Semantic category dissociations in naming: is there a gender effect in Alzheimer's disease?

Several studies on picture naming in Alzheimer's disease have reported inconsistent findings regarding semantic category dissociation. To clarify this point, 26 patients suffering from dementia of the Alzheimer's type (DAT) were given a naming task, based on 60 black and white drawings, which allowed us to take into account several variables that might influence performance, notably word frequency, stimulus familiarity and prototypicality, name and image agreement and visual complexity. On a raw analysis, DAT patients as a group gave a lower performance with stimuli of Living Categories (LC) than with stimuli of Non-Living Categories (NLC), but when all the confounding factors were taken into account the category effect disappeared. Nevertheless, with a multiple single case approach, some patients presented a true dissociation: 11 were significantly better with Non-Living stimuli, and 3 with Living stimuli. In order to find what factors were involved in determining this distribution, we took the distribution of asymmetry indices of each patient, and plotted the individual category effect against the level of the general performance. In our sample, the distribution of asymmetry indices was skewed, and included a definite cluster of male subjects who were better at performing with Non-Living stimuli. Multivariate analysis suggested that the greater discrepancy shown by male patients was due to a protection acting on Non-Living stimuli rather than to a selective hampering of Living stimuli. The greater personal experience of males with Non-Living things could explain the relative preservation of these in male DAT subjects.

A case of simulated, psychogenic or focal pure retrograde amnesia: did an entire life become unconscious?

A case of pure retrograde amnesia following mild head injury is reported. Neuropsychological, psychodynamic and statistical approaches are employed in an attempt to disentangle the clinical picture presented by the patient. Focal retrograde amnesia, psychogenic retrograde amnesia and simulated amnesia are all taken into account. From a public events questionnaire and an inquiry about famous people, consistency analyses showed that the patient was able implicitly to use information she denied having, but at the same time, made us lower the probability of a simulated amnesia. Moreover, psychodynamic analysis showed that the patient's personality structure was compatible with hysterical patterns and we suggest that the patient's memory defect may be related to her personality. It seems less likely, though still possible, that the case may be explained in terms of deliberate simulation. In this case we conclude that the classification along the conscious/unconscious dimension seems more informative than the contrast between psychogenic and organic genesis.

Living musical instruments and inanimate body parts?

In the literature about category effects in semantic memory, body parts and musical instruments are often considered atypical, because in cases with a disproportionate impairment of living categories body parts are relatively spared, while musical instruments are often severely defective. In this study the performance of 57 subjects affected by diseases generally associated with lexical-semantic impairment, for the most part Alzheimer's disease and other forms of cortical degeneration, but also herpetic encephalitis and traumatic brain damage are analyzed. The subjects were given a picture naming task tapping eight categories: three living categories (animals, fruits and vegetables) and three non-living categories (tools, furniture and vehicles), plus body parts and musical instruments. On a preliminary analysis at the group level, body parts were the least impaired category and musical instruments the most severely impaired, the six living and non-living categories being intermediate. However, these differences disappeared after covariance for lexical frequency, name agreement and age of acquisition. The relationship between living categories, non-living categories, musical instruments and body parts was investigated by means of a Lisrel model of Confirmatory Factor Analysis. Two latent variables related to living and non-living categories respectively were defined, and it was found that both body parts and musical instruments were significantly related only with non-living categories. The results showed that the definition of the latent variable expressing the substrate of non-living categories was less satisfactory than that expressing the living categories. On this basis, the conclusions of this study appear statistically definite but their psychological interpretation is less straightforward.

Living and non-living categories. Is there a "normal" asymmetry?

A picture naming task and a semantic memory verbal questionnaire were given to normal subjects to assess the possible asymmetry between knowledge for non-living and living things. We first examined 60 elderly subjects with low education. Asymmetry between non-living and living things was found in the semantic knowledge questionnaire and living things fared worse. This difference was not explained by discrepancy in item frequency, familiarity or prototypicality. Using the same questionnaire, we analysed difficulty judgements given by younger, better-educated subjects: questions about living things were slightly, but significantly more difficult than questions regarding non-living things. In order to check for a possible sample bias, we submitted another verbal questionnaire with an analogous structure to different judges and replicated the previous results. These findings are discussed with regard to the selective semantic memory deficit for living things observed in patients. We suggest that the cognitive pattern presented by these cases may be linked to, but not fully explained by the greater difficulty living things present for normal subjects.

Picture naming and progression of Alzheimer's disease: an analysis of error types.

Seven patients affected by Dementia of the Alzheimer Type (DAT) took part in a longitudinal study aimed at assessing the qualitative and quantitative evolution of picture naming impairment. The follow-up lasted 6-36 months and the patients were examined at intervals of 6 months or longer. We found that the absolute number of lexical-semantic errors tended to be constant or to rise slightly until an advanced stage of DAT severity was reached. However, the proportion of errors of the lexical-semantic type in relation to the overall number of errors showed a decline as the disease progressed, with empty and unrelated responses being increasingly observed. Visual errors were generally a minority; they were produced in different proportions for each patient but did not vary greatly over time. For the observed patients, the proportion of lexical and semantic errors was inversely related to the overall naming performance, following a negative logarithmic function. This finding was replicated analysing cross-sectional data from another 24 DAT patients who were given the same naming task.

Perceptual and associative knowledge in category specific impairment of semantic memory: a study of two cases.

We report two head-injured patients whose knowledge of living things was selectively disrupted. Their semantic knowledge was tested with naming and verbal comprehension tasks and a verbal questionnaire. In all of them there was consistent evidence that knowledge of living things was impaired and that of non-living things was relatively preserved. The living things deficit emerged irrespective of whether the question tapped associative or perceptual knowledge or required visual or non visual information. In all tasks the category effect was still significant after the influence on the performance of the following variables was partialled out: word frequency, concept familiarity, prototypicality, name agreement, image agreement and visual complexity. In the verbal questionnaire dissociations were still significant even after adjustment for the difficulty of questions for normals, that had proven greater for living things. Besides diffuse brain damage, both patients presented with a left posterior temporo-parietal lesion.

Semantic category dissociations: a longitudinal study of two cases.

We report the neuropsychological findings of two patients (LF and EA) with herpes simplex encephalitis. Both patients presented a greater deficit for living than non-living categories in a number of tasks, although EA was much more impaired than LF. We controlled the several stimulus variables that might affect the performance and could demonstrate that the dissociation was not artifactual. Neither LF nor EA revealed a selective or preferential involvement of perceptual semantic knowledge, and both showed a homogeneous impairment of perceptual and associative encyclopaedic notions. At a second examination, carried out from 1 to 2 years later, LF showed a good recovery, whereas EA's improvement was confined to the non-living categories. The lesion of both patients affected the left temporal pole and the basal neocortical regions of the left temporal lobe. The involvement of limbic areas was more marked in LF, while the Wernicke area and the posterior parts of the middle and inferior temporal gyri were only involved in EA. Besides the basal temporal areas, also the posterior temporal regions are likely to play a role in determining the clinical picture of such patients, and their prospect of recovery.

Gender affects word retrieval of certain categories in semantic fluency tasks.

Recent studies suggest that gender influences phonetically-cued fluency and some semantic memory tasks. In this study we analysed the effect of demographic variables on semantic fluency tasks. The semantic categories considered were: animals, fruits, tools and vehicles. The influence of age and education was common to all the categories considered and seems a general characteristic of the semantic fluency task. Gender had a significant effect only with fruits and tools, but a diverging role: females fared better with fruits and males with tools. We discuss whether the source of the gender effect should be located at the level of the semantic representation of each category or at the level of item recall in the short time (one minute) granted for the task.

Semantic category dissociations, familiarity and gender.

We carried out four experiments to assess the extent to which familiarity with certain objects in everyday life is related to gender and can account, at least partially, for the semantic category dissociation observed in a few brain-damaged patients. In the first experiment, 210 normal subjects, half males and half females, were given the names of 60 stimuli from the Snodgrass and Vanderwart's set, 30 belonging to living categories and 30 to non-living categories. The task was to rate their familiarity, based on the frequency with which one (i) thinks or speaks of a given item, (ii) sees it represented in the media, and (iii) is confronted with real exemplars. The three indices were highly correlated and their average value was, therefore, used. Females gave higher familiarity ratings to fruit, vegetables and furniture and males to tools. The second experiment was aimed to verify whether the gender difference was responsible for the category dissociation found following brain damage. A male patient with greater impairment for living categories and a female patient with greater impairment for non-living categories were requested to name the same 60 stimuli and their scores were analysed, partialling out the familiarity effect, measured both with the non-gender specific index of Snodgrass and Vanderwart and with the new gender-specific index. In either case, the category dissociation remained significant. To determine if the mean general population familiarity index was valid for the single subject, we studied whether a cohabitant first degree relative was able to predict a normal subject's familiarity better than the population index. Contrary to expectations, the better predictor was the population index. The test-retest reliability of each subject's familiarity ratings was satisfactory, but not higher than the correlation between the personal judgement of each subject and the population index.

Neuropsychological follow-up of patients operated for aneurysms of anterior communicating artery.

The neuropsychological outcome of 43 patients operated for ACoA aneurysms was assessed with a battery of 15 tests, tapping a wide spectrum of cognitive abilities. As a group ACoA aneurysms patients were impaired on 8 tests, including the three assessing memory. When however, patients falling below the cut-off point determined in normal controls were considered, 42% of the sample was unimpaired and only 35% fell on two or more tests. The analysis of single cases showed that memory was often affected, but short-term memory even more than long-term memory. In addition to the well known memory disorder, the patients showed a wide range of neuropsychological defects, including language and space functions. The hypotheses that could account for this broad-based neuropsychological impairment are discussed.

Neuropsychological follow-up of patients operated for aneurysms of the middle cerebral artery and posterior communicating artery.

This study assessed with a neuropsychological battery the outcome of 27 patients operated on for an aneurysm of the Middle Cerebral Artery a mean of 35 months before, and of 27 patients operated for aneurysms of the Posterior Communicating Artery, a mean of 47 months before. Both groups showed a defective pattern of performance that was related to the hemispheric side of the aneurysm with left-sided patients impaired on naming, verbal fluency and verbal short-term memory and right sided patients on both short-term and long-term spatial memory and discrimination of line orientation. In single cases, the scope of neuropsychological impairment was sometimes wider than that expected only on the basis of the competence of the affected hemisphere.

Is SIB or BNP better than MMSE in discriminating the cognitive performance of severely impaired elderly patients?

The sensitivity of the Mini Mental State Evaluation (MMSE) in severely impaired patients is reduced by a floor effect and limited score range. The Severe Impairment Battery (SIB) and Preliminary Neuropsychological Battery (BNP) may be valid alternatives. We studied a group of 37 severely compromised elderly inpatients to investigate the usefulness of these two test batteries as alternatives to the MMSE. Both proved reliable, but only the SIB had a wider distribution of results with respect to the MMSE in the lower score range. The BNP, that might be thought easier to perform being a simple verification task, could actually not be completed by the most compromised patients. The SIB seems better able than the MMSE to provide cognitive profile in the three diagnostic categories into which patients were subdivided (Psychogeriatric, Psychorganic, Mentally Retarded). We conclude that it may be useful to test patients with the SIB when they yield a MMSE score lower than 10-12 points.

Progressive neuropsychological and extrapyramidal deterioration resembling progressive supranuclear palsy: is aphasia relevant for correct diagnosis?

We describe the case of a woman presenting with a clinical syndrome closely resembling progressive supranuclear palsy, who also showed some progressive neuropsychological defects (aphasia and apraxia) not consistent with a simple loss of timing and activation as is generally postulated in this pathology. The case is discussed with regard to the definition of subcortical dementia and the possible alternative diagnosis of corticobasal degeneration.

Do living and nonliving categories need further fractionation? A study of picture naming in a pathological sample.

A group of 51 patients affected by possible semantic memory deficit were given a picture naming task for the purposes of a comparison between six categories, three of Nonliving nature (tools, furniture, vehicles) and three of a Living nature (animals, fruits, and vegetables). A logistic regression analysis was used for a multiple single case study, where also the items' basic difficulty was included in the model. Besides some patients showing a dissociation between Living and Nonliving categories, other patients showed a finer selectivity on naming, differentiating animals from fruits and vegetables, tools from nonmanipulable objects, and even vehicles from furniture. These results are examined in the light of current theories of semantic category specificity.

Naming deficit in herpes simplex encephalitis.

OBJECTIVES: The preferential involvement of living categories in naming impairment is well recognised in Herpes Simplex Encephalitis (HSE). In this paper we describe naming, neuropsychological and neuroradiological findings with seven fresh HSE cases. MATERIAL & METHODS: Patients were given a picture naming task that included 60 items belonging to 6 different categories (three living, i.e. fruits, vegetables and animals and three non-living, i.e. furniture, vehicles and tools). In the statistical analysis several possible sources of bias as the frequency of the target word, the familiarity with the objects to name, the image complexity and other parameters were taken into account. RESULTS: Four out of seven patients were significantly more impaired with living things. We describe their general cognitive profile and discuss the anatomo-functional aspects of category dissociation. CONCLUSION: Language impairment, disproportionately severe for the naming of living exemplars, is frequently observed in HSE, is clinically relevant and should be specifically investigated.

Global cognitive decline in schizophrenia with remission of symptoms?

The relation of symptoms to cognitive dysfunction in schizophrenia is still controversial. This study was aimed (i) at verifying if a homogeneous sample of 10 young treated outpatients in remission from psychotic symptoms displays a characteristic pattern of cognitive dysfunction and (ii) at testing the issue of a general cognitive impairment. The neuropsychological performance of the patients was confronted with a large control group by means of Equivalent Scores, a normative method widely used in Italy, which allows direct, reliable comparison between tests and between patients. We found that our patients, as a group, were affected by a basic activation deficit in attention and by a semantic impairment. These deficits in symptom-free patients could indicate that their brains are in some ways working differently from those of normal controls and that this pattern is not necessarily linked to psychotic symptoms: their neuropsychological impairment might reflect a basic difference in the way of processing information that is always present and is independent of general intellectual decay.

How can we evaluate interference in attentional tests? A study based on bi-variate non-parametric tolerance limits.

In attentional tasks a basic performance is often contrasted with the same task administered with some additional load, defined here as "interference". However, it is questionable how interference should be quantified. The raw difference between the interference-loaded ("complex") task and the basic task is marred by measurement artefacts. There are alternative ways, but the choice of which solution to employ appears arbitrary. Bivariate non-parametric tolerance limits were introduced as they retain the information linked to the bivariate nature of the observation, and in this study we compared the different approaches for evaluating interference using real data from 209 normal participants who performed Visual Reaction Times (basic and go / no-go) and the Stroop Test. Our analysis indicated that, among the univariate indices, the use of the complex score covaried for the basic score yields the most satisfactory evaluation of interference; however, its use can be decided only after data inspection. Bivariate non-parametric tolerance limits offer advantages in terms of generality of use.

A normative study on visual reaction times and two Stroop colour-word tests.

Two-hundred and nine normal subjects underwent a study aimed at providing norms for some attention tests currently used in neuropsychological examination. Norms were calculated taking into account the demographic variables. Our battery included single visuo-manual and go/no-go reaction times, and two versions of the Stroop Colour-Word Test. For the latter test, we employed a traditional version based on card presentation and a new version based on computer-assisted presentation. We evaluated the intercorrelation of the different tests, and studied the statistical regression models in order to adjust the original scores according to age, education and gender. Normative values were calculated following the Equivalent Scores method. The pattern of intercorrelation of our battery and the regression models of the scores are discussed with reference to the literature. The newly developed computer-assisted presentation of the Stroop test offers some advantages over the traditional version, especially with patients affected by spatial disorders.

Neuropsychological outcome of operated cerebral aneurysms: prognostic factors on 148 patients.

OBJECTIVES: To analyse prognostic factors in patients operated upon for cerebral aneurysms. A previous investigation by our group showed that patients operated later than 10 days after bleeding have a worse neuropsychological prognosis, but the number of patients operated upon within 3 days was not sufficient. Here, a new sample of patients with early surgery is included in the analyses. MATERIAL AND METHODS: Patients numbered 148 (65 with ACoA, 39 with MCA, and 44 with PCoA aneurysms): 56 were operated within 3 days, 44 within 4-10 days, and 48 after at least 10 days from bleeding. A standardized battery of 13 neuropsychological tests was adopted: we considered both the number of defective scores and the average performance. RESULTS: Patients operated later than 10 days after bleeding had a worse prognosis than the 2 groups with early and intermediate surgery, which were not different. Aneurysm site was not relevant. Old age and low education were associated with a worse prognosis. Hunt and Hess scores at operation and post operation were also predictive of the outcome. CONCLUSION: On the whole, patients operated upon later than 10 days after bleeding have a less favourable prognosis than those with earlier operation timing.

Prognostic significance of fibrinopeptide A in survivors of cerebral infarction.

We measured levels of fibrinopeptide A, beta-thromboglobulin, and fibrinogen in the plasma of 27 patients 2 months after their first stroke. Concentrations of fibrinopeptide A, a sensitive index of in vivo hypercoagulability, were significantly higher in the 18 ischemic stroke patients than in 40 age- and sex-matched controls and in the six patients who experienced recurrence within 5 years than in the 12 who remained asymptomatic. On the contrary, fibrinopeptide A levels had no prognostic significance among the nine patients with hemorrhagic stroke. Concentrations of beta-thromboglobulin, an index of platelet activation, were higher in the 27 stroke patients than in the 40 controls, but this index was not associated with stroke recurrence. Fibrinogen levels were not significantly higher in stroke patients than in controls. In a multivariate regression analysis of hemostatic and clinical variables, only fibrinopeptide A levels of greater than 4 ng/ml were significantly related to cerebral infarction. Our results support the role of hypercoagulability in the recurrence of ischemic stroke and may allow identification of subjects at high risk for it. If confirmed in more patients, our results could provide a rationale for clinical trials of anticoagulant therapy in such patients.