How does the brain clear away waste? This task is handled by the brain’s lymphatic drainage system, and attempts to understand how it operates have driven major advances in brain imaging.

A new study published in iScience by researchers at the Medical University of South Carolina reports the first human evidence of a previously unrecognized center of lymphatic drainage in the brain, the middle meningeal artery (MMA).

Using a NASA collaboration that gave them access to real-time MRI tools originally designed to study how spaceflight alters fluid movement in the brain, the MUSC team, led by Onder Albayram, Ph.D., followed the movement of cerebrospinal and interstitial fluids along the MMA in five healthy volunteers over six hours. Their observations showed that cerebrospinal fluid moved slowly and passively, a pattern consistent with lymphatic drainage rather than blood circulation, which would be faster and more pulsatile.

Recently, there has been convergence of thought by researchers in the fields of memory, perception, and neurology that the same neural circuitry that produces conscious memory of the past not only produces predictions of the future, but also conscious perception of the present.

In a new perspective in the Journal of Cognitive Neuroscience, researchers explain that although our conscious perception appears to simply mirror the external world, due to neural processing delays this intuitive feeling must be wrong. Instead, unconscious perceptual mechanisms represent a timeline that is then consciously remembered. Because the default mode network, along with the frontoparietal control and salience networks, are critical for simulation and memory, they are also critical for consciousness.

“The same simulation processes are used whether we are consciously remembering the past, experiencing the present or imagining the future. Perceptual mechanisms represent an ongoing, editable, ‘best estimate’ of our past, present, and future. There is no hard boundary between conscious perception and memory at milliseconds to seconds timescales,” explains corresponding author Andrew Budson, MD, professor of neurology at Boston University Chobanian & Avedisian School of Medicine.