article review on simultanoeus optical stimulation and electrical recording from neuron in-vivo
TRANSCRIPT
Review on
Integrated Device for Combined Optical Neuromodulation and Electrical Recording
for Chronic In-Vivo Applications
By
Md. Kafiul Islam
A0080155M
Supervisor: Dr. Zhi Yang
Outline
• Introduction
Problem Definition
• Paper Summery
Main Contribution
Technical Evaluation
Major Findings
Strength and Weakness
• Conclusion
Problem Definition
How Brain Works…!?
Understanding the circuit-level functional organization of the brain hasimportant implication for both basic and clinical neuroscience.
Understanding of local neural circuit dynamics
– Simultaneous stimulation and recording (with high spatiotemporal resolution)
– Both single-unit activities and local field potential recording
– In-vivo experiments for freely moving or behaving animals
Electrical & Magnetic Stimulation (Conventional)
– Lacks selective neuromodulation (e.g. due to complex patterns of current flow
in electrical micro-stimulation)
Problem Definition (Cont…)
Optogenetics (Recent)
Combined genetics and optics
More selective modulation
Less instrumental interference
Technically scalable
Conventional Optogenetics:
Recording optically evoked signals is limited to individual electrodes adhesively
attached in parallel to optical fiber [12-16] (not integrated, inappropriate for chronic
experiments in freely moving animals)
Can only sample one recording site at a time as an optical fiber is mechanically
attached to an electrode [26]. ( local neural activity unknown)
Loose confinement of etched optical waveguide results in low spatial resolution
where multi-shank silicon probes combined with a bare optical fiber [9, 27].
Main ContributionDevelopment of Optrode-MEA to use in chronic in-vivo neural experiments of freely
moving animals for simultaneous optical stimulation and electrophysiological recording
Single localized optical fiber isintegrated to a commercial 6 x 6 MEAof each 1 mm long microelectrode .
Shape & Dimension of optrodematched with intracortical electrode.
Optrode is mechanically strongenough to penetrate through the duramatter.
Tapered ends of optical fiber areshaped to minimize neuronal damageduring insertion.
Optrode-MEA: Optical Electrode integrated with Micro-Electrode Array
Main Contribution (Cont…)
Capability of Optrode-MEA to optically modulate at one corticalsite while recording from an ensemble of neurons that define thelocal circuit in the vicinity of stimulus site.
Ability to control the excitation volume of brain by controlling theemitted optical power from optrode and its distribution within thebrain tissue.
Demonstrated successfully for potential use in future chronic in-vivo experiments for freely moving animals.
Some Results and Observation
Representative examples of light activation of LFP under a pulse train of
473 nm, 8 Hz and 20 ms pulse duration.
• Power spectrogram and power density plot of optically modulated LFP. Thepower is significantly enhanced at the light stimulation frequency and itsharmonics. (Left)
• LFP power around the pulse stimulation frequency as a function of estimatedlight intensity at the recording electrode site. (Right)
Some Results and Observation (Cont…)
Spatially and temporally resolved neuronal activities from a large cortical area
– The mapping of averaged (N = 100) spike waveforms on each input channel obtained from a sample recording session (Left).
– Pulse-triggered LFPs at various locations show both proximal and distal
field potential in response to the 1 ms pulse stimulation (Right).
Technical Evaluation
Design & fabrication of Optrode described clearly.
Verification of single optrode as in vivo electrophysiologicalrecording tool was demonstrated.
Experiments with two freely moving rats for up to 2 and 8 monthsrespectively to demonstrate successful use in chronic application.
Detail analysis of the experimental results with differentconditions proved the successful demonstration of such device.
Major Findings
Total volume of excitation decided primarily by the optical power
distribution
Different stimulation frequencies might give a new dimension
how the neural network actually responds to optogenetic
excitation.
Diversity in neural responses represents the complicated
dynamics of the photo-modulated cortical network.
No obvious signature of tissue-array interaction or damage found.
Strengths
• The design and fabrication of the device was described in detail
and clearly. The unique design of optrode to use it for in-vivo
chronic application in freely moving animals was also obvious.
• The experiment paradigms were also clearly described and
demonstrated
• The analysis made on the recorded signals relating to different
stimulations was
Strengths (Cont…)
• Allows monitoring of the spread of activity in a network of
neurons in response to the local stimulation.
• The capability of recording the full-spectrum neural signals
offers opportunity to study the dynamics of neuromudulation
by focusing on the power of particular frequency bands.
• The ability to control the excitation volume by controlling the
emitted light power and its distribution within the brain.
Weakness• The skull-anchored optrode-MEA might have less chance of stable
recording from the same single units in comparison with epi-cortical‘floating’ MEA [6]. Moreover, skull mounted device takes largeranatomical workspace.
• Correlation between neural activity and behaviour is not explicitlyunderstandable.
• A significant cortical depression was found to be present. The reasonfor such depression is still unclear.
Weakness (Cont…)
• How to handle the photo-induced artifacts for high scale
experiments is unclear.
• No point on the motion artifacts that could be severe for freely
moving animals.
• Not possible to accurate identification of current sinks and
sources over space and time as no. of recording channels is small
[7].
Conclusion
• Overall a nice presentation of the paper.
• New dimension of information for neural local circuit dynamics.
• Future work can be extension of stimulation sites and recording
channels to allow more neurons and a more global network to
study.
• Investigation with particular behavior/task can be incorporated to
study correlation of neural response with behavior or motor
function.
Thank you
Q&A