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M Fabiani

Publications and source records attributed to M Fabiani.

At least 37 records · Page 2Linked to original sources
PubMed2000

True but not false memories produce a sensory signature in human lateralized brain potentials.

False memories (e.g., recognition of events that did not occur) are considered behaviorally and subjectively indistinguishable from true memories. We report that brain activity differs when true and false memories are retrieved. Strongly associated lists of words were presented to one or the other cerebral hemisphere at study. This led to lateralized brain activity for these words during a centrally presented recognition test, reflecting their lateralized encoding. This activity was absent for nonstudied but strongly associated words falsely recognized as studied items. These results indicate that studied words leave sensory signatures of study experiences that are absent for false memories. In addition, hemifield effects emerged, including a slower reaction time (RT) for false recognition of nonstudied words whose associated lists were presented to the left hemifield (i.e., right hemisphere). These false recognition responses were accompanied by frontal slow wave activity, which may reflect a differential ability of the two hemispheres with respect to semantic processing.

Adult↗
PubMed1999

Immunohistochemical evidence of cytokine networks during progression of human melanocytic lesions.

Melanoma cells in culture express a variety of growth factors and cytokines and some of their autocrine and paracrine roles have been investigated. However, less information is available on the potential dynamic changes in expression of these molecules on cells during melanoma development and progression in situ. Using immunohistochemistry, we tested 40 nevi and primary and metastatic melanoma lesions for the expression of 10 growth factors and cytokines and the respective receptors representing 10 cell surface molecules. Nevi and thin (< 1 mm) primary melanomas showed little expression of ligands except weak reactivity of tumor necrosis factor-alpha (TNF-alpha), transforming growth factor-beta (TGF-beta), interleukin-8 (IL-8) and reactivity of TGF-betaR and c-kit. Marked up-regulation of growth factors, cytokines and receptor expression was observed in thick (> 1 mm) primary melanomas, which were stained with polyclonal or monoclonal antibodies (MAbs) for IL-1alpha, IL-1beta, IL-6, IL-8, TNF-alpha, TGF-beta, granulocyte-macrophage colony-stimulating factor (GMCSF) and stem cell factor (SCF), but not IL-2. Metastases showed similar expression patterns except that SCF was absent. Co-expression of ligand and receptor was observed for TGF-beta, GM-CSF and IL-6, suggesting an autocrine role for these ligands. TNF-alpha appears to be a marker of benign lesions; IL-6 and IL-8 expression is associated with biologically early malignancy; TGF-beta, GM-CSF and IL-1alpha are highly expressed in biologically late lesions; and TNF-beta is an apparent marker of metastatic dissemination. Our results indicate that melanoma cells utilize cascades of growth factors and cytokines for their progression.

Adult↗
PubMed1999

Attention in closed head injury: a critical review.

Closed head injury (CHI) is one of the commonest causes of physical disability and cognitive impairment in young people. In patients with CHI both in the acute and sub-acute phases it is possible to demonstrate a disturbance of cognitive functions that affects their performance in a wide variety of neuropsychological tasks. The most frequent deficits pertain to attention and memory. In reviewing the literature on attention in CHI patients it appears that a debate is still alive about how to interpret the cognitive attentional defect, i. e. whether it is due to a slowing of information processing, to a deficit of 'executive' frontal functions, to a reduction of arousal level, to deficits of selective or divided attention, or to a combination of factors. After a brief general explanation of the neuropsychological cognitive models of attention, an overview of the various studies on attention in CHI will be provided. For the purposes of the review, the studies are grouped according to the different theoretical interpretations in the literature concerning the nature of attentional deficits in CHI patients. Finally, a tentative general interpretation of attentional deficits in CHI, in light of the anatomo-pathological aspects of the brain of CHI patients and of some methodological considerations, is offered.

Arousal↗
PubMed1999

Episodic priming and memory for temporal source: event-related potentials reveal age-related differences in prefrontal functioning.

Event-related potentials (ERPs) were recorded from young (M = 25) and older (M = 71) adults during a recognition memory paradigm that assessed episodic priming. Participants studied two temporally distinct lists of sentences (each with two unassociated nouns). At test, in response to the nouns, participants made old-new, followed by remember (context)-know (familiarity) and source (i.e., list) judgments. Both young and older adults showed equivalent episodic priming effects. However, compared to the young adults, the older adults showed a greater source performance decrement than item memory performance decrement. Both age groups showed equivalent posterior-maximal old-new ERP effects. However, only the young produced a frontal-maximal, late onset old-new effect that differed as a function of subsequent list attribution. Because source memory is thought to be mediated by prefrontal cortex, we conclude that age-related memory differences may be due to a deficit in a prefrontal cortical system that underlies source memory and are not likely to be due to an age-related decline in episodic priming.

Adult↗
PubMed1999

The 'preliminary neuropsychological battery'. An instrument to grade the cognitive level of minimally responsive patients.

An early, formalized cognitive evaluation of'minimally responsive' patients could be important in the planning of their care and rehabilitation as well as in providing a realistic prognosis and studying the modality of the cognitive recovery. A short, bedside, neuropsychologically-oriented test-battery, the Preliminary Neuropsychological Battery, a psychometric tool which enables the cognitive evaluation of these patients and of patients unable to give verbal or complex motor answers, has been devised. The BNP was administered to a sample of 40 head-injured patients and to a sample of 34 healthy subjects. The aim was (i) to evaluate its usefulness, and (ii) to study its correlation with cortical functions as assessed by a more extensive battery. The findings suggest that the BNP is useful for assessing the general cognitive level of head-injured post-comatose patients. It was able to detect patients deserving a wider, analytic, neuropsychological assessment. Attentional defects emerged as an important variable determining the BNP score.

Adolescent↗
PubMed1998

Immune activation in HIV-infected African individuals. Italian-Ugandan AIDS cooperation program.

OBJECTIVE: Immune activation induced by chronic infections, dietary limitations, and poor hygienic conditions is suggested to be present in African HIV infection and is at the basis of the hypothesis that HIV infection in Africa could be prevalently associated with immunopathogenetic mechanisms. Very limited data are nevertheless available supporting this theory, and in particular no data are reported on functional and phenotypic analyses performed on fresh peripheral blood mononuclear cells (PBMC) of African HIV-infected patients living in Africa. DESIGN: Immunological and virological parameters were analysed in fresh PBMC of HIV-infected African and Italian patients with advanced HIV disease and comparable CD4 and CD8 counts, sex, and age. Both functional (antigen- and mitogen-stimulated cytokine production) and phenotypic (activation markers; markers preferentially expressed by T helper (Th) type 2 cells or by memory and naive cells) analyses were performed. Results were compared with those of HIV-seronegative African and Italian controls. HIV plasma viraemia was analysed by competitive polymerase chain reaction (PCR) and branched DNA techniques. RESULTS: (1) The production of mitogen-stimulated IFN-gamma and TNF-alpha as well as the production of env peptide-stimulated IFN-gamma, TNF-alpha, and IL-10 are increased in African HIV infection; (2) the expression of activation and Th2-associated markers is augmented in African HIV infection as is the memory/naive ratio; (3) mitogen-stimulated IFN-gamma and IL-10 production, as well as the expression of activation and Th2-associated markers and the memory/naive ratio, are augmented in African compared with Italian controls; and (4) plasma viraemia is reduced in African compared with Italian HIV-infected individuals. CONCLUSIONS: These results, which are the first to be reported on fresh material from African HIV-infected patients living in Africa, indicate that HIV disease is associated with an abnormal immune hyperactivation and may be accompanied in these patients by lower loads of virus, and show that such activation is present even in HIV-seronegative controls.

Adult↗
PubMed1998

Memory-driven processing in human medial occipital cortex: an event-related optical signal (EROS) study.

Memory-driven processing in medial occipital areas (Area V1 and immediately adjacent structures) was investigated noninvasively using the event-related optical signal (EROS). Subjects viewed two letter stimuli presented in the left and right hemifields, respectively. They then viewed a centrally presented test letter and had to indicate whether this letter was the same as either of the letters presented earlier. The initial EROS response to the test stimulus in medial occipital areas (latency: 50-150 ms) was unilaterally suppressed in the hemisphere previously exposed to the same stimulus. This finding suggests that medial occipital cortex activity is modulated by a rapidly adapting hemispheric-specific pattern recognition mechanism.

Adult↗
PubMed1998

Auditory evoked potentials for the assessment of noise induced hearing loss.

As it has been demonstrated in many animal experiments, noise can damage the cochlea and the central auditory pathways. It is very difficult in clinical studies to separate the relative contribution of both these sites. Auditory evoked potentials ABR, MLR and SVR study retrocochlear nervous conduction and collectively the results of these techniques proved an objective evaluation of the cochlear function. The Authors have studied a group of 130 sport shooters with high frequency hearing loss and found that in 38 ears a clear retrocochlear component could be recognised. Correlation with intensity, frequency and length of exposure to the traumatic noise demonstrates that explosive noise is an agent for NIHL. However athletes exposed to similar noises did not suffer from similar hearing loss, probably because of the well known individual noise susceptibility.

Adult↗
PubMed1998

Individual differences in P3 scalp distribution in older adults, and their relationship to frontal lobe function.

There is evidence that frontal lobe function may diminish in normal aging. The P3 component of the event-related brain potential (ERP) elicited by target events in an oddball paradigm becomes more frontally oriented in elderly subjects. It was hypothesized that the extent to which the P3 distribution is frontally oriented in old subjects may index less efficient frontal lobe function. In this study, bootstrapping methods were used to establish the reliability of the locations of maxima of surface brain activity obtained with ERP recordings from young and old subjects. The results indicated that brain activity maxima are reliable for a given individual. However, among the elderly only, there were also clear individual differences in the distribution of the P3 component elicited by target stimuli in an oddball paradigm. On the basis of these differences, the old subjects were divided into two groups. In line with predictions, those elderly subjects who showed frontal-maximal P3 scalp distributions had lower performance on standardized neuropsychological tests of frontal lobe function than those elderly subjects who showed posterior-maximal scalp topographies.

Adult↗
PubMed1997

Item and source memory: differential age effects revealed by event-related potentials.

The neural substrates of age-related memory differences were evaluated by recording event-related potentials (ERPs) from young and older adults during a recognition memory paradigm. Subjects studied two temporally distinct lists of sentences (each with two nouns) and were tested for their memory of the nouns and of the list (i.e. temporal source) in which they had occurred. Compared with the young, the old showed a greater source than item memory performance decrement. Both age groups showed equivalent posterior-maximal old/new ERP effects. However, only the young produced a frontal-maximal, late onset old/new effect that differed as a function of subsequent source attribution. Age-related explicit memory differences may be due to a deficit in a prefrontal cortical system that underlies source memory.

Adult↗
PubMed1997

Measurements of scattering and absorption changes in muscle and brain.

Non-invasive techniques for the study of human brain function based on changes of the haemoglobin content or on changes of haemoglobin saturation have recently been proposed. Among the new methods, near-infrared transmission measurements may have significant advantages and complement well-established methods such as functional magnetic resonance imaging and positron emission tomography. Near-infrared measurements can be very fast, comparable in speed to electrophysiological measurements, bur are better localized. We will present the demonstration of measurements of millisecond signals due to brain activity in humans following stimulation of the visual cortex. However, major unresolved questions remain about the origin of the signals observed. Optical measurements on exposed cortex in animals show that both the absorption and the scattering coefficient are affected by neural activity. Model calculations show that the signals we detected may originate from rapid changes of the scattering coefficient in a region about 1 to 2 cm below the scalp. We discuss our measurement protocol, which is based on a frequency-domain instrument, and the algorithm to separate the absorption from the scattering contribution in the overall response. Our method produces excellent separation between scattering and absorption in relatively homogeneous masses such as large muscles. The extrapolation of our measurement protocol to a complex structure such as the human head is critically evaluated.

Animals↗
PubMed1997

Fast and localized event-related optical signals (EROS) in the human occipital cortex: comparisons with the visual evoked potential and fMRI.

Localized evoked activity of the human cortex produces fast changes in optical properties that can be detected noninvasively (event-related optical signal, or EROS). In the present study a fast EROS response (latency approximately 100 ms) elicited in the occipital cortex by visual stimuli showed spatial congruence with fMRI signals and temporal correspondence with VEPs, thus combining subcentimeter spatial localization with subsecond temporal resolution. fMRI signals were recorded from striate and extrastriate cortex. Both areas showed EROS peaks, but at different latencies after stimulation (100 and 200-300 ms, respectively). These results suggest that EROS manifests localized neuronal activity associated with information processing. The temporal resolution and spatial localization of this signal make it a promising tool for studying the time course of activity in localized brain areas and for bridging the gap between electrical and hemodynamic imaging methods.

Adult↗
PubMed1997

Dissociations between memory for temporal order and recognition memory in aging.

Young and old subjects participated in an experiment in which trials testing memory for temporal order (recency memory) and recognition memory were randomly intermixed with study trials in a continuous sequence. A dissociation was found between recency and recognition memory performance for pictorial stimuli. Relative to young adults, older adults performed at chance on recency memory trials whereas they were not impaired on recognition memory. Recency performance was correlated with measures derived from the Wisconsin Card Sorting test, whereas recognition performance was not. The results are discussed in terms of the role of the frontal lobes in temporal-order memory and of possible frontal lobe deterioration in normal aging.

Adult↗
PubMed1997

An overview of age-related changes in the scalp distribution of P3b.

In this overview of 7 studies, the scalp distribution of the P3b component (i.e. the P3 or P300) of the event-related potential elicited by target events in young and older adults was assessed. The target P3b data were recorded in either auditory oddball paradigms or in visual study tasks in which orienting activity was manipulated (as a within-subjects variable) in investigations of indirect memory. Some of the studies required choice reaction time responses, whereas others required responses only to the target stimuli. Motor response requirements had a profound effect on the P3b scalp distribution of older but not of younger subjects. The presence of a frontally oriented scalp focus in the topographies of the older adults in most of the tasks described here is consistent with older adults continuing to use prefrontal processes for stimuli that should have already been well encoded and/or categorized. However, although older subjects generally had different P3b scalp distributions than younger subjects, their scalp distributions were modulated similarly by task requirements. These data suggest that similar mechanisms modulate the scalp distribution of P3b in older compared to younger adults. However, in the older adult, these scalp distribution changes in response to task demands are superimposed on a frontally oriented scalp focus due to a putative frontal lobe contribution to target P3b topography.

Adult↗