The human cortex is organized into two broad systems: an extrinsic system that responds to external stimuli and tasks, and an intrinsic system linked to internal, self-related experiences. These systems typically show anti-correlated activity, even at rest. This experiment tested whether meditation can alter that competition. Participants either fixated without meditation or practiced non-dual awareness or focused attention meditations. Anti-correlation between the extrinsic and intrinsic systems was stronger during focused attention and weaker during non-dual awareness compared to fixation. Correlations within each system did not change. The results indicate that the anti-correlation between these systems is not fixed and that different meditation practices can modulate this functional brain organization in distinct ways.
Binocular rivalry, a phenomenon where perception alternates between two incompatible images presented to each eye, has been used to study the neural correlates of conscious vision. This essay critically examines four key questions about its usefulness: what comparison condition is appropriate, how to separate abolished awareness from inattention, whether findings from rivalry generalize to other perceptual phenomena, and whether neural activity linked to rivalry truly constitutes a neural correlate of consciousness. The authors arrive at skeptical answers to these questions but suggest that a more nuanced use of binocular rivalry can still provide insights into neural dynamics and components of consciousness, including those involved in perceptual decision-making.