The emotional control of action: ERP evidence.

It is known that unpleasant emotions can modulate the speed of involuntary movements, yet the effects of aversive stimulation on voluntary motor acts have not been systematically investigated. The effects of aversive stimulation on subsequent movement-related cortical activity were examined using a task invalving compatible and incompatible movements. Negative shifts in the timing of two motor event-related potentials were found subsequent to aversive stimulation for compatible movements only. With analogy to the Fear-Potentiated Startle Reflex, a reactive mechanism affecting covert action, these Fear-Potentiated Movement-Related Potentials (FPMPs) reflect preparation for overt actions performed to cope with particular types of danger. Further analysis revealed a positive deflection in the left frontal cortex prior the execution of incompatible movements, which may reflect inhibitory suppression of externally-triggered imitative tendencies.

EEG dynamics of the frontoparietal network during reaching preparation in humans.

Visuomotor transformation processes are essential when accurate reaching movements towards a visual target have to be performed. In contrast, those transformations are not needed for similar, but non-visually guided, arm movements. According to previous studies, these transformations are carried out by neuronal populations located in the parietal and frontal cortical areas (the so-called "dorsal visual stream"). However, it is still debated whether these processes are mediated by the sequential and/or parallel activation of the frontoparietal areas. To investigate this issue, we designed a task where the same visual cue could represent either the target of a reaching/pointing movement or the go-signal for a similar but non-targeting arm movement. By subtracting the event-related potentials (ERPs) recorded from healthy subjects performing the two conditions, we identified the brain processes underlying the visuomotor transformations needed for accurate reaching/pointing movements. We then localized the generators by means of cortical current density (CCD) reconstruction and studied their dynamics from visual cue presentation to movement onset. The results showed simultaneous activation of the parietal and frontal areas from 140 to 260 ms. The results are interpreted as neural correlates of two critical phases of visuomotor integration, namely target selection and movement selection. Our findings suggest that the visuomotor transformation processes required for correct reaching/pointing movements do not rely on a purely sequential activation of the frontoparietal areas, but mainly on a parallel information processing system, where feedback circuits play an important role before movement onset.

Sleep disturbances in elderly: a subjective evaluation over 65.

Sleep in elderly people shows progressive changes caused by general aging processes. Several alterations are described in medical literature: changes of sleep/wake rhythm and modifications both in sleep duration and in sleep architecture. The aim of our study was to evaluate sleep disturbances in elderly people, with and without cognitive impairment,through a sleep questionnaire. Our population included 1000 subjects, over 65 years of age, stratified by sex and age. The first 600 interviews were included in this report. All patients underwent a mini mental state examination (MMSE) and a questionnaire concerning excessive daytime sleepiness. In our total sample, we found a high prevalence of excessive daytime sleepiness, insomnia, nighttime awakenings, snoring, restlessness and periodic leg movements during sleep. Patients with cognitive dysfunctions showed less difficulty in falling asleep and fewer nighttime awakenings; they snored less frequently and were the only ones to present enuresis and to fall off the bed. Moreover, patients with cognitive impairment presented excessive daytime sleepiness with variable intensity and frequency. In conclusion, our results indicate significant differences in sleep disorders between healthy subjects and patients cognitively impaired. Besides, our subjective evaluation seems to be a useful method to perform an assessment of sleep disturbances in elderly people.

Analysis of cystic intracranial lesions performed with fluid-attenuated inversion recovery MR imaging.

BACKGROUND AND PURPOSE: T1-, T2-, and proton density (PD)-weighted sequences are used to characterize the content of cystic intracranial lesions. Fluid-attenuated inversion recovery (FLAIR) MR sequences produce T2-weighted images with water signal saturation. Therefore, we attempted to verify whether FLAIR, as compared with conventional techniques, improves the distinction between intracranial cysts with a free water-like content versus those filled with a non-free water-like substance and, consequently, aids in the identification of these lesions as either neoplastic/inflammatory or maldevelopmental/porencephalic. METHODS: Forty-five cystic intracranial lesions were studied using T1-weighted, T2-weighted, FLAIR, and PD-weighted sequences. By means of clustering analysis of the ratio in signal intensity between the cystic intracranial lesions and CSF, the intracranial lesions were classified as filled with a free water-like content or with a non-free water-like substance. The results were compared with their true content as evaluated either histologically or on the basis of clinical, neuroradiologic, and follow-up features (necrotic material, 13 cases; accumulation of intercellular proteinaceous/myxoid material, eight cases; keratin, five cases; CSF, 19 cases). Cystic intracranial lesions were divided into two clinical groups, neoplastic/inflammatory and maldevelopmental/porencephalic, to evaluate the level of accuracy of each MR technique. The difference in absolute value signal intensity between CSF and cystic intracranial lesion content was calculated on FLAIR and PD-weighted images. RESULTS: PD-weighted and FLAIR sequences, unlike T1- and T2-weighted sequences, accurately depicted all cystic intracranial lesions containing necrotic or myxoid/proteinaceous intercellular material (non-free water-like) and most CSF-containing cystic intracranial lesions (free water-like). All imaging techniques inaccurately showed some of the keratin-containing cystic intracranial lesions and pineal cysts. The overall error rate was 22% for T1-weighted, 27% for T2-weighted, 9% for FLAIR, and 13% for PD-weighted sequences. The signal intensity difference between CSF and cystic intracranial lesion content was higher with FLAIR imaging. CONCLUSIONS: FLAIR imaging depicts far more accurately the content of cystic intracranial lesions and better reveals the distinction between maldevelopmental/porencephalic and neoplastic/inflammatory lesions than do conventional sequences. FLAIR has the added advantage of a higher signal intensity difference between cystic intracranial lesions and CSF.

Non-invasive multielectrode array for high resolution sampling of scalp-recorded potential fields.

A new non-invasive electrode array has been devised to record electrical signals on the scalp. The electrodes are arranged every 10 mm in a 4 x 8 grid, thus totalling 32. Electrical coupling is assured by a column of conductor gel with a diameter of 2 mm. The electrode array has been used to record multichannel scalp potentials evoked by stimulation of the median nerve at the wrist. It was positioned on the parietal region with the midline corresponding to the external acoustic meatus. The high spatial resolution of this device allows a detailed spatial sampling of the scalp potential field where the electrical activity arising from the parietal and premotor cortex is predominant. Scalp potentials with the system are compared with those with the 10/20 system. The improved spatial resolution allows more precise localization of minimum and maximum of the potential field, though the overall distortion introduced by aliasing in the 10/20 system is not striking. Instead, the amplitudes of the fields are considerably affected by insufficient spatial sampling.

Temporal segmentation and multiple-source analysis of short-latency median nerve SEPs.

Short-latency (10-50 ms) median nerve somatosensory evoked potentials (SEPs) from four normal subjects were analysed by means of temporal segmentation techniques and source derivation methods. In each case the responses were recorded using 32 electrodes. Dipolar optimization was carried out with a time-varying technique, using three different approaches: regional source estimation, spherical source estimation (one radial and one tangential component), and multiple dipolar approach. This was to assess the relative influence on the dipolar solution of the different optimization techniques. The effect of the different number of channels in the estimation procedures has been also investigated. The methods of optimization are crucial, particularly for the orientation of P22. In all cases the source location estimated with the 32-electrode montage was shifted towards the centre of the spheres.

Dependence of the linear model for the nerve compound action potential on the single fibre action potential waveform.

The linear model of the nerve compound action potential (CAP) depends on the assumed waveform for the single fibre action potential (SFAP). A general method has been developed to investigate the influence of the unknown features of the SFAP on the estimation of nerve fibre conduction velocity (CV) distribution. A SFAP waveform is considered consistent with the model and the experimental data if recorded and reconstructed CAPS fit and the distribution is physically meaningful. Experimental CAPS were monopolarly recorded using surface electrodes over the median nerve at the wrist. To fit the model, SFAP waveforms must satisfy some internal relationship. The most important feature is that the ratio between positive and negative areas of the SFAP is almost one and does not vary in different subjects and recording sites. Many SFAP waveforms fit the model, and the relative conduction velocity distributions may be very different. These must be regarded as conventional distributions. As for inter-subject comparison, the dependence of the method on the recording site has been reduced by choosing the place where stimulus intensity and relative motor response amplitude have given values. In this recording environment CV distributions of normal subjects can be properly compared using the same SFAP and deviations from normality evidenced.

A case of receptive amusia with prominent timbre perception defect.

A patient with a right temporal lesion is described who, in recognising sounds and noises, complained of deficits which seemed to be most evident when sounds and noises could be recognised mainly by timbre whereas no deficit was noticed when pitch and rhythm were the main indicators. In addition, some global distortions in musical appreciation were complained of and described as "resonance" or "loss of aesthetic pleasure".