New bands in the sleep stages of spider monkeys (Ateles geoffroyi): Electroencephalographic correlations and spatial distribution.

The study of electroencephalographic (EEG) signals in nonhuman primates has led to important discoveries in neurophysiology and sleep behavior. Several studies have analyzed digital EEG data from primate species with prehensile tails, like the spider monkey, and principal component analysis has led to the identification of new EEG bands and their spatial distribution during sleep and wakefulness in these monkeys. However, the spatial location of the EEG correlations of these new bands during the sleep-wake cycle in the spider monkey has not yet been explored. Thus, the objective of this study was to determine the spatial distribution of EEG correlations in the new bands during wakefulness, rapid eye movement (REM) sleep, and non-REM sleep in this species. EEG signals were obtained from the scalp of six monkeys housed in experimental conditions in a laboratory setting. Regarding the 1-21 Hz band, a significant correlation between left frontal and central regions was recorded during non-REM 2 sleep. In the REM sleep, a significant correlation between these cortical areas was seen in two bands: 1-3 and 3-13 Hz. This reflects a modification of the degree of coupling between the cortical areas studied, associated with the distinct stages of sleep. The intrahemispheric EEG correlation found between left perceptual and motor regions during sleep in the spider monkey could indicate activation of a neural circuit for the processing of environmental information that plays a critical role in monitoring the danger of nocturnal predation.

Human amygdala activation during rapid eye movements of rapid eye movement sleep: an intracranial study.

The amygdaloid complex plays a crucial role in processing emotional signals and in the formation of emotional memories. Neuroimaging studies have shown human amygdala activation during rapid eye movement sleep (REM). Stereotactically implanted electrodes for presurgical evaluation in epileptic patients provide a unique opportunity to directly record amygdala activity. The present study analysed amygdala activity associated with REM sleep eye movements on the millisecond scale. We propose that phasic activation associated with rapid eye movements may provide the amygdala with endogenous excitation during REM sleep. Standard polysomnography and stereo-electroencephalograph (SEEG) were recorded simultaneously during spontaneous sleep in the left amygdala of four patients. Time-frequency analysis and absolute power of gamma activity were obtained for 250 ms time windows preceding and following eye movement onset in REM sleep, and in spontaneous waking eye movements in the dark. Absolute power of the 44-48 Hz band increased significantly during the 250 ms time window after REM sleep rapid eye movements onset, but not during waking eye movements. Transient activation of the amygdala provides physiological support for the proposed participation of the amygdala in emotional expression, in the emotional content of dreams and for the reactivation and consolidation of emotional memories during REM sleep, as well as for next-day emotional regulation, and its possible role in the bidirectional interaction between REM sleep and such sleep disorders as nightmares, anxiety and post-traumatic sleep disorder. These results provide unique, direct evidence of increased activation of the human amygdala time-locked to REM sleep rapid eye movements.

A method for segmentation of dental implants and crestal bone.

PURPOSE: Medical imaging and in particular digital radiographic images offer a great deal of information to dentists in the clinical diagnosis and treatment processes on a daily basis. This paper presents a new method aimed to produce an accurate segmentation of dental implants and the crestal bone line in radiographic images. With this, it is possible computing several measures to biomechanical and clinical evaluation of dental implants positioning and evolution. METHODS: The proposed segmentation method includes two major steps: (1) the preprocessing that combine denoising filters, morphological operations and histogram threshold techniques and (2) the final segmentation involving made-to-measure adjusted and trained active shape models for detecting the precise location of the intended structures. RESULTS: Resulting measurements were compared to manual measurements made by experts on representative radiographs from patients. The calculated intraclass correlation coefficient was 0.75 and showed good reliability of the method, and the Bland-Altman analysis showed 95% of the values within the limits of agreement. The mean of the differences between the manual and method-driven measurements was 0.049 mm ([Formula: see text]) 95% CI, inferior to the established limit (0.15mm). CONCLUSIONS: It was demonstrated that the method achieved a precise segmentation of the intended structures. The validation process on standardized periapical radiographs showed good agreement between the manual measurements and the ones produced by the new method. Future work will be focused on making the method more robust to densitometry changes and to validate the method on non-standardized radiographs.

Experiencias de seguridad y protección radiológicas durante la operación del Centro de Isótopos / Experiences of safety and radiological protection during the operation of the Center of Isotopes

Debido a la importancia que tiene para la comunidad radiológica las experiencias de trabajo de seguridad y protección radiológicas adquiridas durante la implantación del Programa de Seguridad y Protección Radiológica para la operación segura de una planta de producción de isótopos como es el Centro de Isótopos, en este trabajo se presentan la evolución de los requisitos que conforman este programa y las experiencias valiosas aportadas que pueden ser útiles para otros centros de Cuba y Latinoamérica con riesgos radiológicos similares durante el uso de materiales radiactivos.

The present paper deals with the experience acquired during the implementation of Radiation Safety and Protection Program for the safe operation of a plant for production of isotopes such as the Isotope Centre. Considering the importance for the radiology community of that experience, this paper presents the evolution of requirements for this program and provided valuable experience that can be useful for other centres in Cuba and Latin America with similar radiation hazards during the use of radioactive materials.

Effects of alcohol on the performance of the Tower of London task in relation to the menstrual cycle: an electroencephalographic study.

It is well known that the metabolism of alcohol and cognitive functions can vary during the menstrual cycle. Also, both alcohol ingestion and hormonal variations during menstruation have been associated with characteristic changes in electroencephalographic (EEG) activity. The aim of the present study was to determine whether EEG activity during the performance of the Tower of London (TOL) task is affected by previous ingestion of alcohol and whether these EEG patterns vary in relation to different phases of the menstrual cycle. For this purpose, female participants consumed a moderate dose of alcohol or placebo during the follicular and early luteal phases of the menstrual cycle and then, 35 min after liquid ingestion, EEG activity was recorded during the performance of TOL. A deleterious effect of alcohol on TOL performance was potentiated in the follicular phase, related to a higher α1 relative power, probably as a result of the low progesterone levels characteristic of this menstrual phase. These data show the feasibility of examining the interaction of alcohol and menstrual cycle phases on cognitive performance by means of EEG recording, and contribute toward a better understanding of the brain mechanisms that underlie the cognitive changes that occur during the menstrual cycle under the effects of alcohol.

Brain electrical activity changes in treatment refractory schizophrenics after olanzapine treatment.

The aim of the present study was to identify brain electrical activity changes generated by olanzapine (OLZ) in treatment refractory schizophrenics (TRS). 14 paranoid TRS (31.5+/-8.39 years old) were evaluated before and after 8 weeks of OLZ treatment. Psychopathology was evaluated by means of total BPRS and PANSS scores. Resting EEG was recorded in the pre (under typical neuroleptics) and post (under OLZ) sessions. A good response to OLZ was observed in 57% of TRS. A significant reduction in positive and negative symptoms scales of PANSS was found. Absolute power of theta1, theta2, alpha1 bands increased after treatment, while beta2 power showed a decrease. Intrahemispheric correlation increased between different zones of the frontal areas and between frontal and posterior areas, while interhemispheric correlation decreased in theta2. EEG changes were more evident in those patients who had a better response to OLZ. OLZ showed to be effective in TRS, improving psychiatric symptoms and increasing activity synchronization between different areas within each hemisphere that may indicate a functional reorganization, particularly in good responders.

Relationship between resting alpha activity and the ERPs obtained during a highly demanding selective attention task.

In spite of previous reports on the relationship between ongoing EEG and ERPs, there remains a lack of agreement on the nature of their nexuses. The aim of the present study was to evaluate the relationship between resting EEG and the ERP components in two groups of healthy subjects with different levels of performance in a highly demanding selective visual attention task. Young adults were classified according to the amount of their correct responses in the task, into high (HP; averaged hits (AH): 86%) and low performance groups (LP; AH: 59%). EEG was recorded during rest, prior to task performance and absolute (AP) and relative power (RP), as well as inter- (rTER) and intrahemispheric (rTRA) correlation were calculated. ERPs during task performance were also obtained and their amplitude and latency measures were assessed. Results showed that individuals with better behavioral performance had a higher synchronization between both hemispheres during rest as well as higher amplitude and shorter latencies of N2 and P3. Principal Component Analysis revealed that alpha2 AP and RP were inversely related to P2 and N2 latency. Higher values of alpha1 and alpha2 rTER were clustered with higher P3 amplitude and shorter reaction time. In conclusion, the differences in the cortical organization of HP and LP at rest (EEG) seem to be associated to the way the brain reacts during information processing (ERPs).