Giuseppe Vallar

THE ANATOMY OF UNILATERAL NEGLECT AFTER RIGHT- HEMISPHERE STROKE LESIONS. A CLINICAL/CT-SCAN CORRELATION STUDY IN MAN*

The anatomical correlates of extrapersonal visual neglect were investigated in 110 right-handed stroke patients with lesions confined to the right hemisphere. Neglect is much more frequently associated with retrorolandic damage, as compared with frontal lesions. The inferior parietal lobule appears to be the area most frequently involved in patients with cortical lesions showing signs of neglect. When the cerebral lesion is confined to deep structures, neglect occurs much more frequently when grey nuclei such as the thalamus and the basal ganglia are damaged; a remarkable number of negative cases were, however, found. Conversely, lesions limited to the subcortical white matter are rarely associated with neglect. The relevance of these results to anatomophysiological models of directed attention and neglect is discussed.

Exploring the articulatory loop

A series of five experiments explore the influence of articulatory suppression on immediate memory for auditorily presented items with a view to testing the revised concept of an articulatory loop. Experiments 1, 2 and 3 demonstrate that the phonological similarity effect is not abolished by articulatory suppression, whether this occurs only at input or at both input and recall. Experiments 4 and 5 show that the tendency for long words to be less well remembered than short is abolished by articulatory suppression, even when presentation is auditory, provided suppression occurs during both input and recall. These results are consistent with the concept of a loop comprising a phonological store, which is responsible for the phonological similarity effect, coupled with an articulatory rehearsal process that gives rise to the word length effect.

Neuropsychological impairments of short-term memory

List of contributors Acknowledgements General introduction Part I. The Functional Architecture of Auditory-Verbal (Phonological) Short-Term Memory and its Neural Correlates: 1. The impairment of auditory-verbal short-term storage Tim Shallice and Giuseppe Vallar 2. The development of the concept of working memory: implications and contributions of neuropsychology Alan D. Baddeley 3. Multiple phonological representations and verbal short-term memory Frances J. Friedrich 4. Electrophysiological measures of short-term memory Arnold Starr, Geoffrey Barrett, Hillel Pratt, Henry J. Michalewski and Julie V. Patterson Part II. Phonological Short-Term Memory and Other Levels of Information Processing: Studies in Brain-Damaged Patients with Defective Phonological Memory: 5. Auditory and lexical information sources in immediate recall: evidence from a patient with deficit to the phonological short-term store Rita Sloan Berndt and Charlotte C. Mitchum 6. Neuropsychological evidence for lexical involvement in short-term memory Eleanor M. Saffran and Nadine Martin 7. Auditory-verbal span of apprehension: a phenomenon in search of a function? Rosaleen A. McCarthy and Elizabeth K. Warrington 8. Short-term retention without short-term memory Brian Butterworth, Tim Shallice and Frances L. Watson Part III. Short-Term Memory Studies in Different Populations (Children, Elderly, Amnesics) and of Different Short-Term Memory Systems: 9. Developmental fractionation of working memory Graham J. Hitch 10. Adult age differences in working memory Fergus I. M. Craik, Robin G. Morris and Mary L. Gick 11. Lipreading, neuropsychology and immediate memory Ruth Campbell 12. Memory without rehearsal David Howard and Sue Franklin 13. The extended present: evidence from time estimation by amnesics and normals Marcel Kinsbourne and Robert E. Hicks Part IV. Phonological Short-Term Memory and Sentence Comprehension: 14. Short-term memory and language comprehension: a critical review of the neuropsychological literature David Caplan and Gloria S. Waters 15. Neuropsychological evidence on the role of short-term memory in sentence processing Randi C. Martin 16. Short-term memory impairment and sentence processing: a case study Eleanor M. Saffran and Nadine Martin 17. Phonological processing and sentence comprehension: a neuropsychological case study Giuseppe Vallar, Anna Basso and Gabriela Bottini 18. Working memory and comprehension of spoken sentences: investigation of children with reading disorder Stephen Crain, Donald Shankweiler, Paul Macaruso and Eva Bar-Shalom Name index Subject index.

Spatial cognition: evidence from visual neglect

Recent work on human attention and representational systems has benefited from a growing interplay between research on normal attention and neuropsychological disorders such as visual neglect. Research over the past 30 years has convincingly shown that, far from being a unitary condition, neglect is a protean disorder whose symptoms can selectively affect different sensory modalities, cognitive processes, spatial domains and coordinate systems. These clinical findings, together with those of functional neuroimaging, have increased knowledge about the anatomical and functional architecture of normal subsystems involved in spatial cognition. We provide a selective overview of how recent investigations of visual neglect are beginning to elucidate the underlying structure of spatial processes and mental representations.

Unawareness of disease following lesions of the right hemisphere: Anosognosia for hemiplegia and anosognosia for hemianopia

Unawareness of motor and visual-field defects was investigated in 97 right brain-damaged subjects. Both kinds of anosognosia were found to be double-dissociated from more elementary neurological disorders and from personal and extra-personal neglect. The relationships between anosognosia and unilateral neglect are discussed and allusion is made to the implications concerning the neurological organization of higher control functions.

When long-term learning depends on short-term storage

Abstract Since the 1960s, there has been controversy as to whether long-term learning might depend on some form of temporary short-term storage. Evidence that patients with grossly impaired memory span might show normal learning was, however, particularly problematic for such views. We reexamine the question by studying the learning capacity of a patient, P.V., with a very pure deficit in short-term memory. A series of experiments compare her learning capacity with that of matched controls. The first experiment shows that her capacity to learn pairs of meaningful words is within the normal range. A second experiment examines her capacity to learn to associate a familiar word with an unfamiliar item from another language. With auditory presentation she is completely unable to perform this task. Further studies show that when visual presentation is used she shows evidence of learning, but is clearly impaired. It is suggested that short-term phonological storage is important for learning unfamiliar verbal material, but is not essential for forming associations between meaningful items that are already known. Implications for the possible role of a phonological short-term store in the acquisition of vocabulary by children are discussed.

Fractionation of working memory: Neuropsychological evidence for a phonological short-term store

A patient with grossly defective short-term memory but fluent speech was studied in order to pinpoint the locus of the deficit. Her immediate memory for consonant sequences showed a clear phonological similarity effect with auditory presentation, but no effect of similarity when presentation was visual. She showed no effect of articulatory suppression and no effect of word length on span, both of which suggest that she was not using subvocal rehearsal. A further test showed that this was not due to her inability to articulate rapidly since her rate of repeating the number sequence 1–10 and of the alphabet was comparable with normal control subjects. These results are interpreted in terms of the articulatory loop component of a working memory model. It is suggested that the loop comprises a phonological store, with obligatory access by auditory spoken material, and optional access through the control process of subvocal rehearsal. Our patient appears to suffer from a defect of the phonological store. This removes the normal advantage gained from using subvocal rehearsal, and induces her to rely instead on visual storage.

Remission of hemineglect and anosognosia during vestibular stimulation

The effects of vestibular stimulation on extrapersonal and personal neglect and on awareness of disease were investigated in four patients with severe neglect and anosognosia. Neglect phenomena improved in all patients, while an effect on anosognosia was found in two cases. These preliminary findings indicate a possible role of vestibular stimulation on hemispheric activation.

Identification of the central vestibular projections in man: a positron emission tomography activation study

The cerebral representation of space depends on the integration of many different sensory inputs. The vestibular system provides one such input and its dysfunction can cause profound spatial disorientation. Using positron emission tomography (PET), we measured regional cerebral perfusion with various vestibular stimulations to map central vestibular projections and to investigate the cerebral basis of spatial disorientation. We showed that the temporoparietal cortex, the insula, the putamen, and the anterior cingulate cortex are the cerebral projections of the vestibular system in man and that the spatial disorientation caused by unilateral vestibular stimulation is associated with their asymmetric activation.

Unilateral neglect: Personal and extra-personal

Ninety-seven right brain-damaged patients were given two tasks aimed at assessing unilateral neglect in personal and in extra-personal space. The frequency of the two aspects of neglect, as well as their patterns of association with each other and with more elementary neurological disorders are reported and discussed. The results suggest a non-unitary frame of spatial reference for unilateral neglect, which may tentatively be interpreted in terms of a personal vs extra-personal dichotomy.