Brain is never at rest, even during quiet states

Rice neuroengineer Valentin Dragoi looks at how fluctuations in brain activity influence human visual perception.

Valentin Dragoi standing in front of whiteboard

Brain activity fluctuates when a person is alert even in the absence of changes in behavior or sensory stimulation.

In recent decades, researchers have assumed that perceptual tasks are more accurate when brain activity is desynchronized, a state during which a person is more alert or attentive. This suggests that optimal task-performance may occur in this state.

“Our research suggests that, on the contrary, cortical state can both facilitate and suppress perceptual performance in a task-dependent manner,” said Valentin Dragoi, professor of electrical and computer engineering and core faculty member of the Neuroengineering Initiative at Rice, and the Rosemary and Daniel J. Harrison III Presidential Distinguished Chair in Neuroprosthetics at Houston Methodist Research Institute.

Dragoi and his collaborators performed electrical recordings from surface-implanted electrodes in the temporal lobes of subjects while they completed two different perceptual tasks.

The tasks used were detection (identifying a barely perceptible stimulus) and discrimination (comparing the orientation of lines).

Their findings, “Endogenous fluctuations in cortical state selectively enhance different modes of sensory processing in human temporal lobe,” have been published in the open-access journal Nature Communications.

“The findings are important for understanding how fluctuations in brain activity influence human visual perception,” Dragoi said. “That is, the brain is never at rest, and even during quiet states there are spontaneous fluctuations in neural population responses that influence how we perceive the world at any given moment.”

The work suggests potential applications in neural stimulation techniques and prosthetic devices that could now take into account such spontaneous fluctuations in brain activity. When external brain stimulation is applied to improve detectability, Dragoi noted, electrical pulses should be applied when the brain is in a more synchronized state. Conversely, if external brain stimulation is applied to improve discriminability, he suggests that electrical pulses should be applied when the brain is in the desynchronized state.

“We found,” Dragoi said, “that when local brain activity is in a synchronized state, network and perceptual performance are enhanced in a detection task and impaired in a discrimination task, but these effects are reversed when neural population activity is desynchronized.”

In other words, the brain adapts to take advantage of internal fluctuations in the temporal cortex to enhance various modes of sensory processing during perception. The relationship between neural synchronization and perceptual performance is task-dependent. Synchronization sometimes improves and sometimes impairs performance.

Dragoi’s coauthors are Dr. Nitin Tandon, professor of neurosurgery at UTHealth Medical School in Houston and Arun Parajuli, neuro data scientist at the UT Health Science Center at Houston.