Lecture Seven Part 2: Advances in recording and manipulation of neural networks in conscious subjects

Question 1

How can brain tissue oxygen be monitored?

Answer 1

Chronic monitoring of brain tissue oxygen in freely moving rats from a fully implanted telemetry system utilising optogenetics

Question 2

Describe the oxygen sensor;

Answer 2

•Very small (200 m diameter).
•Carbon paste electrode + carbon-silicon oil surface
- inert to fouling.
•Allows for months to potentially a year of sustained, stable oxygen measurements. •Already successfully used within neuroscience in non-telemetry applications.

Question 3

Whats good about the oxygen sensor?

Answer 3

• Lifetime continuous O2with long term stability
• Small size –suitable for rats.
• Fully implantable (freely moving, no tethers –tested in T-maze and water-maze)

Question 4

Why dont we record continuously?

Answer 4

Too much data

Solution: Use scheduled recording?e.g. 15 minutes every 2 hoursIs this enough?

Question 5

When they compared the recording time frequency over 24hrs with associated errors what did they find?

Answer 5

The error associated was highest with the highest frequency of recording within a 24hr window was expected

As time progressed into recording the errors reduced. Around 12 days revealed that 3hrs recording were optimal with low error. for HR, BP and SNA (although with each of these the associated error gets progressively larger)

To exemplify this, 10sec recordings of SNA< BP and HR will leave SNA at 30% error and the other two at around 10%

Question 6

What is the summery of the recording comparisons?

Answer 6

• Good estimate of 24-hour mean with surprisingly little data–Even using one 12 minute recording period gives <5% error for BP
• Error(SNA) > Error(HR) > Error(BP)
• Spread of data throughout day has more effect than the total amount of data

Question 7

What is the limitations of sampling?

Answer 7

• Have not considered requirements of other analysis techniques e.g. spectral analysis
• Errors may be larger in animals with larger circadian variation (e.g. rat)
• The effect of feeding times, cage cleaning etc were not considered. 22 hour average is often used to avoid this.

Question 8

What are the conclusions of sampling?

Answer 8

• Good estimations (<2% error) of the daily average of cardiovascular parameters can be achieved by scheduled sampling
• Best estimates obtained if short sampling periods are spread throughout the 24 hour period
• We can now record for 15 minutes every 2 hours with confidence