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Objective: Although event related oscillations during attentional tasks have been studied comprehensively in the literature, EEG delta and theta during sustained attention task performance has not been extensively examined in the literature. The aim of our research group was to investigate the changes in slow wave oscillations (Delta and Theta) during attentional processes. Methods: Electroencephalography (EEG) of 13 healthy participants was recorded at the Fz, Cz, Pz, Oz locations during the auditory SART task which is a long and repetitive task requires withholding the response to the rare target stimuli. Time frequency decomposition was conducted via wavelet convolution using a Morlet-wavelet from 0.5 to 4 Hz (Delta) and 4 to 8 Hz (Theta). Average amplitude was calculated within 750 ms time window after the stimulus onset. Results: Delta F(3.36)=33.96, p<.001 and theta F(1.68, 20.10)= 29.32, p<.001 activity increased at mid-frontal region at the beginning of the experiment both in time domain (digital filtering) and time-frequency domain. However, decrease in fronto-central theta F(2.24)=3.55, p<.05, r=.36 activity was observed toward the end of the experiment. Conclusion: The changes in attention has been investigated based on new analytical methods event related oscillations (EROs) and inter-trial coherence (ITC) with respect to time domain and the localization of brain in the SART. Overall, sustained attention shown to increase fronto-central delta and theta activity during especially in behavioral inhibition process. This strong frontal midline delta and theta activity which is known to be parallel to executive control also occurs in inhibition control reported consistency with the literature. This increase was attenuated together with decreased delta and theta ITC towards the end of the experiment. Decrease in delta and theta activity can be associated with mental fatigue and decreased attention. [ABSTRACT FROM AUTHOR]

Many studies suggest that separate retinocortical channels with different conduction speeds transmit the information about high and low spatial frequencies (SF). Similarly, separate callosal channels may be responsible for the transfer of different SFs. To test this hypothesis, interhemispheric transfer time (IHTT) was estimated using visual evoked potentials (VEPs) elicited by reversal of different SF checkerboard patterns, which were presented either in the right or left visual hemifield. VEPs were recorded from homologous occipital and parietal leads in 11 subjects. The P100 latencies obtained from directly stimulated hemispheres were defined as retinocortical conduction times. The difference in P100 latencies obtained from directly and indirectly stimulated hemispheres was defined as IHTT (i.e., contralateral P100 latency values subtracted from the ipsilateral latency values). The results, showing faster retinocortical transfer for low SF than for high SF, and the shortest transfer time at parietal leads only for low SF, indicate that the presented stimuli are transferred on separate retinocortical channels. Concerning the interhemispheric transfer (VEP-IHTT), faster right-to-left than left-to-right transfer for both low and high SF stimuli was found, which is in congruence with previous studies. Most important however, the VEP-IHTT was faster for low SF than high SF. These different interhemispheric transfer speeds support the hypothesis that transferring low SF, compared with high SF information, relies on larger callosal fibers. Thus, we conclude that indeed distinct callosal channels respond selectively to the SF content of visual stimuli.