#fMRI

Electrophysiological methods

Which method relies on change in blood-oxygen-level to detect brain activity?

Neurovascular coupling links synaptic activity to hemodynamic changes. Heightened neuronal firing raises glutamate cycling and metabolic demand, triggering vasodilation through nitric oxide and astrocyte signaling, increasing regional cerebral blood volume and flow. Oxygen delivery surpasses consumption, reducing capillary and venular deoxyhemoglobin fraction. Functional MRI sensitive to blood-oxygen-level dependent contrast detects this alteration as T2* signal rise. Electroencephalography records electrical potentials directly, PET tracks glucose analogue uptake, computed tomography measures

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Electrophysiological methods

Which of the following techniques offers the highest temporal resolution?

Temporal resolution defines minimal interval needed to separate successive events. Neuronal communication occurs in milliseconds, requiring recording systems with kilohertz sampling. Electroencephalography directly measures scalp voltage fluctuations at 250-2000 Hz, instantly capturing evoked potentials, epileptic spikes and oscillatory changes. In contrast, computed tomography requires seconds for gantry rotation and reconstruction, magnetic resonance imaging needs seconds for pulse sequences and hemodynamic lag, positron emission tomography depends on tracer accumulation over minutes. Theref

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Electrophysiological methods

Which method is based on BOLD contrast?

Functional MRI routinely uses blood-oxygen-level dependent contrast originating from intrinsic magnetic properties of hemoglobin. Oxyhemoglobin is diamagnetic while deoxyhemoglobin is paramagnetic and creates microscopic magnetic field inhomogeneity shortening T2* relaxation and reducing signal. Enhanced neuronal firing drives neurovascular coupling, increasing local blood flow and influx of oxygenated blood, washing out deoxyhemoglobin, prolonging T2* and raising fMRI intensity. This physiological cascade serves as surrogate for activation. PET relies on radiotracer positron decay, CT quantif

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

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Electrophysiological methods

Which of the following provides functional imaging of brain blood flow and oxygen use?

Functional imaging of cerebral blood flow and oxygen metabolism traditionally relies on coupling between neuronal activity and hemodynamics. Functional magnetic resonance imaging exploits this by detecting changes in deoxyhemoglobin paramagnetism following activation, providing indirect maps of regional flow and oxygen extraction. Increased activity elevates local perfusion, altering signal intensity. Computed tomography images X-ray density for structure, EEG measures electrical potentials with limited spatial specificity, diffusion tensor imaging tracks water diffusion anisotropy for tract a

Ref: NCERT Biology Class XII Principles on Klenow fill-in labeling, Lehninger Chapter 9 DNA cloning techniques, and Molecular Cloning by Sambrook Chapter 10 documenting end-labeling of cohesive termini.

View Details