Depressive disorders impose a significant mental health burden on individuals and our society. Among smokers there is a high comorbidity of depression/depressive symptoms (e.g., Glassman et al., 1998). Here the parietal EEG alpha asymmetry was used as a dimensional neuropsychological marker of depressive symptoms (i.e., the more depressed, the higher alpha power in the right vs. left parietal lobe during visuospatial tasks [Henriques & Davidson, 1997; Rabe et al, 2005]). Participants, all of whom were smokers and none of whom were clinically depressed, were randomly assigned to the Bupropion group (n = 30) or Placebo group (n = 80) in this double blind study. EEG data during the performance of a visuospatial task were collected prior to and after 14 days on bupropion or placebo capsules. It was found that bupropion significantly reduced the right parietal alpha power and parietal asymmetry whereas placebo did not. Self-reports on depressive symptoms with the Beck Depression Inventory (BDI) were also collected but they did not change after bupropion treatment, suggesting that EEG measures are more sensitive to subtle/early bupropion’s antidepressant effects. Finally the close investigation of individual differences showed that positive (vs. negative) parietal asymmetry during pretreatment predicted greater benefits from bupropion treatment. The present study sheds light on the antidepressant mechanisms of bupropion and represents a valuable addition to the paucity of research on the effects of bupropion on brain activity with EEG measures in general.

Over the course of a typical night, sleep is comprised of multiple different stages that involve changes in brainwave patterns. Intracranial EEG (iEEG) is an invasive brain recording technique used in hospital settings in epileptic patients to determine the focus of their seizure activity. The intracranial data recorded allows one to directly observe the neural activity of deep brain structures such as the hippocampus and to detect single unit activity and local field potentials, thus providing a level of physiological detail normally available only in animal studies. In this thesis we employ intracranial data to advance our understanding of sleep neural dynamics in humans, and to this end its focus is in two areas : (1) developing a way of sleep scoring iEEG data and (2) investigating the neural dynamics of a particular waveform found during sleep, the sleep spindle, and its role in memory consolidation. Typically, iEEG recordings do not include electrooculogram or electromyogram recordings, which are normally needed for sleep scoring—especially for scoring rapid-eye movement (REM) sleep. We identified differences in alpha power between wake and REM sleep to develop a methodological way to reliably differentiate between wake and REM sleep states. We also wanted to investigate the neural dynamics involved with a particular brainwave seen during sleep, the sleep spindle, which is thought to be important for sleep-mediated memory consolidation. Historically, sleep spindles were thought to occur synchronously across the cortex, but recent findings using iEEG have identified that sleep spindles can also be local. We utilized intracranial EEG to confirm previous findings that iEEG can identify local sleep spindles. In addition to identifying local sleep spindles, we aimed to investigate the potential role that sleep spindles have on learning and memory using standard targeted memory reactivation paradigms for iii both procedural and declarative memories. We found that local sleep spindles occurred at a specific time following auditory stimulation for both procedural and declarative memories. This work has opened up the use of iEEG recordings to investigations of REM sleep dynamics and laid the groundwork for examining the role of local sleep spindles in memory consolidation. / Master of Science / During a night of sleep, our brain goes through different stages that exhibit changes in brainwave patterns. Intracranial EEG (iEEG) is an invasive brain recording technique used in hospital settings in epileptic patients to determine the focus of their seizure activity; this particular brain recording technique allows one to observe the brain activity of deep brain structures. By using iEEG data, we aimed to (1) develop a way of sleep scoring iEEG data and (2) investigate the neural dynamics of a particular waveform found during sleep, the sleep spindle, and its role in memory consolidation.  Electrooculograms (EOG) are used to record the electrical activity of eye movements, and electromyograms (EMG) are used to measure muscle activity. Both of these recording techniques, in addition to EEG, are needed for sleep scoring, especially rapid eye movement (REM) sleep. However, typical iEEG recordings do not have EOGs and EMGs applied to the patient. Using iEEG data, we were able to identify differences in a specific brainwave, the alpha rhythm, between wakeful brain activity and REM sleep brain activity. Furthermore, we were able to use this difference to reliably score REM sleep in iEEG data without the need for EOGs and EMGs.  We also wanted to investigate the brainwave changes in a particular waveform, the sleep spindle, that has been thought to be important for sleep-mediated memory consolidation. Previous research using typical EEG recordings showed that sleep spindles occur synchronously across the cortex, but recent findings using iEEG have identified that sleep spindles can also occur asynchronously across the cortex. We replicated previous research showing that these local sleep spindles are identifiable using iEEG recordings. In addition to identifying local sleep spindles, we investigated the potential role that sleep spindles have on learning and memory. To do so, we used standard targeted memory reactivation paradigms for two types of memory: declarative and procedural memory. We found that local sleep spindles occurred at a specific time following auditory stimulation for both procedural and declarative memories.  This work has opened up the use of iEEG recordings to investigations of REM sleep dynamics and laid the groundwork for examining the role of local sleep spindles in memory consolidation.

La stimulation transcrânienne par courant alternatif (tACS) est une technique de stimulation non invasive du cerveau qui est d’un intérêt croissant, entre autres pour ses effets sur les ondes cérébrales intrinsèques. Par opposition à la stimulation transcranienne par courant direct (tDCS), la tACS permet l’administration d’un courant sinusoïdal ajusté à la fréquence endogène individuelle d’un individu. Les oscillations cérébrales constituant la bande de fréquence alpha (8-12 Hz) sont parmi les plus étudiées en raison de leurs associations variées avec les fonctions et états cérébraux. Un nombre important d’études ont montré l’efficacité de la tACS de diverses façons pour augmenter la puissance de l’activité EEG dans la bande de fréquence alphal’onde alpha. Cependant, l’hétérogénéité des paramètres de stimulation, particulièrement l’intensité, rend l’implémentation de nouveaux protocoles ardue. En effet, il n’y a actuellement aucun consensus sur les paramètres optimaux de stimulation pour moduler l’activité EEG dans la bande de fréquence alphal’onde alpha. Ce projet a pour but de documenter l’impact différentiel de contrôler les caractéristiques de stimulation tACS, soit l’intensité, la fréquence et le site (antérieur ou postérieur) de stimulation. À cette fin, 20 participants en santé ont pris part à notre étude, chacun soumis à 4 conditions de stimulation tACS, échelonnées sur 2 jours (2 blocs par jour). Pour chaque condition expérimentale, la stimulation tACS a été administrée de façon continue via 2 électrodes pendant 20 minutes. Deux conditions actives de tACS ont été réalisées aux sites PO7-PO8 (Système International EEG 10-10), l’une à Fréquence Alpha Individuelle (IAF) et l’autre à Fréquence Theta Individuelle (ITF), qui ont été prédéterminées par une session EEG, au repos et les yeux ouverts, de 5 minutes a priori. Deux conditions de stimulation ont été effectuées avec les électrodes de stimulation positionnées aux sites F3F4 (Système International EEG 10-20), à IAF ou à intensité SHAM (montée de courant 15 secondes seulement). L’intensité de stimulation a été ajustée en respectant le degré de confort de chaque participant, selon une échelle standardisée de désagréabilité (≤ 40 sur 100), et ne pouvait excéder 6 mA. La seconde séance journalière était exécutée 180 minutes après la première séance de tACS. Afin d’évaluer les niveaux de fatigue, les participants ont eu à réaliser une tâche psychomotrice de vigilance (PVT) durant la tACS. Toutes les conditions ont été contrebalancées. Les résultats suggèrent que la tACS ajustée à IAF a été plus efficace que les conditions ITF et SHAM afin d’augmenter la puissance alpha. Pour les deux sites de stimulation IAF tACS, l’augmentation de puissance spectrale la plus importante a été obtenue en tACS antérieure; par contre cette augmentation est distale et spécifique aux générateurs alpha, en pariéto-occipital. Pour ce qui est du montage tACS postérieur, l’augmentation alpha est observée pour les deux régions cérébrales, frontale et postérieure, tout en démontrant un effet d’augmentation préférentiel sur la puissance alpha, versus les autres bandes de fréquence theta et beta. Cette étude propose une évidence préliminaire que la tACS ajustée à IAF à plus hautes intensités est bien tolérée et démontre que l’optimisation de la technique peut avoir un impact prometteur dans le domaine. / Transcranial alternating current stimulation (tACS) is a non-invasive brain stimulation technique increasingly used for its modulating effect on intrinsic brain oscillations. In comparison to transcranial direct current stimulation (tDCS), tACS allows the administration of a sinusoidal current adjusted to one’s endogenous measured frequency. Oscillations within the alpha band range (8-12 Hz) are among the most studied, given their various associations with brain functions and states. A number of studies have proven to be effective in increasing alpha power using tACS through diverse methods. However, the heterogeneity of stimulation parameters, notably the intensity, makes it difficult to implement new tACS protocol. Indeed, there is currently no consensus on optimal stimulation parameters to modulate the alpha rhythm. The current project aimed to document the differential impact of controlling for key tACS stimulation characteristics, namely the stimulation intensity, the stimulation frequency and the stimulation site (anterior or posterior). To this end, we conducted a study, in which 20 healthy participants underwent four different tACS conditions conducted over two non-consecutive days (2 blocks per day). In each experimental condition, tACS stimulation was continuously delivered via two electrodes for a total duration of 20 minutes. Two active tACS conditions were administered at electrode sites PO7-PO8 (10-10 International System) at either the Individual’s Alpha Frequency (IAF) or at the Individual’s Theta Frequency (ITF), which were a priori determined via a 5-minute pre-stimulation EEG recording with eyes open at rest. Two stimulation conditions were performed with stimulating electrodes positioned over F3-F4 electrode sites, at IAF or sham intensity (ramp-up of 15 seconds). The stimulation intensity was set according to the participant’s own rating of unpleasantness on a standardized unpleasantness scale (≤ 40 out of 100) and could not exceed 6 mA. The second tACS condition was administered 180 minutes after the first tACS condition. To assess for fatigue levels, participants were asked to perform a psychomotor vigilance task (PVT) during tACS. All conditions were counterbalanced. Results suggest that alpha tACS stimulation adjusted to IAF was effective in increasing alpha power. Of the two stimulating sites, anterior alpha tACS stimulation induced greatest increases in alpha power, maximal when set to IAF, although specific to alpha generators’ site. Posterior alpha tACS stimulation showed overall increase both over frontal and posterior brain areas. These effects persisted at the 60-minute recording for the anterior tACS only. The current pilot study provides preliminary evidence that posterior tACS stimulation adjusted to IAF at higher intensities is well tolerated and shows potential as an effective brain stimulation technique to increase posterior alpha power.

This work deals with problems of EEG biofeedback and possibilities of its use in therapy. The method of EEG biofeedback helps patients to achieve the state of relaxation. It is a noninvasive treatment modality. The paper also discussed the requirements for each component unit. The main point of a design and construction of Alpha activity monitor, a device implementing EEG biofeedback focused on sensing electrical activity of the brain, specifically alpha waves. Alpha activity is specific and their parameters are taken into account when selecting components and construction equipment. Custom feedback is then for the appearance of alpha activity mediated by the headphones in acoustic form. The work also includes design of electrical circuits and electrical diagram of the overall apparatus including a list of used parts. Electrical diagrams are formed in the EAGLE 6.1.0.