Unraveling Causal Mechanisms of Top‑Down and Bottom‑Up Visuospatial Attention with Non‑invasive Brain Stimulation

Abstract

Attention is a process of selection that allows us to intelligently
navigate the abundance of information in our world. Attention can
be either directed voluntarily based on internal goals—“top-down” or
goal-directed attention—or captured automatically, by salient stimuli—
“bottom-up” or stimulus-driven attention. Do these two modes of attention
control arise from same or different brain circuits? Do they share similar
or distinct neural mechanisms? In this review, we explore this dichotomy
between the neural bases of top-down and bottom-up attention control,
with a special emphasis on insights gained from non-invasive neurostimulation
techniques, specifically, transcranial magnetic stimulation (TMS).
TMS enables spatially focal and temporally precise manipulation of brain
activity. We explore a significant literature devoted to investigating the
role of fronto-parietal brain regions in top-down and bottom-up attention
with TMS, and highlight key areas of convergence and debate. We also
discuss recent advances in combinatorial paradigms that combine TMS
with other imaging modalities, such as functional magnetic resonance
imaging or electroencephalography. These paradigms are beginning to
bridge essential gaps in our understanding of the neural pathways by
which TMS affects behavior, and will prove invaluable for unraveling
mechanisms of attention control, both in health and in disease.