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Temporal evolution of α and β bands during visual spatial attention

Abstract 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 α band in a time window of 375–500 ms and an increase in the β band at 500–875 ms after stimulus onset, for both attended and unattended stimuli. Statistical analysis showed that the decrease in α and the increase in β were more marked during the attentional condition. In conclusion, these results demonstrate that the decrease in α band and the increase in β band are electrophysiological markers of visual spatial attention.

ABNORMAL ERPS AND HIGH FREQUENCY BANDS POWER IN MULTIPLE SCLEROSIS

Event-related potentials (ERPs) and power spectral density (PSD) were registered during an auditory-oddball paradigm in 11 MS patients. These patients showed a decrease in the amplitude of P2 and N2 components and a delayed P3 latency compared to control subjects suggesting that the attentional orienting mechanism in the auditory modality is affected in MS. The PSD analysis showed that MS patients exhibited an increased power in beta and gamma bands. The combined analysis of frequency and time domain suggested diverse phenomena that occurred in the MS patient group related with the EEG background or the motivational status.

Hemispheric lateralization of language in epileptic right-handed children with unihemispheric discharge.

The epileptic discharge of one hemisphere interferes with brain function. The present study assesses the linguistic disabilities of epileptic patients owing to discharge in one hemisphere. Subjects were classified by age and gender. A significant deterioration of linguistic abilities appeared in adult subjects discharging in the left hemisphere. In children, however, a more symmetric hemispheric pattern of epileptic discharge interference appears with age up to 14 years. Unihemispheric epileptic discharges could also provide information about the degree of lateralization that a given function presents in different developmental stages. This lateralization appears clearly established from the age of 14 to 21 years until late adulthood. These results imply that hemispheric specialization of language is not completed until adolescence. This absence of hemispheric specialization for language in childhood was statistically more significant in boys than in girls, suggesting that the maturation of cortical areas related to language occurs earlier in girls than in boys. Finally, the familial history of left-handedness is a factor delaying the age of left lateralization of language in right-handed children. (J Child Neurol 2002;17:505-509).

Estudio comparado del comportamiento de niños educados en medio familiar y niños educados en instituciones. Una perspectiva etológica

ResumenSe ha realizado un estudio observacional con metodologia etologica en ninos de 4–5 anos: Un grupo de 5 Ss. procedentes de una Casa Cuna y otro grupo de 7 Ss. procedentes de un ambiente familiar. El muestreo se llevo a cabo en un habitat comun para ambos grupos: el recreo de un preescolar, ubicado en otra zona, y en condiciones de juego libre, aunque controlado por monitores adultos. Los resultados obtenidos sugieren la existencia de diferencias entre ambos grupos, que podrian implicar una manera diferente de integracion social de los ninos cuyo habitat primario no es la casa familiar, aunque no es posible establecer una relacion de causalidad directa con la institucionalizacion.

Significado funcional de los componentes de los potenciales evocados visuales en el proceso de atención al espacio y a los objetos

espanolEl proceso atencional permite seleccionar la informacion relevante. Un interrogante en este proceso cognitivo consiste en saber en que momento se realiza la seleccion dentro del procesamiento sensorial. Los estudios mediante Potenciales Evocados (PEs) han mostrado que los componentes primarios (P1 y N1) son modulados tanto por la seleccion espacial como por la del objeto. El objetivo del presente trabajo es estudiar la implicacion de los distintos componentes de los PEs en los mecanismos de atencion basados en el espacio y/o en el objeto mediante un paradigma de priming. Los resultados mostraron que la seleccion espacial modulaba la amplitud de P1, mientras que la seleccion por el objeto modulaba la de N1 y P2. El componente P3a mostro la interaccion del espacio y del objeto en el proceso de atencion. Se sugiere que el proceso atencional visual comienza la seleccion de la informacion usando claves espaciales y continua con mecanismos selectivos mas complejos basados en el espacio, en el objeto y en la interaccion de ambos. EnglishThe attentional process allows to select the relevant information. A query of this cognitive process is in what moment it is carried out the selection during the sensorial process. The studies by means of evoked potentials (ERPs) have shown that the early components (P1 and N1) are modulated by the space selection and/or by the object. The objective of the present work is the study of the implication of the different ERPs components in the mechanisms of attention for the space and for the object using a priming paradigm. The results showed that the space selection modulated the amplitude of the P1 while the selection for the form varied the amplitude of the N1 and P2 components. The P3a component showed the interaction of the space and object attention The conclusion of the present study is that the attentional visual process begins its selection of the information with space cues and it continues with refined selective mechanisms based on the space, object and its interaction