and word recognition as model domains. Additionally, we suggest that, rather than being disparate and independent, these neural circuits are overlapping and subject to the same computational constraints. Specifically, we argue that both word and face recognition rely on fine-grained visual representations but, by virtue of pressure to couple visual and language areas and to keep connection length short, the left hemisphere becomes more finely tuned for word recognition and, consequently, the right hemisphere becomes more finely tuned for face recognition. Thus, both hemispheres ultimately participate in both forms of visual recognition, but their respective contributions are asymmetrically weighted

Dan Roberts

School of Psychology,
Bangor University, UK

Judging faces at word value: Is "pure " alexia the black swan?

Dan presented data from a case-series of 19 pure alexic patients who were impaired at face processing, and concluded that a similar part-based strategy is adopted to recognize words (letter-by-letter reading) and faces (featue-by-feature face processing)

Roberts, D. J., Lambon Ralph, M. A., & Woollams, A. M. (2010). When does less yield more? The impact of severity upon implicit recognition in pure alexia. Neuropsychologia, 48, 2437-2446.
Notes: Pure alexia (PA) is characterised by strong effects of word length on reading times and is sometimes accompanied by an overt letter-by-letter (LBL) reading strategy. Past studies have reported "implicit recognition" in some individual PA patients. This is a striking finding because such patients are able to perform semantic classification and lexical decision at above chance levels even when the exposure duration is short enough to prevent explicit identification. In an attempt to determine the prevalence of this "implicit recognition" effect, we assessed semantic categorisation and lexical decision performance using limited exposure durations in 10 PA cases. The majority of the patients showed above chance accuracy in semantic categorisation and lexical decision. Performance on the lexical decision test was influenced by frequency and imageability. In addition, we found that the extent to which patients showed evidence of "implicit recognition" in both tasks was inversely related to the severity of their reading disorder. This result is consistent with hypotheses which suggest that this effect does not constitute an implicit form of unique word identification but is a reflection of the degree of partial activation within the word recognition system. These results also go some way towards explaining the individual variation in the presence of this effect observed across previous case-study investigations in the literature

Alexander Leff

Institute of Neurology, University College London, UK

During the meeting, spring arrived in Denmark.

Here are two of Randi's student research assistants crossing the yard between the hotel and the conference room:
Ida-Marie Arendt
og
Charlotte Fabricius

Pure alexia group, Copenhagen, May 2013
Jonathan Grainger, Dan Bub, Mike McCloskey, Richard Wise, Matt Lambon-Ralph, Dan Fiset, Anna Woollams, Alex Leff, Branch Coslett;
Rebecca Johnsson, Stan Dehaene, Thomas Habekost, Zoe Woodhead, Brenda Rapp, Argye Hillis, Marlene Behrmann, Dan Roberts;
Randi Starrfelt, Christian Gerlach, Jason Barton, Elizabeth Warrington, Karalyn Patterson;
Laurent Cohen, Tobias Pflugshaupt, Tim Shallice, David Plaut, Jeremy Purcell

Photography and layout: Anders.Gade@psy.ku.dk


Richard Wise, Matt Lambon-Ralph, Karalyn Patterson, Anna Woollams, Dan Bub, Dan Fiset	Zoe Woodhead, Alex Leff, Dan Roberts, Tobias Pflugshaupt, Branch Coslett