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Biomedical subjects

Daniela Mapelli

Publications and source records attributed to Daniela Mapelli.

12 recordsLinked to original sources
PubMed2006

Top-down and bottom-up processes in the extrastriate cortex of cirrhotic patients: an ERP study.

OBJECTIVE: This study aims to evaluate the efficiency of top-down and bottom-up processes in the extrastriate cortex of cirrhotic patients without overt hepatic encephalopathy (HE). METHODS: Reaction times (RTs), accuracy and event-related potentials (ERPs) were recorded during the execution of a visual Simon task in 17 cirrhotic patients and 10 healthy controls. Amplitude and latency of the P1 and N1 (indexes of bottom-up processes) and of the N2pc (index of top-down processes) were measured. RESULTS: Patients were slower than controls, and patients with minimal HE (MHE) were slower than patients without MHE. The distribution analysis of RTs showed that the Simon effect decays with slower RTs in all the groups and that the shape of the distribution was different in MHE patients. No differences were found between cirrhotic patients and controls for P1 and N1 amplitude and latency. In contrast, N2pc latency was delayed in cirrhotic patients compared to controls independently of MHE. CONCLUSIONS: In the extrastriate cortex of cirrhotic patients without HE, top-down processes are altered whereas bottom-up processes are preserved. SIGNIFICANCE: The analysis of exogenous and endogenous visual components of ERPs provides a model to study the functional dissociation between top-down and bottom-up processes inside the extrastriate cortex.

Brain↗
PubMed2005

Attention dysfunction in cirrhotic patients: an inquiry on the role of executive control, attention orienting and focusing.

Attention alterations are reported in cirrhotics. Aiming at clarifying attention functioning in cirrhotics, an inquiry on the functioning of the anterior (AAS) and the posterior (PAS) attention system was performed. Thirty-six cirrhotics without overt hepatic encephalopathy (24 with EEG or TMT-A alterations) and 16 matched control subjects were enrolled. The AAS was studied by the Stroop task measuring selective attention control, the PAS was studied by the Posner task and the Focus task measuring automatic covert orienting and visual focusing of attention respectively. Cirrhotics presented a task-dependent psychomotor slowing (Stroop > Posner > Focus) with an increased percentage of errors in the incongruent condition of the Stroop task [F(1, 57) = 4.9, p < 0.03]. Class C patients had both a selective slowing [F(1, 33) = 4.3, p < 0.05] and an increased percentage of errors in the incongruent condition [F(1, 34) = 5.1, p < 0.05] compared to Class A-B patients and controls. The patients with an altered EEG performed the Stroop test significantly slowly than those without EEG alterations [F(1, 41) = 8.9, p < 0.01] and with a clear trend for a higher number of errors in the incongruent condition [F(1, 39) = 3.8, p < 0.06]. In contrast, attention orienting and focusing were maintained. In conclusion, the AAS is more sensitive than the PAS to the early stages of hepatic encephalopathy.

Attention↗
PubMed2005

Impairment of response inhibition precedes motor alteration in the early stage of liver cirrhosis: a behavioral and electrophysiological study.

Abnormality in movement initiation may partially explain psychomotor delay of cirrhotic patients, even in the absence of overt hepatic encephalopathy (HE). Therefore, the aim of this study was to determine the mechanisms of psychomotor delay observed in patients with cirrhosis in the absence of overt HE. Fourteen patients with nonalcoholic cirrhosis and 12 healthy matched control subjects underwent the lateralized readiness potential (LRP) measurement elicited by a visuospatial compatibility task (Simon task). Stimulus-triggered LRPonset reflects the time in which response is selected, while response-triggered LRP onset reflects motor execution. Cirrhotic patients showed delayed reaction times (RTs) compared to controls, particularly those with trial-making test A (TMT-A) or electroencephalogram (EEG) alterations. Stimulus-triggered LRP onset was found to be delayed in cirrhotic patients compared to controls, with a significant Group-versus-Condition interaction, showing a reduced cognitive ability to cope with interfering codes, even in patients without minimal HE (MHE). Response-triggered LRP was found to be delayed only in the patients with TMT-A or EEG alterations. In conclusion, cirrhotic patients without overt HE display a psychomotor slowing, depending first lyon response inhibition and only later accompanied by impaired motor execution.

Data Interpretation, Statistical↗
PubMed2005

Horizontal and vertical Simon effect: different underlying mechanisms?

Reaction times are usually faster when stimulus and response occur at the same location than when they do not, even if stimulus location is irrelevant to the task (Simon effect). This effect was found with both horizontal and vertical stimulus-response arrangements. The same mechanisms have been proposed to be involved in either case. Here, we compared a horizontal and a vertical Simon task by means of a RT time-course analysis of the Simon effect. Also, we analysed the lateralised readiness potential (LRP), an index of covert response-preparation processes. In the horizontal task, the Simon effect decays over time and pre-activation occurs above the motor cortex ipsilateral to the stimulus. In contrast, the Simon effect does not decay over time and no early incorrect LRP deflection is observed in the vertical task. These findings suggest that typical activation accounts can fit only the horizontal Simon effect, while a translation explanation is more suitable for the vertical Simon effect.

Adult↗
PubMed2005

Mood, cognition and EEG changes during interferon alpha (alpha-IFN) treatment for chronic hepatitis C.

BACKGROUND: This study is aim to investigate concurrent long-term psychiatric, cognitive and neurophysiological measures of alpha-IFN neurotoxicity in the treatment of chronic viral hepatitis. METHODS: Twenty patients with HCV hepatitis were enrolled while treated with alpha-IFN (3-6 MU t.i.w. for 6-12 months). Neurotoxicity was evaluated by psychiatric [Hamilton Depression Rating Scale (HAM-D), Hamilton Scale for Anxiety (HAM-A), Beck Depression Inventory (BDI) and State-Trait Anxiety Inventory (STAI-Y)], complete cognitive and neurophysiological assessments (EEG spectral analysis, P300). Patients were assessed at baseline (t0), 2 (t1) and 6 months (t2) since the beginning of therapy. RESULTS: Depression scores significantly increased (HAM-D: t0=4.4+/-2.6; t1=8.9+/-3.9, p<0.001; and t2=7.7+/-3.8, p<0.001). A concurrent increase was shown also for anxiety (HAM-A: t0=6.0+/-3.2; t1=9.6+/-4.5, p<0.005; and t2=9.1+/-4.5, p<0.005). Significant neurophysiological effects were also detected: increase of alpha power (p<0.05) in frontal derivations, reduction of the mean dominant frequency (p<0.005) and increase of theta power (p<0.05) in parietal derivations. In contrast, no significant cognitive changes occurred. LIMITATIONS: The study was performed on a relative small sample of patients mainly with observational intentions. Biological data (e.g. blood cytokines samples) are not available: they could have given useful information about biological mechanisms related to the alterations observed. CONCLUSIONS: Alpha-IFN treatment caused a time-dependent induction of symptoms of mild depression, concurrent anxiety and EEG changes. These psychiatric and neurophysiological changes can better explain the pharmacological profile of alpha-IFN and could help to address research on at risk population and, particularly, during pegylated-IFN therapy.

Adolescent↗
PubMed2003

The SNARC effect: an instance of the Simon effect?

Our aim was to investigate the relations between the Spatial-Numerical Association of Response Codes (SNARC) effect and the Simon effect. In Experiment 1 participants were required to make a parity judgment to numbers from 1 to 9 (without 5), by pressing a left or a right key. The numbers were presented to either the left or right side of fixation. Results showed the Simon effect (left-side stimuli were responded to faster with the left hand than with the right hand whereas right-side stimuli were responded to faster with the right hand), and the SNARC effect (smaller numbers were responded to faster with the left hand than with the right hand, whereas larger numbers were responded to faster with the right hand). No interaction was found between the Simon and SNARC effects, suggesting that they combine additively. In Experiment 2 the temporal distance between formation of the task-relevant non-spatial stimulus code and the task-irrelevant stimulus spatial code was increased. As in Experiment 1, results showed the presence of the Simon and SNARC effects but no interaction between them. Moreover, we found a regular Simon effect for faster RTs, and a reversed Simon effect for longer RTs. In contrast, the SNARC effect did not vary as a function of RT. Taken together, the results of the two experiments show that the SNARC effect does not simply constitute a variant of the Simon effect. This is considered to be evidence that number representation and space representation rest on different neural (likely parietal) circuits.

Adult↗
PubMed2003

Central nervous system alterations in liver cirrhosis: the role of portal-systemic shunt and portal hypoperfusion.

The role of portal-systemic shunting and portal liver hypoperfusion in the pathophysiology of central nervous system dysfunction (CNSD) of cirrhosis is not yet well defined. It is well known that one of the most important collateral vessels (CVs) is a patent paraumbilical vein (PUV), but there is controversy regarding its clinical significance. We have evaluated the relationships between neuropsychological and EEG alterations, ammonia plasma level (NH4), hepatic function, and portal hemodynamics (Doppler Ultrasound) in 95 cirrhotic patients. Patency, diameter, or flow of PUV or the presence of other CVs were not related to an increased prevalence of neuropsychological or EEG abnormalities. Patients with effective portal flow (EPF = portal flow - PUV flow) lower than 692 mL/min (median) had a significantly higher risk of failing the neuropsychological test, or of having an altered EEG. Low EPF and prothrombin time (<50%), and high NH4 (51 micromol/L) were independent predictors of an abnormal EEG. Considering both low EPF and the numerosity of CVs, only low EPF was found to explain EEG alterations. In conclusion, portal liver hypoperfusion and decreased liver function were associated with an increased risk of CNSD in cirrhotic patients, whereas PUV patency per se was not.

Brain↗
PubMed2003

Automatic spatial coding of perceived gaze direction is revealed by the Simon effect.

In a typical Simon task, the (irrelevant) spatial position of the stimulus interferes with the processing of the salient characteristic (e.g., color). We used the Simon effect to investigate the automatic processing of gaze cues. We show that a simple drawing of schematic eyes automatically generates a spatially defined code of gaze direction. Although completely irrelevant to the task, direction of gaze influenced reaction times in a spatially selective two-choice discrimination based on eye color. Moreover, in one experiment employing an orthogonal manipulation of stimulus position and gaze direction, we found that coding of gaze direction is independent of stimulus spatial coding. Our finding of a "gaze-direction Simon effect" is congruent with the hypothesis that gaze direction is coded by a specialized mechanism.

Adult↗
PubMed2002

Variability of trail making test, symbol digit test and line trait test in normal people. A normative study taking into account age-dependent decline and sociobiological variables.

BACKGROUND AND AIMS: The influence of sociobiological variables and aging on the variability of the Trail Making Tests (TMT), the Symbol Digit Substituting Test (SDT), and the Line Trait Test (LTT) in the general healthy populations are not well known. Even less is known about the reliability at re-testing. This study aimed at determining the reference range of these tests, taking into account sociobiological variables and age, and the re-testing effect. METHODS: We studied 300 healthy subjects from 20 to 80 years of age. The sample was derived by the pooling of two samples stratified by age and sex: a randomized sample of 161 subjects collected from the city registers of Padova, and a convenience sample of 139 subjects collected in 20 towns (mainly rural) of Northern Italy. After normalization, data were assayed for the influence of age, education, job, and gender. RESULTS: Age was found to be a significant independent predictor for all the tests, education for all but the LTT, job only for the TMT-B and a geometrical version of the same test (TMT-G) which was proved to be highly correlated with the TMT-B (r=0.80, p<0.01). Job and the interaction age x education level influenced the difference TMT-B minus TMT-A. From the predicting equations, the normative data and the formulas to obtain Z scores for each test were derived. Reliability was lowest for LTT errors (CV=67%), highest for the SDT (13%), whereas the TMT obtained intermediate values (22-33%, depending on the test). CONCLUSIONS: This study provides the most reliable normative data range for the TMT, SDT and LTT to date because it considers important demographic variables such as age, education and job.

Adult↗
PubMed2002

Attending to objects: costs or benefits?

The single-object advantage is said to occur when performance is faster and/or more accurate when the two targets to be compared appear on one object than when they appear on two different objects. The single-object advantage has been interpreted to suggest that attention can select objects rather than unparsed regions of visual space. In five experiments we explored whether directing attention to one object rather than two objects produces a benefit or a minor cost. Participants were required to compare two target features that belonged to one object, to two objects, or did not belong to any object. In addition, we varied the relevance to the task of object-related global information, such as symmetry of the object and perceptual cluttering of the background. Results showed that attending to one object in comparison to attending to no object produced a benefit only when object-related global information was relevant to the task. In contrast, when object-related global information was irrelevant to the task, attending to one object produced a cost. Thus, it can be concluded that attending to an object does not produce an absolute benefit, but rather produces a smaller cost than attending to two objects.

Attention↗
PubMed2002

Central nervous system alterations in liver cirrhosis: the role of portal-systemic shunt and portal hypoperfusion.

The role of portal-systemic shunting and portal liver hypoperfusion in the pathophysiology of central nervous system dysfunction of cirrhosis is not yet well defined. It is well known that one of the most important collateral vessels (CV) is a patent paraumbilical vein (PUV) but there is controversy regarding its clinical significance. We have evaluated the relationships between neuropsychological and EEG alterations, ammonia plasma level (NH4), hepatic function, and portal hemodynamics (Doppler Ultrasound) in 95 cirrhotic patients. Patency, diameter, or flow of PUV or the presence of other CV were not related to an increased prevalence of neuropsychological or EEG abnormalities. Patients with effective portal flow (EPF = portal flow - PUV flow) lower than 692 mL/min (median) had a significantly higher risk of failing the neuropsychological test, or of having an altered EEG. Low EPF and prothrombin time (<50%), and high NH4 (> or = 51 micromol/L) were independent predictors of an abnormal EEG. Considering both low EPF and the numerosity of CV, only low EPF was found to explain EEG alterations. In conclusion, portal liver hypoperfusion and decreased liver function were associated with an increased risk of central nervous system dysfunction in cirrhotic patients, whereas PUV patency per se was not.

Brain↗