Lab D: introduction of stereotaxic

Stereotaxic surgery (stereotactic surgery)

highly precise surgical technique used to target specific areas of the brain or other structures in 3 dimensions.

• it relies on a stereotaxic apparatus

Stereotaxic Apparatus

instrument that immobilizes the head and allows surgical instruments to be guided to exact coordinates.

Cannula

small hollow surgical instrument, often implanted in the brain during stereotaxic surgery, that provides a pathway for delivering or withdrawing substances with precision.

Purpose of Stereotaxic surgery (stereotactic surgery)

• to deliver drugs, tracers, or viral vectors to a defined brain region

• to implant electrodes for stimulation or recording

• to insert cannulas for future infusion

• to create lesions for experimental or clinical purposes

• to obtain biopsies or perform therapeutic interventions in humans

Stereotactic instrument

used to position an animal’s head so it matches the geometry of the atlas

X-coordinate

Corresponds to movement along the sagittal plane (right-left or medial-lateral)

The Y coordinate

corresponds to movement along the coronal or frontal plane (front-back or anterior-posterior, rostral-caudal)

Z coordinate

corresponds to movement along the horizontal plane(top-bottom, dorsal-ventral (animals like rodents) or superior-inferior (humans))

Stereotactic halo

used in humans

it is anchored directly to the skull with fixation pins, creating a rigid reference frame that does not move with skin or soft tissue

Interaural coordinate

0,0,0 point for birds, point where the two ear bars would touch if allowed to do so perfectly centered in the apparatus

Radiofrequency (RF) lesion

heat from an electrode tip destroys tissue

chemical injection

substances like alcohol, kainic acid, or ibotenic acid kill neurons

electrolytic lesion

direct current passed through an electrode destroys cells and fibers

cryogenic lesion

tissue is temporarily inactivated by cooling with a cryoprobe

surgical aspiration

physical removal of brain tissue, often in accessible cortical areas

electrode implantation

a procedure in which fine electrodes are lowered into specific brain regions to study neural activity.

• Recording electrodes detect the firing patterns of individual neurons or groups of neurons, providing direct information about brain function

• Stimulating electrodes can deliver controlled electrical currents to activate or disrupt circuits, allowing researchers to test casual relationships between brain activity and behavior

optogenetics

implanting fiber-optic cannulas or LED probes to deliver light to neurons that have been genetically modified to express light-sensitives ion channels

• allows specific neurons to be activated in a living rodent

microdialysis

inserting a probe with a semipermeable membrane into a specific brain region to collect extracellular fluid

• allows researchers to monitor neurotransmitter release in real time while the animal is awake and behaving.

Push-pull perfusion

inserting two cannulas into the same brain region, one to infuse artificial cerebrospinal fluid (the push) and the other to withdraw fluid at the same rate sampling of neurotransmitters and metabolites.

• provides a more immediate and less filtered picture of the local chemical environment; it is also more invasive and can cause more tissue disruption than microdialysis.

Deep brain stimulation (DBS) in animal models

implanting stimulating electrodes into subcortical (beneath the cerebral cortex) brain regions to deliver patterned electrical pulses.

• used to study how neural networks control movement, motivation, and other behaviors.

• servers as a way to model human therapies: can treat conditions such as Parkinson’s disease, essential tremor, and obsessive-compulsive disorder

viral vector injections

using modified viruses as delivery tools to introduce genetic material into specific brain regions.

• used in research to make neurons express new protein

tracer studies

injecting specialized molecules intro the brain to map neural pathways. Anterograde tracers move forward from the cell body down to the axon to reveal where neurons send their outputs, while retrograde tracers move backward from axon terminals to the cell body to show where inputs originate.

• allows researchers to create detailed maps of connectivity between brain regions and identify how circuits are organized