Beauchamp:Adaptation

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The goal of these experiments is to assess the effect on the LFP response to a stimulus when that stimulus is immediately preceded by an identical or similar stimulus.

Contents

Multiple-Repetitions Adaptation

Two stimulus categories: 20 selective stimuli (represented below by letters other than X) and 20 nonselective stimuli (represented by letter X)
Randomly inserted in each de-adapting block is the stop-sign stimulus. The patient's task is to press a button every time the stop-sign appears.
Design:
1) X X X X X X X X - de-adapting block
2) A A A A A A A A - Multiple-repetition adaptation
3) X X X X X X X X - de-adapting block
4) B C D E F G H I- Cross adaptation (8 different selective stimuli displayed in a row)
Repeat 20 times. Stimuli are randomized for each block.

Notes:
--Stimuli are shown at 2 Hz for 125 ms.
-- We expect the LFP to adapt most from the first to the second presentation.
Optional variants:
A B A B A B A B - Alternating Adaptation (2 different selective stimuli alternated back and forth)
A X A X A X A X - Time course of adaptation (Repetitions of a selective stimulus interleaved with nonselective (de-adapting) stimuli.
By varying the number of interleaved nonselective stimuli, we can assess how long it takes for the adaptive effect to disappear.

Identical-Stimulus

Stimuli: Two sets
1) adapting stimulus (A) – a high-response stimulus which we expect to demonstrate LFP adaptation
2) Intervening stimuli (X)– 15 unresponsive stimuli which de-adapt neurons

Design: Six-block modules
1) X X X X X X X – De-adaptation block
2) A A X X X X X– a direct repeat of A, and 5 intervening stimuli
3) X X X X X X X – De-adaptation block
4) A X X X X – Single-presentation of A serves as a control condition
5) X X X X X X X – De-adaptation block
6) A X X X X X A - A, five intervening stimuli, and another A

Miscellani
• 2 Hz stimulus presentation time – 500 ms ISI
• One run = 30 modules = 180 blocks
• 1 block = ~10 second; 1 run = 18 minutes
• One of the X stimuli is a stop-sign, and the patient is told to press a button every time a stop-sign appears

Within-Category

Stimuli: Two sets
1) adapting stimuli (A and B) – Two high-response stimulus in the selective category
2) Intervening stimuli (X)– 15 unresponsive stimuli which de-adapt neurons

Design: Twelve-block modules
1) X X X X X X X – De-adaptation block
2) A B X X X X X– A -> B, Quantifies adaptation effect of A on B
3) X X X X X X X – De-adaptation block
4) A X X X X X – Single-presentation of A serves as a control condition
5) X X X X X X X – De-adaptation block
6) A X X X X X B - Quantifies adaptation effect of A on B with 5 intervening trials
7) X X X X X X X – De-adaptation block
8) B A X X X X X– B -> A, Quantifies adaptation effect of B on A
9) X X X X X X X – De-adaptation block
10) B X X X X X – Single-presentation of B serves as a control condition
11) X X X X X X X – De-adaptation block
12) B X X X X X A - Quantifies adaptation effect of B on A with 5 intervening trials


Miscellani
• 1.3 Hz stimulus presentation time – 750 ms ISI
• One run = 30 modules = 360 blocks
• 1 block = ~10 seconds; 1 module = 2 minutes; 1 run = 60 minutes

Cross-modality

Display near-identical stimuli next to each other and calculate adaptation. Hypothesis: Adaptation willl occur if the stimulus feature which this area of cortex is encoding is the same for both stimuli.
Vary stimulus A along different axes: for example, A' is a negative of A
Stimuli: Two sets
1) adapting stimuli (A and A') – High-response stimulus and a somehow similar stimulus
2) Intervening stimuli (X) – 15 unresponsive stimuli which de-adapt neurons

Design: Four-block modules
1) X X X X X X X – De-adaptation block
2) A A' X X X X X– A adjacent to A'. Quantifies adaptation effect of A' on A
3) X X X X X X X – De-adaptation block
4) A X X X X X X – Single-presentation of A serves as a control condition
5) A' A X X X X X - A' adjacent to A. Quantifies adaptation effect of A' on A

[Back to Electrophysiology Protocol]

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