# The role of dynamical criticality in human perception

> **NIH NIH R01** · UNIVERSITY OF PENNSYLVANIA · 2021 · $542,927

## Abstract

PROJECT SUMMARY
Brain activity never ceases. When we are asleep, inattentive, or even under general anesthesia, networks of
interconnected neurons in the human brain continue to spontaneously generate complex activity patterns.
Sensory stimuli perturb this ongoing spontaneous neuronal activity. In order to be consciously detected, the
effect of this perturbation needs to be large enough so as to engage thousands of neurons and persist for at
least several hundred milliseconds. When we are awake and attentive, the smallest stimuli are sufficient to
elicit a large perturbation. Under general anesthesia, however, even the most noxious stimuli do not reach the
threshold for conscious perception. Here we address a fundamental question: why are sensory stimuli able to
perturb neuronal activity in some states but not in others? We hypothesize that the ability of the sensory stimuli
to perturb neuronal activity is related to the property of dynamical systems termed stability. If neuronal
dynamics were unstable, the effect of any perturbation would grow over time without bounds and engage ever
increasing number of neurons. Conversely, if the dynamics were too stable, then all perturbations will quickly
dampen down and fail to reach threshold of perception. Thus, we hypothesize that conscious perception is
most likely to occur when the neuronal dynamics are poised precisely between the stable and unstable
regimes. We refer to this point as critical. To test the criticality hypothesis, we developed novel mathematical
techniques and applied them to neurophysiological recordings in humans and in nonhuman primates. These
preliminary findings strongly support the hypothesis. In the proposed project, we will rigorously test the
criticality hypothesis using electrocorticography (ECoG) in human subjects implanted with electrodes for
epilepsy localization. We will determine how the stability of spontaneous activity varies as a function of sleep
and wake, attentiveness and drowsiness, as well as sedation and general anesthesia. We will validate the
criticality hypothesis and our ability to estimate stability of neuronal activity by predicting responses to electrical
brain stimulation. Using an auditory masked speech detection task, we will also determine whether stability of
neuronal dynamics can be used to predict whether a natural stimulus presented at perceptual threshold will be
consciously detected. While many other measures of neuronal activity have been previously associated with
changes in arousal and perception, at present, it is not possible to apply the existing measures to
unequivocally distinguish between activity in the conscious and unconscious brain. Hence, validating this
criticality hypothesis would be a major advance. In addition to addressing a fundamental issue in neuroscience,
finding an objective and quantifiable measure of sensory responsiveness has profound clinical significance in
neurology and in anesthesiology where diagnoses of covert aw...

## Key facts

- **NIH application ID:** 10188663
- **Project number:** 5R01NS113366-02
- **Recipient organization:** UNIVERSITY OF PENNSYLVANIA
- **Principal Investigator:** TIMOTHY H LUCAS
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $542,927
- **Award type:** 5
- **Project period:** 2020-06-15 → 2025-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10188663

## Citation

> US National Institutes of Health, RePORTER application 10188663, The role of dynamical criticality in human perception (5R01NS113366-02). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10188663. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*