Research Methods in Cognitive Neuroscience Lecture 3 PDF

Research Methods in Cognitive Neuroscience Lecture 3: Structural, Functional & Connectionist Neuroimaging Techniques Structural, Functional & Connectionist Neuroimaging Techniques Topics covered in Lecture 3 01 Comparing Neuroimaging Methods: Comparing...

Research Methods in Cognitive Neuroscience Lecture 3: Structural, Functional & Connectionist Neuroimaging Techniques Structural, Functional & Connectionist Neuroimaging Techniques Topics covered in Lecture 3 01 Comparing Neuroimaging Methods: Comparing Neuroimaging Techniques (I); Comparative Table (II) 02 Structural Neuroimaging Techniques: Computed Tomography (CT) & Magnetic Resonance Imagine (MRI) [I] Functional Neuroimaging Techniques - Electrical Activity Related: (I) Electroencephalography (EEG) & (II) 03 Magnetoencephalography (MEG) [II] Functional Neuroimaging Techniques - Blood Flow Related: (I) Functional Magnetic Resonance Imagine (fMRI); 04 (II) Positron Emission Tomography & (III) Near-Infrared Spectroscopy (NIRS/fNIRS) 05 Connectionist Neuroimaging Techniques: Diffusion Tensor Imaging (DTI) & Variants 06 Overview: Key Terms 2  Comparing Neuroimaging Methods Comparing Structural, Functional & Connectionist Neuroimaging Techniques Structural Neuroimaging Techniques EEG Visualize brain structures MEG Examples: CT & MRI Functional fMRI Structural Functional Neuroimaging Techniques: PET MRI CT Measure brain activity (two general ways): NIRS Blood Flow Tracking: fMRI, PET, NIRS/fNIRS Electrical Activity Tracking: EEG, MEG DTI Connectionist Neuroimaging Techniques: Connectionist Examine brain connectivity Examples: DTI (with subtypes like DSI, QBI) 3  Comparing Neuroimaging Methods Structural connectivity: physical Comparative Table connections between brain regions (e.g., white matter tracts) Spatial Temporal Functional connectivity Technique Type Cost Key Use Resolution Resolution Refers to the correlated activity between brain regions during cognitive tasks or at rest. CT Structural Excellent N/A Moderate Trauma, stroke MRI Structural Excellent N/A High Structural abnormalities Structural Imaging Methods = Excellent spatial resolution, N/A or poor temporal resolution EEG Functional Poor Excellent Low Sleep, epilepsy Functional Imaging Methods = Good temporal resolution, but can have poor spatial resolution MEG Functional Good Excellent High Epilepsy, sensory research fMRI Functional Good Poor High Cognitive tasks (memory, perception etc) Neurodegenerative diseases (Alzheimer's), tumour PET Functional Good Poor High detection, psychiatric disorders (Schizophrenia) Poor to fNIRS/NIRS Functional Good Low Cognitive tasks, portable imaging Moderate DTI Connectional Good N/A High Mapping white matter tracts, connectivity analysis 4  Structural Neuroimaging (I) Computed Tomography (CT) [also: Computed Axial Tomography (CAT)] Computed Tomography (CT) How it works: Uses X-rays to create cross-sectional images of the brain. X-rays pass through tissues, and detectors capture the varying intensities to form images. Lighter colours = Denser areas like bone CT Scan of a Haemorrhagic Stroke CT Scan of a Tumour Darker colours = Less dense like air or blood Uses: Detecting structural brain abnormalities like tumours, strokes, or injuries. Used in early stroke research and trauma cases. Pros Cons - Quick and non-invasive. - Exposure to ionizing radiation. - Good for emergency use - Limited in visualizing soft tissue details - Higher resolution than X-rays. - Low temporal resolution 5  Structural Neuroimaging (II) Magnetic Resonance Imaging (MRI) Magnetic Resonance Imaging (MRI) How it works: MRI relies on strong magnetic fields and radiofrequency pulses The magnetic field aligns protons in water molecules in the brain Radiofrequency pulses momentarily disrupt this alignment As the protons return to their original position, they emit signals that are used to create detailed images of the brain. MRI Scan of Ischemic Strokes (T1) MRI Scan of a Tumour (T1) Uses: Detects structural abnormalities or brain lesions (lesion studies) Cortical thickness, grey and white matter abnormalities Detection of neurodegenerative diseases – Alzheimer’s disease Pros Cons - Excellent spatial resolution - Expensive and less accessible - Useful for identifying structural abnormalities /lesions - Does not provide data on brain activity - Non-invasive - Claustrophobia (enclosed space) 6  Functional Neuroimaging: Electrical Activity Related (I) Electroencephalography (EEG) Electroencephalography (EEG) How it works: EEG uses electrodes placed on the scalp to detect electrical signals (neural oscillations) produced by brain cells (neurons). These electrodes measure changes in voltage over time, reflecting the synchronized activity of large groups of neurons. The data collected are in the form of brain waves, with different frequencies (e.g., alpha, beta, gamma) associated with different cognitive states or activities. Uses: Diagnosing epilepsy, sleep studies, and cognitive research. Excellent for tracking timing of brain processes. Pros - Excellent temporal resolution: Cons - Can capture brain activity in real time, good - Poor spatial resolution: for tracking changes in cognitive states - Inverse Problem: It cannot precisely localize the - Inexpensive brain areas generating the electrical signals - Non-invasive. - Limited to surface brain activity 7  Functional Neuroimaging: Electrical Activity Related (I) Magnetoencephalography (MEG) Magnetoencephalography (MEG) How it works: Detects magnetic fields generated by the electrical activity of neurons. Similar to EEG but measures magnetic, not electrical signals. Uses: Localizing brain activity with better spatial precision than EEG. Used in epilepsy and brain pathology research. Useful for studying sensory processing Pros Cons - Excellent temporal resolution - Expensive - Good spatial resolution - Requires specialised equipment - Requires shielded environment 8  Functional Neuroimaging: Blood Flow Related (I) Functional Magnetic Resonance Imaging (fMRI) Functional Magnetic Resonance Imaging (fMRI) How it works: Tracks brain activity by measuring changes in blood oxygen levels (BOLD signal). Active brain areas use more oxygen, causing changes in the magnetic properties of blood. Blood oxygenation measured as a proxy for neuronal activity Pros Cons - Good spatial resolution for - Expensive and inaccessible Uses: identifying active brain regions - Poor temporal resolution (cannot track rapid brain activity). - Non-invasive - Indirect measure of neuronal activity (relies on blood flow). Identifying brain regions - Provides structural & functional data - Requires participants to sit still for long periods of time activated by specific tasks or stimuli. Studies on cognitive functions (e.g., memory, perception). 9  Functional Neuroimaging: Blood Flow Related (II) Positron Emission Tomography (PET) Positron Emission Tomography (PET) How it works: Uses radioactive tracers injected into the body to highlight areas of activity. The tracers emit positrons that collide with electrons, producing gamma rays. Detectors capture these gamma rays, creating images that show metabolic activity. Uses: Commonly used in research on neurodegenerative diseases (e.g., Alzheimer's, Parkinson's), as well as tumour detection & psychiatric disorders. Pros Cons - Tracks cerebral blood flow & metabolism - Expensive - Can trace neurotransmitters - Exposure to radioactive tracers - Good spatial resolution - Poor temporal resolution 10  Functional Neuroimaging: Blood Flow Related (III) Near-Infrared Spectroscopy (NIRS/fNIRS) Near-Infrared Spectroscopy (NIRS/fNIRS) How it works: Near-infrared light is passed through the scalp to measure changes in blood oxygenation. Oxygenated and deoxygenated haemoglobin absorb light differently, indicating brain activity. Measures cortical brain function by detecting blood flow, similar to fMRI but less invasive. Uses: Studying brain function on cognitive tasks and the like in real-world environments (portable, non-invasive). Pros Cons -Portable and more affordable than fMRI. -Limited penetration depth -Can be used with infants + young children -Only measures superficial cortical activity 11  Connectionist Neuroimaging Diffusion Tensor Imaging (DTI) Diffusion Tensor Imaging (DTI) How it works: Measures water diffusion in the brain to map white matter tracts (brain connectivity). Variants include DSI (Diffusion Spectrum Imaging) and QBI (Q-Ball Imaging). Uses: Mapping brain connectivity (structural connections between regions). Studying disorders like multiple sclerosis, traumatic brain injury. Cons Pros - Moderate spatial resolution. - Excellent for visualising white matter tracts - Cannot directly measure functional - Non-invasive connectivity (measures water diffusion) 12  ? Key terms Comparisons b/w Neuroimaging Methods (Table) ? Structural vs. Functional Connectivity Structural Neuroimaging: ? CT: X-ray-based structural imaging MRI: Magnetic-based structural imaging QUESTIONS? ? Functional Neuroimaging EEG: Electrical activity tracking ? MEG: Magnetic field recording fMRI: Functional imaging using blood flow PET: Tracer-based metabolic imaging fNIRS: Near-infrared for cortical oxygenation NB: Pros & Cons Connectionist Neuroimaging + Uses of the DTI: White matter tract mapping different Methods 13