Controlling brain state prior to stimulation of parietal cortex prevents deterioration of sustained attention

Sustained attention is a limited resource which declines during daily tasks. Such decay is exacerbated in clinical and aging populations. Recent research has demonstrated that inhibition of the intraparietal sulcus (IPS) using low-frequency transcranial magnetic stimulation (LF-rTMS) can lead to an upregulation of functional communication within the attention network. Attributed to functional compensation for the inhibited node, this boost outlasts the stimulation for tens of minutes. Despite the neural change, no behavioral correlate has been found in healthy subjects, a necessary direct evidence of functional compensation. To understand the functional significance of neuromodulatory induced fluctuations on attention, we sought to boost the impact of LF-rTMS through controlling neural excitability prior to LF-rTMS, with the goal to impact behavior. Brain state was controlled using high-frequency transcranial random noise stimulation (HF-tRNS), shown to increase and stabilizes neuronal excitability. Using fMRI-guided stimulation protocols combining HF-tRNS and LF-rTMS, we tested the post-stimulation impact on sustained attention via a multiple object tracking task (MOT). Whilst attention deteriorated across time in the control conditions, HF-tRNS followed by LF-rTMS maintained attention performance up to 94 minutes, doubling the length of successful sustained attention. Multimethod stimulation was also more effective when targeting right IPS, supporting the notion of specialized attention processing in the right hemisphere. Used in a cognitive domain dependent on network-wide neural activity, this tool may be effective in causing lasting neural compensation important for clinical rehabilitation.