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M J Cardoso

Publications and source records attributed to M J Cardoso.

8 recordsLinked to original sources
PubMed2005

Alternate response preparation in a visuomotor serial task.

The preparation of a particular motor pattern is related to the information available that enables the actor to predict the correct response to a forthcoming stimulus. In many situations, however, prediction is not possible. In such cases, the individual can guess the probable parameters of the next stimulus. The authors attempted to establish the bias in the motor intention for movement and its interaction with a possible memory trace of the stimulus-response mapping produced by the preceding stimulus. Two letters were presented bilaterally, and participants (N=21) had to discriminate the target letter and respond with the compatible hand. The present findings support the existence of a memory trace of the previous stimulus-response mapping.

Adult↗
PubMed2004

Gender differences in event-related potentials during visual-spatial attention.

The aim of present work is to test possible gender differences in the ERPs to the standards during the performance of a visual-spatial attention task. The sample: 20 subjects (10 women) aged 18-24. Electrodes: F3, F4, C3, C4, P3, P4, T5, T6, O1, O2. ANOVA tests were computed with the following factors: attention, gender, visual field, hemisphere, and electrodes. Results showed that men presented higher amplitudes in P1 and in P3b than did women, and women presented higher amplitudes in the temporal N1 than did men. For the P3, the amplitude in frontal-central regions for the attended condition was higher in men than in women, and men presented a gender-specific right frontal functional asymmetry that was not present in women. Since these components are related with the modulation of visual processing by the effect of spatial attention, the intra- and inter-gender differences obtained suggest possible differences in the processing of visual information in both genders. However, the fact that the brain generators could have a different orientation is also a possible explanation for the differences obtained in the ERPs in both genders.

Adolescent↗
PubMed2001

Temporal evolution of alpha and beta bands during visual spatial attention.

Event-related potentials (ERPs) are an electrophysiological index of various cognitive processes such as attention. However, this kind of analysis does not allow observation of differences in the spectral content taking place during a sensory, cognitive or motor task. The goal of the present work was to compute the temporal dynamics of EEG oscillations using a technique called temporal spectral evolution (TSE). The electroencephalogram (EEG) was recorded during the presentation of flashed stimuli that were randomly presented to the left or right visual field. Subjects were asked to pay attention, alternately in different blocks of trials, to the left or to the right to detect an infrequent target. The results showed a decrease in the alpha band in a time window of 375-500 ms and an increase in the beta band at 500-875 ms after stimulus onset, for both attended and unattended stimuli. Statistical analysis showed that the decrease in alpha and the increase in beta were more marked during the attentional condition. In conclusion, these results demonstrate that the decrease in alpha band and the increase in beta band are electrophysiological markers of visual spatial attention.

Adolescent↗
PubMed2001

Current source density analysis of CNV during temporal gap paradigm.

The present report studied the contingent negative variation during Gap and Non-Gap conditions using visual stimulation and manual responses. The reaction times during the Gap condition were facilitated compared with those of the Non-Gap condition. The contingent negative variation component was obtained during the preparatory period from electrodes placed at 58 scalp sites for both Gap and Non-Gap conditions. The comparison between both conditions: Gap and non-gap did not show statistically significant differences during the preparatory period. The topography of the voltage and current source density maps showed three different foci: (i) an early negativity centred in electrodes overlying the supplementary motor area and cingulate motor areas, (ii) an activation over the primary motor cortex contralateral to the finger movement, and (iii) a bilateral activation on posterior sites. All these results suggest that the facilitation induced by the warning stimuli occurs in neural circuits that would be recruited for the subsequent processing of the imperative stimulus. The facilitation of the reaction times during the gap condition with respect to non-gap condition must be justified by neural events occurring during the gap period.

Adolescent↗
PubMed1998

Frequency analysis of the EEG during spatial selective attention.

In this study, we recorded the event-related potentials (ERPs) elicited by stimuli appearing at attended and unattended locations. The voltage amplitudes and latencies of the P1, N1, P2, N2 and P3 visual components showed statistically significant differences in the attended condition with respect to the unattended one. The power spectral density of the EEG following stimulus onset was calculated. The difference between the spectral densities of the attended and unattended conditions was computed. Statistically significant differences were found in the decrease of alpha (9-11 Hz) and the increase of beta (15-17 Hz) frequencies during the attention condition with respect to the unattended condition. These results suggest that the arrival of a visual stimulus during the attended condition generates a complex reorganization of neuronal activity in both time and frequency domains.

Adolescent↗
PubMed1997

[Hormone replacement therapy and cancer of the breast. 2. Should a woman with cancer of the breast receive hormone replacement therapy?].

The common menopausal symptoms of a growing number of women treated for breast cancer poses difficult therapeutic decisions to the Gynaecologist. It has been extensively demonstrated that hormonal replacement therapy (HRT) is the most effective treatment of such symptoms, as well as protecting women from cardiovascular disease, osteoporosis and increased mortality related to these disorders. However, breast cancer is classically considered a contraindication to HRT. In this paper we review the existing evidence regarding the influence of HRT on breast cancer. A computerized bibliographical search (MEDLINE) of literature in the English-language literature published in the last 15 years was conducted, followed by a hand search of references found in these papers. Evidence on the response of breast cancer cells to HRT is derived from animal studies, tissue growth system experiments, indirect epidemiological data and clinical data. While the bulk of experimental evidence points towards a proliferative effect of estrogen on breast cancer cells, almost all clinical reports have found no adverse effects of HRT on these patients. In our opinion, currently existing evidence does not justify the denial of HRT to breast cancer patients whose quality of life is at stake. Such is the case of women with intense menopausal symptoms unresponsive to alternative therapies. This opinion is shared by numerous other authors and a small number of eminent institutions. We believe it is safer to avoid HRT, in asymptomatic women as long-term regimens would be needed for protection against cardiovascular disease and osteoporosis, and the risks of such regimens have yet to be evaluated. We also believe that large randomized trials are now ethically justified and greatly needed to obtain safer data on this subject.

Antineoplastic Agents, Hormonal↗
PubMedDate not supplied

[Temporal spectral evolution of electroencephalogram. Methodology and applications].

INTRODUCTION: The event related potentials (ERPs) allow to study the evolution of the cerebral electric activity related with the diverse sensorial, motors and cognitive processes. However, the ERPs and the spectral analyses based in Fast Fourier Transform, are not able to show the variations along the time of the spectral content of the electroencephalogram (EEG). OBJECTIVE: The present work will show the necessary methodology to obtain the temporal dynamics of the frequency (TSE) in the EEG, a technique described by Salmelin and Hari (1994) that allows the analysis of the modulations of any spectral band along the time. SUBJECTS AND METHODS: The presented data correspond to the electroencephalographic registration of 20 human subjects during an experiment of visual spatial attention. RESULTS: The modulations of the ERPs differ of the observed by the spectral techniques in latency and topography. Likewise, comparing different spectral techniques is proven that the TSE allows to define with more temporal precision the variations on the spectral content. CONCLUSION: The application of the TSE technique to the same EEG signal that is used for obtaining the ERPs, allows the inclusion of the variable time in the spectral analysis of the EEG, what can be crucial to understand the physiological bases of some neuropathologies.

Adolescent↗