Invasive Techniques

Question 1

Stereotaxic surgery (3)

Answer 1

Requires use of stereotaxic atlas and instrument

Early 1900’s (1940’s humans)

Requires use of stereotaxic headframe, stereotaxic atlas and probe/instrument

makes use of a three-dimensional coordinates system to locate small targets inside the body and to perform on them

Question 2

Lesion methods (8)

Answer 2

• Bilateral and unilateral lesions
• Several procedures each requiring careful interpretation of effects

Aspiration lesions
Radio-frequency lesions
Knife cuts
Cryogenic blockade
Electrical stimulation
Electrophysiological recording

Question 3

bregma

Answer 3

the point or area of the skull where the sagittal and coronal junction joining the parietal and frontal bones come together.

Question 4

Stereotaxic surgery: Image guided surgery (key things) (3)

Answer 4

• encoded arm idea (the arm marks spots down)
• gps idea
• bregma

Question 5

Aspiration lesions (4)

Answer 5

One of the oldest lesioning techniques (early 1800’s)

craniotomy (remove section of skull)
retract dura

removing brain tissue using suction (glass pipette)

particularly useful for the removal of tissue of the surface of the brain

Question 6

Aspiration lesions: Advantages: (2)

Answer 6

• visually-guided removal of specific brain region(s)
• allows for the near-complete and confirmed removal of large areas of cortex

Question 7

Aspiration lesions: Dis-advantages: (2)

Answer 7

• requires that the targeted region be visible (or at minimum, surgically accessible)
• difficult to preserve all neighbouring tissue and/or fibres of passage

Question 8

Radio-frequency lesions (RF Ablation, RFA) (1) method (3) heating (2)

Answer 8

consists of creating a lesion using heat through an intracranially placed electrode coupled to an RF generator

• electrode is electrically insulated except at the tip, where the active electrode is located.
• electric current flows in the circuit between the active and dispersive electrodes

electric field between the two contacts oscillates with the RF frequency (~500,000 cps)

frictional heating within the tissue results from the RF ionic oscillation

• greatest heating takes place in the region of highest current density, which is near the tip of the active electrode

Question 9

leucotome (1) and its use (1)

Answer 9

a cannula through which a wire is inserted and used to cut the white matter in the brain in lobotomy.

• stop communication from one part to another

Question 10

prefrontal lobotomy (2)

Answer 10

surgical division of the central core of the white matter within the frontal lobes

• is empirically designed to sever the connections of the frontal cortex and especially to interrupt the projections which connect the frontal regions with the thalamus and hypothalamus.

Question 11

Cryogenic blockade (3)

Answer 11

Cryoloops, Cryoplates, Cryotips

cooling down neurons until they stop functioning and firing

Thermocouple: measure temp to ensure that the cells don’t break

Question 12

Cryogenic blockade pros and cons (4+2)

Answer 12

Pros:
- Neural compensation (i.e. plasticity)
- Reversibility
- Within-subject design (internal double-dissociations, act as own control)
- Control over parameters

Limitations
- Fixation (plates vs loops & tips)
- Distances

Question 13

Electrical stimulation (4)

Answer 13

Lesioning can be used to remove, damage, or inactivate a structure

Electrical stimulation may be used to “activate” a structure

Parameters: amplitude, pulsewidth, waveform shapes, and frequency

Stimulation of a structure may have an effect opposite to that seen when the structure is lesioned

Question 14

Intracellular unit recording (2+4)

Answer 14

is the measurement of voltage or current across the membrane of a cell.

It typically involves an electrode inserted in the cell and a reference electrode outside the cell.

Membrane potential of a neuron
- Single-unit recording
- Measure the potential difference between two electrodes using a DC amplifier

Electrode penetrates cell membrane, sudden change in measured potential (Neg.)

• Problem: Damage cell

Question 15

Extracellular unit recording (define (1), how it’s detected (2), method (2))

Answer 15

= recordings of electrical potentials produced by a cell, either in extracellular fluid near the cell of interest, or non-invasively
- Firing of a neuron

Action P: current flows in and out through excitable regions, creates potential fields.

• Electrode near neuron detects these extracellular potential fields, creating a spike.

Typically:

• Glass micropipettes for resting- and action-potentials and metal electrodes for extracellular spike measures.
• Each type is different in properties, such as resistance and impedance, which can be limitations

Question 16

Multiple-unit recording (1) + use (1)

Answer 16

Firing of many neurons
- Singles vs Arrays/Tetrodes/Etc.
- Ensembles

Singles vs Arrays/Tetrodes/Etc.

“the underlying motivation is that only by observing the activity of many neurons in concert can we hope to understand how collective computation in the brain occurs.”

Question 17

Invasive electrophysiological recording methods include the following: (4)

Answer 17

Intracellular unit recording

Extracellular unit recording

Multiple-unit recording

Invasive EEG recording

Question 18

Patch-Clamp Recording: Single-unit recording

Answer 18

• Increase SNR (signal to noise ratio)
• Record from whole cell or just patch
• Seal allows for measure of very small currents

Question 19

Invasive EEG recording- intracranial electroencephalography(iEEG)
(1+ (2) types+ method (1)+ pro (1))

Answer 19

electrodes placed directly on the exposed surface of the brain to record electrical activity from thecerebral cortex.

• in the operating room (intraoperative iEEG)
• outside of surgery (extraoperative iEEG)
• a craniotomy(a surgical incision into the skull) is required to implant the electrode grid

better spatial resolution than convention scalp-electrode EEG because electrical signal does not need to pass through low conductance bone of skull

Question 20

Intracellular unit recording graph appearance

Answer 20

measures membrane potential per milliseconds

sharp like stocks graph

Question 21

Multiple-Unit Recording graph appearance

Answer 21

no. of action potential per second

wider waves

Question 22

Extracellular Unit Recording graph appearance

Answer 22

voltage per seconds

like multiple lines.

Question 23

Invasive EEG Recording graph appearance

Answer 23

voltage per milliseconds

basically looks like an EEG graph (denser curve)

Question 24

Which of the following is an advantage that intracellular recordings have over extracellular recordings?

Answer 24

They can record synaptic and receptor potentials.

Question 25

Advantages of Extracellular recordings (3)

Answer 25

Extracellular recordings are used to monitor neuronal activity from outside the cell.

It provides a means to measure patterns of action potentials within many areas of the peripheral and central nervous systems.

In addition, massed activity can also be recorded.