The Infraslow Frequency Oscillatory Transcranial Direct Current Stimulation Over the Left Dorsolateral Prefrontal Cortex Enhances Sustained Attention

Abstract

BackgroundThe vigilance fluctuation and decrement of sustained attention have large detrimental consequences to most tasks in daily life, especially among the elderly. Non-invasive brain stimulations (e.g., transcranial direct current stimulation, tDCS) have been widely applied to improve sustained attention, however, with mixed results.ObjectiveAn infraslow frequency oscillatory tDCS approach was designed to improve sustained attention.MethodsThe infraslow frequency oscillatory tDCS (O-tDCS) over the left dorsolateral prefrontal cortex at 0.05 Hz was designed and compared with conventional tDCS (C-tDCS) to test whether this new protocol improves sustained attention more effectively. The sustained attention was evaluated by reaction time and accuracy.ResultsCompared with the C-tDCS and sham, the O-tDCS significantly enhanced sustained attention by increasing response accuracy, reducing response time, and its variability. These effects were predicted by the evoked oscillation of response time at the stimulation frequency.ConclusionSimilar to previous studies, the modulation effect of C-tDCS on sustained attention is weak and unstable. In contrast, the O-tDCS effectively and systematically enhances sustained attention by optimizing vigilance fluctuation. The modulation effect of O-tDCS is probably driven by neural oscillations at the infraslow frequency range.

Natural frequencies of neural activities and cognitions may serve as precise targets of rhythmic interventions to the aging brain

“…Rhythmicity is a critical component for the regulation of neural activities related to cognitive and other important functions. Rhythmic brain stimulation techniques have been demonstrated to improve or restore neural activities at particular frequencies ( Klink et al, 2020 ; Qiao et al, 2022 ), indicating it may be a novel strategy for the restoration of functions in aging by entraining the altered frequencies in aging brain to those in younger and healthy brain. Still, though it is of great promise, future work is highly demanded and warranted to (1) explicitly examine and characterize the efficacy of this kind of technology, helping maximize its benefits at individual level ( Knyazeva et al, 2018 ; Jafari et al, 2020 ; Wang et al, 2022 ); and (2) determine the optimal design of this intervention that would be appropriate for different populations (e.g., those with and without neurodegenerative diseases), including the immediate and longer-term effects, dose-response relationship, etc.…”

“…These techniques are usually imposed physically or psychologically. The former primarily includes repetitive transcranial magnetic stimulation (rTMS), transcranial alternating current stimulation (tACS), and oscillatory transcranial direct current stimulation (O-tDCS) ( Wischnewski et al, 2019 ; Chou et al, 2020 ; Qiao et al, 2022 ); and the latter includes cognitive tasks or sensory stimulations focusing on particular frequencies ( Norcia et al, 2015 ; Wang et al, 2016 , 2019 ).…”

“…For example, the resonant frequencies in Brodmann areas 6, 7, and 19 appeared at about 29, 18.6, and 10.8 Hz, respectively, in people about 30 years old ( Rosanova et al, 2009 ). Another example is that the natural frequency of sustained attention occurred at around 0.05 Hz in children and young adults ( Qiao et al, 2022 ). The resonances at natural frequencies of neural activities ( Rosanova et al, 2009 ) related to sensorimotor or other behavioral performances ( Lu et al, 2017 ; Klimesch, 2018 ) have been demonstrated.…”

“…Appropriately characterizing these natural frequencies, which are the promising targets for rhythmic stimulations, is thus important for the design of these techniques. Recently, Qiao et al (2022) observed that as compared to conventional tDCS, the O-tDCS targeting the potential natural frequency (i.e., 0.05 Hz) of sustained attention may induce significantly greater effects on this function, suggesting that using the natural-frequency-based rhythmic stimulation can further help the higher-order cognitive function. These findings indicate that natural frequencies may serve as precise and efficient targets of rhythmic interventions to improve cognitive and other functions ( Lee et al, 2021 ), holding great promise of retarding the age-related decline of brain functions by reversing frequency shift and temporal dedifferentiation in aging brains (see Figure 1 ).…”

The enigma of infra-slow fluctuations in the human EEG

“…This inference was supported by a transcranial magnetic stimulation (TMS) study demonstrating that the amplitude of motor evoked potentials (MEP) induced by pulses of TMS were sensitive to the phases of EEG-ISF ( de Goede and van Putten, 2019 ). In a recent study ( Qiao et al, 2022 ) an anodal transcranial Direct Current Stimulation (tDCS) on the left dorsolateral prefrontal cortex in the infraslow frequency band (0.05 Hz) enhanced sustained attention more strongly than the conventional tDCS suggesting that this effect was achieved by infraslow modulation of neuronal excitability.…”