Prism adaptation in patients with unilateral lesion of the parietal or cerebellar cortex: A pilot study on two single cases using a concurrent exposure procedure

Neuroimaging studies showed that prism adaptation (PA), a widely used tool for the rehabilitation of neglect, involves a wide network of brain regions including the parietal cortex and the cerebellum. In particular, the parietal cortex has been suggested to mediate the initial stage of PA through conscious compensatory mechanisms as a reaction to the deviation induced by PA. The cerebellum, on the other side, intervenes in sensory errors prediction to update internal models in later stages. It has been suggested that two mechanisms may underlie PA effects: recalibration, a strategic cognitive process occurring in the initial stages of PA, and realignment, a fully automatic reorganization of spatial maps emerging later and more slowly in time. The parietal lobe has been proposed to be involved mainly in the recalibration whereas the realignment would be carried over by the cerebellum. Previous studies have investigated the effects of a lesion involving either the cerebellum or the parietal lobe in PA taking into account both realignment and recalibration processes. Conversely, no studies have compared the performance of a patient with a cerebellar lesion to that of a patient with a parietal lesion. In the present study, we used a recently developed technique for digital PA to test differences in visuomotor learning after a single session of PA in a patient with parietal and a patient with cerebellar lesions, respectively. The PA procedure, in this case, includes a digital pointing task based on a concurrent exposure technique, which allows patients to fully see their arm during the pointing task. This procedure has been shown to be as effective as the terminal exposure condition in neglect rehabilitation albeit different processes take place during concurrent exposure condition compared to the most used terminal exposure (allowing to see only the final part of the movement). Patients' performances were compared to that of a control group. A single session of PA was administered to 1) a patient (BC) with left parieto-occipital lesion involving SPL and IPL, 2) a patient (TGM) with a stroke in the territory sub-served by the SCA in the cerebellum, and 3) 14 healthy controls (HC). The task included three conditions: before wearing prismatic goggles (pre-exposure), while wearing prisms (exposure) and after removing the goggles (post-exposure). Mean deviations were calculated for the following phases: pre-exposure, early-exposure, late-exposure, post-exposure. The presence of after-effect was calculated as the difference between pre-exposure and post-exposure conditions. For each of these conditions, patients' performance was compared to that of the control group by using a modified Crawford t-test. We found that the patient with the parietal lesion had a significantly different performance in the late-exposure and in the post-exposure compared to both HC and the patient with the cerebellar lesion. Conversely, no differences were observed between TGM and HC across all the conditions. Our results show an increase in the magnitude of the adaptation during the late stage of PA in the patient with the parietal lesion whereas no differences in the performance between the cerebellar patient and the controls were found. These results confirm previous studies suggesting that the parietal cortex is an important node of a wider network involved in PA effect. Furthermore, results in the cerebellar patient suggest that visuomotor learning is not affected by lesions of the SCA territory when a concurrent exposure is used as, in such case, it less relies on sensory errors prediction to update internal models. Results are discussed considering the novelty of the applied PA technique.

Magnetoencephalography reveals differences in brain activations for fast and slow responses to simple multiplications

Despite decades of studies, it is still an open question on how and where simple multiplications are solved by the brain. This fragmented picture is mostly related to the different tasks employed. While in neuropsychological studies patients are asked to perform and report simple oral calculations, neuroimaging and neurophysiological studies often use verification tasks, in which the result is shown, and the participant must verify the correctness. This MEG study aims to unify the sources of evidence, investigating how brain activation unfolds in time using a single-digit multiplication production task. We compared the participants' brain activity-focusing on the parietal lobes-based on response efficiency, dividing their responses in fast and slow. Results showed higher activation for fast, as compared to slow, responses in the left angular gyrus starting after the first operand, and in the right supramarginal gyrus only after the second operand. A whole-brain analysis showed that fast responses had higher activation in the right dorsolateral prefrontal cortex. We show a timing difference of both hemispheres during simple multiplications. Results suggest that while the left parietal lobe may allow an initial retrieval of several possible solutions, the right one may be engaged later, helping to identify the solution based on magnitude checking.

Sleep disorders and cognitive dysfunction in acromegaly

PURPOSE

In the general population, sleep disorders are associated with an increased risk of cognitive impairment. The prevalence of sleep disorders, such as sleep apnea, in acromegalic patients is higher than in the general population, and they may have additional risk of cognitive impairment due to acromegaly treatment and comorbidities. We aim to study the relationship between sleep disturbances and cognitive dysfunction in a group of acromegalic patients.

METHODS

We studied 67 consecutive acromegalic patients. We performed a neurocognitive assessment and patients completed the Acromegaly Quality of Life Questionnaire (AcroQoL), Epworth Sleepiness Scale, and Pittsburgh Sleep Quality Index.

RESULTS

Of the 67 acromegaly patients in the study, 38.8% were male and median age at the neurological examination was 56 (IQR 48, 65). Approximately 6-10% of patients had impaired cognitive assessment, depending on the test. In linear regression models adjusted for age, sex, BMI, disease duration, and disease activity, poorer sleep quality was associated with lower global cognitive z-score (B = -0.03, 95% CI -0.06, -0.002). Daytime somnolence was associated with poorer physical AcroQoL sub-score (B = -0.04, 95% CI -0.08, -0.002). Sleep quality was associated with poorer overall AcroQoL (B = -0.03, 95% CI -0.05, -0.006), physical AcroQoL (B = -0.04, 95% CI -0.07, -0.005), psychological AcroQoL (B = -0.02, 95% CI -0.04, -0.001), and social AcroQoL (B = -0.02, 95% CI -0.04, -0.0009).

CONCLUSIONS

In acromegaly patients, we found robust evidence that poor sleep quality is associated with poorer quality of life, and some evidence that it is associated with poorer cognitive function.

Balancing the 2 Hemispheres in Simple Calculation: Evidence From Direct Cortical Electrostimulation

How do the parietal lobes contribute to simple calculation? Clinical and neuroimaging methods, which are based mainly on correlational evidence, have provided contrasting results so far. Here we used direct cortical electrostimulation during brain surgery to causally infer the role of the left and right parietal lobes in simple calculation. Stimulation provoked errors for addition and multiplication in different parietal areas on both hemispheres. Crucially, an innovative qualitative error analysis unveiled the functional contrast of the 2 parietal lobes. Right or left stimulation led to different types of substitution errors in multiplication, unveiling the function of the more active hemisphere. While inhibition of the left hemisphere led mainly to approximation errors, right hemisphere inhibition enhanced retrieval within a stored repertory. These results highlight the respective roles of each hemisphere in the network: rote retrieval of possible solutions by the left parietal areas and approximation to the correct solution by the right hemisphere. The bilateral orchestration between these functions guarantees precise calculation.

Numerical activities of daily living in adults with neurofibromatosis type 1

BACKGROUND

This study aimed to identify the mathematical domains affected in adults with neurofibromatosis 1 (NF1) and the impact of the numerical difficulties on the patients' activities of daily living.

METHODS

We assessed 28 adult patients with NF1 and 28 healthy control participants. All participants completed the standardised battery of numerical activities of daily living along with clinical batteries of cognitive (Mini-Mental State Examination) and daily functioning (instrumental activities of daily living). The group comparisons of the performance on numerical activities of daily living were carried out using t-test correcting for multiple comparisons.

RESULTS

The results showed that the NF1 group performed worse than controls in written subtractions, written multiplication, multiplication principles and digit comprehension (dot counting) tasks. Importantly, no significant differences in numerical ecological tasks were found between patients and controls, suggesting a possible use of compensatory strategies in daily living abilities in spite of calculation deficits.

CONCLUSION

The findings indicate that NF1 affects calculation but not the basic comprehension or representation of numbers in adult patients. These data have important implications for designing cognitive interventions tailored to the cognitive profile of individuals with NF1.

Re-assessing acalculia: Distinguishing spatial and purely arithmetical deficits in right-hemisphere damaged patients

Arithmetical deficits in right-hemisphere damaged patients have been traditionally considered secondary to visuo-spatial impairments, although the exact relationship between the two deficits has rarely been assessed. The present study implemented a voxelwise lesion analysis among 30 right-hemisphere damaged patients and a controlled, matched-sample, cross-sectional analysis with 35 cognitively normal controls regressing three composite cognitive measures on standardized numerical measures. The results showed that patients and controls significantly differ in Number comprehension, Transcoding, and Written operations, particularly subtractions and multiplications. The percentage of patients performing below the cutoffs ranged between 27% and 47% across these tasks. Spatial errors were associated with extensive lesions in fronto-temporo-parietal regions -which frequently lead to neglect- whereas pure arithmetical errors appeared related to more confined lesions in the right angular gyrus and its proximity. Stepwise regression models consistently revealed that spatial errors were primarily predicted by composite measures of visuo-spatial attention/neglect and representational abilities. Conversely, specific errors of arithmetic nature linked to representational abilities only. Crucially, the proportion of arithmetical errors (ranging from 65% to 100% across tasks) was higher than that of spatial ones. These findings thus suggest that unilateral right hemisphere lesions can directly affect core numerical/arithmetical processes, and that right-hemisphere acalculia is not only ascribable to visuo-spatial deficits as traditionally thought.

TMS of supplementary motor area (SMA) facilitates mental rotation performance: Evidence for sequence processing in SMA

In the present study we applied online transcranial magnetic stimulation (TMS) bursts at 10Hz to the supplementary motor area (SMA) and primary motor cortex to test whether these regions are causally involved in mental rotation. Furthermore, in order to investigate what is the specific role played by SMA and primary motor cortex, two mental rotation tasks were used, which included pictures of hands and abstract objects, respectively. While primary motor cortex stimulation did not affect mental rotation performance, SMA stimulation improved the performance in the task with object stimuli, and only for the pairs of stimuli that had higher angular disparity between each other (i.e., 100° and 150°). The finding that the effect of SMA stimulation was modulated by the amount of spatial orientation information indicates that SMA is causally involved in the very act of mental rotation. More specifically, we propose that SMA mediates domain-general sequence processes, likely required to accumulate and integrate information that are, in this context, spatial. The possible physiological mechanisms underlying the facilitation of performance due to SMA stimulation are discussed.

Right hemisphere dysfunction and emotional processing in ALS: an fMRI study

Emotional processing may be abnormal in amyotrophic lateral sclerosis (ALS). Our aim was to explore functional anatomical correlates in the processing of aversive information in ALS patients. We examined the performance of nine non-demented ALS patients and 10 healthy controls on two functional MRI (fMRI) tasks, consisting of an emotional attribution task and a memory recognition task of unpleasant versus neutral stimuli. During the emotional decision task, subjects were asked to select one of three unpleasant or neutral words. During the memory task, subjects were asked to recognize words presented during the previous task. Controls showed, as expected, greater activation in the right middle frontal gyrus during selection of unpleasant than neutral words, and a greater activation mainly in right-sided cerebral areas during the emotional recognition task. Conversely, patients showed a general increase in activation of the left hemisphere, and reduced activation in right hemisphere in both emotional tasks. Such findings may suggest extra-motor neurodegeneration involving key circuits of emotions, mostly negative, commonly involved in FTD.

Quality of life and psychological well-being in GH-treated, adult PWS patients: a longitudinal study

BACKGROUND

Prader-Willi syndrome (PWS) is a congenital alteration of chromosome pair 15. It is characterized by short stature, muscular hypotonia, hyperphagia, obesity, behavioural and emotional disturbances, hypogonadism and partial Growth Hormone (GH) deficiency. The aim of this study was to assess the long-term effect of GH treatment on the psychological well-being and Quality of Life (QoL) in an adult PWS group.

METHODS

A total of 13 PWS patients, their diagnosis confirmed by genetic tests, and their parents were recruited for this study. The participants were administered the 36-Items Short Form Health Survey (SF-36) and the Psychological General Well-Being Index (PGWBI), for the assessment of QoL and psychological well-being, at the beginning of GH treatment, and at following intervals of 6, 12 and 24 months. Modified versions of the same questionnaires were given to the parents.

RESULTS

Significant improvement with respect to the baseline was found, on both scales, in the evaluation of both physical and psychological well-being, although the parents' evaluation was less optimistic than that of the patients.

CONCLUSION

Our findings suggest that the amelioration of QoL and psychological status is sustained in patients who continue GH treatment.

Decision-making in obesity: a study using the Gambling Task

The present study addresses the issue of whether a "decision-making disorder" could account for the behavioral problems of severely obese patients (BMI score >34) who are not classified by traditional psychiatric Eating Disorder tests. The neuropsychological test employed, the Gambling Task (GT), is not directly related to the food domain, but it is sensitive to failure in making long-term advantageous choices. A comparison was made of 20 obese subjects (OS) and 20 normal-weight subjects (NWS) matched in age, education and IQ. The subjects' personalities and food behavior were assessed from psychological questionnaires, and then the Gambling Task was administered. The number of "good" choices made by the two groups during GT performance differed significantly, and the OS did not learn to maximize advantageous choices like the NWS did. OS behavior could be consistent with a prefrontal cortex defect that implies difficulties in inhibition of excessive food intake.

Mathematical skills in Prader-Willi Syndrome

OBJECTIVES

This paper investigates mathematical skills in Prader-Willi Syndrome (PWS), a pathological condition because of congenital alterations of chromosome pair 15. The following questions were addressed: (1) Are mathematical skills in PWS relatively more impaired with respect to other cognitive functions (as has been repeatedly but anecdotally reported)?; and (2) What is the nature of the mathematical impairment?

METHODS

The first study employed the Wechsler Adult Intelligence Scale (WAIS) and an extensive battery of cognitive tasks for which norms are known. Both batteries include a mathematical section. The second study used a theoretically motivated series of mathematical tasks specifically designed to individually assess the different cognitive components underlying mathematical skills.

RESULTS

Mathematical skills were found to be the most impaired cognitive abilities together with short-term memory capacity. No specific mathematical domain was seen to be unaffected in PWS participants. The clearest deficits observed concern 'syntactic' processes in number transcoding, multiplication, number facts retrieval and calculation procedures.

CONCLUSION

Failure of mathematical skills is the most distinctive feature in the cognitive profile of PWS. However, to determine whether this is indeed a specific pattern of performance related to PWS, results must be compared with those obtained with patients manifesting other genetic disorders.

Anomia for people names in DAT--evidence for semantic and post-semantic impairments

Proper name anomia is a frequent finding among patients in the early stages of Alzheimer's disease. The present study investigates naming of famous persons in a group of DAT patients, a group of persons with mild cognitive impairment (MCI) and healthy controls. The study is aimed at distinguishing the relative contributions of semantic and post-semantic factors to difficulties in proper name retrieval. As shown by a significantly lower score in answering semantic questions, DAT patients retrieve less biographical knowledge related to famous persons than healthy elderly subjects and persons with mild cognitive impairment. This finding is in line with the frequent observation of semantic deficits in early and moderate DAT. The high number of Tip-of-the-Tongue (TOT) answers in DAT found in relation to few spontaneously named items shows that post-semantic deficits are as important as semantic deficits in determining anomia for people names in DAT. Moreover, DAT patients were less sensitive to phonological cueing than healthy persons or persons with mild cognitive impairment. These findings suggest that proper name anomia in DAT is not only due to semantic deficits, but also to problems in accessing the phonological representation, as well as to a degradation of phonological representations. Thus, naming deficits in DAT differ not only quantitatively, but also qualitatively from the difficulties of healthy elderly persons. No significant differences were found between persons with mild cognitive impairment and healthy controls in proper name retrieval.

Proper names in patients with early Alzheimer's disease

The objective of this study was to seek evidence of the particular sensitivity of proper name retrieval and to check the usefulness of proper names as diagnostic material in the early stages of Alzheimer's disease (AD). Whether a generalized naming deficit is an early symptom of AD it is not yet clear. Previous studies suggest that proper names might be the category of names that is indeed more sensitive to AD. Seventy AD patients (subdivided into "very mild", "mild" and "moderate") and 47 control subjects participated in the study. The performances in two short distinct tests requiring proper name retrieval (Naming People on Definition and Naming Faces), one test of common name retrieval, short (MMSE, 3MS) and long (MODA) batteries for the detection of dementia were compared. Proper name retrieval tests were shown to be more sensitive to early AD than any other tests and batteries that failed to distinguish "very mild" AD from controls. These findings suggest that proper name retrieval tasks might be profitably included in diagnostic tools for the early diagnosis of AD.

Common daily activities in the virtual environment: a preliminary study in parkinsonian patients

Patients with Parkinson's disease (PD) create behavioral motor strategies by using external cues to facilitate their movements. Virtual reality (VR) could work as an external stimulus in order to explore the motor plans by means of creation of mental images. We tested 2 women with PD aged 68 and 69 years, and 10 normal control subjects. Patients underwent a neuropsychological assessment to evaluate cognitive abilities involved in the tasks required by the VR session. VR environment reproduces common daily activities situations at home, such as eating or using the bathroom. VR describes the alterations of the motor plans in PD by a point of view different from the clinical one, by testing "pure" mental sequences of the execution of a movement, without the interference of motor disability.

Noun verb dissociation in Parkinson's disease

A noun/verb dissociation with a relative verb deficit was found in patients affected by Parkinson's disease, even in relatively early stages, when mental deterioration is not severe. This finding is compatible with earlier observations, according to which verbs are dealt with in more anterior regions with respect to nouns. It also supports the speculation that the co-ordination and the manipulation of information associated with a verb world rely on the frontostriatal system.

Lexical representation and processing of morphologically complex words: evidence from the reading performance of an Italian agrammatic patient

The study of patients with acquired language disorders has provided crucial evidence for contemporary theories on mental lexical representation. This is particularly true for the representation of morphologically complex words. In this paper we analyzed the performance of a patient (M.B.) affected by agrammatism and dyslexia. M.B. was required to read aloud simple and morphologically complex words. The patient's pattern of errors was interpreted as the result of a predominant use of the lexical routine (phonological dyslexia). Three reading tasks were developed which allowed us to test M.B.'s ability to read morphologically complex words (reading of regular and irregular plurals; reading of high- and low-frequency singular and plural nouns; reading of evaluative suffixes). Errors were determined by frequency effect rather than by type of suffix (i.e., inflectional or derivational). High-frequency morphologically complex items seemed to meet stored representations, thus avoiding the parsing procedures that are required for less frequent items. These results are in keeping with dual route models of lexical representation of morphologically complex words.

Letter and number writing in agraphia: a single-case study

The gradual recovery of writing abilities of a patient whose processing of Arabic numerals and alphabetic script evolved differently over time is reported. Writing of multidigit numerals was achieved when writing of letters was nil. However, despite an initial advantage for numbers, the final examination disclosed fluent and correct writing of letters and words together with specific syntactic difficulties in complex Arabic numerals. The differential improvement for Arabic and alphabetic stimuli is partly explained in terms of different processing requirements rather than in terms of script-specific mechanisms only.

Executive deficits appearing in the initial stage of Alzheimer's disease

The presence of executive deficits has been sought at a stage of Alzheimer's disease where currently used neuropsychological batteries could not yet distinguish Alzheimer's patients from normal age- and education-matched controls. This study shows that, at this early stage, those patients that 6 months later are found to show clear signs of Alzheimer's had been significantly worse than normal controls in an executive function task adapted from the Brown-Peterson procedure.

Naming of musical notes: a selective deficit in one musical clef

We investigated the ability to perform solfeggio, i.e. oral reading of musical notes in MP, a 65 year-old female professional musician, who, following a left temporoparietal ischemia, showed a complex pattern of amusia. The deficit on which we focused was her inability to read orally the bass (F) clef, often substituting it with the violin (G) clef. This problem could not be attributed to a lack of comprehension. The patient could in fact correctly perform on the piano the same sequences she erroneously read aloud; she was also able to correctly judge whether two strings, one in bass clef and the other in violin clef, represented the same sequence of notes. The problem seems to lie in the inability to retrieve note names keeping into account the clef-rule. It is hypothesized that, in the production of note names, this function requires the identification and application of syntactic-like information, in analogy with what is thought to happen in the retrieval of other words.

ERP indexes of functional differences in brain activation during proper and common names retrieval

Functional neuroimaging and neuropsychological findings suggest that memory retrieval of common and proper names is subserved by different neuro-functional systems but little is known about the topographic localization of neural generators. In the present study brain electrical activity was recorded with a high density electrode montage in healthy young volunteers during lexical retrieval upon written definition. ERPs spatio-temporal mapping showed on one side a strong activation of left anterior temporal and left central-frontal areas for proper names, and on the other side a greater involvement of occipital areas for common names retrieval. The specific pattern of bio-electrical activity recorded during proper names retrieval might index the activation of neural circuits for recalling names of high contextual complexity, poor of sensory-motor associations and dependent on precise spatio-temporal coordinates.

Left anterior lobectomy and category-specific naming

Damasio and colleagues (1996) have proposed that the left anterior temporal region supports knowledge pertaining to living objects, whereas more posterior temporal regions play a critical role in naming nonliving things. Accordingly, one might expect that left-sided anterior temporal lobectomy should have a more profound effect on the naming of living as opposed to nonliving things. As part of a multicenter collaborative project, seventy-nine patients (all left-hemisphere speech dominant) were tested pre- and post-left-temporal lobectomy on a task that required naming of living and nonliving items equated for name frequency, familiarity, and visual complexity. Consistent with the proposals of Damasio et al. (1996), left temporal lobectomy impaired naming ability, particularly for living things. When individual outcomes were considered, twice as many patients showed a relative decline in naming living as opposed to nonliving things.

Proper names in the early stages of Alzheimer's disease

A short proper name retrieval test was found to discriminate between unselected subjects and age- and education- matched patients affected by Alzheimer's type dementia at a stage where the Mini-Mental State Examination could not detect a difference between these groups. The proper name retrieval task also compared favorably with the 3MS, a more sensitive, modified version of the MMSE. These findings suggest that proper name retrieval could be used to an advantage and become a routine component of short batteries for the early detection of Alzheimer's disease.

Writing and rewriting numerals: a dissociation within the transcoding processes

In the present study we report the case of A.B., a patient with a specific, though not isolated, deficit in transcoding verbal to Arabic numerals. Despite perfect production of Arabic numerals in a writing to dictation task, she frequently produced syntactic errors when the input was in written verbal form (e.g., duecentotrenta [two hundred and thirty] --> 20030). In absence of problems in the verbal comprehension system, A.B.'s performance is difficult to accommodate within current models of number processing. In the attempt to interpret the present findings, we suggest that different numerical codes, i.e, spoken and written verbal numerals, activate with different efficiency the transcoding algorithm.

Numerical skills and aphasia

The aim of this study was to investigate numerical difficulties in 50 patients with left hemispheric lesions. Aphasic patients were grouped according to their type of aphasia diagnosed by the Aachener Aphasia Test. The overall error rate in various transcoding and calculation tasks was clearly correlated with the severity of the language deficit, global aphasics being the most impaired patients. Broca's and Wernicke's aphasics scored similarly at the quantitative level, and amnesic aphasics were less impaired. Interestingly, qualitative analysis of the errors indicated that each group presented with specific difficulties, partially reflecting the nature of the language problems. In simple calculation, multiplication was found to be the most impaired operation, in particular in Broca's aphasics. This result supports the hypothesis that the retrieval of multiplication facts is preferentially mediated by verbal processing. Calculation procedures were mainly impaired in Wernicke's and global aphasics.

Repetition priming in simple addition depends on surface form and typicality

Repetition priming and recognition memory for numbers were measured in four experiments using single-digit addition. Results of the first two experiments indicate that when numbers were presented as number words and dot configurations, preexposure of the same problem in the same notation produced greater reaction-time benefit than did preexposure of the same problem in Arabic-digit notation. In contrast, when numbers were presented as Arabic digits, preexposure of the same problem in Arabic digit, number word, and dot notation produced the same amount of priming. In the third experiment, priming was shown to be greatest, for all three notations, when the task performed on preexposure trials (addition or multiplication) matched the task performed on repetition trials (addition). Results of the fourth experiment, measuring recognition memory, were comparable to the priming results in the sense that memory was superior when notation matched across repetitions if the test involved number words and dot configurations but not Arabic digits. These data are interpreted in terms of models of numerical cognition, and they support the hypothesis that the influence of surface form on repetition priming depends on the typicality of the input for the task.

The processing of compound words: a study in aphasia

The naming difficulties of an aphasic patient (MB) are almost exclusively confined to compound words. The paraphasias in response to compounds always reflect the compound structure of the targets. Frequent semantically adequate substitution errors suggest the separate processing of single components at the lemma level. MB's specific difficulties probably arise when two lemmas are defined by one lexical entry, as we suggest for compounds. The compound structure, as well as the positions of the single lemmas within the compound, would be specified before lemmas are accessed. The lack of a positional effect in substitution errors suggests a parallel activation of the two components.

A deficit for arithmetical procedures: lack of knowledge or lack of monitoring?

A patient is described with a specific deficit for arithmetical procedures. Unlike in previously described cases, where the observed problems could be attributed to the systematic application of disturbed algorithms, this patient's difficulty seems to stem from an inability to monitor the sequence of operations that calculation procedures specify. Criteria are provided for distinguishing impairments in written calculation due to the application of defective knowledge of the procedures from those determined by lack of monitoring. The role of monitoring and control processes in different calculation components is also discussed.

The grammatical properties of mass nouns: an aphasia case study

A patient (F.A.) is described who, as a consequence of brain damage, shows an isolated deficit concerning the use, across a series of tasks, of the grammatical properties of mass/non-countable nouns. Her use of grammar is otherwise perfect. This behaviour dissociates from that of other patients who have severe grammatical difficulties, but do not show any impairment in the mass nouns tasks that F.A. fails. This case is thought to demonstrate how specific grammatical rules, that are said to be stored at the lemma level of lexical retrieval, are indeed independently represented and accessible.

Hemispheric specialization for sign language

Most studies on sign lateralization provide inconclusive results about the role of the two hemispheres in sign language processing, whereas the cases reported in the clinical literature show sign language impairment only following left hemisphere damage, suggesting a similar neural organization to spoken languages. By discriminating different levels of processing, a tachistoscopic study found that in deaf subjects matches of sign language handshapes based on equivalence of meaning are processed faster in the right visual field, thus demonstrating a left hemisphere superiority.

Dichaptic scanning of Braille letters by skilled blind readers: lateralization effects

Dichaptic scanning of Braille letters was studied in 14 skilled blind readers, using Posner's paradigm. A right-hand (left-hemisphere) advantage was found when letters could be matched on the basis of their names (Name Identity Condition), a genuinely linguistic task, while no effects of lateralization appeared when matching could be performed on the basis of perceptual identity (Perceptual Identity Condition) or on "Different" responses. This result provides information about the cerebral lateralization of Braille reading and casts doubts about the current claim that linguistic material, when presented in the tactile modality, is initially analysed in a spatial code by the right hemisphere.

The representation of arithmetical facts: evidence from two rehabilitation studies

We report the improvement following rehabilitation of two patients with a selective deficit on multiplication facts. The remediation experiments were conducted in specific designs to test a series of hypotheses about both the process of reacquisition and organisation of arithmetical facts in memory. The results show a significant and stable recovery and the pattern of reacquisition reflects the different strategy used by the patients to relearn the multiplication facts. Quantitative and qualitative changes in error patterns in the course of remediation reveal the underlying (re)organization of the memory network representing multiplication facts.

Generating visual mental images: deficit after brain damage

This is the first non-retrospective neuropsychological group study using a componential task analysis for the study of imagery. Seventy unilaterally brain damaged patients were tested on a series of tasks with the intent of isolating genuine deficits of the image generation process. The main finding is that the image generation seems to be more frequently disturbed after a left posterior damage. Suggestions are provided for further investigations.

Concepts and facts in calculation

A patient is described who is affected by an inability to recall and use 'arithmetical facts' of one-digit multiplications and divisions. This loss contrasts with the preservation of a wide set of complex notions that the patient exploits in order to overcome his deficit and get the right result. This observation helps in isolating and describing an important component of arithmetical long-term memory that is not overlearnt and the functioning of which is not automatic or mechanistic. An account of such a component is lacking in models of arithmetic currently referred to in cognitive neuropsychology. In a remediation study, performed over several weeks, the effect of training was selective for each single arithmetical fact: not even skills with multiplication complements (e.g. 6 x 3, 3 x 6) fully benefited from the rehabilitation of a specific fact. This suggests that the storage format of each fact is independent from that of other facts.

Anomia for people's names

The case of an anomia for people's names is reported. The study of this dissociation helps to clarify the difference in processing between proper and common names. Associated deficits in this and previously described cases provide support for the idea that an inability to retrieve arbitrary relations is the basis of the naming difficulty. This would confirm the role of proper names as purely referring expressions.

Production of proper names: a clinical case study of the effects of phonemic cueing

The production of proper names is a task that in everyday life is particularly prone to temporary failures, especially in elderly subjects. The reason for this is still rather obscure but indications in recent literature suggest an independent status for proper names in comparison with common ones, which may entail differences in processing or in processing demands. The main sources of empirical evidence come, on the one hand, from studies of face and person identity recognition and, on the other, from neuropsychological observations. All the findings appear to concur in supporting theoretical distinctions that have been made for a long time in the field of philosophy of language. These distinctions have directed the endeavours of experimental research. The present study describes, for the first time, a neuropsychological patient who shows, in certain conditions, a sparing of proper names despite an otherwise deeply troubled linguistic production. This finding may appear to be counterintuitive, considering the fact that proper names are viewed, in general, as more difficult to produce than common ones. However, in consideration also of other emerging neuropsychological and experimental findings, it is proposed that possible differences in lexical access for the two categories of common and proper names may explain the phenomenon and still be consistent with mainstream philosophical theories.

Reading aloud in jargonaphasia: an unusual dissociation in speech output

A patient is described who showed several dissociations between oral and written language processing after bilateral retrorolandic vascular lesion. Dissociation was firstly between abolished auditory comprehension and preserved written comprehension and then involved confrontation naming, clearly superior in the written modality. The third striking dissociation involved oral output; spontaneous speech, although fluent and well articulated, consisted of neologistic jargon, while reading aloud was clearly superior though not perfect. Data are discussed with reference to a cognitive model of word processing. The pattern of dissociation in word production may be due to a failure in retrieving the phonological word form from the semantic system.

Analysis of the spontaneous writing errors of normal and aphasic writers

Samples of spontaneous writing were collected from 150 normal subjects, 13 Broca's aphasics, 23 Wernicke's aphasics and 14 conduction aphasics. The errors obtained were classified using a system derived from investigations of slips of the pen in normal subjects. All three aphasic groups made a higher proportion of word-level errors than did the normal writers. Word-level errors tended to be selection errors (substitutions, blends, neologisms, and omissions) rather than movement errors (anticipations, perseverations and reversals). Conduction aphasics showed proportionately more letter movement and fewer letter selection errors than normal writers while Wernicke's and Broca's aphasics showed similar proportions. Graphic and phonetic similarity was no more important a determinant of letter errors in aphasics than in normals. The span of movement errors was particularly restricted in the Broca's and conduction aphasics. Asking patients to write connected text yields insight into the nature of the underlying disorder that could not be obtained from studying the writing of single words.

An unusual case of perseveration sparing body-related tasks

A patient who, following left occipital and posterior callosal lesion, showed a massive pattern of perseveration with sparing of body related tasks is described. It is thought that such dissociation would reflect independence of body related tasks at the level of internal representation.

Word formation: new evidence from aphasia

Three aphasic patients are described whose speech contains invented word-forms which are legal combinations of meaningful parts of real words, like "fratellismo" (brother + ness) instead of "fratellanza" (brother + hood), and from combinations of meaningless and meaningful parts, like "terness + ico" (where "ico" is a real adjectival ending). These phenomena are previously unreported. On the assumption that brain-damaged patients use residual rather than novel abilities, these forms, along with the patients' predominant use of real compound words, indicate that speakers have a procedure for composing polymorphemic words online, but this is employed just when trying to find a whole word fails.

Study of the temporal variables in the spontaneous speech of three neologistic jargonaphasics

Hesitation analysis of spontaneous production from three neologistic jargonaphasics is described. The results appear to differ from patient to patient as far as the relative proportion in the number and length of pauses before correct words and mistakes is concerned. Generalization of the conclusion beyond single cases may not therefore be legitimate.

Evidence from aphasia for the role of proper names as pure referring expressions

Here we describe a patient who, as a result of brain damage, had a dramatic inability to retrieve proper names, and who thus offered the opportunity of observing the distinction made in the brain between proper and common names. Although category specific aphasic disturbances are relatively common, this patient's anomia for proper names is very rare: only two other cases have been described so far. The opposite phenomenon, a selective sparing of proper names, has also been recently observed. It is widely assumed that double dissociations such as this reflect the premorbid organization of the cognitive system: the categories of proper and common nouns, therefore, would be separately represented or, at least, separately accessed in the intact brain. The only other such deficits, including the inability to learn arbitrary links between words and to guess the titles of pieces of music, are believed to be indicative of a problem in dealing with purely referential relations. This, in turn, would indirectly confirm the role of proper names as pure referring expressions.

Impaired grating discrimination following right hemisphere damage

We investigated the effect of unilateral brain lesions on visual discrimination of low-, middle- and high-frequency gratings. The performance of patients with right hemisphere lesions was significantly impaired compared with that of both controls and patients with left hemisphere lesions. This impairment was largely limited to patients with right posterior hemispheric lesions and was present with all spatial frequencies. These findings run counter to the hypothesis that high and low spatial frequencies are preferentially processed by different hemispheres.

Impairment in localization of body parts following brain damage

A patient is described who was unable, on various conditions and modalities, to localize body parts. Her difficulty could not be accounted for by other neuropsychological disturbances and seemed to be body specific, since she had no trouble at localizing single parts of objects. The pattern of her errors suggests that her disturbance involved the conceptual representation of individual body parts. This case supports the hypothesis that knowledge of one's own body is stored at some level, independently of other kinds of knowledge; it also appears to be organized as a set of concepts representing single body parts, where functionally similar parts are closely related to each other irrespective of their actual distance on the body.

Right hemisphere patients' judgements on emotions

A triadic comparison technique was used to assess brain-damaged patients' ability to judge the relatedness of a number of emotions, using either a pictorial or verbal material. Emotionally neutral material served as a control. Right hemisphere patients also differed from normals in processing emotions when presented with verbal material. It is suggested that central rather than only peripheral aspects in recognition of emotions are disturbed after injury to the right hemisphere.

The role of the right hemisphere in processing negative sentences in context

Given a pattern consisting of x1, x2,..., xn similar elements and y1, which is perceived as different from the former, it is more plausible to assert that y is not x rather than to assert that x is not y (Wason, J. verb. Learn verb. Behav. 4, 7-11, 1965). In order to appreciate such a difference, the entire set has to be considered. Right-hemisphere brain-damaged patients were submitted to a series of visually presented patterns, each pattern consisting of seven similar items and one dissimilar item. Their task was to complete a statement referring to a single element of each pattern. Statements were either simple affirmative or negative sentences. Errors and reaction times were recorded. Patients with a right-hemisphere injury were found to be insensitive to the plausible-implausible dimension in completing negative sentences. It is hypothesized that right-hemisphere brain-damaged patients are less adequate in this task because they are less capable in putting each element into the visual context.

Localization of body parts in brain injured subjects

The issues which were dealt with in this study were whether the determinants of failure in body part identification differed as a function of modality of stimulus presentation or as a function of response conditions, and whether such differences could be attributed to neurologically determined variables, or to a generalized disorder of awareness of body topology. No evidence was found to support any of these latter factors as an explanation for impaired body part identification. Rather it can be concluded that a common factor underlies success in identifying body parts under all conditions and that this factor is the strength and precision of the conceptual representation of individual body parts.