Major oral aphtous ulceration in HIV-1 infection: successful response after highly active antiretroviral therapy.
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Adult↗
Biomedical subjects
M Alegre
Publications and source records attributed to M Alegre.
Topography of cortical activation differs for fundamental and harmonic frequencies of the steady-state visual-evoked responses. An EEG and PET H215O study.
In humans, visual flicker stimuli of graded frequency (2-90 Hz) elicit an electroencephalographic (EEG) steady-state visual-evoked response (SSVER) with the same fundamental frequency as the stimulus and, in addition, a series of harmonic responses. The fundamental component of the SSVER is generated by increased synaptic activity in primary visual cortex (V1). We set out to determine the cortical origin of the harmonic responses in humans. For this purpose, we recorded the SSVERs at 5 different frequencies (5, 10, 15, 25, and 40 Hz) and measured regional cerebral blood flow (rCBF) with positron emission tomography-H(2)(15)O at rest and during visual stimulation at the same frequencies. The rCBF contrast weighted by the amplitude of the SSVERs first harmonics showed activation of a swath of cortex perpendicular to V1, including mostly the inferior half of the parieto-occipital sulcus. This area overlapped minimally with the primary visual cortex activated by the fundamental frequency. A different method, estimating EEG cortical source current density with low-resolution brain electromagnetic tomography, gave the same results. Our finding suggests that the inferior portion of the banks of the parieto-occipital sulci contains association visual cortex involved in the processing of stimuli that can be as simple as a flickering light source.
Adult↗
Successful treatment of major oral aphthous ulcers in HIV-1 infection after highly active antiretroviral therapy.
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Adult↗
Cortical gamma activity during auditory tone omission provides evidence for the involvement of oscillatory activity in top-down processing.
Perception is an active process in which our brains use top-down influences to modulate afferent information. To determine whether this modulation might be based on oscillatory activity, we asked seven subjects to detect a silence that appeared randomly in a rhythmic auditory sequence, counting the number of omissions ("count" task), or responding to each omission with a right index finger extension ("move" task). Despite the absence of physical stimuli, these tasks induced a 'non-phase-locked' gamma oscillation in temporal-parietal areas, providing evidence of intrinsically generated oscillatory activity during top-down processing. This oscillation is probably related to the local neural activation that takes place during the process of stimulus detection, involving the functional comparison between the tones and the absence of stimuli as well as the auditory echoic memory processes. The amplitude of the gamma oscillations was reduced with the repetition of the tasks. Moreover, it correlated positively with the number of correctly detected omissions and negatively with the reaction time. These findings indicate that these oscillations, like others described, may be modulated by attentional processes. In summary, our findings support the active and adaptive concept of brain function that has emerged over recent years, suggesting that the match of sensory information with memory contents generates gamma oscillations.
Acoustic Stimulation↗
Slow oscillatory activity and levodopa-induced dyskinesias in Parkinson's disease.
The pathophysiology of levodopa-induced dyskinesias (LID) in Parkinson's disease is not well understood. We have recorded local field potentials (LFP) from macroelectrodes implanted in the subthalamic nucleus (STN) of 14 patients with Parkinson's disease following surgical treatment with deep brain stimulation. Patients were studied in the 'Off' medication state and in the 'On' motor state after administration of levodopa-carbidopa (po) or apomorphine (sc) that elicited dyskinesias in 11 patients. The logarithm of the power spectrum of the LFP in selected frequency bands (4-10, 11-30 and 60-80 Hz) was compared between the 'Off' and 'On' medication states. A peak in the 11-30 Hz band was recorded in the 'Off' medication state and reduced by 45.2% (P < 0.001) in the 'On' state. The 'On' was also associated with an increment of 77. 6% (P < 0.001) in the 4-10 Hz band in all patients who showed dyskinesias and of 17.8% (P < 0.001) in the 60-80 Hz band in the majority of patients. When dyskinesias were only present in one limb (n = 2), the 4-10 Hz peak was only recorded in the contralateral STN. These findings suggest that the 4-10 Hz oscillation is associated with the expression of LID in Parkinson's disease.
Action Potentials↗
Continuous positive airway pressure as treatment for catathrenia (nocturnal groaning).
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Continuous Positive Airway Pressure↗
Imitating versus non-imitating movements: differences in frontal electroencephalographic oscillatory activity.
Non phase-locked oscillatory changes were studied in seven healthy volunteers during two different reaction time movement paradigms, in which the stimulus was a wrist movement (either extension or flexion) performed by another person seated in front of the subject (examiner). In the first paradigm (imitation), the subject was instructed to perform the same movement observed. In the second paradigm (non-imitation), the subject was instructed to perform the opposite movement (flexion when an extension was observed, and vice-versa). Changes in the 7-37 Hz range band were determined by means of Gabor transforms. A frontal energy increase (event-related synchronization, ERS) around 15 Hz could be observed in the frontal region after the examiner's movement; this frontal ERS was significantly larger in the non-imitation paradigm. A typical alpha and beta movement-related event-related desynchronization/synchronization (ERD/ERS) pattern was also observed in both paradigms in the central region. The beta-ERD was significantly larger in the imitation paradigm. Our results show that the motor preparation mechanisms involved in an imitated and a non-imitated movement are different.
Adult↗
High frequency oscillations in the somatosensory evoked potentials (SSEP's) are mainly due to phase-resetting phenomena.
A small series of high frequency oscillations (HFOs) overlapping the earliest part of the N20 wave can be observed in the somatosensory evoked potentials (SSEPs) of normal subjects. We tried to elucidate whether these high frequency components are mainly due to phase-resetting phenomena, to the emergence of new oscillations related to the stimuli, or to a combination of both. Averaged median-nerve SSEPs from seven healthy subjects were studied by means of time-frequency analysis. The presence of new oscillatory activities was evaluated by averaging the energy of the single-trial time-frequency transforms in the HFOs range (400-1000 Hz). To study phase-resetting phenomena, we measured inter-trial coherence (ITC) in the same frequency range. A marked inter-trial coherence related to the HFOs was found, whereas energy changes (related to the emergence of new oscillations) were minimal. The combination of these three different approaches suggests that the HFOs are mainly due to resettings of the ongoing EEG activity originated in response to the stimuli. The emergence of new activities does not seem to be a relevant mechanism in the formation of these components.
Adult↗
Nodules on the tongue in an HIV-positive patient.
Syphilis is a sexually transmitted disease caused by Treponema pallidum. Epidemiological studies show that rates have increased dramatically in recent y, especially in human immunodeficiency virus (HIV)-seropositive patients. Although lesions most frequently develop on the genital area, they are presently frequently detected in the oral cavity. We present an HIV-positive patient without antiretroviral treatment and immunologically stable, with firm nodules on the tongue. Following serological tests, clinical symptoms and histopathological findings, lesions were diagnosed as secondary syphilis. A spectacular improvement was achieved with specific treatment. To our knowledge this is the first case described in the literature of secondary syphilis presenting as nodular, painless lesions on the lingual mucosa.
Adult↗
Alpha and beta changes in cortical oscillatory activity in a go/no go randomly-delayed-response choice reaction time paradigm.
OBJECTIVE: Predictable movements induce oscillatory changes over the contralateral motor cortex that begin before the movement, but their significance has not been fully established. We studied non-phase-locked changes in cortical oscillatory activity in a S1-centred double-stimulus go/no go paradigm with random interstimulus interval. METHODS: About 58 reference-free EEG channels were analyzed by means of Gabor transforms in a group of 10 healthy subjects. A 2000 Hz tone (S1go, 84% probability) indicated the subject to make a brisk wrist extension after a second 2000 Hz tone (S2go). The S1-S2 interval was either 1.5, 3 or 4.5 s. A 1000 Hz tone (S1 no go, 16% probability) indicated the subject not to move (and wait for another S1 tone). RESULTS: A frontal 15 Hz synchronization was observed after S1 in all conditions. No further significant changes were observed in the no go condition. A small pre-S2 alpha and beta desynchronization could be observed only in the 3 and 4.5s-interval go conditions, being larger in the latter. CONCLUSIONS: These results suggest that the predictability of the timing of a movement influences the appearance of the pre-movement oscillatory changes; not only motor planning (the 'go' decision) is necessary, but also an estimation of when to move. SIGNIFICANCE: Our findings provide new insight on the relationship between the decision-making process, movement, and cortical oscillatory activity.
Adult↗
Movement-related changes in oscillatory activity in the human subthalamic nucleus: ipsilateral vs. contralateral movements.
A voluntary movement is accompanied by a series of changes in neuronal oscillatory activity in the subthalamic nucleus (STN). These changes can be recorded through electrodes implanted for deep brain stimulation to treat Parkinson's disease in the time interval between the surgery and the internalization of the connections to the batteries. Both baseline activity and movement-related changes are different in the 'on' and 'off' medication motor states. In the 'off' state a low frequency activity in the alpha-beta range (8-25 Hz) that dominates the spectrum is interrupted during the movement, while in the 'on' state baseline frequencies are higher and a peri-movement gamma increase (70-80 Hz) is usually observed. Similar changes have been described with electrocorticographic recordings over the primary motor cortex but the gamma increase was only present during contralateral movements. We compared ipsi- and contralateral movement-related changes in STN activity, using a time-frequency analysis of the recordings obtained simultaneously in both STN and the scalp (electroencephalography) during right and left hand movements. The movement-related changes observed in the STN in the 'on' and the 'off' states were similar to those described previously in terms of predominant frequency bands, but we found bilateral changes in the STN during movements of either hand. A contralateral earlier start of the beta STN changes was mostly observed when the moving hand corresponded to the less-affected side, irrespective of hand dominance. These results suggest that movement-related activity in the STN has, by and large, a bilateral representation and probably reflects cortical input.
Aged↗
Gamma band responses to target and non-target auditory stimuli in humans.
We studied the EEG oscillatory changes in the gamma band during auditory oddball paradigms in two different conditions (counting targets and reading). A time-frequency analysis was performed for standard and target stimuli. The study revealed an early (26-59 ms) phase-locked oscillation. Around 200 ms, a non-phase locked response was found for standard and target stimuli in temporal posterior electrodes. At about 360 ms, a phase-locked oscillation was observed only after target stimuli in the "counting targets" condition. During the "reading" task this late activity was not found, and energy increases were lower than during "counting" task. The early oscillation may be related to the sensory processing of the stimuli. The response around 200 ms may be involved in auditory mismatch and/or memory retrieval, and late activity is probably a P300-related response. Attention enhances all these activities.
Acoustic Stimulation↗
Frontal and central oscillatory changes related to different aspects of the motor process: a study in go/no-go paradigms.
We studied alpha and beta EEG oscillatory changes in healthy volunteers during two different auditory go/no-go paradigms, in order to investigate their relationship with different components of the motor process. In the first paradigm (S2-centered), the initial tone (S1) was constant (warning), and the second tone (S2) indicated the subject whether to move or not. In the second paradigm (S1-centered), S1 indicated whether to move or not, while S2 just indicated the timing of the movement. A medial frontal beta energy increase was found in all conditions after the stimulus that forces the subject to decide whether to move or not (S1 or S2 depending on the paradigm). In both go conditions, a central alpha and beta energy decrease began after the go decision, reaching minimum values during the movement; it was followed by a beta post-movement increase, limited to the central contralateral area. In the no-go conditions, a marked fronto-central beta synchronization appeared after the decision not to move. In conclusion, our study was able to dissociate the beta oscillatory changes related to movement preparation and execution (central decrease/increase) from those associated with decision-making (medial frontal increase) and motor inhibition (fronto-central increase).
Adult↗
Potentials evoked by chirp-modulated tones: a new technique to evaluate oscillatory activity in the auditory pathway.
OBJECTIVE: Steady-state potentials are oscillatory responses generated by a rhythmic stimulation of a sensory pathway. The frequency of the response, which follows the frequency of stimulation, is maximal at a stimulus rate of 40 Hz for auditory stimuli. The exact cause of these maximal responses is not known, although some authors have suggested that they might be related to the 'working frequency' of the auditory cortex. Testing of the responses to different frequencies of stimulation may be lengthy if a single frequency is studied at a time. Our aim was to develop a fast technique to explore the oscillatory response to auditory stimuli, using a tone modulated in amplitude by a sinusoid whose frequency increases linearly in frequency ('chirp') from 1 to 120 Hz. METHODS: Time-frequency transforms were used for the analysis of the evoked responses in 10 subjects. Also, we analyzed whether the peaks in these responses were due to increases of amplitude or to phase-locking phenomena, using single-sweep time-frequency transforms and inter-trial phase analysis. RESULTS: The pattern observed in the time-frequency transform of the chirp-evoked potential was very similar in all subjects: a diagonal band of energy was observed, corresponding to the frequency of modulation at each time instant. Two components were present in the band, one around 45 Hz (30-60 Hz) and a smaller one between 80 and 120 Hz. Inter-trial phase analysis showed that these components were mainly due to phase locking phenomena. CONCLUSIONS: A simultaneous testing of the amplitude-modulation-following oscillatory responses to auditory stimulation is feasible using a tone modulated in amplitude at increasing frequencies. The maximal energies found at stimulation frequencies around 40 Hz are probably due to increased phase-locking of the individual responses.
Acoustic Stimulation↗
Movement-related changes in cortical oscillatory activity in ballistic, sustained and negative movements.
We studied movement-related EEG oscillatory changes in the alpha, beta and low-gamma frequency bands in three different paradigms of movement, namely ballistic, sustained, and negative (muscle relaxation). A time-frequency analysis of non-phase-locked activity in the 7-47 Hz range was performed on movement-centred EEG sweeps using wavelet filters and Gabor transforms. All three movements were accompanied by a decrease in beta activity that began contralaterally about 1.5 s prior to the onset of movement but that extended to both sides near the beginning of the movement. This decrease was followed by a rebound after the end of the movement in the ballistic and negative movements. A decrease was also seen in the alpha band during the three paradigms, which began later (1 s before movement) and lasted longer. An increase in gamma activity was only seen during ballistic and sustained movements, while a decrease in gamma energy was observed during negative movements. It was concluded that changes in the beta band of the EEG before movement are related to the preparation for the movement, but an important afferent component may be present in the later changes. Gamma band activity may be just involved in the execution of the movement, related to muscle contraction.
Alpha Rhythm↗
Beta electroencephalograph changes during passive movements: sensory afferences contribute to beta event-related desynchronization in humans.
Non-phase-locked beta oscillatory changes during passive movements were studied in six healthy volunteers, and compared with those observed in a similar group during ballistic movements. Passive movements consisted of brisk wrist extensions done with the help of a pulley system. Changes in the beta band were determined by means of wavelet and Gabor transforms, and compared statistically with a pre-movement period. In this paradigm, a marked beta energy loss (event-related desynchronization, ERD) was present after the beginning of the movement, followed by a beta energy increase (event-related synchronization, ERS). The ERD/ERS was similar to that observed during ballistic movements, but without pre-movement components. Although both changes were maximal in the contralateral central electrode, the beta ERD showed a more bilateral topography. These findings suggest that afferent proprioceptive inputs may play a role in the final part of the beta ERD observed during voluntary movements.
Adult↗
Ictal paralysis mimicking Todd's phenomenon.
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Adult↗
[Lamotrigine in the adult-onset epilepsy: efficacy and long-term safety].
BACKGROUND: LTG is a new antiepileptic drug that is nowadays very often used in epileptic patients. OBJECTIVES: To determine efficacy and safety of Lamotrigine (LTG) in the first five years after its marketing in patients at a third level university hospital, as well as its impact on the management of classic antiepileptic drugs (AED). PATIENTS AND METHOD: We reviewed retrospectively our Epilepsy Unit Database. One hundred patients were treated with LTG in a 5-year period. Efficacy was evaluated comparing seizure frequency in a 6-month period before and after LTG. The type of epilepsy, side effects, blood levels and concomitant treatments were considered in the analysis. RESULTS: LTG was effective in all groups of epileptic patients studied. Eighteen percent of patients became seizure-free. Seventeen percent of patients improved more than 50%. Fifty-seven percent of patients remained treated with LTG after four years of follow-up. Side effects were mild, but frequent; only four patients discontinued LTG because of adverse effects. Serum levels were usually high, but showed no relation with clinical efficacy. The mean number of AED taken per patient increased. CONCLUSIONS: LTG is a safe an effective drug in epilepsy. It has a clear impact in the management of the epileptic patients.
Adolescent↗