Slow oscillation electrical brain stimulation during waking promotes EEG theta activity and memory encoding

Abstract

The application of transcranial slow oscillation stimulation (tSOS; 0.75 Hz) was previously shown to enhance widespread endogenous EEG slow oscillatory activity when applied during a sleep period characterized by emerging endogenous slow oscillatory activity. Processes of memory consolidation typically occurring during this state of sleep were also enhanced. Here, we show that the same tSOS applied in the waking brain also induced an increase in endogenous EEG slow oscillations (0.4 -1.2 Hz), although in a topographically restricted fashion. Applied during wakefulness tSOS, additionally, resulted in a marked and widespread increase in EEG theta (4 -8 Hz) activity. During wake, tSOS did not enhance consolidation of memories when applied after learning, but improved encoding of hippocampus-dependent memories when applied during learning. We conclude that the EEG frequency and related memory processes induced by tSOS critically depend on brain state. In response to tSOS during wakefulness the brain transposes stimulation by responding preferentially with theta oscillations and facilitated encoding.transcranial slow oscillation stimulation ͉ sleep ͉ plasticity ͉ cortex ͉ tDCS (transcranial direct current stimulation)

Standing Waves as an Explanation for Generic Stationary Correlation Patterns in Noninvasive EEG of Focal Onset Seizures

“…Such endogenous fields mediate a kind of cortical ''self-monitoring'' (Weiss and Paulsen, 2010), which seems to be particularly relevant for low frequencies below 8 Hz (Anastassiou et al, 2011). Hence, it is conceivable that endogenous fields play an active and constructive role during information processing, as, for example, memory tasks during waking state (Kirov et al, 2009) or sleep-assisted memory consolidation (Marshall et al, 2006).…”

Imaging human brain networks to improve the clinical efficacy of non-invasive brain stimulation

“…It produces longer-lasting changes (> 5 minutes) in local oscillatory activity, and is associated with pronounced behavioral changes. For example, low-frequency delta oscillations induced with tACS, important in memory consolidation during sleep, are enhanced in both the sleeping (Marshall et al, 2004) and waking brain (Kirov et al, 2009). It appears tACS entrains the membrane potential to oscillate at the given stimulation frequency (Zaehle et al, 2010), thus synchronizing activity within and between cortical regions (Helfrich et al, 2014;Voss et al, 2014).…”

Transcranial Alternating Current Stimulation Modulates Large-Scale Cortical Network Activity by Network Resonance

“…Constant waveforms [transcranial direct current stimulation (tDCS)] either suppress or enhance activity as a function of electrode polarity (Nitsche and Paulus, 2000). Recent studies have demonstrated that transcranial alternating current stimulation (tACS) can induce frequency-specific effects on brain dynamics measured by electroencephalography (EEG; Kirov et al, 2009;Moliadze et al, 2010;Zaehle et al, 2010;Zaghi et al, 2010) and behavioral tasks. Specifically, this targeted stimulation paradigm has been applied to modulate vision Laczó et al, 2012), motor function Pogosyan et al, 2009;Feurra et al, 2011b;Brignani et al, 2013), somatosensation (Feurra et al, 2011a;Wach et al, 2013), and higher-order cognitive function (Polanía et al, 2012;Sela et al, 2012;Brittain et al, 2013).…”