Standard Oddball Stimulus

Overview

The Standard Oddball stimulus is designed to investigate predictive coding and stimulus-specific adaptation in the visual cortex. The experiment presents a series of visual gratings where a "standard" stimulus is repeatedly shown, establishing sensory expectations, which are occasionally violated by "deviant" stimuli that differ in orientation, contrast, or temporal frequency.

Stimulus Structure

Standard Oddball Protocol

The figure above illustrates the three main components of the standard oddball protocol:

  1. Orientation Tuning Component: 16 different orientations (0°-337.5° in 22.5° steps) presented with regular 1-second intervals between stimuli.

  2. Standard-Oddball Component:

  3. Regular presentations of the standard stimulus (0° orientation)
  4. Occasional presentations of deviant stimuli:
    • Orientation deviants (45° and 90°)
    • Temporal frequency deviant (0 Hz, stationary)
    • Contrast deviant (blank screen)

  5. All with fixed, regular intervals between stimuli (creating a predictable rhythmic presentation)

  6. Receptive Field Mapping: Small, localized gratings presented at positions defined in the receptive field CSV file.

Script Location

The stimulus script is located at: - /code/stimulus-control/src/Standard_oddball_slap2.bonsai

Hardware Requirements

  • SLAP2 imaging system
  • Behavior device with encoder/wheel for tracking animal movement
  • Digital outputs (DO2) for synchronization with recording equipment

Stimulus Parameters

Basic Parameters

  • Display Type: Drifting gratings
  • Spatial Frequency: 0.04 cycles per degree
  • Temporal Frequency: 2 Hz (standard)
  • Contrast: 1.0 (full contrast)
  • Size: 360° (full-field gratings)
  • Stimulus Duration: 343 ms
  • Inter-stimulus Interval: 343 ms (configurable "Delay" parameter)

Configurable Parameters

The script contains several externalized parameters that can be adjusted: - NbBaselineGrating: Number of standard gratings (default: 20) - NbMismatchPerCondition: Number of repetitions for each deviant condition (default: 1) - NbReceptiveFieldRepeats: Number of repetitions for receptive field mapping (default: 1)

Experimental Design

1. Orientation Tuning Component

The experiment includes presentation of 16 different orientations: - 0°, 22.5°, 45°, 67.5°, 90°, 112.5°, 135°, 157.5° - 180°, 202.5°, 225°, 257.5°, 270°, 292.5°, 315°, 337.5°

These orientations are presented in randomized order to characterize orientation tuning of neurons.

2. Standard-Oddball Paradigm

The core of the experiment consists of:

  • Standard Stimulus: 0° orientation grating with 2 Hz temporal frequency (repeated ~20 times)
  • Deviant Stimuli:
    • Orientation deviants: 45° and 90° oriented gratings
    • Temporal frequency deviant: 0 Hz (stationary grating at 0° orientation)
    • Contrast deviant: 0 contrast (blank screen) with 2 Hz temporal frequency

Each deviant type violates a different expectation established by the standard stimulus: - Orientation deviants test orientation-specific adaptation - Temporal frequency deviant tests motion expectation - Contrast deviant tests luminance expectation

3. Receptive Field Mapping

The experiment includes a mapping component with smaller gratings (20° diameter) presented at locations defined in receptive_field.csv. These specialized mapping gratings have: - Higher spatial frequency (0.08 cpd) - Higher temporal frequency (4 Hz) - Higher contrast (0.8) - Shorter duration (250 ms) - No inter-stimulus interval (0 ms delay)

The receptive field mapping coordinates and orientations are loaded from the CSV file and randomized for each presentation sequence.

Data Collection

The script logs all stimulus parameters and timing information to CSV files: - orientations_logger.csv: Contains timing of stimulus events - orientations_orientations.csv: Records the parameters of each stimulus presentation

Animal running data is collected via an encoder on Port 2 of the behavior device.

Synchronization

  • TTL pulses (100ms) are generated at stimulus onset via DO2 output
  • SLAP2 recording is automatically started and stopped during the experiment

Running the Experiment

  1. Start the Bonsai workflow
  2. Press the spacebar to begin the experiment
  3. The experiment can be terminated with the End key

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