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Written by Yijie Zhao, edited by Yixuan Ku, Sizhen Wang Working memory, as an advanced cognitive function, has long been considered to be dominated by the activities of the frontal top network [1, 2]
.
In recent years, more and more studies have found that the sensory cortex is also involved in the representation of working memory, and may regulate different aspects of working memory together with the frontoparietal brain area.
This theory is called the sensory recruitment hypothesis.
【3-5】
.
However, this hypothesis is still controversial.
Whether the sensory cortex is necessary in the representation of working memory and its key role in working memory remains to be revealed
.
On September 2, 2021, the team of Professor Yixuan Ku from the Department of Psychology of Sun Yat-sen University published a research paper entitled "Sensory Recruitment Revisited: Ipsilateral V1 Involved in Visual Working Memory" on Cerebral Cortex, which discussed in depth the work of the sensory cortex The role of memory
.
Zhao Yijie, a postdoctoral fellow of the Institute of Brain-inspired Research of Fudan University, is the first author of the article, and Professor Ku Yixuan from the Department of Psychology, Sun Yat-sen University is the corresponding author of the article
.
The study found that both the ipsilateral and contralateral primary visual cortex of the memory target are involved in the representation of memory content through high-resolution functional magnetic resonance imaging combined with a voxel-based reverse neural coding model.
Importantly, the contralateral cortex The characterization only appeared in the early stage of the maintenance phase, while the characterization of the ipsilateral cortex continued to the late stage of the maintenance phase
.
Working memory refers to the ability to temporarily store sensory input information in the memory system to serve goal-oriented tasks
.
This is a key core cognitive function, which is closely related to a variety of cognitive processes such as language, decision-making, and reasoning
.
Early studies have found that there is a continuous firing of prefrontal neurons in the maintenance phase of working memory [1], and subsequently, similar neuronal firings in the primary sensory cortex have also been found [2]
.
However, there are still controversies about the involvement and role of the sensory cortex in working memory
.
Studies have found that in visual working memory, the continuous representation of the primary visual cortex is easily disturbed, and this interference does not affect behavioral performance.
Therefore, researchers believe that sensory cortex activity is not a key element in working memory [6 】
.
The research supporting the sensory participation hypothesis found that the primary visual cortex activity in the maintenance stage of visual working memory can distinguish memory content, and at the same time, the result of this neural decoding is related to behavioral performance [3-5]
.
A previous study by Professor Ku Yixuan’s team on tactile working memory found that applying a single pulse of transcranial magnetic stimulation to the primary somatosensory cortex (SI) can affect the performance of working memory, and this effect does not only appear in In the case of stimulating the contralateral brain area of the limb, the stimulation of the ipsilateral primary somatosensory cortex in the delayed late stage will also affect working memory [7]
.
In this study, the researcher aims to further explore how the ipsilateral and contralateral visual cortex respectively represent the content of working memory in the process of visual working memory tasks
.
The study uses functional magnetic resonance to measure brain activity changes with tasks.
First, population receptive field (pRF) positioning is used (receptive field is the basic structure and functional unit of visual system information processing, which refers to a neuron in the visual field.
In the reaction area), the different visual sub-areas of each participant was finely divided (Figure 1a)
.
In addition, each participant will complete another stimulus mapping task, combining the pRF results to determine the voxel activated by the stimulus at each spatial position in the field of view in the experiment, and in each visual These activated voxels are used as regions of interest (ROI) for memory characterization analysis in the subregions
.
The main experiment of this research uses the visual delayed recall task (Figure 1b).
Two rasters (sample array) are first presented on the computer screen.
In the maintenance phase after the raster disappears, a clue appears in the center of the screen to instruct the participant Remember which grating stimulus, then, during the test (probe array), the subject needs to use the mouse to adjust the angle of the grating to match the original angle of the grating at that position in their memory
.
The working memory experiment uses a multivariate data analysis method (Figure 1c): the inverted encoding model (IEM).
The basic assumption is that each voxel is composed of different orientation-selective neurons, and the representation of these neurons Encoding contributes to the characterization of this voxel, which is expressed in the form of a weighted average
.
Therefore, the magnetic resonance signal can be used to reconstruct the angle representation in the memory, so as to obtain the characteristic tuning curve of each brain area to the target stimulus, and the central characteristic response (CCR) of the curve is used as an index to evaluate the reconstruction intensity
.
Figure 1 Experimental process and data analysis method (picture source: Ku Yixuan laboratory) The researcher first verified the encoding of memory content in the visual cortex, and the results showed that the use of IEM to decode neural activities can successfully reconstruct the visual cortex.
The representation of the target memory angle (Figure 2), and this representation only exists in the early visual cortex such as V1, V2, and V3
.
Figure 2 Angle reconstruction of visual hierarchy (picture source: Ku Yixuan laboratory) Subsequently, the researcher classifies the receptive field corresponding to the visual stimulus.
For each quadrant of the stimulus, based on the principle of retinal topology positioning, it can be divided into: contralateral -Stimulate the ROI and contralateral in the perception field-Feel the ROI in the field and the ipsilateral ROI
.
IEM reconstruction of these three types of brain data respectively found that the ROI in the contralateral receptive field corresponding to the stimulus successfully represented the content of working memory, while the ROI in the contralateral receptive field did not participate in the characterization, which is a physiologically predictable result; However, it is interesting that the ipsilateral ROI can also represent the content of working memory (Figure 3), which shows that the aforementioned ipsilateral sensory cortex is also involved in the information encoding of working memory
.
Figure 3 Angle reconstruction of different regions of interest (picture source: Ku Yixuan laboratory) So, what are the temporal dynamics of the ipsilateral and contralateral visual cortex during working memory processing? The researchers further investigated the pattern of different ROI reconstruction intensity over time.
The corresponding ROI in the contralateral receptive field of the target stimulus only appeared in the early stage of the retention phase, while the ipsilateral ROI was more persistent.
The results suggest that the ipsilateral and contralateral brain regions may play a time-series characterization role in the maintenance of working memory information (Figure 4)
.
Figure 4 Curve of reconstruction intensity over time (picture source: Ku Yixuan laboratory) Conclusion and discussion, inspiration and prospects of the article It supports the "sensory participation hypothesis" that the primary sensory cortex is indeed involved in the processing of visual working memory
.
The research results further point out that, unlike the contralateral processing of visual sensory information, in visual working memory, the ipsilateral brain area is also involved in the coding of working memory and lasts longer
.
In this process, there may be communication between the ipsilateral and contralateral brain areas, and there may be feedforward and feedback information communication with the frontoparietal cortex, and ultimately accurately characterize basic visual characteristics such as angle
.
The results of this study found the representation of ipsilateral brain regions, but there are still many interesting questions to be answered
.
First of all, classic experiments confirmed that visual sensory information is processed on the contralateral side of the primary visual cortex.
Then how does the processed information from the contralateral brain area be transmitted to the ipsilateral brain area, whether it is transmitted through the corpus callosum or the feedback information from the higher cortex, or Subcortical structure delivery (relay) information requires more detailed experimental design and even animal electrophysiological research to further answer; secondly, the current research results are only for the case of working memory load of 1, and the situation under higher load.
It needs to be further explored, but this involves finer regional division.
When there are more stimuli presented at the same time, the resolution of the receptive field measurement and the accuracy of spatial positioning are higher, and higher fields may be required ( 7T) and observations with higher spatial resolution (mm and sub-mm levels); finally, how other high-level cognitive activities, such as attention, will affect these representations is also an interesting question, which will help to further understand the relationship between attention and working memory
.
Further answers to these questions will advance our understanding of the architecture of the human cerebral cortex; understanding the interaction mechanism of feedforward and feedback pathways will also help advance brain-like artificial neural networks, especially cyclic neural networks RNN Design
.
Original link: https://doi.
org/10.
1093/cercor/bhab300 First author Zhao Yijie (first row left 5), corresponding author Ku Yixuan (second row left 5) (Photo source: Ku Yixuan laboratory) Ku Yixuan, Sun Yat-sen University professor, doctoral supervisor, outstanding young and middle-aged talents of the "Hundred Talents Program", undergraduate and Ph.
D.
at Tsinghua University, postdoctoral at the University of California, San Francisco
.
Presided over a number of national, provincial and ministerial projects, the Shanghai Pujiang Talent Program, the backbone of the National 973 Project, the sub-project leader and project convener of major projects of the National Social Science Fund
.
Mainly engaged in the study of cognitive neural mechanisms of memory and emotion, and published more than 50 papers in internationally renowned SCI/SSCI journals.
Among them, the corresponding author's results were published in authoritative journals in the fields of Brain Stimulation, Cerebral Cortex, Journal of Neuroscience, and served as He is an external reviewer of well-known journals at home and abroad, and the National Natural Science Foundation of China and the United States
.
This research group (Memory and Emotion Lab) integrates memory and emotion research, and recruits distinguished researchers, postdoctoral fellows and research assistants throughout the year, and accepts doctoral and master students.
See the research group homepage
.
Undergraduates and postgraduates of all majors are welcome to study and research in the research group, please email kuyixuan@mail.
sysu.
edu.
cn
.
Selected articles from previous issues [1] JAMA Neurol︱ Attention! Young people are more likely to suffer from "Alzheimer's disease"? [2] Brain | For the first time! PAX6 may be a key factor in the pathogenesis of Alzheimer's disease and a new therapeutic target [3] Sci Adv︱ blockbuster! DNA methylation protein DNMT1 mutation can induce neurodegenerative diseases [4] Cell︱ new discovery! New enlightenment of midbrain-regulated movement phenomenon for the treatment of Parkinson’s disease [5] Cereb Cortex︱MET tyrosine kinase signal transduction timing abnormality is a key mechanism affecting the development and behavior of normal cortical neural circuits in mice [6] Nat Biomed Eng︱ The team of academician Ye Yuru develops a new strategy for whole-brain gene editing-mediated treatment of Alzheimer's disease [7] Luo Liqun Science's heavy review System interpretation ︱ Neural circuit structure-a system that makes the brain "computer" run at high speed [8] Sci Adv ︱Important discovery! The calcium homeostasis regulatory protein Calhm2 regulates the activation of microglia and participates in the process of Alzheimer's disease [9] EMBO J︱ new discovery! AGHGAP11B promotes the expansion of the neocortex into adulthood and improves cognitive ability [10] Cell Death Differ︱ Qi Yitao/Wu Hongmei and others cooperate to reveal the molecular mechanism of SUMO modification regulating neurogenesis in adult mice [11] Cereb Cortex︱A2A receptor antagonist can Reversal of sequence learning impairment induced by abnormal aggregation of α-Syn [1] Fuster JM, Alexander GE.
1971.
Neuron Activity Related to Short-Term Memory.
Science.
173:652–654.
[2] Zhou YD, Fuster JM.
1996.
Mnemonic neuronal activity in somatosensory cortex.
Proc Natl Acad Sci.
93:10533–10537.
[3] Bettencourt KC, Xu Y.
2015.
Decoding the content of visual short-term memory under distraction in occipital and parietal areas.
.
In recent years, more and more studies have found that the sensory cortex is also involved in the representation of working memory, and may regulate different aspects of working memory together with the frontoparietal brain area.
This theory is called the sensory recruitment hypothesis.
【3-5】
.
However, this hypothesis is still controversial.
Whether the sensory cortex is necessary in the representation of working memory and its key role in working memory remains to be revealed
.
On September 2, 2021, the team of Professor Yixuan Ku from the Department of Psychology of Sun Yat-sen University published a research paper entitled "Sensory Recruitment Revisited: Ipsilateral V1 Involved in Visual Working Memory" on Cerebral Cortex, which discussed in depth the work of the sensory cortex The role of memory
.
Zhao Yijie, a postdoctoral fellow of the Institute of Brain-inspired Research of Fudan University, is the first author of the article, and Professor Ku Yixuan from the Department of Psychology, Sun Yat-sen University is the corresponding author of the article
.
The study found that both the ipsilateral and contralateral primary visual cortex of the memory target are involved in the representation of memory content through high-resolution functional magnetic resonance imaging combined with a voxel-based reverse neural coding model.
Importantly, the contralateral cortex The characterization only appeared in the early stage of the maintenance phase, while the characterization of the ipsilateral cortex continued to the late stage of the maintenance phase
.
Working memory refers to the ability to temporarily store sensory input information in the memory system to serve goal-oriented tasks
.
This is a key core cognitive function, which is closely related to a variety of cognitive processes such as language, decision-making, and reasoning
.
Early studies have found that there is a continuous firing of prefrontal neurons in the maintenance phase of working memory [1], and subsequently, similar neuronal firings in the primary sensory cortex have also been found [2]
.
However, there are still controversies about the involvement and role of the sensory cortex in working memory
.
Studies have found that in visual working memory, the continuous representation of the primary visual cortex is easily disturbed, and this interference does not affect behavioral performance.
Therefore, researchers believe that sensory cortex activity is not a key element in working memory [6 】
.
The research supporting the sensory participation hypothesis found that the primary visual cortex activity in the maintenance stage of visual working memory can distinguish memory content, and at the same time, the result of this neural decoding is related to behavioral performance [3-5]
.
A previous study by Professor Ku Yixuan’s team on tactile working memory found that applying a single pulse of transcranial magnetic stimulation to the primary somatosensory cortex (SI) can affect the performance of working memory, and this effect does not only appear in In the case of stimulating the contralateral brain area of the limb, the stimulation of the ipsilateral primary somatosensory cortex in the delayed late stage will also affect working memory [7]
.
In this study, the researcher aims to further explore how the ipsilateral and contralateral visual cortex respectively represent the content of working memory in the process of visual working memory tasks
.
The study uses functional magnetic resonance to measure brain activity changes with tasks.
First, population receptive field (pRF) positioning is used (receptive field is the basic structure and functional unit of visual system information processing, which refers to a neuron in the visual field.
In the reaction area), the different visual sub-areas of each participant was finely divided (Figure 1a)
.
In addition, each participant will complete another stimulus mapping task, combining the pRF results to determine the voxel activated by the stimulus at each spatial position in the field of view in the experiment, and in each visual These activated voxels are used as regions of interest (ROI) for memory characterization analysis in the subregions
.
The main experiment of this research uses the visual delayed recall task (Figure 1b).
Two rasters (sample array) are first presented on the computer screen.
In the maintenance phase after the raster disappears, a clue appears in the center of the screen to instruct the participant Remember which grating stimulus, then, during the test (probe array), the subject needs to use the mouse to adjust the angle of the grating to match the original angle of the grating at that position in their memory
.
The working memory experiment uses a multivariate data analysis method (Figure 1c): the inverted encoding model (IEM).
The basic assumption is that each voxel is composed of different orientation-selective neurons, and the representation of these neurons Encoding contributes to the characterization of this voxel, which is expressed in the form of a weighted average
.
Therefore, the magnetic resonance signal can be used to reconstruct the angle representation in the memory, so as to obtain the characteristic tuning curve of each brain area to the target stimulus, and the central characteristic response (CCR) of the curve is used as an index to evaluate the reconstruction intensity
.
Figure 1 Experimental process and data analysis method (picture source: Ku Yixuan laboratory) The researcher first verified the encoding of memory content in the visual cortex, and the results showed that the use of IEM to decode neural activities can successfully reconstruct the visual cortex.
The representation of the target memory angle (Figure 2), and this representation only exists in the early visual cortex such as V1, V2, and V3
.
Figure 2 Angle reconstruction of visual hierarchy (picture source: Ku Yixuan laboratory) Subsequently, the researcher classifies the receptive field corresponding to the visual stimulus.
For each quadrant of the stimulus, based on the principle of retinal topology positioning, it can be divided into: contralateral -Stimulate the ROI and contralateral in the perception field-Feel the ROI in the field and the ipsilateral ROI
.
IEM reconstruction of these three types of brain data respectively found that the ROI in the contralateral receptive field corresponding to the stimulus successfully represented the content of working memory, while the ROI in the contralateral receptive field did not participate in the characterization, which is a physiologically predictable result; However, it is interesting that the ipsilateral ROI can also represent the content of working memory (Figure 3), which shows that the aforementioned ipsilateral sensory cortex is also involved in the information encoding of working memory
.
Figure 3 Angle reconstruction of different regions of interest (picture source: Ku Yixuan laboratory) So, what are the temporal dynamics of the ipsilateral and contralateral visual cortex during working memory processing? The researchers further investigated the pattern of different ROI reconstruction intensity over time.
The corresponding ROI in the contralateral receptive field of the target stimulus only appeared in the early stage of the retention phase, while the ipsilateral ROI was more persistent.
The results suggest that the ipsilateral and contralateral brain regions may play a time-series characterization role in the maintenance of working memory information (Figure 4)
.
Figure 4 Curve of reconstruction intensity over time (picture source: Ku Yixuan laboratory) Conclusion and discussion, inspiration and prospects of the article It supports the "sensory participation hypothesis" that the primary sensory cortex is indeed involved in the processing of visual working memory
.
The research results further point out that, unlike the contralateral processing of visual sensory information, in visual working memory, the ipsilateral brain area is also involved in the coding of working memory and lasts longer
.
In this process, there may be communication between the ipsilateral and contralateral brain areas, and there may be feedforward and feedback information communication with the frontoparietal cortex, and ultimately accurately characterize basic visual characteristics such as angle
.
The results of this study found the representation of ipsilateral brain regions, but there are still many interesting questions to be answered
.
First of all, classic experiments confirmed that visual sensory information is processed on the contralateral side of the primary visual cortex.
Then how does the processed information from the contralateral brain area be transmitted to the ipsilateral brain area, whether it is transmitted through the corpus callosum or the feedback information from the higher cortex, or Subcortical structure delivery (relay) information requires more detailed experimental design and even animal electrophysiological research to further answer; secondly, the current research results are only for the case of working memory load of 1, and the situation under higher load.
It needs to be further explored, but this involves finer regional division.
When there are more stimuli presented at the same time, the resolution of the receptive field measurement and the accuracy of spatial positioning are higher, and higher fields may be required ( 7T) and observations with higher spatial resolution (mm and sub-mm levels); finally, how other high-level cognitive activities, such as attention, will affect these representations is also an interesting question, which will help to further understand the relationship between attention and working memory
.
Further answers to these questions will advance our understanding of the architecture of the human cerebral cortex; understanding the interaction mechanism of feedforward and feedback pathways will also help advance brain-like artificial neural networks, especially cyclic neural networks RNN Design
.
Original link: https://doi.
org/10.
1093/cercor/bhab300 First author Zhao Yijie (first row left 5), corresponding author Ku Yixuan (second row left 5) (Photo source: Ku Yixuan laboratory) Ku Yixuan, Sun Yat-sen University professor, doctoral supervisor, outstanding young and middle-aged talents of the "Hundred Talents Program", undergraduate and Ph.
D.
at Tsinghua University, postdoctoral at the University of California, San Francisco
.
Presided over a number of national, provincial and ministerial projects, the Shanghai Pujiang Talent Program, the backbone of the National 973 Project, the sub-project leader and project convener of major projects of the National Social Science Fund
.
Mainly engaged in the study of cognitive neural mechanisms of memory and emotion, and published more than 50 papers in internationally renowned SCI/SSCI journals.
Among them, the corresponding author's results were published in authoritative journals in the fields of Brain Stimulation, Cerebral Cortex, Journal of Neuroscience, and served as He is an external reviewer of well-known journals at home and abroad, and the National Natural Science Foundation of China and the United States
.
This research group (Memory and Emotion Lab) integrates memory and emotion research, and recruits distinguished researchers, postdoctoral fellows and research assistants throughout the year, and accepts doctoral and master students.
See the research group homepage
.
Undergraduates and postgraduates of all majors are welcome to study and research in the research group, please email kuyixuan@mail.
sysu.
edu.
cn
.
Selected articles from previous issues [1] JAMA Neurol︱ Attention! Young people are more likely to suffer from "Alzheimer's disease"? [2] Brain | For the first time! PAX6 may be a key factor in the pathogenesis of Alzheimer's disease and a new therapeutic target [3] Sci Adv︱ blockbuster! DNA methylation protein DNMT1 mutation can induce neurodegenerative diseases [4] Cell︱ new discovery! New enlightenment of midbrain-regulated movement phenomenon for the treatment of Parkinson’s disease [5] Cereb Cortex︱MET tyrosine kinase signal transduction timing abnormality is a key mechanism affecting the development and behavior of normal cortical neural circuits in mice [6] Nat Biomed Eng︱ The team of academician Ye Yuru develops a new strategy for whole-brain gene editing-mediated treatment of Alzheimer's disease [7] Luo Liqun Science's heavy review System interpretation ︱ Neural circuit structure-a system that makes the brain "computer" run at high speed [8] Sci Adv ︱Important discovery! The calcium homeostasis regulatory protein Calhm2 regulates the activation of microglia and participates in the process of Alzheimer's disease [9] EMBO J︱ new discovery! AGHGAP11B promotes the expansion of the neocortex into adulthood and improves cognitive ability [10] Cell Death Differ︱ Qi Yitao/Wu Hongmei and others cooperate to reveal the molecular mechanism of SUMO modification regulating neurogenesis in adult mice [11] Cereb Cortex︱A2A receptor antagonist can Reversal of sequence learning impairment induced by abnormal aggregation of α-Syn [1] Fuster JM, Alexander GE.
1971.
Neuron Activity Related to Short-Term Memory.
Science.
173:652–654.
[2] Zhou YD, Fuster JM.
1996.
Mnemonic neuronal activity in somatosensory cortex.
Proc Natl Acad Sci.
93:10533–10537.
[3] Bettencourt KC, Xu Y.
2015.
Decoding the content of visual short-term memory under distraction in occipital and parietal areas.
