Maro G Machizawa | Hiroshima University (original) (raw)

Papers by Maro G Machizawa

Visual working memory (VWM) is a temporary storage system capable of retaining information that c... more Visual working memory (VWM) is a temporary storage system capable of retaining information that can be accessed and manipulated by higher cognitive processes, thereby facilitating a wide range of cognitive functions. Electroencephalography (EEG) is used to understand the neural correlates of VWM with high temporal precision, and one commonly used EEG measure is an event-related potential called the contralateral delay activity (CDA). In a landmark study by Vogel and Machizawa (2004), the authors found that the CDA amplitude increases with the number of items stored in VWM and plateaus around three to four items, which is thought to represent the typical adult working memory capacity. Critically, this study also showed that the increase in CDA amplitude between two-item and four-item arrays correlated with individual subjects’ VWM performance. Although these results have been supported by subsequent studies, a recent study suggested that the number of subjects used in experiments inv...

International Journal of Psychophysiology, Jun 1, 2023

The Japanese Journal of Ergonomics, Jul 30, 2022

bioRxiv (Cold Spring Harbor Laboratory), Dec 7, 2021

Recent studies highlight interoception as essential to processing healthy emotion and to patholog... more Recent studies highlight interoception as essential to processing healthy emotion and to pathology of major depressive disorder. However, it is unclear how individual differences in healthy people with high depression risk (HDR) relate to neurophysiological underpinnings for interoception and emotional reactions under different degrees of certainty. We examined whether the degree of depression risk mediates the relationship between heartbeat-evoked potential (HEP) as a neurophysiological marker for cardiac interoception and heart rate (HR) or heart rate variability (HRV) as indices for cardiac reactivity. In a concurrent EEG-ECG experiment, 26 healthy participants underwent an emotion-evoking pictureevaluation task. Each of differential auditory cues was associated with certainty of the upcoming pleasant or unpleasant picture. The results showed that HDR reduced neural sources in anticipation and enhanced physiological reactions to uncertain, unpleasant pictures. These results suggest that weak predictions and augmented prediction errors for negative emotional stimuli reflect depression risk. Moreover, depression risk significantly mediated the relationship between HEP and HR for unexpected unpleasant stimuli. Strong association between brain and heart reactivity was observed in HDR individuals, suggesting a potential involvement of alternations in baroreflex sensitivity. This study provides evidence that interoception and autonomic regulation in the cardiac domain is altered by depression risk and highlights that specific component of brain-heart interactions would offer insights into the underlying mechanism of autonomic nerve system and interoception disturbances associated with depression risk.

Frontiers in Neuroinformatics

The complexity and high dimensionality of neuroimaging data pose problems for decoding informatio... more The complexity and high dimensionality of neuroimaging data pose problems for decoding information with machine learning (ML) models because the number of features is often much larger than the number of observations. Feature selection is one of the crucial steps for determining meaningful target features in decoding; however, optimizing the feature selection from such high-dimensional neuroimaging data has been challenging using conventional ML models. Here, we introduce an efficient and high-performance decoding package incorporating a forward variable selection (FVS) algorithm and hyper-parameter optimization that automatically identifies the best feature pairs for both classification and regression models, where a total of 18 ML models are implemented by default. First, the FVS algorithm evaluates the goodness-of-fit across different models using the k-fold cross-validation step that identifies the best subset of features based on a predefined criterion for each model. Next, the...

Neuroimaging data is complex and high-dimensional that poses challenges for machine learning (ML)... more Neuroimaging data is complex and high-dimensional that poses challenges for machine learning (ML) applications. Of varieties of reasons contributing on accuracy decoding, variable feature selection is one of crucial steps for determining target feature in data analysis, especially in the context of neuroimaging studies where the number of features is often much larger than the number of observations. Therefore, optimization of feature selection from such high-dimensional neuroimaging data has been challenging using conventional ML algorithms. Here, we introduce an efficient ML package incorporating a forward variable selection (FVS) algorithm that optimizes the identification of features for both classification and regression models. In our framework, the best ML model and feature pairs that explain the inputs can be automatically determined. Moreover, the toolbox can be executed in a parallel environment for efficient computation. The parallelized FVS algorithm iteratively selects ...

bioRxiv (Cold Spring Harbor Laboratory), Feb 10, 2021

Neurofeedback (NF) aptitude, which refers to an individual's ability to change its brain activity... more Neurofeedback (NF) aptitude, which refers to an individual's ability to change its brain activity through NF training, has been reported to vary significantly from person to person. The prediction of individual NF aptitudes is critical in clinical NF applications. In the present study, we extracted the resting-state functional brain connectivity (FC) markers of NF aptitude independent of NF-targeting brain regions. We combined the data

2022 Ninth International Conference on Software Defined Systems (SDS)

Scientific Reports, Oct 6, 2022

Trust attitude is a social personality trait linked with the estimation of others' trustworthines... more Trust attitude is a social personality trait linked with the estimation of others' trustworthiness. Trusting others, however, can have substantial negative effects on mental health, such as the development of depression. Despite significant progress in understanding the neurobiology of trust, whether the neuroanatomy of trust is linked with depression vulnerability remains unknown. To investigate a link between the neuroanatomy of trust and depression vulnerability, we assessed trust and depressive symptoms and employed neuroimaging to acquire brain structure data of healthy participants. A high depressive symptom score was used as an indicator of depression vulnerability. The neuroanatomical results observed with the healthy sample were validated in a sample of clinically diagnosed depressive patients. We found significantly higher depressive symptoms among low trusters than among high trusters. Neuroanatomically, low trusters and depressive patients showed similar volume reduction in brain regions implicated in social cognition, including the dorsolateral prefrontal cortex (DLPFC), dorsomedial PFC, posterior cingulate, precuneus, and angular gyrus. Furthermore, the reduced volume of the DLPFC and precuneus mediated the relationship between trust and depressive symptoms. These findings contribute to understanding social-and neuralmarkers of depression vulnerability and may inform the development of social interventions to prevent pathological depression.

Mental imagery (MI) is the ability to generate visual phenomena in the absence of sensory input. ... more Mental imagery (MI) is the ability to generate visual phenomena in the absence of sensory input. MI is often likened to visual working memory (VWM): the ability to maintain and manipulate visual representations. How MI is recruited during VWM is yet to be established. In a modified orientation change-discrimination task, we examined how behavioural (proportion correct) and neural (contralateral delay activity; CDA) correlates of precision and capacity map onto subjective ratings of vividness and number of items in MI within a VWM task. During the maintenance period, seventeen participants estimated the vividness of their MI or the number of items held in MI while they were instructed to focus on either precision or capacity of their representation and to retain stimuli at varying set sizes (1, 2 and 4). Vividness and number ratings varied over set sizes; however, subjective ratings and behavioral performance were not correlated, except for vividness rating at set size 1. There were ...

The Proceedings of the Annual Convention of the Japanese Psychological Association, Sep 10, 2014

Cerebral Cortex, 2020

Visual working memory (VWM) refers to our ability to selectively maintain visual information in a... more Visual working memory (VWM) refers to our ability to selectively maintain visual information in a mental representation. While cognitive limits of VWM greatly influence a variety of mental operations, it remains controversial whether the quantity or quality of representations in mind constrains VWM. Here, we examined behavior-to-brain anatomical relations as well as brain activity to brain anatomy associations with a “neural” marker specific to the retention interval of VWM. Our results consistently indicated that individuals who maintained a larger number of items in VWM tended to have a larger gray matter (GM) volume in their left lateral occipital region. In contrast, individuals with a superior ability to retain with high precision tended to have a larger GM volume in their right parietal lobe. These results indicate that individual differences in quantity and quality of VWM may be associated with regional GM volumes in a dissociable manner, indicating willful integration of inf...

Recent studies highlight interoception as essential to processing healthy emotion and to patholog... more Recent studies highlight interoception as essential to processing healthy emotion and to pathology of major depressive disorder (MDD). It has been reported that interoceptive responses are impaired in MDD and in healthy individuals with a high depressive risk (HDR). However, it is unclear how individual differences in HDR relate to neurophysiological underpinnings for interoceptive and emotional reactions under different degrees of certainty. We examined whether HDR mediates the relationship between a neurophysiological marker for interoception, heartbeat-evoked potential (HEP), and an index for cardiac reactivity, heart rate (HR) or heart rate variability (HRV). In a concurrent EEG-ECG experiment, 26 healthy participants underwent an emotion-evoking picture-evaluation task. Each of differential auditory cues was associated with certainty of the upcoming pleasant or unpleasant picture. The results showed attenuated HRV activity for certain cues in HDR individuals. Neural and physiol...

Frontiers in Cellular Neuroscience, 2022

Post-operative cognitive dysfunction (POCD) can be a serious surgical complication, and patients ... more Post-operative cognitive dysfunction (POCD) can be a serious surgical complication, and patients undergoing cardiac procedures are at particular risk for POCD. This study examined the effect of blocking neuroinflammation on behavioral and neurogenic deficits produced in a rat model of cardiopulmonary bypass (CPB). Minocycline, a drug with established anti-inflammatory activity, or saline was administered daily for 30 days post-CPB. Treatment with minocycline reduced the number of activated microglia/macrophages observed in the dentate gyrus of the hippocampus at 6 months post-CPB, consistent with an anti-inflammatory action in this CPB model. Behavioral testing was conducted at 6 months post-CPB utilizing a win-shift task on an 8-arm radial maze. Minocycline-treated animals performed significantly better than saline-treated animals on this task after CPB. In addition, the CPB-induced reduction in adult neurogenesis was attenuated in the minocycline-treated animals. Together, these f...

Cognitive limits of working memory play a pivotal role in many varieties of mental operations in ... more Cognitive limits of working memory play a pivotal role in many varieties of mental operations in our daily life. The previously separate literatures on visual attention and on visual working memory are converging, with growing interest in how visual attention may relate to visual short-term memory and how hemispheric specificities constrain such higher cognitive functions. In addition, it has been debated whether the numbers of items (quantity) or the precision with which they are retained (quality) constrain human visual working memory. With psychophysical, electrophysiological, and neuroanatomical imaging approaches, I provide evidence for attentional and hemispheric interplays contributing to the maintenance of working memory in vision and audition. Here, I report exploratory analysis of how individual behavioural differences in separable aspects of attention may relate to particular aspects of visual working memory (in Chapter 2) and how structure of human parietal areas are ass...

The Proceedings of the Annual Convention of the Japanese Psychological Association, Sep 20, 2017

Physiology & Behavior, 1988

Journal of Neurophysiology, 2010

Human neuroimaging studies have implicated a number of brain regions in long-term memory formatio... more Human neuroimaging studies have implicated a number of brain regions in long-term memory formation. Foremost among these is ventrolateral prefrontal cortex. Here, we used double-pulse transcranial magnetic stimulation (TMS) to assess whether the contribution of this part of cortex is crucial for laying down new memories and, if so, to examine the time course of this process. Healthy adult volunteers performed an incidental encoding task (living/nonliving judgments) on sequences of words. In separate series, the task was performed either on its own or while TMS was applied to one of two sites of experimental interest (left/right anterior inferior frontal gyrus) or a control site (vertex). TMS pulses were delivered at 350, 750, or 1,150 ms following word onset. After a delay of 15 min, memory for the items was probed with a recognition memory test including confidence judgments. TMS to all three sites nonspecifically affected the speed and accuracy with which judgments were made durin...

Visual working memory (VWM) is a temporary storage system capable of retaining information that c... more Visual working memory (VWM) is a temporary storage system capable of retaining information that can be accessed and manipulated by higher cognitive processes, thereby facilitating a wide range of cognitive functions. Electroencephalography (EEG) is used to understand the neural correlates of VWM with high temporal precision, and one commonly used EEG measure is an event-related potential called the contralateral delay activity (CDA). In a landmark study by Vogel and Machizawa (2004), the authors found that the CDA amplitude increases with the number of items stored in VWM and plateaus around three to four items, which is thought to represent the typical adult working memory capacity. Critically, this study also showed that the increase in CDA amplitude between two-item and four-item arrays correlated with individual subjects’ VWM performance. Although these results have been supported by subsequent studies, a recent study suggested that the number of subjects used in experiments inv...

International Journal of Psychophysiology, Jun 1, 2023

The Japanese Journal of Ergonomics, Jul 30, 2022

bioRxiv (Cold Spring Harbor Laboratory), Dec 7, 2021

Recent studies highlight interoception as essential to processing healthy emotion and to patholog... more Recent studies highlight interoception as essential to processing healthy emotion and to pathology of major depressive disorder. However, it is unclear how individual differences in healthy people with high depression risk (HDR) relate to neurophysiological underpinnings for interoception and emotional reactions under different degrees of certainty. We examined whether the degree of depression risk mediates the relationship between heartbeat-evoked potential (HEP) as a neurophysiological marker for cardiac interoception and heart rate (HR) or heart rate variability (HRV) as indices for cardiac reactivity. In a concurrent EEG-ECG experiment, 26 healthy participants underwent an emotion-evoking pictureevaluation task. Each of differential auditory cues was associated with certainty of the upcoming pleasant or unpleasant picture. The results showed that HDR reduced neural sources in anticipation and enhanced physiological reactions to uncertain, unpleasant pictures. These results suggest that weak predictions and augmented prediction errors for negative emotional stimuli reflect depression risk. Moreover, depression risk significantly mediated the relationship between HEP and HR for unexpected unpleasant stimuli. Strong association between brain and heart reactivity was observed in HDR individuals, suggesting a potential involvement of alternations in baroreflex sensitivity. This study provides evidence that interoception and autonomic regulation in the cardiac domain is altered by depression risk and highlights that specific component of brain-heart interactions would offer insights into the underlying mechanism of autonomic nerve system and interoception disturbances associated with depression risk.

Frontiers in Neuroinformatics

The complexity and high dimensionality of neuroimaging data pose problems for decoding informatio... more The complexity and high dimensionality of neuroimaging data pose problems for decoding information with machine learning (ML) models because the number of features is often much larger than the number of observations. Feature selection is one of the crucial steps for determining meaningful target features in decoding; however, optimizing the feature selection from such high-dimensional neuroimaging data has been challenging using conventional ML models. Here, we introduce an efficient and high-performance decoding package incorporating a forward variable selection (FVS) algorithm and hyper-parameter optimization that automatically identifies the best feature pairs for both classification and regression models, where a total of 18 ML models are implemented by default. First, the FVS algorithm evaluates the goodness-of-fit across different models using the k-fold cross-validation step that identifies the best subset of features based on a predefined criterion for each model. Next, the...

Neuroimaging data is complex and high-dimensional that poses challenges for machine learning (ML)... more Neuroimaging data is complex and high-dimensional that poses challenges for machine learning (ML) applications. Of varieties of reasons contributing on accuracy decoding, variable feature selection is one of crucial steps for determining target feature in data analysis, especially in the context of neuroimaging studies where the number of features is often much larger than the number of observations. Therefore, optimization of feature selection from such high-dimensional neuroimaging data has been challenging using conventional ML algorithms. Here, we introduce an efficient ML package incorporating a forward variable selection (FVS) algorithm that optimizes the identification of features for both classification and regression models. In our framework, the best ML model and feature pairs that explain the inputs can be automatically determined. Moreover, the toolbox can be executed in a parallel environment for efficient computation. The parallelized FVS algorithm iteratively selects ...

bioRxiv (Cold Spring Harbor Laboratory), Feb 10, 2021

Neurofeedback (NF) aptitude, which refers to an individual's ability to change its brain activity... more Neurofeedback (NF) aptitude, which refers to an individual's ability to change its brain activity through NF training, has been reported to vary significantly from person to person. The prediction of individual NF aptitudes is critical in clinical NF applications. In the present study, we extracted the resting-state functional brain connectivity (FC) markers of NF aptitude independent of NF-targeting brain regions. We combined the data

2022 Ninth International Conference on Software Defined Systems (SDS)

Scientific Reports, Oct 6, 2022

Trust attitude is a social personality trait linked with the estimation of others' trustworthines... more Trust attitude is a social personality trait linked with the estimation of others' trustworthiness. Trusting others, however, can have substantial negative effects on mental health, such as the development of depression. Despite significant progress in understanding the neurobiology of trust, whether the neuroanatomy of trust is linked with depression vulnerability remains unknown. To investigate a link between the neuroanatomy of trust and depression vulnerability, we assessed trust and depressive symptoms and employed neuroimaging to acquire brain structure data of healthy participants. A high depressive symptom score was used as an indicator of depression vulnerability. The neuroanatomical results observed with the healthy sample were validated in a sample of clinically diagnosed depressive patients. We found significantly higher depressive symptoms among low trusters than among high trusters. Neuroanatomically, low trusters and depressive patients showed similar volume reduction in brain regions implicated in social cognition, including the dorsolateral prefrontal cortex (DLPFC), dorsomedial PFC, posterior cingulate, precuneus, and angular gyrus. Furthermore, the reduced volume of the DLPFC and precuneus mediated the relationship between trust and depressive symptoms. These findings contribute to understanding social-and neuralmarkers of depression vulnerability and may inform the development of social interventions to prevent pathological depression.

Mental imagery (MI) is the ability to generate visual phenomena in the absence of sensory input. ... more Mental imagery (MI) is the ability to generate visual phenomena in the absence of sensory input. MI is often likened to visual working memory (VWM): the ability to maintain and manipulate visual representations. How MI is recruited during VWM is yet to be established. In a modified orientation change-discrimination task, we examined how behavioural (proportion correct) and neural (contralateral delay activity; CDA) correlates of precision and capacity map onto subjective ratings of vividness and number of items in MI within a VWM task. During the maintenance period, seventeen participants estimated the vividness of their MI or the number of items held in MI while they were instructed to focus on either precision or capacity of their representation and to retain stimuli at varying set sizes (1, 2 and 4). Vividness and number ratings varied over set sizes; however, subjective ratings and behavioral performance were not correlated, except for vividness rating at set size 1. There were ...

The Proceedings of the Annual Convention of the Japanese Psychological Association, Sep 10, 2014

Cerebral Cortex, 2020

Visual working memory (VWM) refers to our ability to selectively maintain visual information in a... more Visual working memory (VWM) refers to our ability to selectively maintain visual information in a mental representation. While cognitive limits of VWM greatly influence a variety of mental operations, it remains controversial whether the quantity or quality of representations in mind constrains VWM. Here, we examined behavior-to-brain anatomical relations as well as brain activity to brain anatomy associations with a “neural” marker specific to the retention interval of VWM. Our results consistently indicated that individuals who maintained a larger number of items in VWM tended to have a larger gray matter (GM) volume in their left lateral occipital region. In contrast, individuals with a superior ability to retain with high precision tended to have a larger GM volume in their right parietal lobe. These results indicate that individual differences in quantity and quality of VWM may be associated with regional GM volumes in a dissociable manner, indicating willful integration of inf...

Recent studies highlight interoception as essential to processing healthy emotion and to patholog... more Recent studies highlight interoception as essential to processing healthy emotion and to pathology of major depressive disorder (MDD). It has been reported that interoceptive responses are impaired in MDD and in healthy individuals with a high depressive risk (HDR). However, it is unclear how individual differences in HDR relate to neurophysiological underpinnings for interoceptive and emotional reactions under different degrees of certainty. We examined whether HDR mediates the relationship between a neurophysiological marker for interoception, heartbeat-evoked potential (HEP), and an index for cardiac reactivity, heart rate (HR) or heart rate variability (HRV). In a concurrent EEG-ECG experiment, 26 healthy participants underwent an emotion-evoking picture-evaluation task. Each of differential auditory cues was associated with certainty of the upcoming pleasant or unpleasant picture. The results showed attenuated HRV activity for certain cues in HDR individuals. Neural and physiol...

Frontiers in Cellular Neuroscience, 2022

Post-operative cognitive dysfunction (POCD) can be a serious surgical complication, and patients ... more Post-operative cognitive dysfunction (POCD) can be a serious surgical complication, and patients undergoing cardiac procedures are at particular risk for POCD. This study examined the effect of blocking neuroinflammation on behavioral and neurogenic deficits produced in a rat model of cardiopulmonary bypass (CPB). Minocycline, a drug with established anti-inflammatory activity, or saline was administered daily for 30 days post-CPB. Treatment with minocycline reduced the number of activated microglia/macrophages observed in the dentate gyrus of the hippocampus at 6 months post-CPB, consistent with an anti-inflammatory action in this CPB model. Behavioral testing was conducted at 6 months post-CPB utilizing a win-shift task on an 8-arm radial maze. Minocycline-treated animals performed significantly better than saline-treated animals on this task after CPB. In addition, the CPB-induced reduction in adult neurogenesis was attenuated in the minocycline-treated animals. Together, these f...

Cognitive limits of working memory play a pivotal role in many varieties of mental operations in ... more Cognitive limits of working memory play a pivotal role in many varieties of mental operations in our daily life. The previously separate literatures on visual attention and on visual working memory are converging, with growing interest in how visual attention may relate to visual short-term memory and how hemispheric specificities constrain such higher cognitive functions. In addition, it has been debated whether the numbers of items (quantity) or the precision with which they are retained (quality) constrain human visual working memory. With psychophysical, electrophysiological, and neuroanatomical imaging approaches, I provide evidence for attentional and hemispheric interplays contributing to the maintenance of working memory in vision and audition. Here, I report exploratory analysis of how individual behavioural differences in separable aspects of attention may relate to particular aspects of visual working memory (in Chapter 2) and how structure of human parietal areas are ass...

The Proceedings of the Annual Convention of the Japanese Psychological Association, Sep 20, 2017

Physiology & Behavior, 1988

Journal of Neurophysiology, 2010

Human neuroimaging studies have implicated a number of brain regions in long-term memory formatio... more Human neuroimaging studies have implicated a number of brain regions in long-term memory formation. Foremost among these is ventrolateral prefrontal cortex. Here, we used double-pulse transcranial magnetic stimulation (TMS) to assess whether the contribution of this part of cortex is crucial for laying down new memories and, if so, to examine the time course of this process. Healthy adult volunteers performed an incidental encoding task (living/nonliving judgments) on sequences of words. In separate series, the task was performed either on its own or while TMS was applied to one of two sites of experimental interest (left/right anterior inferior frontal gyrus) or a control site (vertex). TMS pulses were delivered at 350, 750, or 1,150 ms following word onset. After a delay of 15 min, memory for the items was probed with a recognition memory test including confidence judgments. TMS to all three sites nonspecifically affected the speed and accuracy with which judgments were made durin...