The anatomy of category-specific object naming in neurodegenerative diseases

Neuropsychological studies suggest that knowledge about living and nonliving objects is processed in separate brain regions. However, lesion and functional neuroimaging studies have implicated different areas. To address this issue, we used voxel-based morphometry to correlate accuracy in naming line drawings of living and nonliving objects with gray matter volumes in 152 patients with various neurodegenerative diseases. The results showed a significant positive correlation between gray matter volumes in bilateral temporal cortices and total naming accuracy regardless of category. Naming scores for living stimuli correlated with gray matter volume in the medial portion of the right anterior temporal pole, whereas naming accuracy for familiarity-matched nonliving items correlated with the volume of the left posterior middle temporal gyrus. A previous behavioral study showed that the living stimuli used here also had in common the characteristic that they were defined by shared sensory semantic features, whereas items in the nonliving group were defined by their action-related semantic features. We propose that the anatomical segregation of living and nonliving categories is the result of their defining semantic features and the distinct neural subsystems used to process them

The neural correlates of verbal and nonverbal semantic processing deficits in neurodegenerative disease

Objective—To investigate the neural correlates of verbal and non-verbal semantic processing in neurodegenerative disease. Background—Semantic memory is often impaired in neurodegenerative disease. Neuropsychological and functional neuroimaging studies suggest that the semantic processing of verbal and non-verbal stimuli may depend on partially distinct brain networks. Methods—We examined this possibility using voxel-based morphometry to correlate performance on verbal and non-verbal versions of a semantic association task with regional gray matter atrophy in 144 individuals with a variety of neurodegenerative diseases. Results—Results showed that, regardless of stimulus type, semantic processing correlated with atrophy in both temporal lobes. In addition, material-specific correlations were found in left temporal regions for verbal stimuli and the right fusiform gyrus for non-verbal stimuli. Conclusions—These results provide evidence for a differential role of the left and right hemispheres in the extraction of semantic information from verbal and pictorial representations. Areas in the right inferior temporal lobe may be necessary to access structural descriptions of visually presented object

Differential Activity for Animals and Manipulable Objects in the Anterior Temporal Lobes

Neuropsychological evidence has highlighted the role of the anterior temporal lobes in the processing of conceptual knowledge. That putative role is only beginning to be investigated with fMRI as methodological advances are able to compensate for well-known susceptibility artifacts that affect the quality of the BOLD signal. In this article, we described differential BOLD activation for pictures of animals and manipulable objects in the anterior temporal lobes, consistent with previous neuropsychological findings. Furthermore, we found that the pattern of BOLD signal in the anterior temporal lobes is qualitatively different from that in the fusiform gyri. The latter regions are activated to different extents but always above baseline by images of the preferred and of the nonpreferred categories, whereas the anterior temporal lobes tend to be activated by images of the preferred category and deactivated (BOLD below baseline) by images of the nonpreferred category. In our experimental design, we also manipulated the decision that participants made over stimuli from the different semantic categories. We found that in the right temporal pole, the BOLD signal shows some evidence of being modulated by the task that participants were asked to perform, whereas BOLD activity in more posterior regions (e.g., the fusiform gyri) is not modulated by the task. These results reconcile the fMRI literature with the neuropsychological findings of deficits for animals after damage to the right temporal pole and suggest that anterior and posterior regions within the temporal lobes involved in object processing perform qualitatively different computations.Psycholog

The semantic representation of social groups and its neural substrate

Neuropsychological studies described brain damaged patients with a deficit at recognizing exemplars from some semantic categories while being still able to recognize exemplars from other categories, and vice versa. This evidence suggested that categories such as animals, plants, artifacts and conspecifics might be independently organized in the brain. Several theories tried to explain the category specificity, and proposed that concepts are represented in the brain according to the modality of their features, on the relevance of a domain for survival or on the degree of inter-correlation between features. Perhaps one limitation on investigation on how categories are represented in the brain has to do with the poor characterization of the concept about conspecifics often limited to famous and familiar persons as unique entities, and as such not very comparable with the other categories of stimuli. Recent findings suggested that even the knowledge about categories of conspecifics defined as social groups might well be represented independently of other categories.In the current thesis I investigated whether social group knowledge is indeed represented independently of other categories, consistently with previous findings, and the eventual neural substrates of such knowledge. In two different studies, I tested the knowledge of patients with brain tumors and neurodegenerative diseases about social groups, animate and inanimate entities. Correlating patients\u2019 behavioural performance with structural MRI data, I found that the lesion of a left-lateralized set of areas was selectively associated with the impairment in naming social group pictures. Specifically, inferior frontal gyrus, insula and anterior temporal cortex were associated with social group processing in both the studies. Since these areas were reported to be involved in emotional processing, In a third study with healthy individuals, I tested whether one of the above brain regions, within the opercular part of inferior frontal gyrus, might be involved in processing social groups per se or in processing the valence of stimuli. Results revealed that this area was involved in the processing of negative stimuli and suggested that the semantic impairment in processing social groups might be related to the intrinsic emotional value of this category of stimuli. This pattern of findings suggests that human conceptual knowledge is associated with modality-specific processing areas, and that social group representation might interacts with emotional features

Semantic Dementia: a specific network-opathy

Semantic dementia (SD) is a unique syndrome in the frontotemporal lobar degeneration spectrum. Typically presenting as a progressive, fluent anomic aphasia, SD is the paradigmatic disorder of semantic memory with a characteristic anatomical profile of asymmetric, selective antero-inferior temporal lobe atrophy. Histopathologically, most cases show a specific pattern of abnormal deposition of protein TDP-43. This relatively close clinical, anatomical and pathological correspondence suggests SD as a promising target for future therapeutic trials. Here, we discuss outstanding nosological and neurobiological challenges posed by the syndrome and propose a pathophysiological model of SD based on sequential, regionally determined disintegration of a vulnerable neural network

Food knowledge depends upon the integrity of both sensory and functional properties: a VBM, TBSS and DTI tractography study

Food constitutes a fuel of life for human beings. It is therefore of chief importance that their recognition system readily identifies the most relevant properties of food by drawing on semantic memory. One of the most relevant properties to be considered is the level of processing impressed by humans on food. We hypothesized that recognition of raw food capitalizes on sensory properties and that of transformed food on functional properties, consistently with the hypothesis of a sensory-functional organization of semantic knowledge. To test this hypothesis, patients with Alzheimer's disease, frontotemporal dementia, primary progressive aphasia, and healthy controls performed lexical-semantic tasks with food (raw and transformed) and non-food (living and nonliving) stimuli. Correlations between task performance and local grey matter concentration (VBM) and white matter fractional anisotropy (TBSS) led to two main findings. First, recognition of raw food and living things implicated occipital cortices, typically involved in processing sensory information and, second, recognition of processed food and nonliving things implicated the middle temporal gyrus and surrounding white matter tracts, regions that have been associated with functional properties. In conclusion, the present study confirms and extends the hypothesis of a sensory and a functional organization of semantic knowledge

Value and efficacy of transcranial direct current stimulation in the rehabilitation of neurocognitive disorders: A critical review since 2000.

open3siNon-invasive brain stimulation techniques, including transcranial direct current stimulation (t-DCS) have been used in the rehabilitation of cognitive function in a spectrum of neurological disorders. The present review outlines methodological communalities and differences of t-DCS procedures in neurocognitive rehabilitation. We consider the efficacy of tDCS for the management of specific cognitive deficits in four main neurological disorders by providing a critical analysis of recent studies that have used t-DCS to improve cognition in patients with Parkinson’s Disease, Alzheimer’s Disease, Hemi-spatial Neglect and Aphasia. The evidence from this innovative approach to cognitive rehabilitation suggests that tDCS can influence cognition. However, the results show a high variability between studies both on the methodological approach adopted and the cognitive functions aspects. The review also focuses both on methodological issues such as technical aspects of the stimulation ( electrodes position and dimension; current intensity; duration of protocol) and on the inclusion of appropriate assessment tools for cognition. A further aspect considered is the best timing to administer tDCS: before, during after cognitive rehabilitation. We conclude that more studies with shared methodology are needed to have a better understanding of the efficacy of tDCS as a new tool for rehabilitation of cognitive disorders in a range of neurological disordersopenCappon, D; Jahanshahi, M; Bisiacchi, PCappon, Davide; Jahanshahi, M; Bisiacchi, Patrizi

Primary progressive aphasia : neuropsychological analysis and evolution

Tese de doutoramento, Ciências Biomédicas (Neurociências), Universidade de Lisboa, Faculdade de Medicina, 2015Frontotemporal lobar degeneration (FTLD) is the second leading cause of early-onset ( 2) revealed some clusters composed mostly by nonfluent or by semantic PPA cases. However, we could not evidence any group chiefly composed of logopenic PPA cases. Hence, findings obtained with the application of unsupervised data mining approaches do not clearly support a logopenic PPA. However further, supervised learning studies may indicate distinct results. Behaviour changes may occur early in PPA but the frequency of these symptoms across the three variants is still controversial. In the third study, 94 consecutive PPA patients (26 nonfluent, 36 semantic, 32 logopenic) underwent language and neuropsychological assessments. The presence of behavioural changes was ascertained by semi-structured informant-based interviews using the Blessed Dementia Rating Scale. Eighty-two percent of the cases endorsed at least one behaviour change. Nonfluent patients presented significantly more behaviour changes and scored more often (46.2%) the item “hobbies relinquished” when compared to logopenic patients. These differences in behaviour symptoms probably reflect distinct underlying neurodegenerative diseases. PPA is a neurodegenerative disorder with no effective pharmacological treatment. Cognition-based interventions are adequate alternatives, but their benefit has not been thoroughly explored. The aim of this last investigation was to study the effect of speech and language therapy (SLT) on naming ability in PPA. An open parallel prospective longitudinal study involving two centers was designed to compare patients with PPA submitted to SLT (1 h/week for 11 months, on average) with patients receiving no therapy. Twenty patients were enrolled and undertook baseline language and neuropsychological assessments; among them, 10 received SLT and 10 constituted an age- and education-matched historical control group. The primary outcome measure was the change in group mean performance on the Snodgrass and Vanderwart Naming Test between baseline and follow-up assessments. Intervention and control groups did not significantly differ on demographic and clinical variables at baseline. A mixed repeated measures ANOVA revealed a significant main effect of therapy (F(1,18) = 10.763; p = 0.005) on the performance on the Snodgrass and Vanderwart Naming Test. Although limited by a non-randomized open study design with a historical control group, the present study suggests that SLT may have a benefit in PPA, and it should prompt a randomized, controlled, rater-blind clinical trial. Conclusion: Despite the recent harmonization efforts, the delineation of certain PPA variants is still controversial. The present results show that neuropsychology is a key instrument not only for the clear definition of PPA subtypes but also for the study of the abnormal mechanisms and features underlying the main forms of PPA. Moreover, a neuropsychological approach to disease management seems to be feasible. Specifically, SLT emerges as an alternative and adequate approach to tackle the increasing language deficits experienced in all PPA phenotypes for some time. The emergence of promising disease-modifying therapies in the context of FTLD, in association with these cognitive-based interventions, will certainly be the future of PPA disease management