NIRS fNIRS and Cortical Spreading Depression
NIRS fNIRS and Cortical Spreading Depression
NIRS (Near-Infrared Spectroscopy) and fNIRS (functional Near-Infrared Spectroscopy) are non-invasive techniques that use near-infrared light to measure changes in blood oxygenation and deoxygenation in the brain. These changes are directly related to neuronal activity, as active brain regions demand more oxygen and nutrients, leading to alterations in blood flow and local oxygenation. Below, we detail how fNIRS infers these changes and how they relate to the activation of specific functions in the cerebral cortex.
NIRS-fNIRS
Basic Principle of fNIRS
fNIRS is based on the property that near-infrared light (700-900 nm) can penetrate biological tissues, such as the skull and brain, and be absorbed by specific molecules, primarily:
- Oxygenated Hemoglobin (HbO): Absorbs more light around 850 nm.
- Deoxygenated Hemoglobin (HbR): Absorbs more light around 750 nm.
By measuring light absorption at different wavelengths, fNIRS can infer the relative concentrations of HbO and HbR, which reflect blood oxygenation and deoxygenation.
Relationship Between Neuronal Activity and Oxy/Deoxy Changes
When a brain region is activated (e.g., during a cognitive or motor task), the following occurs:
1. Increased Neuronal Metabolism: Active neurons consume more oxygen and glucose.
2. Hemodynamic Response: To meet the demand, there is an increase in local blood flow (known as neurovascular coupling).
3. Changes in Oxy/Deoxy:
- HbO concentration increases due to greater blood flow.
- HbR concentration decreases as oxygen is extracted from the blood for neuronal use.
These changes are detected by fNIRS and used to infer brain activity.
Pathway to Infer Brain Activation with fNIRS
1. Data Collection
- Sources and Detectors: fNIRS uses light emitters (sources) and detectors placed on the scalp. Light is emitted and detected after passing through brain tissue.
- Oxy/Deoxy Signals: Light absorption is measured at two or more wavelengths to calculate HbO and HbR concentrations.
2. Signal Processing
- Filtering: Signals are filtered to remove noise (e.g., from heart rate and respiration).
- Mathematical Modeling: Algorithms convert light absorption measurements into HbO and HbR concentrations.
3. Inference of Brain Activation
- Hemodynamic Response Pattern: During a task, an increase in HbO and a decrease in HbR are expected. This pattern is compared to the baseline (resting state).
- Spatial Localization: The arrangement of sources and detectors on the scalp allows mapping changes to specific cortical regions.
4. Correlation with Brain Functions
- Specific Tasks: Different tasks (motor, cognitive, visual) activate specific cortical regions. For example:
- Primary Motor Cortex: Activated during movements.
- Prefrontal Cortex: Activated during memory or decision-making tasks.
- Comparison with Other Techniques: fNIRS results can be validated with techniques like fMRI, which also measure hemodynamic responses.
Advantages of fNIRS
- Portability: Can be used in natural environments, unlike techniques like fMRI.
- Low Cost: More affordable compared to other neuroimaging techniques.
- Temporal Resolution: Captures rapid changes in oxygenation (temporal resolution of ~0.1 seconds).
- Non-Invasive: Does not require contrast injections or exposure to radiation.
Limitations of fNIRS
- Depth of Penetration: Infrared light only reaches superficial cortical regions (2-3 cm depth).
- Spatial Resolution: Inferior to techniques like fMRI.
- Artifacts: Head movements or changes in skin perfusion can interfere with signals.
Practical Example
Imagine an experiment where a participant performs a working memory task:
- Task: The participant must remember a sequence of numbers.
- Measurement: fNIRS detects an increase in HbO and a decrease in HbR in the prefrontal cortex.
- Inference: This suggests that the prefrontal cortex is active during the task, consistent with its role in executive functions and working memory.
fNIRS is a powerful tool for inferring changes in cerebral blood oxygenation and deoxygenation, which are directly related to neuronal activity. By measuring HbO and HbR, fNIRS allows mapping the activation of specific cortical functions, offering valuable insights into the brain's functional organization and its responses to cognitive, motor, or sensory tasks.
1. Emotion: A Shock with Rapid Decay
Emotions involve activation of cortical and subcortical circuits, but fNIRS can specifically contribute to the study of the cortex:
- Cortical Activity Monitoring: fNIRS can measure changes in blood oxygenation in cortical areas like the prefrontal cortex and insula, which are involved in emotional processing.
- Complementarity with EEG Microstates: While EEG captures rapid electrical activity, fNIRS provides information on associated hemodynamic changes, offering a more complete view of cortical dynamics during emotions.
- Evoked Potentials and Hemodynamic Responses: fNIRS can detect hemodynamic responses associated with cortical evoked potentials, helping correlate rapid electrical events with metabolic changes.
2. Feelings: A Metabolic and Connectomic Structure
Feelings involve metabolic changes and connectome reorganization, and fNIRS can contribute to cortical studies:
- Cortical Metabolic Changes: fNIRS can measure oxygen consumption and cerebral blood flow in the cortex, providing insights into the metabolic basis of prolonged feelings.
- Cortical Functional Connectivity: fNIRS can study functional connectivity between cortical regions, helping identify how persistent feelings, like frustration, reorganize the cortical connectome.
- Episodic Memories and Cortical Plasticity: By monitoring hemodynamic changes in areas like the prefrontal cortex, fNIRS can help understand how feelings are consolidated as episodic memories.
3. Cortical Spreading Depression (CSD) and EEG-DC as Biomarkers
CSD and EEG-DC are proposed as biomarkers of prolonged emotional states. fNIRS can complement these approaches in the cortex:
- Monitoring Cortical Depolarization Waves: fNIRS can detect changes in cerebral blood flow associated with CSD in the cortex, providing insights into the spread of depolarization waves and their metabolic consequences.
- Correlation with EEG-DC: fNIRS can be used alongside EEG-DC to correlate slow electrical potential variations with hemodynamic changes in the cortex, helping understand the relationship between electrical and metabolic activity during emotional states.
- Biomarkers of Emotional Disorders: Abnormal cortical oxygenation patterns detected by fNIRS can serve as complementary biomarkers for disorders like depression and anxiety.
4. Relationship with Emotional States and Feelings
fNIRS can contribute to understanding specific emotional states, such as deep sadness, anxiety, bipolarity, and post-traumatic stress, focusing on the cortex:
- Deep Sadness and Depression: fNIRS can identify hemodynamic activity patterns in the prefrontal cortex associated with persistent depressive states.
- Anxiety and Hypervigilance: fNIRS can monitor activation of the prefrontal cortex and other cortical areas, helping understand the maintenance of alert states.
- Bipolarity and Emotional Oscillations: fNIRS can detect rapid changes in cortical oxygenation associated with oscillations between mania and depression.
- Post-Traumatic Stress Disorder (PTSD): fNIRS can help identify patterns of cortical functional connectivity associated with the consolidation of traumatic memories.
5. CSD as a Mechanism of Short-Term Emotional Memory
CSD may be involved in the consolidation of emotional memories. fNIRS can contribute:
- Detection of Cortical Metabolic Changes: fNIRS can monitor changes in blood flow and cortical oxygenation associated with CSD, helping understand how depolarization waves consolidate emotional memories.
- Correlation with EEG Microstates: fNIRS can be used alongside EEG to correlate microstate patterns with cortical hemodynamic changes, providing a more complete view of memory consolidation.
6. Implications and Conclusion
fNIRS and NIRS can be valuable tools for therapeutic interventions focused on the cortex:
- Neuromodulation: fNIRS can monitor the effects of transcranial magnetic stimulation (TMS) on cortical oxygenation and functional connectivity.
- Neurofeedback: fNIRS can provide real-time feedback on cortical hemodynamic activity, helping patients modulate emotional states.
- Pharmacology: NIRS can assess the effects of medications on cortical metabolism and functional connectivity.
7. References and Evidence
- CSD and fNIRS: Studies already use fNIRS to monitor hemodynamic changes associated with CSD in the cortex in migraine models.
- EEG Microstates and fNIRS: Research combining EEG and fNIRS shows how microstate patterns are related to cortical oxygenation changes.
- Connectome and fNIRS: fNIRS has been used to study cortical connectome reorganization in psychiatric disorders.
fNIRS and NIRS offer a complementary approach to EEG, CSD, and connectome analysis, providing valuable insights into the metabolic and hemodynamic dynamics of the cerebral cortex during acute and prolonged emotional states. While they cannot access subcortical structures like the amygdala, these techniques are powerful for studying cortical activity, and their integration with other methodologies can open new perspectives for research and treatment of emotional and psychiatric disorders.
Basic Principle of fNIRS
fNIRS is based on the property that near-infrared light (700-900 nm) can penetrate biological tissues, such as the skull and brain, and be absorbed by specific molecules, primarily:
- Oxygenated Hemoglobin (HbO): Absorbs more light around 850 nm.
- Deoxygenated Hemoglobin (HbR): Absorbs more light around 750 nm.
By measuring light absorption at different wavelengths, fNIRS can infer the relative concentrations of HbO and HbR, which reflect blood oxygenation and deoxygenation.
Relationship Between Neuronal Activity and Oxy/Deoxy Changes
When a brain region is activated (e.g., during a cognitive or motor task), the following occurs:
1. Increased Neuronal Metabolism: Active neurons consume more oxygen and glucose.
2. Hemodynamic Response: To meet the demand, there is an increase in local blood flow (known as neurovascular coupling).
3. Changes in Oxy/Deoxy:
- HbO concentration increases due to greater blood flow.
- HbR concentration decreases as oxygen is extracted from the blood for neuronal use.
These changes are detected by fNIRS and used to infer brain activity.
Pathway to Infer Brain Activation with fNIRS
1. Data Collection
- Sources and Detectors: fNIRS uses light emitters (sources) and detectors placed on the scalp. Light is emitted and detected after passing through brain tissue.
- Oxy/Deoxy Signals: Light absorption is measured at two or more wavelengths to calculate HbO and HbR concentrations.
2. Signal Processing
- Filtering: Signals are filtered to remove noise (e.g., from heart rate and respiration).
- Mathematical Modeling: Algorithms convert light absorption measurements into HbO and HbR concentrations.
3. Inference of Brain Activation
- Hemodynamic Response Pattern: During a task, an increase in HbO and a decrease in HbR are expected. This pattern is compared to the baseline (resting state).
- Spatial Localization: The arrangement of sources and detectors on the scalp allows mapping changes to specific cortical regions.
4. Correlation with Brain Functions
- Specific Tasks: Different tasks (motor, cognitive, visual) activate specific cortical regions. For example:
- Primary Motor Cortex: Activated during movements.
- Prefrontal Cortex: Activated during memory or decision-making tasks.
- Comparison with Other Techniques: fNIRS results can be validated with techniques like fMRI, which also measure hemodynamic responses.
Advantages of fNIRS
- Portability: Can be used in natural environments, unlike techniques like fMRI.
- Low Cost: More affordable compared to other neuroimaging techniques.
- Temporal Resolution: Captures rapid changes in oxygenation (temporal resolution of ~0.1 seconds).
- Non-Invasive: Does not require contrast injections or exposure to radiation.
Limitations of fNIRS
- Depth of Penetration: Infrared light only reaches superficial cortical regions (2-3 cm depth).
- Spatial Resolution: Inferior to techniques like fMRI.
- Artifacts: Head movements or changes in skin perfusion can interfere with signals.
Practical Example
Imagine an experiment where a participant performs a working memory task:
- Task: The participant must remember a sequence of numbers.
- Measurement: fNIRS detects an increase in HbO and a decrease in HbR in the prefrontal cortex.
- Inference: This suggests that the prefrontal cortex is active during the task, consistent with its role in executive functions and working memory.
fNIRS is a powerful tool for inferring changes in cerebral blood oxygenation and deoxygenation, which are directly related to neuronal activity. By measuring HbO and HbR, fNIRS allows mapping the activation of specific cortical functions, offering valuable insights into the brain's functional organization and its responses to cognitive, motor, or sensory tasks.
1. Emotion: A Shock with Rapid Decay
Emotions involve activation of cortical and subcortical circuits, but fNIRS can specifically contribute to the study of the cortex:
- Cortical Activity Monitoring: fNIRS can measure changes in blood oxygenation in cortical areas like the prefrontal cortex and insula, which are involved in emotional processing.
- Complementarity with EEG Microstates: While EEG captures rapid electrical activity, fNIRS provides information on associated hemodynamic changes, offering a more complete view of cortical dynamics during emotions.
- Evoked Potentials and Hemodynamic Responses: fNIRS can detect hemodynamic responses associated with cortical evoked potentials, helping correlate rapid electrical events with metabolic changes.
2. Feelings: A Metabolic and Connectomic Structure
Feelings involve metabolic changes and connectome reorganization, and fNIRS can contribute to cortical studies:
- Cortical Metabolic Changes: fNIRS can measure oxygen consumption and cerebral blood flow in the cortex, providing insights into the metabolic basis of prolonged feelings.
- Cortical Functional Connectivity: fNIRS can study functional connectivity between cortical regions, helping identify how persistent feelings, like frustration, reorganize the cortical connectome.
- Episodic Memories and Cortical Plasticity: By monitoring hemodynamic changes in areas like the prefrontal cortex, fNIRS can help understand how feelings are consolidated as episodic memories.
NIRS fNIRS and Cortical Spreading Depression
3. Cortical Spreading Depression (CSD) and EEG-DC as Biomarkers
CSD and EEG-DC are proposed as biomarkers of prolonged emotional states. fNIRS can complement these approaches in the cortex:
- Monitoring Cortical Depolarization Waves: fNIRS can detect changes in cerebral blood flow associated with CSD in the cortex, providing insights into the spread of depolarization waves and their metabolic consequences.
- Correlation with EEG-DC: fNIRS can be used alongside EEG-DC to correlate slow electrical potential variations with hemodynamic changes in the cortex, helping understand the relationship between electrical and metabolic activity during emotional states.
- Biomarkers of Emotional Disorders: Abnormal cortical oxygenation patterns detected by fNIRS can serve as complementary biomarkers for disorders like depression and anxiety.
4. Relationship with Emotional States and Feelings
fNIRS can contribute to understanding specific emotional states, such as deep sadness, anxiety, bipolarity, and post-traumatic stress, focusing on the cortex:
- Deep Sadness and Depression: fNIRS can identify hemodynamic activity patterns in the prefrontal cortex associated with persistent depressive states.
- Anxiety and Hypervigilance: fNIRS can monitor activation of the prefrontal cortex and other cortical areas, helping understand the maintenance of alert states.
- Bipolarity and Emotional Oscillations: fNIRS can detect rapid changes in cortical oxygenation associated with oscillations between mania and depression.
- Post-Traumatic Stress Disorder (PTSD): fNIRS can help identify patterns of cortical functional connectivity associated with the consolidation of traumatic memories.
5. CSD as a Mechanism of Short-Term Emotional Memory
CSD may be involved in the consolidation of emotional memories. fNIRS can contribute:
- Detection of Cortical Metabolic Changes: fNIRS can monitor changes in blood flow and cortical oxygenation associated with CSD, helping understand how depolarization waves consolidate emotional memories.
- Correlation with EEG Microstates: fNIRS can be used alongside EEG to correlate microstate patterns with cortical hemodynamic changes, providing a more complete view of memory consolidation.
6. Implications and Conclusion
fNIRS and NIRS can be valuable tools for therapeutic interventions focused on the cortex:
- Neuromodulation: fNIRS can monitor the effects of transcranial magnetic stimulation (TMS) on cortical oxygenation and functional connectivity.
- Neurofeedback: fNIRS can provide real-time feedback on cortical hemodynamic activity, helping patients modulate emotional states.
- Pharmacology: NIRS can assess the effects of medications on cortical metabolism and functional connectivity.
7. References and Evidence
- CSD and fNIRS: Studies already use fNIRS to monitor hemodynamic changes associated with CSD in the cortex in migraine models.
- EEG Microstates and fNIRS: Research combining EEG and fNIRS shows how microstate patterns are related to cortical oxygenation changes.
- Connectome and fNIRS: fNIRS has been used to study cortical connectome reorganization in psychiatric disorders.
fNIRS and NIRS offer a complementary approach to EEG, CSD, and connectome analysis, providing valuable insights into the metabolic and hemodynamic dynamics of the cerebral cortex during acute and prolonged emotional states. While they cannot access subcortical structures like the amygdala, these techniques are powerful for studying cortical activity, and their integration with other methodologies can open new perspectives for research and treatment of emotional and psychiatric disorders.
Dinâmica da Troca de Conectomas Cerebrais
Trilhas da Frustração - EEG Microstates, CSD e Conectoma
A Mente é um Sistema Complexo que Busca Pertencimento sem Consciência
Interocepção da Homeostase Corporal
Acoplamento Eletromagnético e Ephaptic Coupling
NeuroInsight of CSD - A Emoção é Bioelétrica - O Sentimento é Metabólico - Cortical Spreading Depression
NIRS fNIRS - Depressão Cortical Propagada
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