MIT professor reveals the origin of consciousness and thought in the brain

Scientists have spent decades trying to understand whether the layered sheet of tissue that covers your brain follows one common pattern for handling information. Each region of the cortex contains six layers stacked in a familiar arrangement, and that repeating design suggested that your mental life might rely on a shared blueprint. If that were true, each layer would produce its own steady pattern of electrical activity, no matter which part of the cortex you examine. Until recently, no one had been able to show that this pattern truly exists across many regions and species.

A new set of studies now points to a rhythm that seems to run through the primate brain. When researchers placed thin probes through the cortical sheet of macaque monkeys, they found a reliable pattern of brain waves.

Fast gamma activity, which reflects local processing and information flow, was strongest in the upper layers. Slower alpha and beta activity, which helps regulate networks and set goals, dominated deeper layers. The team called this arrangement the spectrolaminar motif. Its consistency surprised them because earlier work often reported scattered and conflicting findings.

The scientists gathered data from 14 regions that handle many tasks, including visual processing, movement, planning and higher thinking. Their thin electrodes measured the ebb and flow of electrical activity across all six layers. They repeated this across five macaques and hundreds of probe insertions. No matter where they looked, the same trend appeared. Gamma waves grew stronger as the probes moved toward the upper layers, while alpha and beta power climbed toward the deep layers.

To confirm the results, the team examined brain tissue after creating tiny lesions at known probe positions. These markers helped them align electrical activity with actual layers. They found that gamma power peaked in layer 3. Alpha and beta waves peaked in layer 6. The crossover point, where both rhythms reached similar strength, sat near layer 4. Across probes, this boundary landed within only a few dozen micrometers of the histological center of layer 4, a remarkably tight match for living recordings.

This strong link between anatomy and rhythm suggested something deeper. It meant the cortex might follow a shared rulebook for how it organizes electrical patterns that support perception, memory and decision making.

The reliable gradient of waves inspired a new tool called FLIP, which identifies cortical layers using only frequency information. Instead of relying on anatomical landmarks or stimulus-based current source density maps, FLIP scans for the opposing gradients of alpha-beta and gamma power. When both slopes are strong and run in opposite directions, it marks the position of the superficial and deep layers and flags the crossover near layer 4.

The researchers also built a more flexible version called vFLIP. By testing many combinations of frequency bands, vFLIP increased the rate of detection of the spectrolaminar motif across recordings. Both algorithms performed better than classic methods that depend on how the cortex responds to sensory input. Those older approaches often fail outside visual areas or when probes enter the cortex at oblique angles. In contrast, the spectrolaminar motif appeared even when probes were not perfectly aligned with the layers.

The pattern also emerged quickly. With only a few seconds of data, the gradient appeared. Within a minute of recording, probe placement could be estimated with notable precision. That speed could allow researchers, and one day clinicians, to adjust probe depth almost in real time.

The team then asked whether this motif holds beyond macaques. In marmosets, a smaller primate, the pattern was almost universal. Human data, taken from clinical recordings in patients undergoing monitoring for epilepsy or movement disorders, showed the same general gradient in most cases.

Mice, however, offered a different picture. Their gradients were less consistent and often involved wider or shifted frequency ranges. Similarity analyses across species showed that macaques, marmosets and humans shared more features with each other than with rodents. That suggests the spectrolaminar motif may reflect the special organization of the primate cortex, which supports rich communication between many regions during thought.

While the gradient offers a structural map of cortical activity, it also connects with a larger body of work on how brain waves shape cognition. Earl K. Miller, a neuroscientist at MIT, has studied brain rhythms for more than 30 years. He argues that waves help the cortex organize itself by guiding how information moves. In his view, the brain carries out analog computations through traveling waves that collide, combine and shift across large expanses of cortex.

Miller’s research shows that slower beta waves carry top-down rules and goals, while faster gamma waves carry sensory details and moment-by-moment information. During tasks that rely on working memory or predictions, beta rhythms constrain gamma rhythms to enforce your intentions. When you need to pull stored information into awareness, beta power relaxes to let gamma rise.

These wave patterns do more than synchronize local circuits. They travel across the cortex and may offer a fast way to shape networks without waiting for synapses to rewire. His lab has shown that waves can set the timing of computations, carry information across long distances and even help link distant brain areas into organized, flexible networks that support conscious awareness.

Studies with anesthesiologist Emery N. Brown show how anesthesia disrupts these rhythms. When consciousness fades, the balance between beta and gamma collapses. Waves no longer propagate normally across regions. Their travels stall or fall out of phase with each other. These shifts suggest that consciousness relies on the brain’s ability to maintain these coordinated rhythms.

The discovery of the spectrolaminar motif gives scientists a new way to map brain layers quickly and reliably. This could improve research on attention, memory and perception by offering a shared reference point across labs and species.

FLIP and vFLIP may also one day guide placement of clinical electrodes used in epilepsy monitoring, deep brain stimulation and brain-computer interfaces. Because many disorders involve abnormal beta or gamma rhythms, distorted gradients could provide early warnings or markers for conditions such as Parkinson’s disease, schizophrenia or Alzheimer’s disease.

Understanding how these rhythms shape thought may help researchers build treatments that restore healthy patterns of communication across the cortex.

Research findings are available online in the journal Nature Neuroscience.

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