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Buiatti, T., Skrap, M., & Shallice, T. (2012). Left- and right-hemisphere
forms of phonological alexia. Cognitive Neuropsychology, 29, 531-549.
Notes: We studied the ability of patients with lesions arising from
operation for an anterior or posterior (left or right) brain tumour to read
a set of words and pronounceable nonwords. In line with previous works, we
observed that damage to the left posterior or left anterior cortex can give
rise to phonological alexia, where the reading performance of nonwords is
affected more than that of words. More surprisingly, similar effects were
found in the right posterior group. However, there were significant
differences in the error types, for both complex and positional errors,
between phonological alexic patients in the three location groups. The
findings present difficulties for the position held by theorists of the
triangle model that phonological alexia arises from impairments in the
language production system or in a general-purpose orthographic-phonological
translation system. They also pose new questions about the possible role of
the right posterior cortex in letter sequence representation
Cognitive Neuroscience Sector, SISSA, Trieste, Italy
Rosazza, C., Appollonio, I., Isella, V., & Shallice, T. (2007).
Qualitatively different forms of pure alexia. Cognitive Neuropsychology,
24, 393-418.
Notes: T. Shallice, International School for Advanced Studies (SISSA-ISAS),
Trieste
In this study we investigated two patients with pure alexia, F.C. and
L.D.S., in order to make inferences about how processes and levels involved
in the early stage of visual word recognition are organized and how they can
be selectively damaged. Moreover, we investigated whether pure alexia can be
caused by different functional deficits. F.C. and L.D.S. were presented with
tasks of letter processing and tasks of orthographic integration. There was
a clear double dissociation between the pattern of performance of F.C. and
L.D.S. F.C. was able to process single letters rapidly and accurately, but
was unable to group together the letters that he had correctly identified.
By contrast, L.D.S. was slower and more impaired at letter identification,
but she could use letter groups to assist reading. Thus, two different forms
of pure alexia emerged: F.C. has a higher level deficit in integrating
letters, whereas L.D.S. has a lower level deficit in letter processing. The
results support the assumption of a functional organization of the reading
process that involves a series of orthographic units (i.e., single letters,
sublexical letter groups, and the lexical unit), which can be selectively
damaged. Finally, our data present difficulties for models of pure alexia
that assume all patients to have a low-level processing deficit
Shallice, T. & Rosazza, C. (2006). Patterns of peripheral paralexia: pure
alexia and the forgotten visual dyslexia? Cortex, 42, 892-897.
Notes: International School for Advanced Studies - SISSA-ISAS, Trieste,
Italy. t.shallice@ucl.ac.uk
The concept of visual dyslexia put forward by Marshall and Newcombe (1973)
is assessed. After a long period of neglect it was resurrected in the late
1990s in a narrow form. In the current paper it is proposed that a wider
form of the functional syndrome is useful to include amongst other
conditions attentional dyslexia and neglect dyslexia. The variety of
sub-forms would correspond to the behavioural effects of the different ways
in which the orthographic processing systems can be impaired. What
distinguishes the broader form from pure alexia is that the patient lacks
the capacity to use a serial letter processing strategy, and so
interpretation of visual dyslexia in terms of the impairment to the
orthographic processing systems is not contaminated by the use of a
compensatory strategy that results in processing operations which are
qualitatively very different from the normal and highly opaque. The lack of
a serial letter processing strategy makes visual dyslexia a much more
transparent functional syndrome
McLeod, P., Shallice, T., & Plaut, D. C. (2000). Attractor dynamics in word
recognition: converging evidence from errors by normal subjects, dyslexic
patients and a connectionist model. Cognition, 74, 91-114.
Notes: Department of Experimental Psychology, Oxford University, Oxford, UK.
peter.mcleod@psy.ox.ac.uk ; ABSTRACT: People make both semantic and visual
errors when trying to recognise the meaning of degraded words. This result
mirrors the finding that deep dyslexic patients make both semantic and
visual errors when reading aloud. We link the results with the demonstration
that a recurrent connectionist network which produces the meaning of words
in response to their spelling pattern produces this distinctive combination
of errors both when its input is degraded and when it is lesioned. The
reason why the network can simulate the errors of both normal subjects and
patients lies in the nature of the attractors which it develops as it learns
to map orthography to semantics. The key role of attractor structure in the
successful simulation suggests that the normal adult semantic reading route
may involve attractor dynamics
Behrmann, M. & Shallice, T. (1995). Pure alexia: A nonspatial visual
disorder affecting letter activation. Cognitive Neuropsychology, 12,
409-454.
Notes: Several different interpretations have been offered to explain the
mechanism giving rise to the linear relationship between word length and
reading time shown by patients with pure alexia or letter-by-letter reading.
One interpretation attributes this word length effect to a spatial
impairment in which there is a left- right gradient of processing
efficiency. This fundamental resource limitation requires that the patient
focus on each letter in turn to increase its signal-to-noise ratio and
discriminability, especially for letters towards the end of the string. An
alternative view attributes the word length effect to a letter activation
deficit that disrupts the rapid and efficient processing of single letters.
In this paper, we examine these two hypotheses in relation to DS, a
letter-by-letter reader. DS is able to distribute her attention to multiple
locations in parallel and her performance is unaffected by the absolute or
relative spatial location of the letters in a string. She is, however,
impaired at reporting the identity of a letter independent of its spatial
location and requires an abnormally long time to process each letter.
Furthermore, investigations of DS's reading, using Howard's (1991) analyses
of reaction time distributions, suggest that she processes each letter in a
sequentially order. Based on the results of these studies, we propose that
prototypic pure alexia is a nonspatial visual disorder that affects the
activation of individual letters
Shallice, T. (1991). Precis of From neuropsychology to mental structure.
Behavioral and Brain Sciences, 14, 429-437,457-469.
Notes: Neuropsychological results are increasingly cited in cognitive
theories although their methodology has been severely criticised. The book
argues for an eclectic approach but particularly stresses the use of
single-case studies. A range of potential artifacts exists when inferences
are made from such studies to the organisation of normal function - for
example, resource differences among tasks, premorbid individual differences,
and reorganisation of function. The use of "strong" and "classical"
dissociations minimises potential artifacts. The theoretical convergence
between findings from fields where cognitive neuropsychology is well
developed and those from the normal literature strongly suggests that the
potential artifacts are not critical. The fields examined in detail in this
respect are short-term memory, reading, writing, the organisation of input
and output speech systems, and visual perception. Functional dissociation
data suggest that not only are input systems organised modularly, but so are
central systems. This conclusion is supported by findings on impairment of
knowledge, visual attention, supervisiory functions, memory and
consciousness
G.Vallar & T. Shallice (Eds.), Neuropsychological impairments of
short-term memory (pp. 477-508). Cambridge: Cambridge University Press.
Shallice, T. (1988). From neuropsychology to mental structure.
Cambridge: Cambridge University Press.
Notes: 462 pp. 16 chapters organized in 4 parts: I.INTRODUCING COGNITIVE
NEUROPSYCHOLOGY. 1.From the diagram makers to cognitive neuropsychology.
2.The cognitive neuropsychology approach. II.CONVERGING OPERATIONS: SPECIFIC
SYNDROMES AND EVIDENCE FROM NORMAL SUBJECTS. 3.The short-term memory
syndrome. 4.The peripheral dyslexias. 5.The central dyslexias. 6.The
agraphias. 7.Language operations: Are input and output processes separate.
8.The generality of the approach: The case of visual perception.
III.INFERENCES FROM NEUROPSYCHOLOGICAL FINDINGS. 9.On method: A rejection of
ultra-cognitive neuropsychology. 10.On method: Single case studies.
11.Functional specialisation. IV.CENTRAL PROCESSES: EQUIPOTENTIALITY OR
MODULARITY? 12.Selective impairments of knowledge. 13.The allocation and
direction of processing resources: Visual attention. 14.The allocation of
processing resources: Higher-level control. 15.Amnesia: What is memory for?
16.Modularity and consciousness
Shallice, T. & Warrington, E. K. (1987). Single and multiple component
central dyslexic syndromes. In M.Coltheart, K. Patterson, & J. C. Marshall
(Eds.), Deep dyslexia (2 ed., pp. 119-145). London: Routledge & Kegan
Paul.
Shallice, T. & Saffran, E. (1986). Lexical processing in the absence of
explicit word identification: Evidence from a letter-by-letter reader.
Cognitive Neuropsychology, 3, 429-458.
Notes: The lexical decision performance of a letter-by-letter reader, ML,
was analysed for words presented for too short an exposure duration for him
to identify or name them. His level of performance was surprisingly good by
comparison with that of previously reported patients. In addition he gave a
very similar pattern of responses to inappropriately affixed words as to
appropriately affixed ones. His performance on these tasks could not be
attributed to neglect or to the use of letter sequential dependencies. In
addition, with the same exposure duration, ML showed "semantic access"
characteristics in word categorization tasks. This evidence for lexical
processing in the absence of explicit identification is discussed in
relation to alternative accounts of letter-by-letter reading.
Shallice, T. & McCarthy, R. (1985). Phonological reading: From patterns of
impairment to possible procedures. In K.E.Patterson, J. C. Marshall, & M.
Coltheart (Eds.), Surface dyslexia: Neuropsychological and cognitive
studies of phonological reading (1 ed., pp. 361-397). London: Erlbaum.
Shallice, T., McLeod, P., & Lewis, K. (1985). Isolating cognitive modules
with the dual-task paradigm: are speech perception and production separate
processes? Quarterly Journal of Experimental Psychology A,Human
Experimental Psychology, 37, 507-532.
Warrington, E. K. & Shallice, T. (1984). Category specific semantic
impairments. Brain, 107, 829-854.
Notes: We report a quantitative investigation of the visual identification
and auditory comprehension deficits of 4 patients who had made a partial
recovery from herpes simplex encephalitis. Clinical observations had
suggested the selective impairment and selective preservation of certain
categories of visual stimuli. In all 4 patients a significant discrepancy
between their ability to identify inanimate objects and inability to
identify living things and foods was demonstrated. In 2 patients it was
possible to compare visual and verbal modalities and the same pattern of
dissociation was observed in both. For 1 patient, comprehension of abstract
words was significantly superior to comprehension of concrete words.
Consistency of responses was recorded within a modality in contrast to a
much lesser degree of consistency between modalities. We interpret our
findings in terms of category specificity in the organization of meaning
systems that are also modality specific semantic systems
Shallice, T., Warrington, E. K., & McCarthy, R. (1983). Reading without
semantics. Quarterly Journal of Experimental Psychology A,Human
Experimental Psychology, 35, 111-138.
Notes: Analysis of the reading of a neurological patient (HTR) indicates
that it is based on the operation of a relatively unimpaired phonological
route. Quantitative investigations of type of error, reading speed and the
effects of lexicality and spelling-to-sound regularity all support this
conclusion. Spelling-to-sound regularity is shown to influence reading not
only through regular words being read better than irregular, but also
through mildly irregular words being better read than very irregular ones. A
model is presented of the operation of the phonological route and of its
progressive impairment in certain types of neurological disease
Shallice, T. & Coughlan, A. K. (1980). Modality specific word comprehension
deficits in deep dyslexia. Journal of Neurology, Neurosurgery and
Psychiatry, 43, 866-872.
Notes: A deep dyslexic patient was tested on a series of experiments
designed to assess her comprehension of abstract words. On tests where a
precise semantic representation of words was required, performance was much
poorer with visual than with auditory presentation. However, on some but not
all categorisation tests performance with both modalities was good. It is
argued that deep dyslexia can result from a modality-specific deficit in
attaining the meaning of words together with a disorder of the phonological
reading route
Warrington, E. K. & Shallice, T. (1980). Word-form dyslexia. Brain, 103,
99-112.
Notes: In this study we have reported our investigation of two patients with
an acquired dyslexia characterized by letter-by-letter reading, whole word
reading being apparently impossible. It has been shown that this phenomenon
of letter-by-letter reading cannot be accounted for by visual or perceptual
factors nor by impairment of visual span of apprehension. The exceptionally
slow speed of reading was documented and a clear relationship between word
length and reading speed established. Performance on tasks considered to
maximize whole word reading which at the same time prevent the possibility
of letter-by-letter reading, namely, reading script and reading with
tachistoscopic presentation, was impaired. The satisfactory performance of
these two patients on tasks of picture interpretation suggests that the two
components of the syndrome simultanagnosia, letter-by-letter reading and
piecemeal perception of complex scenes, are dissociable. Three alternative
explanations of letter-by-letter reading are considered and we conclude that
in this type of acquired dyslexia there is damage to the system through
which a visual word-form is attained
Warrington, E. K. & Shallice, T. (1979). Semantic access dyslexia. Brain,
102, 43-63.
Notes: An analytical investigation of the residual reading capacities of a
single patient with dyslexia without dysgraphia is reported. Both his
ability to name and to comprehend letters and words were severely impaired.
The major finding of this investigation was AR's striking capacity for
categorizing words he could not read. In addition there was evidence of
semantic priming effects. Thus AR was frequently able to achieve partial
comprehension of words he could not read. The orthodox interpretation of the
dyslexia without dysgraphia in terms of a disconnection syndrome is shown to
be inappropriate, at least for the present case, where the deficit appears
to be within the semantic domain; it is argued that this type of dyslexia is
due to an impairment in accessing semantic information
Shallice, T. & Warrington, E. K. (1975). Word recognition in a phonemic
dyslexic patient.
Quarterly Journal of Experimental Psychology, 27,
187-199.
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