Amazing stuff! However, it took almost 3 years for this research from preprint to be published as a journal article!
Ethical questions: The study apparently involved 17 patients with epilepsy, but that was not mentioned in the abstract.
"... Researchers ... recently carried out a study aimed at better understanding how the brain prepares for unexpected visual experiences. Their paper, published in Nature Neuroscience, suggests that fast, large-amplitude, brief bursts of oscillatory activity in the hippocampus (i.e., hippocampal ripples) influence how the visual cortex, the part of the brain responsible for processing visual information, responds to surprising stimuli after they appear. ...
This experiment involved 17 patients with epilepsy who had electrodes implanted in their brains as part of their treatment. ...
When participants were less certain about what image would next appear on screen, the team observed a greater frequency of specific patterns of activity in the hippocampus, called hippocampal ripples. Interestingly, these ripples of activity occurred more often and lasted longer before an unexpected stimulus appeared than before a familiar one. ..."
From the abstract:
"To encode information efficiently, our perceptual system should detect when situations are unpredictable (that is, informative) and modulate brain dynamics to prepare for encoding. Under uncertainty, there is an increased need to generate predictions about upcoming information, a process that has been proposed to require coordinated activity between the hippocampus and neocortex.
Here we show, with direct recordings from the human hippocampus and visual cortex, that after exposure to unpredictable visual stimulus streams, hippocampal ripple activity increases in frequency and duration before stimulus presentation.
Prestimulus hippocampal ripples suppress changes in visual cortex gamma activity associated with uncertainty and modulate poststimulus prediction error gamma responses in higher-level visual cortex to surprising stimuli.
We reveal a function of hippocampal ripples in facilitating the propagation of visual stimuli based on the expected information gain.
These results, therefore, link hippocampal ripples with predictive coding accounts of neuronal message passing and precision-weighted prediction errors, revealing a mechanism relevant for perceptual synthesis and subsequent memory encoding."
Fig. 2: The frequency and duration of hippocampal ripples increase with uncertainty or expected information gain.
Fig. 5: Surprise-driven responses.
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