Social groups have a representation of their own: Clues from neuropsychology

The most relevant evidence for the organization of the conceptual knowledge in the brain was first provided by the patterns of deficits in brain-damaged individuals affecting one or another semantic category. Patients with various etiologies showed a disproportionate impairment in producing and understanding names of either living (fruits, vegetables, animals) or nonliving things (tools, vehicles, clothes). These double dissociations between spared and impaired recognition of living and nonliving things led to suggest that these categories are discretely represented in the brain. Recently social groups were found to be represented independently of traditional living and nonliving categories. Here we tested 21 patients with different types of primary dementia with three word sorting tasks tapping their conceptual knowledge about living and nonliving entities and social groups. Patients double dissociated in categorizing words belonging to the three categories. These findings clarify that knowledge about social groups is distinct from other semantic categories.

Evaluation of emotion processing in HIV-infected patients and correlation with cognitive performance

BACKGROUND

Facial emotion recognition depends on cortical and subcortical networks. HIV infection of the central nervous system can damage these networks, leading to impaired facial emotion recognition.

METHODS

We performed a cross-sectional single cohort study consecutively enrolling HIV + subjects during routine outpatient visits. Age, gender and education-matched HIV-negative healthy individuals were also selected. Subjects were submitted to a Facial Emotion Recognition Test, which assesses the ability to recognize six basic emotions (disgust, anger, fear, happiness, surprise, sadness). The score for each emotion and a global score (obtained by summing scores for each emotion) were analyzed. General cognitive status of patients was also assessed.

RESULTS

A total of 49 HIV + and 20 HIV - subjects were enrolled. On the Facial Emotion Recognition Test, ANOVA revealed a significantly lower performance of HIV + subjects than healthy controls in recognizing fear. Moreover, fear facial emotion recognition was directly correlated with Immediate Recall of Rey Words. The lower the patients' neurocognitive performance the less accurate they were in recognizing happiness. AIDS-defining events were negatively related to the correct recognition of happiness.

CONCLUSIONS

Fear recognition deficit in HIV + patients might be related to the impaired function of neural networks in the frontostriatal system. AIDS events, including non-neurological ones, may have a negative effect on this system. Inclusion of an emotion recognition test in the neuropsychological test battery could help clinicians during the long term management of HIV-infected patients, to better understand the cognitive mechanisms involved in the reduction of emotion recognition ability and the impact of this impairment on daily life.

Cardiovascular risk factors and carotid intima-media thickness are associated with lower cognitive performance in HIV-infected patients

OBJECTIVES

The aim of the study was to investigate the relationship between metabolic comorbidities, cardiovascular risk factors or common carotid intima-media thickness (cIMT) and cognitive performance in HIV-infected patients.

METHODS

Asymptomatic HIV-infected subjects were consecutively enrolled during routine out-patient visits at two clinical centres. All patients underwent an extensive neuropsychological battery and assessment of metabolic comorbidities and cardiovascular risk factors. Moreover, cIMT was assessed by ultrasonography. Cognitive performance was evaluated by calculating a global cognitive impairment (GCI) score obtained by summing scores assigned to each test (0 if normal and 1 if pathological).

RESULTS

A total of 245 patients (median age 46 years; 84.1% with HIV RNA < 50 copies/mL; median CD4 count 527 cells/μL) were enrolled in the study. Cardiovascular risk factors were highly prevalent in our population: the most frequent were dyslipidaemia (61.2%), cigarette smoking (54.3%) and hypertension (15.1%). cIMT was abnormal (≥ 0.9mm) in 31.8% of patients. Overall, the median GCI score was 2 [interquartile range (IQR) 1-4]; it was higher in patients with diabetes (P = 0.004), hypertension (P = 0.030) or cIMT ≥ 0.9 mm (P < 0.001). In multivariate analysis, it was confirmed that diabetes (P = 0.007) and cIMT ≥ 0.9 mm (P = 0.044) had an independent association with lower cognitive performance. In an analysis of patients on combination antiretroviral therapy (cART), abacavir use was independently associated with a better cognitive performance (P = 0.011), while no association was observed for other drugs or neuroeffectiveness score.

CONCLUSIONS

Diabetes, cardiovascular risk factors and cIMT showed a strong association with lower cognitive performance, suggesting that metabolic comorbidities could play a relevant role in the pathogenesis of HIV-associated neurocognitive disorders in the recent cART era.

Unilateral spatial neglect in degenerative brain pathology

OBJECTIVE

In an attempt to interpret neglect as a disconnection syndrome, it is currently proposed that the disorder results from disorganization of large-scale networks involved in attentional spatial processes rather than of individual brain areas. We hypothesize that as degenerative brain diseases are "system pathologies," degeneration could be restricted to some of the neural subsystems implicated in the functional organization of spatial attention and different neglect syndromes could emerge depending on the patterns of the subsystems involved.

METHOD

We studied five neglect patients: one with corticobasal degeneration (CBD), three with Posterior Cortical Atrophy (PCA) and one with frontotemporal dementia (FTD).

RESULTS

The patient with CBD and left parietoccipital atrophy showed right allocentric neglect; the three patients with PCA mostly distributed in the right posterior regions showed left egocentric extrapersonal neglect; the patient with FTD, who displayed more severe frontotemporal atrophy on the right, had left motor-executive neglect for both personal and extrapersonal space. All patients also presented a deep breakdown of spatial working memory.

CONCLUSION

Our data would confirm that left neglect is more frequent than right neglect also in degenerative pathology and that damage to different neural substrates can produce different types of neglect. Our findings are also consistent with the hypothesis that both lateralized and nonlateralized attention disorders contribute to generate the syndrome. We suggest that evidence from degenerative diseases may contribute to construction of models of spatial attention.

Efavirenz associated with cognitive disorders in otherwise asymptomatic HIV-infected patients

BACKGROUND

Despite the availability of potent antiretroviral regimens (combination antiretroviral therapy [cART]), HIV-associated neurocognitive disorders (HAND) are increasingly recognized. Our aim was to investigate the prevalence and treatment-related correlates of HAND, exploring the potential neurotoxicity of antiretrovirals on cognitive functions.

METHODS

We performed a cross-sectional single cohort study by consecutively enrolling asymptomatic HIV+ subjects during routine outpatient visits. Each patient was submitted to a comprehensive neuropsychological battery and was considered cognitively impaired on the basis of results obtained in matched healthy HIV-negative subjects. CNS penetration effectiveness (CPE) rank was calculated for cART regimens according to 2010 CHARTER criteria. Factors associated with cognitive impairment were investigated by linear or logistic regression analysis.

RESULTS

A total of 146 patients were enrolled. Of these, 129 (88.4%) were on cART and 59.6% of them were on current regimen from ≥1 year. Sixty-nine patients (47%) were classified as cognitively impaired (35.6% asymptomatic and 11.6% mild neurocognitive impairment). In the multivariate analysis, efavirenz use (odds ratio [OR] = 4.00; p = 0.008) and non-Italian nationality (OR = 3.46; p = 0.035) were associated with increased risk of cognitive impairment, whereas higher education was associated with a lower risk (OR = 0.85; p = 0.002). Furthermore, efavirenz use and age ≥65 years independently predicted worse performance on the double barrage and the Stroop test (time). No association between CPE rank and cognitive impairment was observed.

CONCLUSIONS

A high prevalence of HAND was observed in apparently asymptomatic HIV+ individuals. HAND was associated with efavirenz use, suggesting the potential neurotoxicity of this drug. Routine neuropsychological examinations could help clinicians make correct diagnoses and manage mild, but clinically relevant, forms of HAND.

BuChE K variant is decreased in Alzheimer's disease not in fronto-temporal dementia

Alzheimer's disease (AD) is characterized by a significant reduction in AcetylCholinesterase and an increase in ButyrylCholinesterase (BuChE) activity. The existence of polymorphic regions on the BuChE gene has been previously described; the most frequently found polymorphism is the so-called K variant, which leads to a 30% decreased enzymatic activity. Different studies reported a positive association between K variant and AD, strongest among late-onset AD and Apolipoprotein E (APOE) e4 carriers. We analyzed APOE and BuChE polymorphisms in 167 AD and 59 fronto-temporal dementia (FTD) patients compared with 129 healthy controls (HC). We reported a significantly lower frequency of the BuChE K variant in AD compared with HC and FTD and a significant increased frequency of the K variant in FTD. These results are in agreement with the known increase of the BuChE activity in AD and support the evidence of different molecular pathways involved in the pathogenesis of AD and FTD.

Verbal short-term memory and cerebellum: evidence from a patient with congenital cerebellar vermis hypoplasia

The impairment of phonological short-term memory has been reported in adults with cerebellar lesions. At the same time, a role of the cerebellum in speech production has been hypothesized. Cerebellar malformations have been related to developmental problems and language acquisition in children. We describe a 5-year-old male child with cerebellar vermis hypoplasia who presented a severe linguistic deficit. On language testing, verbal production was almost absent, while comprehension was partially spared. Digit span was markedly reduced. An extensive examination of phonological short-term memory confirmed a deficit at this level. Positron Emission Tomography revealed hypometabolism both in the cerebellum and the supratentorial areas involved in language function. This finding supports the hypothesis that the cerebellum is included in a cerebro-cerebellar network, that underlies the phonological short-term memory, whose integrity is necessary for language acquisition.

Mental representation of normal subjects about the sources of knowledge in different semantic categories and unique entities

According to the "sensory-motor model of semantic knowledge," different categories of knowledge differ for the weight that different "sources of knowledge" have in their representation. Our study aimed to evaluate this model, checking if subjective evaluations given by normal subjects confirm the different weight that various sources of knowledge have in the representation of different biological and artifact categories and of unique entities, such as famous people or monuments. Results showed that the visual properties are considered as the main source of knowledge for all the living and nonliving categories (as well as for unique entities), but that the clustering of these "sources of knowledge" is different for biological and artifacts categories. Visual data are, indeed, mainly associated with other perceptual (auditory, olfactory, gustatory, and tactual) attributes in the mental representation of living beings and unique entities, whereas they are associated with action-related properties and tactile information in the case of artifacts.

Different views about the nature of gender-related asymmetries in tasks based on biological or artefact categories

Sex-related asymmetries in the ability to process different semantic categories have been reported both in normal subjects and in brain-damaged patients, but the nature of these asymmetries is still controversial. Some authors suggest that these differences might be due to social-role related familiarity factors, whereas others attribute them to inborn neural differences rooted in evolution. Drawing in part on this second line of thought, some authors have suggested that gender-related asymmetries might be due to differences in stimulus processing between men and women, namely, to the tendency of females to focus mainly on perceptual features and of males to focus equally on both perceptual and functional features. To test this hypothesis, we asked 53 male and 65 female undergraduate students to evaluate the relevance of a number of perceptual and functional features in the representation of various kinds of biological and artefact categories. Contrary to the hypothesis, evaluation of the weight of different sources of knowledge in representing living and artefact categories was similar in males and females.

Frontotemporal dementia to Alzheimer's disease

Behavioral manifestations may dominate the clinical picture of the frontal variant of frontotemporal dementia (fv-FTD) for a long time before the appearance of true cognitive deficits. On the other hand, a deficit in the episodic memory domain represents the main manifestation of Alzheimer's disease (AD), Many behavioral disorders have been described in the clinical course of both FTD and AD; however, apathy and personality changes characterize frontal dementias, while depression dominates in AD, at least in the earlier stages. Depending on the distribution of neural damage, different patterns of noncognitive manifestations may be expected in different subtypes of FTD, Recent research on the social cognition deficit in FTD has offered new insights into the relationship between cognition and behavior, suggesting that some aspects of the behavioral changes in dementia may be generated by impairment in this domain.

Attention and memory in the preclinical stage of dementia

The aim of this study was to investigate whether attention may be specifically impaired in Alzheimer's disease from the early stages of the disease. Subgroups of patients with different types of mild cognitive impairment were selected according to standard criteria. Patients and controls were given tasks exploring various subcomponents of attention and executive functions. Only subgroups of mild cognitive impairment characterized by memory disorders obtained lower scores than controls on attention and executive tasks. On the basis of the scores obtained on the Clinical Dementia Rating at the 1-year follow-up, patients were redistributed into 2 groups: those who developed and those who did not develop dementia. Patients who presented evolution to dementia already had, at baseline, lower scores than patients who did not evolve on tasks exploring attention and executive functions. The results suggest that not only memory disorders but also attention/executive deficits may characterize dementia at the onset.

Central and peripheral aspects of writing disorders in Alzheimer's disease

It is currently assumed that lexical and phonological dysgraphia emerge in different stages of Alzheimer's disease (AD) as a consequence of the progressive impairment of lexical and phonological knowledge. We studied patients affected by mild and severe dementia. No differences emerged in the distribution of surface and orthographic errors in the two groups of patients. Attention and memory disorders correlated with central and peripheral errors and language disorders with central errors. Our data suggest that AD dysgraphia is firstly produced by a reduction of general cognitive resources and only marginally by disorders of specific spelling sub-components.

The deficit for the word-class “verb” in corticobasal degeneration: Linguistic expression of the movement disorder?

We describe five patients with corticobasal degeneration who had apraxia with an ideational component and reduced action/verb naming ability. Patients also had difficulty in a series of tasks devised to explore the conceptual representation of actions associated with manipulable objects, such as action recognition, action miming and pantomime recognition; however, their ability to name manipulable objects was comparatively preserved. According to the current interpretation of ideational apraxia [De Renzi, E., & Lucchelli, F. (1988). Ideational apraxia. Brain, 111, 1173-1185] we considered the patients' apraxic disorder as the motor expression of decay of the action representation and we hypothesized that this may also have contributed to the action-naming deficit. The results are discussed within a "multimodal model" of semantic memory in which the concept of action is seen as the product of the integration between sensorial and motor attributes. We suggest that corticobasal degeneration might offer a unique opportunity to validate this model because it is typically characterized by a frontoparietal damage [Gibb, W. R., Luthert, P. J., & Marsden, C. D. (1989). Corticobasal degeneration. Brain, 1, 1171-1192] that prevents integration of sensory and motor information. We conclude that the selective impairment of action/verb should also be studied from the point of view of a movement disorder and not only in terms of a lexical-semantic deficit.

Frontotemporal dementia to Alzheimer's disease

Behavioral manifestations may dominate the clinical picture of the frontal variant of frontotemporal dementia (fv-FTD) for a long time before the appearance of true cognitive deficits. On the other hand, a deficit in the episodic memory domain represents the main manifestation of Alzheimer's disease (AD). Many behavioral disorders have been described in the clinical course of both FTD and AD; however, apathy and personality changes characterize frontal dementias, while depression dominates in AD, at least in the earlier stages. Depending on the distribution of neural damage, different patterns of noncognitive manifestations may be expected in different subtypes of FTD. Recent research on the social cognition deficit in FTD has offered new insights into the relationship between cognition and behavior, suggesting that some aspects of the behavioral changes in dementia may be generated by impairment in this domain.

Can cognitive and behavioural disorders differentiate frontal variant-frontotemporal dementia from Alzheimer's disease at early stages?

Frontal variant-Frontotemporal dementia (fvFTD) and Alzheimer's disease (AD) patients matched for severity of dementia at the Clinical Dementia Rating (CDR) received neuropsychological testing in order to explore if the dysexecutive disorder might characterise fvFTD at early stage, when AD is dominated by the episodic memory defect. We also determined if the behavioural syndrome was more severe in fvFTD than AD, and if specific patterns of behavioural symptoms could differentiate the two types of dementia, using the Neuropsychiatry Inventory (NPI). AD patients performed worse than fvFTD not only in memory but also in executive tasks. Apathy and eating disorders proved to be more severe or frequent in fvFTD even if the two groups did not differ in the total NPI score. CDR score significantly correlated with the NPI score in fvFTD and with the MMSE in AD. Our data confirm that the memory disorders may differentiate the two types of dementia; however, the dysexecutive syndrome is as severe, and even more severe in AD. The severity of the behavioural syndrome is comparable in the two groups but the nature of the behavioural disorders may vary to some extent. We conclude that AD dementia at early stage is a behavioural-cognitive syndrome, while in fvFTD the behavioural disorders appear when the cognitive deficit is still relatively mild.

A stimulus-centered reading disorder for words and numbers: Is it neglect dyslexia?

A single case, RCG, showing a unilateral reading disorder without unilateral spatial neglect was studied. The disorder was characterized by substitutions of the initial (left) letters of words, nonwords and Arabic numbers, independently of egocentered spatial coordinates. MRI showed a bilateral lesion with the involvement of the splenium. Although, within the framework of the visual word recognition model proposed by Caramazza and Hillis (1990), RCG disorder could be defined as a stimulus-centered neglect dyslexia, we discuss the hypothesis of a dissociation in neural correlates and mechanisms between the syndrome of unilateral spatial neglect and such a unilateral reading disorder.

Reality orientation therapy combined with cholinesterase inhibitors in Alzheimer's disease: randomised controlled trial

BACKGROUND

Reality orientation therapy combined with cholinesterase inhibitors has not been evaluated in patients with Alzheimer's disease.

AIMS

To perform such an evaluation.

METHOD

We randomly assigned 79 of 156 patients treated with donepezil to receive a reality orientation programme. Caregivers of the treatment group were trained to offer the programme at home 3 days a week, 30 min/day, for 25 consecutive weeks, and were invited to stimulate and involve patients in reality-based communication.

RESULTS

The treatment group showed a slight improvement in Mini-Mental State Examination (MMSE) scores (mean change +0.2, s.e.=0.4) compared with a decline in the control group (mean change -1.1, s.e.=0.4; P=0.02). Similarly for the Alzheimer's Disease Assessment Scale--Cognition (treatment group mean change +0.4, s.e.=0.8; control group -2.5, s.e.=0.8; P=0.01). The intervention had an equal effect on cognition in those with mild (MMSE score > or = 20) and moderate (score <20) dementia. No significant effect was observed for behavioural and functional outcomes.

CONCLUSIONS

Reality orientation enhances the effects of donepezil on cognition in Alzheimer's disease.

Oxidative imbalance and cathepsin D changes as peripheral blood biomarkers of Alzheimer disease: A pilot study

Markers of oxidative stress in peripheral blood from patients with Alzheimer disease (AD) were analyzed. Thirty-three AD patients were recruited. Plasma antioxidant power (AOP), plasma Cystatin C as well as Cathepsin D in PBL were evaluated. We found that the AOP levels were significantly decreased in AD patients if compared to healthy donors, while the plasma level of Cystatin C was significantly higher. Importantly, a significantly decreased expression of Cathepsin D in PBL was also observed. These results suggest that oxidative imbalance in the peripheral blood of AD patients could mirror oxidative changes previously described in the central nervous system.

BEHAVIOR IN DEGENERATIVE DEMENTIAS: MOOD DISORDERS, PSYCHOTIC SYMPTOMS AND PREDICTIVE VALUE OF NEUROPSYCHOLOGICAL DEFICITS

We studied mood disorders (MD) and psychotic symptoms (PS) in patients with fronto -temporal dementia (FTD) and Alzheimer's disease (AD) by means of different diagnostic instruments. These were: a subjective scale (subsets of survey psychiatric assessment schedule: SPAS), an objective scale (subsets of neuropsychiatric inventory: NPI) and a projective task (Wartegg completion task: WCT). A general tendency of NPI to over estimate the presence of symptoms compared to SPAS was observed, but distribution and severity of symptoms were quite homogeneous in the two dementia-groups, independently of the diagnostic scales. At variance with the scales, the WCT showed a more severe impairment in FTD than in AD. The regression analysis selected neuropsychological models able to predict behavioral disorders only in FTD, in particular, a planning deficit predicted PS. These data confirm the hypothesis that a damage in the frontal areas constitutes the neurobiological basis of PS in degenerative brain diseases. Furthermore, they suggest that mostly in FTD, behavioral disorders, as well as cognitive deficits, should be considered a direct expression of neural damage.

Impairment of verb processing in frontal variant-frontotemporal dementia: a dysexecutive symptom

Object and action naming and comprehension were tested in frontotemporal dementia (frontal variant, FTD), in Alzheimer's disease (AD) and in controls. Although lower scores were obtained by all groups, we can confirm that actions were proportionally more impaired in FTD. The correlation between action naming deficit and severity of dementia was stronger in this group than in AD. The correlation analysis also suggested that the naming disorder was different in nature in FTD (mostly a dysexecutive deficit) and in AD (mostly a linguistic disorder). Our explanation is that since verbs are supposed to be more demanding of executive resources than nouns, a higher sensitivity to verbs should be expected in any brain pathology, but mostly in FTD in which executive resources are typically reduced.

Speech and language in primary progressive anarthria

We describe a patient with a progressive loss of speech up to muteness due to frontal atrophy. The clinical and neuropsychological examination documented a severe progressive articulatory disorder associated with a mild language deficit consisting of agrammatic production and spelling errors. Investigation of the patient's auditory-verbal short-term memory system revealed a selective impairment of the articulatory rehearsal system (covert re-circulation of verbal information), suggesting that not only overt but also covert articulation is impaired in this pathology. The conclusion is drawn that pure anarthria is a disorder of executive aspects of language. The hypothesis is advanced that language deficits such as spelling errors and agrammatic features might be due to ineffective covert articulation.

Grammatical class effects in brain-damaged patients: functional locus of noun and verb deficit

Two patients are described with grammatical class dissociation: CG, a semantic-dementia patient who presented a disproportionate impairment of nouns compared to verbs; SA, a patient with a left parietal lesion who presented impaired sentence production and a disproportionate deficit for verbs compared to nouns. The results are discussed within the current models on semantic memory and lexical access.

Segregation of the Neural Correlates of Language and Phonological Short-Term Memory

A left-handed patient is reported who developed a selective deficit of phonological short-term memory, but not aphasia, following an ischaemic lesion in the temporal parietal region of the left hemisphere The phonological short-term store was selectively damaged compared to the rehearsal system. The patient also showed impaired comprehension of spoken (but not written) connected language. This study suggests that language and phonological short-term memory may be mediated by segregated neural systems that develop independently in the two hemispheres. The relationship between phonological short-term memory and auditory comprehension is also discussed.

Naming in patients with Alzheimer's disease: influence of age of acquisition and categorical effects

The role of age of acquisition (AoA) and other variables classically supposed to influence lexical semantic tasks is explored in Alzheimer's disease (AD) patients. A naming test that included living and nonliving items was given to patients and controls. Measures of AoA of the test items were obtained from normal subjects. Living items were acquired earlier than nonliving items. Semipartial correlation analyses were performed to determine the independent contribution of each variable to naming. The "category" (living vs. nonliving items) was included as an independent factor. It emerged that AoA, name agreement and category (with living category predicting lower scores) were the main predictors of naming in AD patients. Only factor agreement reached significance in control groups. The hypothesis is discussed that the category dissociation may be produced by the different nature of the semantic correlation network that makes the categories differentially demanding of processing resources.

Right side neglect in right cerebellar lesion

A patient is described who developed right side hemineglect after a right cerebellar lesion. This spatial disorder was interpreted as a secondary effect of a deficit of the motor organisation in the right hemispace due to left frontal diaschisis. The pathological base may be the interruption of a highly integrated system which includes the lateral cerebellum and the contralateral frontal lobe.

Anatomical and psychological mechanism of reduplicative misidentification syndromes

Reduplicative misidentifications syndromes (RMS) are rare memory disorders characterized by the subjective conviction that a place, person or event is duplicated. Even if RMS often follow a right frontal lesion, several studies have stressed the importance of bilateral hemispheric pathology. Moreover, from a psychological perspective, there is uncertainty if this symptom should be considered just as a kind of confabulation or if it should be associated with personal psychosocial and behavioral aspects. We report a patient who developed normal pressure hydrocephalus and RMS one year after a post-traumatic right frontal lesion. At the first neuropsychological evaluation, we found mild impairment of all functions, associated with the presence of reduplicative paramnesia. After the ventricle-peritoneal shunt intervention, we observed a progressive improvement of all functions but the frontal ones. The memory deficit became less specific and the RMS disappeared. We therefore postulate that a focal right frontal lesion is not sufficient to cause RMS per se. Our clinical report suggests that paramnesic events held on reasonable ground, not being just a kind of confabulation.

Predictors of cognitive decline in the early stage of probable Alzheimer's disease

Several papers have attempted to find neurological and neuropsychological predictors of progression in Alzheimer's disease (AD) till now. Despite this quite large amount of works, different and not univocal conclusions have been reported in this field. Different study samples, different end-points and differences in statistical methods can explain much of the inconsistency in the results obtained. In our study, AD patients were examined in a very early stage of the disease to avoid any possible risk to examine subjects at different times of evolution. All the patients underwent an extensive neuropsychological test battery twice (baseline and follow-up) spaced out over about 1 year and were divided into two groups of fast decliners (FD) and slow decliners (SD) on the basis of their rate of decay at the MMSE score. Verbal memory tests, mental control abilities and attention-demanding tasks seem to play a pivotal role in distinguishing the two groups of subjects in the early stage of the disease. Moreover, FD patients show a worse performance than SD at the baseline in most of the cognitive domains explored. In conclusion, different subtypes of AD do exist and an important predictor of progression is represented by the severity of the cognitive impairment at the onset.

Phonological grouping is specifically affected in cerebellar patients: a verbal fluency study

OBJECTIVES

Recent clinical and functional neuroimaging evidence points towards a cerebellar role in verbal production. At present it is not clear how the cerebellum participates in language production. The aim was to investigate the influence of cerebellar lesions on verbal fluency abilities with specific focus on the verbal searching strategies employed by patients with cerebellar damage.

METHODS

Twenty five patients with focal or degenerative cerebellar disease and 14 control subjects were tested in a timed verbal fluency task requiring word production under forced (phonemic or semantic) conditions. To analyse the verbal searching strategy employed, semantic and phonemic cluster analyses were also performed.

RESULTS

Performances of cerebellar patients were comparable with those of controls in the semantic task; conversely their performances were significantly impaired when tested in the letter task. Cluster analysis results showed that the verbal fluency impairment is linked to specific damage of phonemically related retrieval strategies.

CONCLUSION

Cerebellar damage impairs verbal fluency by specifically affecting phonemic rule performances while sparing semantic rule ones. These findings underline the importance of the cerebellar computing properties in strategy development in the linguistic domain.

Olivopontocerebellar atrophy: paraneoplastic syndrome of brain tumour?

We describe a patient who, three years after the onset of an olivopontocerebellar atrophy, developed a right cerebral tumour. The cerebellar symptomatology also included, as in other cerebellar patients previously described, a peripheral dysgraphia. Because this deficit of writing is generally reported in patients with right cerebral lesion, the authors hypothesized that functional alterations of supratentorial structures preceding the tumour by years may be able to damage the neural substrates connecting cerebral and cerebellar structures and to produce cerebellar atrophy.

Linguistic and non-linguistic abilities in a patient with early left hemispherectomy

A patient who underwent early removal of the left hemisphere because of Sturge-Weber syndrome was submitted to detailed linguistic and visuospatial batteries. The performances were compared to performances of subjects matched for age, education and IQ, but without focal cerebral lesions. Language was mildly impaired but to the same extent as in IQ controls. On the contrary, visuospatial abilities were clearly worse than in IQ controls, and the most preserved visuospatial abilities seemed to be the less sophisticated ones. Non literal comprehension of language, a function generally attributed to the right hemisphere, was intact. This same pattern, that is, preservation of language and impairment of visuospatial abilities, also seems to occur in subjects who have undergone surgical removal of the right hemisphere; in other words, the cognitive pattern seems the same regardless of which hemisphere is removed. These observations suggest that no matter which hemisphere is removed, functional reorganisation follows a hierarchical criterion which privileges the linguistic function, and the visuospatial functions most essential for independent survival.

Verbal short-term store-rehearsal system and the cerebellum. Evidence from a patient with a right cerebellar lesion

We describe an 18-year-old patient who underwent surgical removal of the right cerebellar hemisphere for the presence of a neoplastic lesion. After surgery, the patient's neuropsychological examination was normal except for a transient selective verbal short-term memory (STM) impairment characterized by reduced verbal digit span and rapid forgetting of verbal material. An extensive examination of the patient's deficit was performed in order to identify which of the two components of STM (phonological short-term store and/or rehearsal system) was impaired. The functional locus of the deficit was identified at the level of the phonological output buffer, a component of the rehearsal system, as suggested by the pattern of results obtained, namely: the improvement of the digit span seen with pointing compared with the verbal response; the advantage of auditory over visual presentation of digits; and the lack of a phonological-similarity effect with visual presentation of letters. On the other hand, the functioning of the phonological store was demonstrated by the normal amplitude of the recency effect in free recall of words and by the phonological-similarity effect with auditory presentation of letters. Our finding is consistent with previous functional (PET) studies showing the involvement of the right cerebellum during tasks requiring silent recirculation of verbal information. We conclude that the cerebellum takes part in the planning of speech production at a level that does not require an overt articulation.

Cerebellum and procedural learning: evidence from focal cerebellar lesions

The aim of the present study was to investigate the influence of focal cerebellar lesions on procedural learning. Eight patients with cerebellar lesions and six control subjects were tested in a serial reaction-time task. A four-choice reaction-time task was employed in which the stimuli followed (or not) a sequence repeated 10 times, with the subjects aware (or not) of the item sequence. Learning was manifested by the reduction in response latency over the sequential blocks. Acquisition of declarative knowledge of the sequence was also tested. Reaction times displayed by patients with cerebellar lesions, even though they tended to be longer than those of control subjects in all testing conditions, significantly differed from control subjects only when the stimuli were presented in sequence. The reaction times in sequential trials were still statistically significant when simple motor response times were taken into account. Cerebellar patients were also significantly impaired in detecting and repeating the sequence. On the other hand, when the sequence was learned before testing, motor performances were significantly improved in all subjects. These data indicate that cerebellar lesions induce specific impairment in the procedural learning of a motor sequence and suggest a role of the cerebellar circuitry in detecting and recognizing event sequences.

Verbal fluency and agrammatism

Since the beginning of this century it has been documented that cerebellar lesions induce speech deficits but these were thought to result from lack of motor coordination in the muscular activity needed for phonation. The pure motor nature of the cerebellum has been challenged on different grounds, and cerebellar activation has been documented in language-related tasks independently from motor activity. This chapter reviews the available evidence in favor of a cerebellar contribution to linguistic processing, focusing mainly on clinical observations in patients. The clinical findings are discussed in the light of recent theories on cerebellar functions.

Spatial dysgraphia and cerebellar lesion: a case report

Spatial dysgraphia is a writing disorder that occurs in patients with right hemisphere lesion. We report a patient with cerebellar atrophy and spatial dysgraphia. To explain this finding, we hypothesize a discoordination between planning of the movement and performance due to a lack of the cerebellar modulation between supratentorial (premotor cortex) and peripheral (proprioceptive) afference during the ongoing handwriting movement.

The phonological short-term store-rehearsal system: patterns of impairment and neural correlates

Two left brain-damaged patients (L.A. and T.O.) with a selective impairment of auditory-verbal span are reported. Patient L.A. was unable to hold auditory-verbal material in the phonological store component of short-term memory. His performance was however normal on tasks requiring phonological judgements, which specifically involve the phonological output buffer component of the rehearsal process. He also showed some evidence that rehearsal contributed to the immediate retention of auditory-verbal material. Patient T.O. never made use of the rehearsal process in tasks assessing both immediate retention and the ability to make phonological judgements, but the memory capacity of the phonological short-term store was comparatively preserved. These contrasting patterns of impairment suggest that the phonological store component of verbal short-term memory was severely impaired in patient L.A., and spared, at least in part, in patient T.O. The rehearsal process was preserved in L.A., and primarily defective in T.O. The localisation of the lesions in the left hemisphere (L.A.: inferior parietal lobule, superior and middle temporal gyri; T.O.: sub-cortical premotor and rolandic regions, anterior insula) suggests that these two sub-components of phonological short-term memory have discrete anatomical correlates.

Naming deficit for non-living items: neuropsychological and PET study

We report a patient with progressive left hemisphere atrophy who presented a lexical retrieval deficit more pronounced in naming non-living items than in naming living items. Word frequency and familiarity strongly influenced the performance, but the dissociation persisted when the items were controlled for these factors. In addition, the prevalent deficit for non-living items in respect to living items could be confirmed in tasks where other patients presented the opposite pattern. A PET study showed a significant hypometabolism in the left hemisphere regions suggesting that, at variance with living deficit which is observed in patients with bilateral lesions, non-living deficit is produced by unilateral left hemispheric lesions. This patient confirms that living and non-living categories may dissociate and that distinct neural systems subsume their knowledge.

Influence of disorders of visual perception in word-to-picture matching tasks in patients with Alzheimer's disease

Patients affected by early Alzheimer's disease were given word-to-picture matching tasks in which the foils shared lexical-semantic, phonological, or visual-perceptual features with the target. The aim of the study was to evaluate the influence of the visual perceptual deficit in lexical comprehension tasks based on pictorial material. The results demonstrated that perceptual deficits are common in Alzheimer's disease. This finding is in agreement with the hypothesis that multiple modular deficits in Alzheimer's disease contribute to impaired comprehension.

The production of specific and generic associates of living and nonliving, high- and low-familiarity stimuli in Alzheimer's disease

The goal of this paper was to address three issues relevant to the semantic-lexical deficit of Alzheimer's disease (AD) patients: (1) the nature of the deficit (contrasting the loss of information with the difficulty of intentional access hypothesis), (2) stimulus familiarity effects, (3) semantic category effects (contrasting living with nonliving categories). Sixteen patients affected by AD and 11 matched control subjects were given a naming task, a word-picture matching task and a generative associative naming task, constructed by using as stimuli the same 40 items. Stimuli were either living or nonliving items of high, medium, and low familiarity. Responses given on the generative associative naming task were classified as generic (poorly informative) or specific (more informative). As expected, AD patients were poorer than controls both in naming and in word-to-picture matching tasks. In the generative associative naming task, AD patients tended to produce fewer specific than generic associations with respect to controls. Category effects had a significant influence on performance only on the naming task, but not on the word-to-picture matching or on the generative associative naming task. Stimulus familiarity, on the other hand, strongly influenced performance both in AD patients and in controls: naming and comprehension were better for high familiarity items with respect to low familiarity items. For generative associative naming, the tendency of AD patients to produce fewer specific than generic associations was mainly significant for low familiarity items.

Letter dyslexia in a letter-by-letter reader

We describe a letter-by-letter patient who produced misreading errors in both letters in isolation and in words. All errors were visual in nature. We hypothesized an access deficit to the abstract visual representation of letters that prevents letter identification. This deficit could account for the patient's letter-by-letter behavior, since each letter constituted a potential identification problem. An access deficit, moreover, could also explain the patient's letter visual errors. In access processing, in fact, the letters sharing common structural features in their abstract representations were the ones more frequently mismatched.

Automatic semantic facilitation in Alzheimer's disease

To explore the nature of semantic deficit in Alzheimer's disease patients (AD patients) we compared two tasks that are known to be very different with respect to the type of attentional demand and conscious effort they require: lexical decision (automatic) in a semantic priming paradigm and semantic relatedness judgements (intentional). In order to minimise post-lexical facilitation we devised a semantic priming experiment that met an automatic condition as much as possible, and we selected patients without severe word recognition deficits. AD patients showed reduced accuracy in the semantic relatedness judgements as compared to controls. Some effect of priming was found, but this was weaker than in normals. AD patients also differed from controls on targets preceded by a nonlinguistic prime (neutral condition) where their reaction times were slower as compared to neutral condition.

Peripheral aspects of writing can be differentially affected by sensorial and attentional defect: evidence from a patient with afferent dysgraphia and case dissociation

This study reports a patient with right posterior cerebral atrophy who was affected by afferent dysgraphia, characterised by case dissociation: cursive better than upper-case print. The patient also had severe visuocostructional deficit and simultanagnosia. The hypothesis advanced to explain this dissociation is that cases are not equally dependent on visual and kinaesthetic control. Thus, if visual and kinaesthetic feedback (or the attention to them) are impaired by cerebral lesions, upper case can be expected to be more impaired than cursive.

Neuroanatomical correlates of category-specific semantic disorders: a critical survey

Previous studies of category-specific semantic disturbances have focused their attention on the intrinsic cognitive structure of these disorders. The present survey aims to evaluate the relationships between disrupted semantic category and localisation of the underlying brain damage, in order to establish whether the injured brain areas house just those neurophysiological mechanisms that should have critically contributed to the acquisition of the disrupted semantic categories. We took into account in our review two double dissociations concerning respectively: (1) the impairment of a specific linguistic category--we contrast those disorders selectively affecting verbs (action names) with those selectively affecting nouns (object names); (2) the impairment of a specific conceptual/semantic domain--we contrast disorders selectively affecting living beings with those preferentially affecting man-made artefacts. The hypothesis that different categories of knowledge may be closely intertwined with different sources of sensory-motor information, was substantially confirmed. The lesion preferentially encroached on the left frontal lobe when the category "verbs" was selectively affected; it involved the left temporal lobe and the posterior association areas when the category "nouns" was preferentially disrupted; it involved bilateral temporo-limbic structures and inferior temporal lobes when the category "living beings" was selectively disrupted; it usually encroached on the left fronto-parietal areas when man-made artefacts and body parts were preferentially affected. These data support the hypothesis that: (a) action schemata may critically contribute to the development of the semantic representation of verbs, (b) mechanisms of sensory integration may play an important role in establishing the semantic representation of nouns; (c) high-level visual processing and multi-modal sensory convergency may critically contribute to organising the semantic representation of living beings; (d) motor-kinaesthetic integration may play a leading role in developing the semantic representation of man-made artefacts.

Hypothesis on the nature of comprehension deficit in a patient with transcortical mixed aphasia with preserved naming

Patients with poor comprehension and preserved naming have been occasionally described. Such patients, who are affected by transcortical aphasia, have been taken as evidence of the possibility of naming an object while bypassing the semantic system. We describe a patient affected with mixed transcortical aphasia who presented a clear dissociation between ability in naming and difficulties in performing word-picture matching tasks. The pattern is explained by the existence of covert compulsory automatic naming that interferes with less automatic procedures involved in word-picture matching. In fact, when we tried to oppose automatic naming by using, in word-picture matching tasks, pictures difficult to name, the comprehension improved. This finding excludes a semantic deficit at the basis of poor comprehension of our patient. We suggest that the dissociation between naming and comprehension could be an expression of a computational limitation within the processes involved in word-picture matching, due to the competition for limited processing resources by automatically activated hyperactive naming.