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A patient with a severe dyscalculia and a mild arabic number dyslexia is described. He could perform simple addition and subtraction sums with oral presentation. However with written arabic number sums he was impaired with addition but not with subtraction. These findings require modifications to current models of arithmetic processing which have suggested that numerical inputs are converted into abstract internal representations before arithmetical processing can occur.

In this paper we describe a patient with a severe global dysphasia who provides an example of a category specific access impairment. Using matching to sample techniques it was possible to demonstrate the selective preservation of her ability to comprehend proper nouns coupled with impaired comprehension of common nouns. It was found that for the object names category M.E.D. performed better on the first presentation of an item than she did on subsequent presentations. Her performance was also found to be affected by presentation rate and an analysis of her responses showed marked inconsistency when the same stimuli were administered more than once. This category specific access impairment suggests the relative independence of the cognitive mechanisms responsible for the access of different semantic categories.

A single case study of an attentional dyslexic is reported. The patient B.A.L. was able to read single letters and single words presented in isolation without difficulty. However, his reading of prose was very disrupted and his ability to read rows of letters and words was significantly impaired. A “flanking” procedure, in which there was a single target item, flanked by other stimuli, was used in a series of experiments to analyse his dyslexic impairment. First it was established that his attentional deficit was specific to reading in so far as the patient did not have comparable difficulties with pictorial material. His performance in the flanking experiments was consistently impaired; and furthermore was unaffected by speed of presentation, the number of flanking stimuli, and the spatial arrangement of the flanking stimuli. The important exception was when the flanking stimuli were of a different category. There was no decrement in performance when target letters were flanked by words or when words were flanked by letters. This study both corroborates and extends the original account of attentional dyslexia (S hallice and W arrington , Neuropsychologia15, 31–41, 1977) in terms of a damaged “filter” mechanism controlling the transition from a parallel to a serial stage of reading processing. The categorical effects reported here indicate that such a filter must be post lexical and suggest further that there are multiple filters in the reading system.

The theoretical distinction between arithmetic facts and procedures was first made by Groen and Parkman (1972). This was confirmed with a neuropsychological single case described by Warrington (1982) who had impaired arithmetical facts but well preserved arithmetical procedures. Since this time there have been several patients described who showed a selective impairment of arithmetic facts. There have also been reports of cases with impaired arithmetical procedures. However, there has not yet been a case reported with the selective impairment of procedures in the context of intact arithmetic facts. This paper describes a patient, SR, with probable Alzheimer's dementia who had well preserved addition, multiplication and subtraction facts but who nevertheless had severe difficulties with a range of arithmetical procedures such as multidigit sums, decimals and fractions. The implications of this case for current theoretical models are discussed.

Following a 5 cm left frontal lobectomy for the removal of a mixed astrocytoma-oligodendroglioma, a 51 year old right handed man showed a marked dissociation between his performance on standard neuropsychological tests and his everyday behaviour. In contrast to his intact neuropsychological test performance, he was impaired on a test of "strategy application" which requires goal articulation, plan specification, self-monitoring, and evaluation of outcomes, as well as the establishment of mental "markers" to trigger specific behaviour. Strategy application disorder can therefore be produced by a unilateral circumscribed frontal lobe lesions.

This report describes a person who confabulated following an anterior communicating artery aneurysm. His confabulation was limited to one very circumscribed area of his life and remained stable for twelve weeks, eventually improving with rehabilitation. It is argued that a content-specific confabulation of this nature challenges current theories of confabulation, and an integrative explanation is given based on previous findings by Burgess and Shallice (1996b) of the mechanisms of autobiographical recollection in healthy people.

In this study we describe an investigation into the residual written word retrieval skills of M.E.D., a patient with a severe aphasia. M.E.D.'s performance on written naming and writing to dictation tasks showed a distinctive pattern of performance across semantic categories. The patient's ability to write the names of countries and famous people was consistently superior to her ability to write the names of objects. These results could be considered as indicative of a double dissociation in the proper nouns category, as there are already patients on record who have a selective deficit in retrieving proper nouns.

We report a quantitative investigation of three patients who presented with a profound prosopagnosia. They were tested on a series of tests of face perception, face recognition, and paired associate learning using faces. A patient with marked perceptual difficulties but no difficulty whatever in recognizing faces was tested as a control. The control patient's performance was as bad or worse on the tests of perception of faces, and it is concluded that impaired performance on tests of face perception does not contribute to difficulties in recognizing familiar faces. The major difference between the three prosopagnosic patients was the evidence of covert recognition in two of these cases but not in the third. We use this evidence to argue that the perceptual/mnestic distinction is an inappropriate classification and would suggest instead that the two types may be described in terms either of a disconnection of the face recognition units or of damage to the units themselves.