Riccardo Barbarotto

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.

Slowly progressive semantic impairment with category specificity

Abstract We describe the case of an architect, MF, who in his fifties presented a 10-year progressive cognitive deterioration similar to that recently classified as semantic dementia. For a long period general intelligence, non-lexical aspects of language, memory and pre-semantic stages of visual perception were spared. MF showed a lexical-semantic deficit that was more severe for living things, famous people and architectural knowledge and concerned both visual and encyclopaedic information. Visual and encyclopaedic knowledge about tools, vehicles and furniture was completely spared for a long time. On MRI, our patient presented severe atrophy of the temporal lobes, that most severely affected the right side and also involved basal neocortex, hippocampus and parahippocampal gyri.

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: 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 EAs 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.

Picture reality decision, semantic categories and gender: A new set of pictures, with norms and an experimental study

We present a new corpus of 80 pictures of unreal objects, useful for a controlled assessment of object reality decision. The new pictures were assembled from parts of the Snodgrass and Vanderwart [J. Exp. Psychol., Hum. Learning Memory 6; 1980: 174] set and were devised for the purpose of contrasting natural categories (animals, fruits and vegetables), artefacts (tools, vehicles and furniture), body parts and musical instruments. We examined 140 normal subjects in a free-choice and a multiple-choice object decision task, assembled with 80 pictures of real objects and above 80 new pictures of unreal objects in order to obtain a difficulty index for each picture. We found that the tasks were more difficult with pictures representing natural entities than with pictures of artefacts. We found a gender by category interaction, with a female superiority with some natural categories (fruits and vegetables, but not animals), and a male advantage with artefacts. On this basis, the difficulty index we calculated for each picture is separately reported for males and females. We discuss the possible origin of the gender effect, which has been found with the same categories in other tasks and has a counterpart in the different familiarity of the stimuli for males and females. In particular, we contrast explanations based on socially determined gender differences with accounts based on evolutionary pressures. We further comment on the relationship between data from normal subjects and the domain-specific account of semantic category dissociations observed in brain-damaged patients.

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

Several studies on picture naming in Alzheimers disease have reported inconsistent findings regarding semantic category dissociation. To clarify this point, 26 patients suffering from dementia of the Alzheimers 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.

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 nonliving, 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.

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 outcome of patients operated upon for an intracranial aneurysm: analysis of general prognostic factors and of the effects of the location of the aneurysm.

One hundred and fourteen patients operated on for an intracranial aneurysm were followed up in order to investigate their neuropsychological outcome and to detect if there were any clinical features assessed around the time of operation that had prognostic significance. The neuropsychological examination evaluated language, apraxia, memory, intelligence and spatial ability. In the statistical analysis the overall severity of neuropsychological disorder was studied. Late surgery timing had a negative influence upon the neuropsychological outcome. There was not a difference between different aneurysm sites. Several patients with an apparently good clinical outcome showed neuropsychological deficits. Neuropsychological assessment is important in the evaluation of outcome after subarachnoid haemorrhage.

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 patients personality structure was compatible with hysterical patterns and we suggest that the patients 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.