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1980s and 1970s
When neuroimaging techniques emerged like PET and fMRI
Lesion Studies
Examination of effects of destruction of brain tissue through stroke, accident, or surgery.
Ex: Phineas Gage, “The man who dies laughing”
Brodmann’s Cortical Mapping
Used staining techniques and identified 52 brain regions based on anatomy according to their functions, but does not provide map of anatomical connectivity
Tract Tracing
Uses marker chemicals like radioactive amino acids or horseradish peroxide (HRP) to track neural pathways and explore anatomical connectivity.
Marker chemicals identifies where a cell projects to. Only possible in dead creatures.
Resting Potential
The electrical charge difference across the membrane of a neuron when it is not actively sending a signal, typically around -70mV.
Myelin Loss
Disrupts electrical transmission (Ex: multiple sclerosis)
Extra cellular fluid
Na+ and Cl-
Intracellular fluid
K+ and A- (organic anions)
Action Potential
A rapid influx of sodium ions (Na+) into the neuron, which causes depolarization, followed by the efflux of potassium ions (K+) that leads to repolarization, creating a temporary electrical signal that travels along the axon.
Sodium-potassium pumps
A cellular mechanism that pumps sodium ions (Na+) out of the cell and potassium ions (K+) into the cell, maintaining the electrochemical gradient essential for action potentials.
All-or-none phenomenon
The principle that a neuron fires completely or not at all; once the threshold is reached, an action potential is generated without variations in intensity.
Single cell recordings
A technique used to measure the electrical activity of a single neuron, often through insertion of a microelectrode.
Mirror Neurons
A type of brain cell that responds both when an individual performs an action and when they observe someone else performing that same action, believed to play a key role in understanding actions, intentions, and empathy.
Electroencephalography (EEG)
Technique used to measure electrical activity of neural populations through electrodes placed on the scalp.
Can measure event-related potential (ERPs)
Can help diagnose epilepsy and tumors
Fine temporal resolution but low spatial resolution
Event-related potentials (ERPs)
Electrical responses in the brain resulting from specific sensory, cognitive, or motor events, measured through EEG.
Gamma Wave (26-45 Hz)
A type of brainwave measured by EEG, associated with high-level cognitive functions, attention, memory processing, and sensory perception.
Beta Wave (12-25 Hz)
Brainwaves associated with alertness, active thinking, and concentration, commonly observed during wakeful, attentive states.
Alpha Wave (7.5-13 Hz)
A type of brainwave measured by EEG, associated with a relaxed, calm state of wakefulness and often observed during meditation or when closing the eyes.
Theta Wave (3.4-7.5 Hz)
Transition between wake and sleep, meditation, creativity, hypnagogic state, memory retrieval, synchronous
Delta Wave (<4 Hz)
Deep sleep, unconscious states
MEG (Magnetoencephalography)
A non-invasive imaging technique used to measure the magnetic fields produced by neuronal activity in the brain, providing high spatial resolution for studying brain functions.
Must be used in a room that blocks all alien magnetic fields (expensive)
Used for medical diagnosis
CT Scan
A medical imaging technique that uses X-rays to create detailed cross-sectional images of the body, allowing for accurate diagnosis of conditions such as tumors, injuries, and internal bleeding.
Positron Emission Tomography (PET)
Neuroimaging technique that detects gamma rays emitted indirectly by a tracer, typically a radioactive glucose substance, to visualize brain activity and diagnose conditions when brain performs a task.
Ways must be found to filter out potentially irrelevant background activity.
fMRI (functional magnetic resonance imaging)
An imaging technique that measures and maps brain activity by detecting changes in blood flow, providing insights into neural processes rather than direct neural firing.
Cheaper than PET and no injections
BOLD (Blood Oxygenated Level Dependent) Contrast
A type of contrast in fMRI that uses the changes in blood flow and oxygen levels in the brain to indicate brain activity. When brain cells become active, they require more oxygen and blood flow, which leads to changes in the ratio of oxygenated to deoxygenated hemoglobin.
Deoxygenated hemoglobin has different magnetic properties than oxygenated hemoglobin, causing changes in the MRI signal.
fMRI detects these changes in the MRI signal, enabling researchers to map brain activity.
Knife-edge scanning microscope (KESM)
3D reconstruction of brain tissue by strip of tissue but by diamond-tipped knife. White light source illuminated strip of tissue as it comes off blade which reflects an image to camera.
Penfield Studies
Electrical stimulation of association areas of brain during open brain surgery while patient is fully conscious.
Homonculus
“Little man” representation of sensory/motor cortical areas
rTMS (repetitive transcranial magnetic stimulation)
Magnetic pulses from coil placed on surface of skull stimulates neurons beneath the scalp.
Stimulation may energize brain’s left frontal lobe and cause nerve cells to form new functioning circuits.
Treats depression
ECT (electroconvulsive therapy)
Jolt of electricity from electrodes on scalp induces controlled seizures to treat severe depression.
Increases Norepinephrine or calms neural centers active in depression
May stimulate neurogenesis and new synaptic connections in hippocampus and amygdala
Fast-acting and effective for suicide-prevention, but comes with high relapse rate and memory impairment risks
tDCS (transcranial Direct current stimulation)
Weak current on scalp on left or dorsolateral prefrontal cortex.
Safer than ECT
Deep Brain Stimulation
Neurosurgical procedure where implanted electrodes (“brain pacemaker”) stimulates targeted brain areas
Often used at Parkinson’s treatment.
Optogenetics
Insertion of opsin in genes into neurons to control them with light of a particular wavelength that dictates whether the neurons fire or not.
Experiment where it produced hallucinations in mice
Can be used for precise identification of specific neurons and neural networks
Could potentially be used for depression treatment, chronic pain, seizures, or restoration of vision in the blind in the future
Voxel
3D version of a pixel (“volume” & “pixel”)
Voxel size trade-off
Smaller voxel = higher spatial resolution but weaker signals
Often needed to increase voxel size to capture fluctuations in BOLD signal, but also increases range of types of brain tissue in each voxel which can distortions the signal.
Network Neuroscience
Watching brain activity when people are doing nothing
Closer to their natural state
Helps understand schizophrenia, PTSD, and mapping circuits
