Monkey Brains Alternated Between Seen and Hidden Faces 15 Times a Second

Neural recordings from two rhesus macaques suggest that the brain may represent a consciously seen face and a suppressed face in rapidly alternating time windows, rather than holding only the visible image continuously. The team reports switching about 15 times per second in a bioRxiv preprint posted on October 16, 2026.

Key Number: The two neural representations alternated roughly 15 times per second while the visual input and presumed percept remained stable.

Two faces reached the eyes, but only one was expected to be seen

The researchers used binocular flash suppression. First, one face was shown to one eye. A second face then appeared to the other eye while the first image remained physically present. Human observers usually report seeing the newer image while the earlier one disappears from awareness.

Fourteen human participants confirmed that this setup generally produced the expected percept. The macaques could not describe what they saw, so the researchers assumed that the newer face dominated their awareness in the same way. That assumption is central to interpreting the neural states as conscious and suppressed.

The same neurons appeared to time-share two representations

Neuropixels probes recorded activity in face-selective regions of the inferotemporal cortex and in prefrontal cortex. The team first measured the pattern associated with each face when shown alone. During suppression trials, it then classified short periods of activity according to which face pattern they resembled.

The population signal did not settle permanently on the presumed visible face. It alternated between brief periods dominated by that face and periods dominated by the suppressed one. During each type of period, the researchers could reconstruct features of the corresponding image from the recorded activity. Feature tuning was stronger during the periods associated with conscious perception.

This is not a system for reading arbitrary thoughts. A related NewTqnia report on decoding typed sentences from brain signals explains why reconstruction in a constrained experiment should not be confused with unrestricted access to a person’s mind.

Why timing changes the consciousness question

Many experiments ask which brain regions respond differently when a stimulus is consciously perceived. The new result proposes an additional dimension: the same neural population may carry both visible and suppressed content at different moments. Averaging activity over longer intervals could blur those alternating states into one mixed signal.

That interpretation does not explain why one representation reaches awareness while the other does not. It instead suggests that conscious access may depend partly on how neural states are selected over time. Outside researchers quoted by Nature described the methods as rigorous and the result as interesting, while cautioning that parts of the finding were less surprising than the online attention implied.

What should happen next

The claim will become stronger if other laboratories reproduce the alternation with larger samples, different visual categories and methods that provide an independent behavioral indication of the animal’s percept. Researchers must also test whether the timing pattern survives alternative ways of defining the short neural states, and whether it occurs beyond the face-processing network.

Image: Illustration of the binocular-suppression experiment. Credit: Hesse et al., bioRxiv (2026), CC BY 4.0.