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The patient does not feel pain, but the cells continue to diligently sort words on nouns and verbs.
Under general anesthesia, a person does not hear the world as in the usual state. Consciousness is disconnected, conversations do not turn into memories, and after the operation, the patient cannot retell sounds from the operating room. But a new study shows that the brain does not completely close with anesthesia. He continues to catch sounds, distinguishes words and even guess what will sound next.
Scientists have studied the work of the hippocampus - a deep region of the brain that is involved in memory, training and orientation in space. Usually the hippocampus is associated with memorization of events and an internal map of the surrounding world. The new work adds an important detail: even under general anesthesia, this structure continues to disassemble speech and sound sequences, although a person does not realize anything and then does not remember anything.
Researchers at Baylor College of Medicine worked with seven patients who had anterior temporal lobectomy. With such an operation, surgeons remove part of the tissue of the temporal lobe to help people with severe epilepsy. During the intervention, patients were under general anesthesia, and doctors temporarily introduced the thin neuropixels into the hippocampus.
Neuropixels are neurosoldons to record the activity of individual brain cells. They allow you to simultaneously read the electrical signals of hundreds of neurons. For neuroscience, this possibility is rare: usually the human brain is studied indirectly, through scanning or superficial electrodes. In this experiment, scientists have seen individual cells respond to sounds right during surgery.
After installing the sensors in the operating room, the audio was included. One patients were played by recurring tones, among which sometimes there was a sound of a different frequency. Others listened to the release of the podcast The Moth Radio Hour with a regular human speech.
The first experiment checked whether the brain noticed under anesthesia a simple violation of the pattern. If the same tones go one after the other, and then suddenly a different sound appears, the waking brain quickly emits a deviation. In patients under anesthesia, the hippocampus also began to distinguish between ordinary and rare signals, but not immediately.
In the first minutes, the activity of neurons could not yet be understood whether the brain caught the difference. Then the answers of individual cells began to change. Neurons reacted more and more to a rare sound, and in about 10 minutes the hippocampus learned to better highlight the violation in sequence. It turns out that the brain under anesthesia did not just miss the noise through the auditory system, but continued to study.
The second part of the study was about speech. While the podcast sounded in the operating room, the neurons of the hippocampus reacted to the features of the words. Some cells often responded to nouns, others to verbs or other parts of speech. The activity of neurons also reflected semantic connections. For example, the words “cat” and “dog” the brain processed as close in meaning, and the “pen” fell into a more distant semantic area.
The most important detail is related to the prediction of speech. The hippocamp under anesthesia not only recognized the already spoken words, but also tried to predict the following. Similarly, the language processes the waking brain: a person is constantly waiting for the continuation of the phrase and during the conversation clarifies expectations. The new work shows that part of this mechanism is preserved even without conscious perception.
After the operation, patients did not remember either tones or stories from the podcast. There are no conscious memories left.
The results coincide with earlier observations: some patients after anesthesia a little more often learned the words that sounded during the operation, although they did not remember the audition itself. A new study shows a possible explanation. The brain can process sound at the level of neurons, but consciousness does not access this information.
The authors emphasize an important limitation. All seven participants received intravenous anesthesia, and the main drug was propofol. It is not yet possible to say whether the brain will also process speech in other schemes of anesthesia. It is also unclear how similar processes are going in a dream, coma or other states unconscious.
The practical question has already arisen. If the patient’s brain under anesthesia continues to analyze the sounds and speech, doctors should be more attentive to conversations in the operating room. The study does not prove that such conversations turn into memories or harm patients. But the work shows that anesthesia does not disable consciousness as deafly as it seemed for a long time, and the sound environment during surgery may not be an empty background for the brain.
Under general anesthesia, a person does not hear the world as in the usual state. Consciousness is disconnected, conversations do not turn into memories, and after the operation, the patient cannot retell sounds from the operating room. But a new study shows that the brain does not completely close with anesthesia. He continues to catch sounds, distinguishes words and even guess what will sound next.
Scientists have studied the work of the hippocampus - a deep region of the brain that is involved in memory, training and orientation in space. Usually the hippocampus is associated with memorization of events and an internal map of the surrounding world. The new work adds an important detail: even under general anesthesia, this structure continues to disassemble speech and sound sequences, although a person does not realize anything and then does not remember anything.
Researchers at Baylor College of Medicine worked with seven patients who had anterior temporal lobectomy. With such an operation, surgeons remove part of the tissue of the temporal lobe to help people with severe epilepsy. During the intervention, patients were under general anesthesia, and doctors temporarily introduced the thin neuropixels into the hippocampus.
Neuropixels are neurosoldons to record the activity of individual brain cells. They allow you to simultaneously read the electrical signals of hundreds of neurons. For neuroscience, this possibility is rare: usually the human brain is studied indirectly, through scanning or superficial electrodes. In this experiment, scientists have seen individual cells respond to sounds right during surgery.
After installing the sensors in the operating room, the audio was included. One patients were played by recurring tones, among which sometimes there was a sound of a different frequency. Others listened to the release of the podcast The Moth Radio Hour with a regular human speech.
The first experiment checked whether the brain noticed under anesthesia a simple violation of the pattern. If the same tones go one after the other, and then suddenly a different sound appears, the waking brain quickly emits a deviation. In patients under anesthesia, the hippocampus also began to distinguish between ordinary and rare signals, but not immediately.
In the first minutes, the activity of neurons could not yet be understood whether the brain caught the difference. Then the answers of individual cells began to change. Neurons reacted more and more to a rare sound, and in about 10 minutes the hippocampus learned to better highlight the violation in sequence. It turns out that the brain under anesthesia did not just miss the noise through the auditory system, but continued to study.
The second part of the study was about speech. While the podcast sounded in the operating room, the neurons of the hippocampus reacted to the features of the words. Some cells often responded to nouns, others to verbs or other parts of speech. The activity of neurons also reflected semantic connections. For example, the words “cat” and “dog” the brain processed as close in meaning, and the “pen” fell into a more distant semantic area.
The most important detail is related to the prediction of speech. The hippocamp under anesthesia not only recognized the already spoken words, but also tried to predict the following. Similarly, the language processes the waking brain: a person is constantly waiting for the continuation of the phrase and during the conversation clarifies expectations. The new work shows that part of this mechanism is preserved even without conscious perception.
After the operation, patients did not remember either tones or stories from the podcast. There are no conscious memories left.
The results coincide with earlier observations: some patients after anesthesia a little more often learned the words that sounded during the operation, although they did not remember the audition itself. A new study shows a possible explanation. The brain can process sound at the level of neurons, but consciousness does not access this information.
The authors emphasize an important limitation. All seven participants received intravenous anesthesia, and the main drug was propofol. It is not yet possible to say whether the brain will also process speech in other schemes of anesthesia. It is also unclear how similar processes are going in a dream, coma or other states unconscious.
The practical question has already arisen. If the patient’s brain under anesthesia continues to analyze the sounds and speech, doctors should be more attentive to conversations in the operating room. The study does not prove that such conversations turn into memories or harm patients. But the work shows that anesthesia does not disable consciousness as deafly as it seemed for a long time, and the sound environment during surgery may not be an empty background for the brain.
