Prediction of behavioral performance by alpha-band phase synchronization in working memory.

Working memory (WM) is a cognitive system with limited capacity that can temporarily store and process information. The purpose of this study was to investigate functional connectivity based on phase synchronization during WM and its relationship with the behavioral response. In this regard, we recorded EEG/Eye tracking data of seventeen healthy subjects while performing a memory-guided saccade (MGS) task with two different positions (near eccentricity and far eccentricity). We computed saccade error as memory performance and measured functional connectivity using Phase Locking Value (PLV) in the alpha frequency band (8-12 Hz). The results showed that PLV is negatively correlated with saccade error. Our finding indicated that during the maintenance period, PLV between the frontal and visual area in trials with low saccade error increased significantly compared to trials with high saccade error. Furthermore, we observed a significant difference between PLV for near and far conditions in the delay period. The results suggest that PLV in memory maintenance, in addition to predicting saccade error as behavioral performance, can be related to the coding of spatial information in WM.

Alpha oscillation during the performance of a new variant of working memory-guided saccade task: Evidence from behavioral and electroencephalographic analyses.

Working memory (WM) can be considered as a limited-capacity system which is capable of saving information temporarily with the aim of processing. The aim of the present study was to establish whether eccentricity representation in WM could be decoded from eletroencephalography (EEG) alpha-band oscillation in parietal cortex during delay-period while performing memory-guided saccade (MGS) task. In this regard, we recorded EEG and Eye-tracking signals of 17 healthy volunteers in a variant version of MGS task. We designed the modified version of MGS task for the first time to investigate the effect of locating stimuli in two different positions, in a near (6°) eccentricity and far (12°) eccentricity on saccade error as a behavioral parameter. Another goal of study was to discern whether or not varying the stimuli loci can alter behavioral and eletroencephalographical data while performing the variant version of MGS task. Our findings demonstrate that saccade error for the near fixation condition is significantly smaller than the far from fixation condition. We observed an increase in alpha power in parietal lobe in near vs far conditions. In addition, the results indicate that the increase in alpha (8-12 Hz) power from fixation to memory was negatively correlated with saccade error. The novel approach of using simultaneous EEG/Eye-tracking recording in the modified MGS task provided both behavioral and electroencephalographic analyses for oscillatory activity during this new version of MGS task.

Evaluation of Morphology and Anatomical Measurement of Nasopalatine Canal Using Cone Beam Computed Tomography.

OBJECTIVES: Precise radiographic assessment of the nasopalatine canal is required to prevent implant failure. The purpose of the current study was to determine the three dimensional (3D) morphology, as well as the dimensions of the nasopalatine canal using cone beam computed tomography (CBCT). MATERIALS AND METHODS: In this descriptive cross-sectional study, maxillary CBCT images from 300 patients (150 men, 150 women) were retrospectively evaluated. Sagittal and coronal views were reviewed to determine the nasopalatine canal morphology and dimensions. The difference in canal dimensions between men and women was evaluated using the Student's t-test while the difference in canal morphology between the two sexes was assessed using Chi-square test. RESULTS: A total of 199 (66.3%) patients had type A canal (cylindrical without a branch), 69 (23%) had type B canal (a canal with a branch in the upper part), and 32 (10.7 %) had type C canal (a canal with a branch in the middle part). Incisive foramen diameter was 4.7±1.11mm on the sagittal section. Alveolar bone width in the anterior part of the canal was 12.3±1.7mm in the upper one third, 10.7±1.7mm in the middle one third, and 9.8±1.4mm in the lower one third. The angle of canal with palate was 109.5±5.7°. On the coronal sections, canal length was 14.1±3.0mm, incisive foramen diameter was 4.6±1.0mm, and canal diameter in the nasal floor was 5.1±1.0mm. CONCLUSIONS: Significant differences in canal morphology were observed among the patients and CBCT was useful in determining nasopalatine canal morphology and its dimensions before implant placement.