Beauchamp:Old Protocols

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July Subjects Plan

7/7/2008 PRE-GAME
1. Identify potential electrodes with combined fMRI/CT
2. Create log file on log computer
3. Identify which channels have been assigned to set A and B
4. Record resting activity to make sure system is working

Microelectrode array experiments
If the new electrodes are ready, it will be a top priority to investigate their properties. A good start will be to compare small electrode LFPs with nearby big electrode LFPs.

A. Recording:

1) Are small electrodes more selective than big electrodes? e.g. if an electrode likes faces, does a small electrode respond to fewer faces than a big electrode?

2) Is response amplitude/latency to a preferred stimulus any different?
Probably not, but we may have to adjust the pre-amp or amplifier settings.

3) Receptive Field Size
do small electrodes have smaller RFs than big electrodes?

4) Gamma oscillation
Are oscillations in the gamma band more correlated among nearby electrodes than far electrodes?

B. Stimulation
If would be really interesting to compare perception thresholds. We might predict thresholds would be lower with small electrodes because of high current density.
If the RFs are more selective (#1 above) then we might evoke percept with a small electrodes (because we are stimulating neurons with similar selectivity) where we could not with a big electrode.

Regular electrode experiments
0) Stimulate the big electrodes overlying visually responsive/identified areas.
1) General Selectivity – 10 minutes

• 80 stimuli, 20 blocks

• One-back task (patient reports repetitions of images)

--Identify selective electrodes
--Choose selective category
2) "Stop-sign" Repeat Adaptation – 10 minutes

• 20 selective stimuli, 20 nonselective stimuli, 20 blocks

• Stop-sign task (patient reports stop-signs)

• Need to code a modified version of the current Selectivity plugin to satisfy these conditions:

1. the patient is supposed to press the button after stop-signs instead of after repeats

2. Selective stimuli are directly repeated every 8-12 images

3. The stimulus preceding the repeat is always a nonselective stimulus

3) "One-back" Repeat Adaptation – 10 minutes

• 20 stims from selective category, 5 stims from each nonselective category

• One-back task

• 2 Hz presentation rate

• Get enough trials such that we can measure choice probability

• Need the plugin to be modified such that:

1. Selective stimuli are directly repeated every 8-12 images

2. The stimulus preceding the repeat is always a nonselective stimulus

4) "One-back" Cross Adaptation – 10 minutes

• 20 stims from selective category, 5 stims from each nonselective category

• Altered one-back task - subject is told to respond to two selective-category stimuli in a row

5) Multiple-repetitions adaptation - 5 minutes

• 20 selective stimuli, 20 nonselective stimuli, 2 Hz presentation, patient is told to press button when he/she sees the stopsign.

• 8 nonselective stimuli (including stop-sign), 8 presentations of the same selective stimulus, 8 nonselective stimuli (w/ stopsign), 8 different selective stimuli.

6) "Stop-Sign" Adaptation – 20 minutes

• Adapting stimuli A and B

• 20 blocks -> 20 direct repeats

• 2 Hz presentation rate

• 8-12 intervening stimuli

Subject AC Electrophysiology Protocol

Setup
• Identify at least 16 electrodes of interest using the combined fMRI functional map and CAT scan.
[Images here]
• Create log file AC[birthday].doc on log computer
• Identify which channels ITC has assigned electrodes set A and B to
• Record resting activity to make sure system is working

Day 1 Experiment Lineup (5/1/08)
1) General Selectivity – 5 minutes

• 80 stimuli, 20 blocks

• One-back task

--Identify selective electrodes
--Choose selective category

2) "One-Back" Selectivity – 5 minutes

• 20 stims from selective category, 5 stims from each nonselective category

• One-back task

3) Receptive Field Mapping with preferred stimulus – 10 minutes

• Homogenized stimuli are 400x400 pixels, and are shown at 25 degrees of the visual field in selectivity plugin. We want the stimulus to be large enough to recogize whilst small enough such that we can draw a high-resolution receptive field map and compare it to RFs from other brain areas. As a reference, the color paper's RF mapping used a colored square that was 1/11 of the screen's width. We did a run with RG that was -10 to 10 azimuth and elevation in spatial extent, with 11 x 11 locations, and 5 x 5 degree stimuli. Let's use this as our standard.

3b) Receptive Field Mapping with other category's stimulus - 15 minutes

• Choose another preferred stimulus, if possible from a different category, and map the receptive field.

• Prediction: if a different category, RF may be different (more foveal for faces, more peripheral for houses)

--Choose adapting stimuli A and B: two highly responsive stimuli
--Choose 15 intervening stimuli - from non-test categories
4) Direct-Repeat Adaptation – 18 minutes

• Adapting stimulus A

• 20 blocks -> 20 direct repeats

5) Direct-Repeat Adaptation – 18 minutes

• Adapting stimulus B br>

• 20 blocks -> 20 direct repeats

--Finished at 5:20 pm

Day 2 Experiment Lineup (5/2/08)
1) "Stop-Sign" Selectivity – 8 minutes

• 20 stims from selective category, 5 stims from each nonselective category

• Stop-sign task – Same plugin, just tell patient to press button when he sees the stopsign

2) Direct-Repeat Adaptation – 18 minutes

• Adapting stimulus C

• 20 blocks -> 20 direct repeats

3) Within-Category Adaptation – 30 minutes

• Adapting stimuli A and B

• 30 adapting stimulus pairs → 360 blocks

Day 3 Experiment Lineup (5/3/08)
1) Direct-Repeat Adaptation – 18 minutes

• Adapting stimulus A

• 0.8 Hz presentation time to ensure that LFP has returned to baseline before the repeat appears

• 20 blocks -> 20 direct repeats

2) Choice Probability - 15 minutes

• Take two stimuli which elicit responses from two different electrodes. Overlay them in a series of images, with varied contrasts of each image. Use these images in the selectivity task.

3) Within-Category Adaptation – 30 minutes

• Adapting stimuli A and B

• 20 blocks -> 20 direct repeats/ 20 category-repeats

If we have extra time:

• If an electrode has very fine selectivity, create stimuli to explore its tuning -- the selective object from different angles, colors, etc.

• Continue RF mapping for a finer map by making the spatial extent and stimulus spacing smaller. Keep the size of the stimulus the same so as not to degrade its recognizability.

• If we have a broadly selective electrode, we can try RF-mapping stimuli from different categories.

• "Scrambled Selectivity" - Pick out a preferred and non-preferred stimulus and make scrambled versions of them at different levels of coherence. Show them at random in the stop-sign task and see if the average response correlated with the amount of image coherence.

• Repeat the above experiments using another electrode's selectivity

• Multiple presentations of same stimulus:

Use object selectivity plug-in, and only choose stimulus A.

Show the stimulus 10 times in a row, Stop and save.

Use object selectivity plugin with 10 non-selective stims to de-adapt.

Alternate 5 times

• Repeat experiment 4 and 7 with other stimuli

• Repeat experiments 2 and 6 to gather more data

• Ryan Ash 12:50, 21 April 2008 (EDT):