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In daily life, time is continuously changing, and the space we are in is also continuously changing with our activities
.
The things we experience every day can correspond to the space-time dimension, that is, the time and place where things happen
.
For example, what happened somewhere on the way from home to work this morning
.
So, how does the brain keep track of the space we are in to form a continuous memory of the events we experience every day? To answer this question, we need to understand one of the core brain areas related to spatial navigation and memory—the hippocampus
.
In 2014, the Nobel Prize in Physiology or Medicine was awarded to John O'Keefe, May-Britt Moser and Edvard I.
Moser for their discovery of spatial location characteristics in rat hippocampus and entorhinal cortex, respectively.
There are select specific "location cells" and "grid cells"
.
The activities of these neurons have a very precise and regular selectivity to the animal's location, forming a code similar to a map in the environment, that is, a "cognitive map"
.
Whether this finding in rats is conservative in primates is still unknown
.
Most of the research on primates is carried out under the head-fixed behavior paradigm, mainly in the virtual environment to study the spatial representation characteristics of the hippocampus
.
However, whether the spatial representation based on virtual reality is consistent with that in the real environment remains controversial
.
On October 12, 2021, New York University Dora E.
Angelaki and Mao Dun (co-correspondence and first author, now a researcher at the Center for Excellence in Brain Science and Intelligent Technology of the Chinese Academy of Sciences) jointly published an article Spatial modulation of hippocampal activity on Neuron in freely moving macaques, showing the characteristics of spatial information representation of the neural activity in the hippocampus of freely moving macaques
.
In order to study the representational characteristics of primate hippocampus for real environmental spatial information, the author developed a new experimental paradigm
.
Researchers trained rhesus monkeys to forage freely in an open open field, and combined precise motion capture, wireless eye movement recording and radio physiological technology to study the neurons and fields in the hippocampus of rhesus monkeys (including hippocampus, entorhinol, and palpebra) The correlation between potential activity and various spatial information
.
The author’s experimental research shows that, compared with rodents, the field potential activity of rhesus monkeys does not show continuous theta oscillations during exercise
.
The occasional lower frequency θ oscillations (less than 5 Hz) are related to the onset of movement and are in sharp contrast to β oscillations
.
At the same time, the low-frequency θ and β oscillation frequencies are closely related to movement speed and acceleration
.
At the neuron level, similar to the rat, the neuronal firing in the hippocampus of the macaque is very sparse, and the overall firing frequency presents a log-normal distribution
.
The firing of neurons in the lower parenchyma presents a relatively low sparsity
.
Traditional analysis methods have shown that neuronal activity in the hippocampus of rhesus monkeys presents selective specific firing activities (ie tuning characteristics) for a variety of spatial information, including horizontal position, horizontal head orientation, translational speed, etc.
, and some neuronal activities can be simultaneously Encode a variety of spatial information
.
However, the grid code is very weak, which is in sharp contrast with the results of rats and mice.
.
However, traditional analysis methods have some problems.
One is that they ignore the possible interdependence between various spatial variables, resulting in the found tuning of a variable may be a false positive: if two variables are related to each other, Then the tuning characteristics may reflect a stronger tuning to another variable that is not considered, rather than tuning to a single variable at the moment
.
Therefore, the researchers adopted a robust model-based analysis method, while considering the common influence of the following multiple variables on neuronal activity
.
These variables include horizontal position, facing position (position in the environment where the head is pointing, 3D variables), distance and angle relative to the environmental boundary, head tilt angle relative to the gravity axis, head rotation speed, head height, translational speed, And the horizontal head orientation angle
.
Researchers have observed that neurons in the hippocampus have a certain degree of tuning to all variables
.
In all the sub-regions (hippocampus, entorhinal, underpinning), neurons have the strongest coding for facing position
.
Similar to rats and mice, the pedicle neurons have strong codes for the horizontal head orientation
.
The horizontal position code is relatively weak, which is in contrast to the results of rats and mice
.
In addition, the coding of various types of spatial information by macaques has certain topological characteristics in the long axis of the hippocampus (from front end to back end), and the mixed coding has certain enhancements from front end to back end
.
In general, spatial representations show diversity, and the range of neuron cluster coding covers a wide space
.
The researchers then compared the neuron's tuning characteristics of the macaque's facing position and the position of the eye
.
Synchronous analysis of head-related variables and eye movement information revealed that most neuronal activity reflects the encoding of facing position rather than the position of the eye.
This result contrasts with the findings of other research groups
.
This may be because, unlike this work, in the work of other research groups, the heads of macaques cannot freely translate or rotate in three-dimensional space
.
Similarly, the encoding of the horizontal orientation angle mainly reflects the characterization of the direction seen by the head rather than the eyes
.
Researchers also found a strong correlation between neural activity in the hippocampus and eye movement
.
Among them, the eye saccade has a strong regulation on the hippocampal neurons and field potentials: neuronal activity corresponds to the time when the saccade occurs, forming a sequential firing; the field potential θ band energy has a strong positive correlation with the eye saccade amplitude
.
The above-mentioned research shows that the neural activity of the hippocampus of the free-moving macaque represents the characteristics of spatial information
.
In the discussion part of the paper, the author discussed in detail the particularity of the spatial representation of the hippocampus of this primate species, comparison with other species, and some limitations of the study
.
This work is just the beginning, and the author hopes that this work can provide a certain reference for follow-up related research
.
There are more interesting questions to be studied in the future
.
The future work of the author’s laboratory will take rhesus monkeys as experimental objects, and expand from the following three aspects: 1) the influence of different environments and tasks on the spatial representation of multiple brain regions; 2) the comparison of spatial representations in virtual reality and real environments; 3) reality The interrelationship between space and abstract space representation
.
Mao Dun's research group is currently recruiting postdoctoral fellows and research assistants.
Interested students are welcome to contact
.
For details, please see the homepage of the laboratory: http://
.
Original link: https://doi.
org/10.
1016/j.
neuron.
2021.
09.
032 Plate maker: Notes for reprinting on the 11th [Non-original article] The copyright of this article belongs to the author of the article.
Personal forwarding and sharing are welcome.
Reprinting without permission is prohibited.
The author has all legal rights, and offenders must be investigated
.
.
The things we experience every day can correspond to the space-time dimension, that is, the time and place where things happen
.
For example, what happened somewhere on the way from home to work this morning
.
So, how does the brain keep track of the space we are in to form a continuous memory of the events we experience every day? To answer this question, we need to understand one of the core brain areas related to spatial navigation and memory—the hippocampus
.
In 2014, the Nobel Prize in Physiology or Medicine was awarded to John O'Keefe, May-Britt Moser and Edvard I.
Moser for their discovery of spatial location characteristics in rat hippocampus and entorhinal cortex, respectively.
There are select specific "location cells" and "grid cells"
.
The activities of these neurons have a very precise and regular selectivity to the animal's location, forming a code similar to a map in the environment, that is, a "cognitive map"
.
Whether this finding in rats is conservative in primates is still unknown
.
Most of the research on primates is carried out under the head-fixed behavior paradigm, mainly in the virtual environment to study the spatial representation characteristics of the hippocampus
.
However, whether the spatial representation based on virtual reality is consistent with that in the real environment remains controversial
.
On October 12, 2021, New York University Dora E.
Angelaki and Mao Dun (co-correspondence and first author, now a researcher at the Center for Excellence in Brain Science and Intelligent Technology of the Chinese Academy of Sciences) jointly published an article Spatial modulation of hippocampal activity on Neuron in freely moving macaques, showing the characteristics of spatial information representation of the neural activity in the hippocampus of freely moving macaques
.
In order to study the representational characteristics of primate hippocampus for real environmental spatial information, the author developed a new experimental paradigm
.
Researchers trained rhesus monkeys to forage freely in an open open field, and combined precise motion capture, wireless eye movement recording and radio physiological technology to study the neurons and fields in the hippocampus of rhesus monkeys (including hippocampus, entorhinol, and palpebra) The correlation between potential activity and various spatial information
.
The author’s experimental research shows that, compared with rodents, the field potential activity of rhesus monkeys does not show continuous theta oscillations during exercise
.
The occasional lower frequency θ oscillations (less than 5 Hz) are related to the onset of movement and are in sharp contrast to β oscillations
.
At the same time, the low-frequency θ and β oscillation frequencies are closely related to movement speed and acceleration
.
At the neuron level, similar to the rat, the neuronal firing in the hippocampus of the macaque is very sparse, and the overall firing frequency presents a log-normal distribution
.
The firing of neurons in the lower parenchyma presents a relatively low sparsity
.
Traditional analysis methods have shown that neuronal activity in the hippocampus of rhesus monkeys presents selective specific firing activities (ie tuning characteristics) for a variety of spatial information, including horizontal position, horizontal head orientation, translational speed, etc.
, and some neuronal activities can be simultaneously Encode a variety of spatial information
.
However, the grid code is very weak, which is in sharp contrast with the results of rats and mice.
.
However, traditional analysis methods have some problems.
One is that they ignore the possible interdependence between various spatial variables, resulting in the found tuning of a variable may be a false positive: if two variables are related to each other, Then the tuning characteristics may reflect a stronger tuning to another variable that is not considered, rather than tuning to a single variable at the moment
.
Therefore, the researchers adopted a robust model-based analysis method, while considering the common influence of the following multiple variables on neuronal activity
.
These variables include horizontal position, facing position (position in the environment where the head is pointing, 3D variables), distance and angle relative to the environmental boundary, head tilt angle relative to the gravity axis, head rotation speed, head height, translational speed, And the horizontal head orientation angle
.
Researchers have observed that neurons in the hippocampus have a certain degree of tuning to all variables
.
In all the sub-regions (hippocampus, entorhinal, underpinning), neurons have the strongest coding for facing position
.
Similar to rats and mice, the pedicle neurons have strong codes for the horizontal head orientation
.
The horizontal position code is relatively weak, which is in contrast to the results of rats and mice
.
In addition, the coding of various types of spatial information by macaques has certain topological characteristics in the long axis of the hippocampus (from front end to back end), and the mixed coding has certain enhancements from front end to back end
.
In general, spatial representations show diversity, and the range of neuron cluster coding covers a wide space
.
The researchers then compared the neuron's tuning characteristics of the macaque's facing position and the position of the eye
.
Synchronous analysis of head-related variables and eye movement information revealed that most neuronal activity reflects the encoding of facing position rather than the position of the eye.
This result contrasts with the findings of other research groups
.
This may be because, unlike this work, in the work of other research groups, the heads of macaques cannot freely translate or rotate in three-dimensional space
.
Similarly, the encoding of the horizontal orientation angle mainly reflects the characterization of the direction seen by the head rather than the eyes
.
Researchers also found a strong correlation between neural activity in the hippocampus and eye movement
.
Among them, the eye saccade has a strong regulation on the hippocampal neurons and field potentials: neuronal activity corresponds to the time when the saccade occurs, forming a sequential firing; the field potential θ band energy has a strong positive correlation with the eye saccade amplitude
.
The above-mentioned research shows that the neural activity of the hippocampus of the free-moving macaque represents the characteristics of spatial information
.
In the discussion part of the paper, the author discussed in detail the particularity of the spatial representation of the hippocampus of this primate species, comparison with other species, and some limitations of the study
.
This work is just the beginning, and the author hopes that this work can provide a certain reference for follow-up related research
.
There are more interesting questions to be studied in the future
.
The future work of the author’s laboratory will take rhesus monkeys as experimental objects, and expand from the following three aspects: 1) the influence of different environments and tasks on the spatial representation of multiple brain regions; 2) the comparison of spatial representations in virtual reality and real environments; 3) reality The interrelationship between space and abstract space representation
.
Mao Dun's research group is currently recruiting postdoctoral fellows and research assistants.
Interested students are welcome to contact
.
For details, please see the homepage of the laboratory: http://
.
Original link: https://doi.
org/10.
1016/j.
neuron.
2021.
09.
032 Plate maker: Notes for reprinting on the 11th [Non-original article] The copyright of this article belongs to the author of the article.
Personal forwarding and sharing are welcome.
Reprinting without permission is prohibited.
The author has all legal rights, and offenders must be investigated
.
