Browsing by Subject "electroencephalography"

Visual working memory (VWM) maintains information for future usage. Several studies show that the cortical oscillations in the γ-frequency band (from 30 to 120 Hz) are modulated by the VWM performance. However, less is known about the cortical sources underlying the modulation of these oscillations in VWM. To address this question, we recorded human neuronal activity with magneto- and electroencephalography (M/EEG) during a delayed-matching-to-sample VWM task with three different task conditions, within which participants were instructed to focus on different object features in turn. In addition, anatomical data was acquired with magnetic resonance imaging for source modeling purposes. We then estimated the cortical amplitude dynamics across frequencies from three to 90 Hz during the VWM retention period for these three different conditions. We found that the amplitudes of the γ –frequency band oscillations were strengthened in the occipito-temporal cortical areas during the VWM for shapes but not for color or spatial locations. These data suggest that γ –band oscillations are fundamental in VWM, especially for visual stimuli requiring perceptual feature binding. Furthermore, cortical γ –band oscillations were found to be load dependently strengthened in the frontal cortex, where the central executive and attention associated processes are believed to take place. These data support the previous hypotheses stating that γ –band oscillations contribute to the maintenance of object representations in VWM.

Previous research has linked music training to enhanced processing of unattended auditory stimuli as indexed by such auditory event-related potential (ERP) responses as mismatch negativity (MMN) and P3a. Music training has also been linked with enhanced cognitive abilities more generally, and executive functions have been proposed to mediate this link. The current study concentrates on the processing of unattended auditory stimuli and how this relates to two aspects of executive functions: task-switching and inhibition. Sixty-seven music trained (music group) and non-trained (control group) adolescents and young adults were split into age groups, 14–16 year olds (younger) and 17–20 year olds (older), and compared in their performance on inhibition and task-switching task as well as the neural processing of unattended auditory stimuli. The ERPs were recorded in response to an oddball paradigm consisting of frequent major and infrequent minor chords. The music group demonstrated larger MMN and P3a amplitudes than the control group during the chord paradigm. The younger music group showed better performance in an inhibition task than the younger control group. However, no other differences in task performance were found between the groups. Also, no link between MMN or P3a and task performance was found. Therefore, the results of the current study are in line with the previous findings that music training is linked to enhanced early neural processing of unattended auditory stimuli. However, the results were partly in disagreement with previous reports of enhanced executive functions in musicians as a link between executive functions and music training was only observed in the younger participants, and only in regard to the inhibition task.

Sleep spindles are thalamocortical oscillations that occupy the sigma band with trait-like inter-individual variability. Sleep spindles associate with reasoning abilities according to several studies, but some discrepancy exists in the strength and even direction of the associations. This may, to some extent, be due to methodological differences. The stage of brain maturation also affects spindle manifestation. In this community-based study, associations between spindle characteristics and reasoning abilities are examined in an understudied age group, adolescents. An all-night polysomnography was conducted at homes of 178 adolescents (104 girls). Working memory, visuospatial reasoning and verbal reasoning were measured in the same evening. An automatic algorithm was used to detect slow (10–13 Hz) and fast (13–16 Hz) spindles in frontal and central scalp derivations in NREM 2 sleep stage. The associations between spindle variables (density and intensity) and the cognitive test scores were analyzed with linear regression. Genders apart, the analyses were conducted first on the whole group and then separately on the Above Median (AM) and Below Median (BM) intelligence subgroups. In the analyses with all subjects, higher central fast density associated with better verbal reasoning in girls. When examining the subgroups separately, this association was not perceived in the AM group but appeared prominently in the BM group girls. No other associations were found between the spindle variables and the cognitive test scores. A positive spindle-intelligence relation is an established finding in females, but more commonly the association is typified by fluid/visuospatial reasoning and frontal brain areas. In the present study, young age may have related to the accentuated relative significance of more caudal brain regions and verbal intelligence in relation to spindles. The ongoing neural maturation and the heterogeneity of the sample may have contributed to the nature of the findings. More adolescent studies are needed to gain understanding of the matter.