Francesco Tomaiuolo

The dissociation of color from form and function knowledge

We report on two brain-damaged subjects who exhibit the uncommon pattern of loss of object color knowledge, but spared color perception and naming. The subject P.C.O., as in previously reported patients, is also impaired in processing other perceptual and functional properties of objects. I.O.C., in contrast, is the first subject on record to have impaired object color knowledge, but spared knowledge of object form, size and function. This pattern of performance is consistent with the view that semantic information about color and other perceptual properties of objects is grounded in modality-specific systems. Lesion analysis suggests that such grounding requires the integrity of the mesial temporal regions of the left hemisphere.

Gross morphology and morphometric sequelae in the hippocampus, fornix, and corpus callosum of patients with severe non-missile traumatic brain injury without macroscopically detectable lesions: a T1 weighted MRI study

Objective: The gross morphology and morphometry of the hippocampus, fornix, and corpus callosum in patients with severe non-missile traumatic brain injury (nmTBI) without obvious neuroradiological lesions was examined and the volumes of these structures were correlated with performance on memory tests. In addition, the predictability of the length of coma from the selected anatomical volumes was examined. Method: High spatial resolution T1 weighted MRI scans of the brain (1 mm3) and neuropsychological evaluations with standardised tests were performed at least 3 months after trauma in 19 patients. Results: In comparison with control subjects matched in terms of gender and age, volume reduction in the hippocampus, fornix, and corpus callosum of the nmTBI patients was quantitatively significant. The length of coma correlated with the volume reduction in the corpus callosum. Immediate free recall of word lists correlated with the volume of the fornix and the corpus callosum. Delayed recall of word lists and immediate recall of the Rey figure both correlated with the volume of the fornix. Delayed recall of the Rey figure correlated with the volume of the fornix and the right hippocampus. Conclusion: These findings demonstrate that in severe nmTBI without obvious neuroradiological lesions there is a clear hippocampal, fornix, and callosal volume reduction. The length of coma predicts the callosal volume reduction, which could be considered a marker of the severity of axonal loss. A few memory test scores correlated with the volumes of the selected anatomical structures. This relationship with memory performance may reflect the diffuse nature of the damage, leading to the disruption of neural circuits at multiple levels and the progressive neural degeneration occurring in TBI.

Episodic memory impairment in patients with Alzheimer's disease is correlated with entorhinal cortex atrophy: A voxel-based morphometry study

The aims of this study were to investigate the pattern of cortical atrophy and the relationships between memory performances and the brain regions in Alzheimer’s Disease (AD). optimized voxel-based morphometry (VBM) was applied to the MRI brain images of 18 probable AD and 18 healthy subjects (HS). Patients performed verbal and visuo-spatial episodic and shortterm memory tests. Contrasting of AD group with HS, and anatomobehavioural correlations were carried out in order to identify regional atrophic changes and neuro-cognitive aspects in AD group. We found evidence of gray matter (GM) volume reduction in AD in the medial temporal, parietal and frontal areas bilaterally and in the left anterior thalamic nuclei. Performance on the episodic memory delayed recall tests co-varied with GM volume in the left entorhinal cortex. The pattern of cortical atrophy likely reflects the heterogeneous level of dementia severity in our AD group. The anatomical region affected in the left hemisphere indicates a sufferance at multiple levels of the Polysynaptic Hippocampal Pathway, which is involved in declarative memory. Findings on the entorhinal cortex and the delayed memory scores support the role of the entorhinal cortex in episodic memory. Damage to the entorhinal cortex, deafferenting the hippocampus from neocortical inputs, interferes with episodic memory consolidation in AD patients.

Morphology and morphometry of the corpus callosum in Williams syndrome: a T1-weighted MRI study.

Williams syndrome (WS) is characterised by a defined genetic aetiology and a specific cognitive profile. It provides an opportunity to examine associations between neuroanatomy, behaviour, and genetics. High-resolution T1-weighted MRI of the brain of 12 patients with WS and 12 normal control subjects were used to estimate the shape and volume of the corpus callosum (CC), as well as the voxel intensity values as a measure its water content. The CC of patients with WS was more convex than that of normal control subjects and overall smaller in volume, particularly in the splenium and in the caudal part of the callosal body. In addition, there were higher ratio values of voxel intensity (i.e. less water content) in the mid-section of the body and the caudal part of the body of the CC. These combined features indicate an aberrant development of the CC in patients with WS and document some of the anatomical abnormalities that may underlie some of the cognitive impairments observed in subjects with WS.

SELECTIVE DEFICIT FOR PEOPLE’S NAMES FOLLOWING LEFT TEMPORAL DAMAGE: AN IMPAIRMENT OF DOMAIN-SPECIFIC CONCEPTUAL KNOWLEDGE

As a consequence of a head trauma, APA presented with selective anomia for the names of familiar people, in the absence of comparable disorders for common names and other proper names. Face recognition was normal; and naming performance was unaffected by stimulus and response types. Selective proper name anomia was not due to effects of frequency of usage or of age of acquisition, or to selective memory/learning deficits for the names of people. Even though APA was able to provide at least some information on many celebrities whom she failed to name, she was clearly impaired in all tasks that required full conceptual information on the same people (but she performed flawlessly in similar tasks that involved common names). This pattern of performance indicates that in our subject the inability to name familiar persons results from damage to conceptual information. It is argued that detailed analyses of conceptual knowledge are necessary before it is concluded that a subject with proper name anomia suffers from a purely output disorder, as opposed to a conceptual disorder. The behaviour observed in APA is consistent with the domain-specific hypothesis of conceptual organisation (Caramazza & Shelton, 1998), and in this framework can be explained by assuming selective damage to knowledge of conspecifics. The anatomo-clinical correlates of our subjects disorder are discussed with reference to recent hypotheses on the neural structures representing knowledge of familiar people.

The Neural Correlates of Grammatical Gender: An fMRI Investigation

In an fMRI experiment, subjects saw a written noun and made three distinct decisions in separate sessions: Is its grammatical gender masculine or feminine (grammatical feature task)? Is it an animal or an artifact (semantic task)? Does it contain a /tch/ or a /k/ sound (phonological task)? Relative to the other experimental conditions, the grammatical feature task activated areas of the left middle and inferior frontal gyrus and of the left middle and inferior temporal gyrus. These activations fit in well with neuropsychological studies that document the correlation between left frontal lesions and damage to morphological processes in agrammatism, and the correlation between left temporal lesions and failure to access lexical representations in anomia. Taken together, these data suggest that grammatical gender is processed in a left fronto-temporal network. In addition, the observation that the grammatical feature task and the phonology task activated neighboring but distinct regions of the left frontal lobe provides a plausible neuroanatomical basis for the systematic occurrence of phonological errors in aphasic subjects with morphological deficits.

Gross Anatomy of the Corpus Callosum in Alzheimer’s Disease: Regions of Degeneration and Their Neuropsychological Correlates

Background/Aims: Differences in the gross shape of the corpus callosum (CC) and its subregional areas were investigated on brain MRI of patients with probable Alzheimer’s disease (AD) and age- and gender-matched healthy normal control subjects. The AD patients differed from the normal control subjects in terms of a more convex shape and a reduced area of the CC. Methods: As for the comparisons of the subregional areas of the CC, we adapted a splitting method which takes into account the modification of the global shape of the CC, and we implemented it by normalizing the CC, to avoid the bias introduced by the observed callosal shape variability. Results: The application of this method unveiled that the regional CC reductions were located in the anterior and posterior third of the CC, i.e. where small myelinated fibers are more frequent. None of the neuropsychological scores collected at the time of the MRI investigation of AD could predict a regional and/or overall callosal area reduction. The only measure that correlated with area of the isthmus of the CC was the MMSE that was administered to all participants. Conclusions: This latter result may be used as an in vivo indicator of the progress of neocortical disintegration in AD.

Language disorder in a child with early left thalamic lesion.

Abstract In this paper we present the case of a child with early left thalamic vascular damage who subsequently developed a language disorder. At 3 years and 8 months, her language was poor and unintelligible and showed phonetic, phonological and morpho-syntactic disorders. She did not exhibit any signs of mental retardation. After specific speech therapy, she improved in all linguistic skills. Given the lack of reports on thalamic lesions in children, this paper describes the effect of a thalamic injury in the earliest phases of language acquisition in a child who showed consistent phonological disorders. This case seems to confirm early hemispheric specialisation and the importance of a timely therapy.

Functional Anatomy of Motor Recovery After Early Brain Damage

Functional magnetic resonance imaging and transcranial magnetic stimulation were used to examine a 34 year-old right-handed patient, who, at the age of 6 years, had experienced sudden right hemiplegia, seizures, and stupor during a bout of measles encephalitis, followed by incomplete distal right motor recovery. Morphological MRI showed massive unilateral enlargement of the left ventricle, associated with extreme thinning of the white and gray matter, with partial preservation of the pyramidal tract. Functional MRI and transcranial magnetic stimulation revealed reorganization of the motor cortices, and integrity of the corticospinal pathway, respectively. Our findings indicate that complete hand motor recovery may require functional connections between the motor cortical areas and cortical-subcortical structures, in addition to the retained integrity of the primary sensorimotor area and pyramidal tract.