Scanner Pulse Recorder Component

The Scanner Pulse Recorder is a specialized global component designed for fMRI hyperscanning experiments. It continuously records scanner TR (repetition time) pulses throughout an experiment, enabling precise synchronization between brain imaging data and experimental paradigms.

Key Features

• Continuous recording of scanner TR pulses (keyboard triggers)
• Automatic detection of TriggerComponent transitions
• Pre-trigger and post-trigger pulse tracking
• Configurable trigger key (default: '5' from Current Designs interface)
• Invisible operation (no visual UI to distract participants)
• Precise timestamps for each pulse

When to Use

Use the Scanner Pulse Recorder when you need to:

• Synchronize fMRI brain data with experimental timing
• Track the number of TR volumes before and after experiment start
• Record continuous scanner pulses in hyperscanning setups
• Align multi-participant fMRI data with experimental paradigms

Hardware Requirements

Typical fMRI Setup

1. Scanner: Siemens 3T Prisma (or similar) configured to send TTL trigger at each TR
2. Interface: Current Designs 932 (or fORP) converts TTL signals to keyboard presses
3. Trigger Key: Usually '5' key (configurable)

The scanner sends a pulse at every TR (volume acquisition), and the interface converts these to keyboard events that HyperStudy can capture.

Configuration

Basic Settings

Setting	Description	Default
Trigger Key	Keyboard key to listen for	5
Record Post-Trigger	Continue recording after TriggerComponent completes	true

Configuration Example

{
  "globalComponents": {
    "scanner-pulse-recorder": {
      "type": "scannerpulserecorder",
      "enabled": true,
      "config": {
        "triggerKey": "5",
        "recordPostTrigger": true
      }
    }
  }
}

How It Works

Experiment Flow

1. Experiment starts - Scanner Pulse Recorder begins listening for trigger key
2. Scanner starts - Pulses begin arriving (recorded as pre_trigger phase)
3. TriggerComponent completes - Component detects this transition automatically
4. Experiment continues - Pulses recorded as post_trigger phase (if enabled)
5. Experiment ends - Recording stops

Automatic Trigger Detection

The component automatically detects when a TriggerComponent completes by monitoring state transitions. This works regardless of where the TriggerComponent is positioned in your experiment sequence.

For example, if your experiment has:

• State 0: Instructions
• State 1: TriggerComponent (waiting for scanner)
• State 2: Video stimulus

The Scanner Pulse Recorder will correctly identify the transition from State 1 to State 2 as the trigger completion point.

Data Collection

Event Structure

Each pulse is recorded with the following data:

Field	Type	Description
eventType	string	'scanner_pulse'
pulseNumber	number	Sequential count (1, 2, 3...)
experimentPhase	string	'pre_trigger', 'post_trigger', or 'complete'
timeSinceFirstPulse	number	Milliseconds since first pulse detected
timeSinceTrigger	number	Milliseconds since TriggerComponent completed (null if pre-trigger)
preTriggerPulseCount	number	Total pulses before TriggerComponent completed
stateIndex	number	Current experiment state index
timestamp	string	ISO timestamp of the pulse

Example Data

{
  "eventType": "scanner_pulse",
  "category": "scanner",
  "componentId": "scanner-pulse-recorder",
  "componentType": "scannerpulserecorder",
  "data": {
    "key": "5",
    "pulseNumber": 15,
    "experimentPhase": "post_trigger",
    "timeSinceFirstPulse": 28000,
    "timeSinceTrigger": 5000,
    "preTriggerPulseCount": 10,
    "stateIndex": 2
  },
  "metadata": {
    "participantId": "participant-123",
    "roomId": "room-456",
    "experimentId": "fmri-study-1",
    "stateId": "video-stimulus"
  },
  "timestamp": "2024-01-15T10:30:15.000Z"
}

Phase Definitions

Phase	Description
pre_trigger	Pulses received while TriggerComponent is active (waiting for scanner)
post_trigger	Pulses received after TriggerComponent completes
complete	Pulses received after experiment marked complete

Use Cases

Hyperscanning fMRI Synchronization

In a two-participant fMRI hyperscanning study:

1. Both participants are in separate scanners
2. Each participant's computer has a Scanner Pulse Recorder
3. Experiment waits for both participants' scanners to trigger
4. Each recorder tracks its own scanner's pulses independently
5. Post-hoc analysis aligns brain data using pulse counts

Single-Participant fMRI

For single-participant studies:

1. Record pre-trigger pulses to know scanner warm-up time
2. Use pulse count to align brain volumes with experimental events
3. Export data for integration with neuroimaging analysis pipelines

Integration with TriggerComponent

The Scanner Pulse Recorder is designed to work alongside the Trigger Component. A typical fMRI experiment setup:

1. TriggerComponent (focus component): Waits for initial scanner trigger to start experiment
2. Scanner Pulse Recorder (global component): Continuously records all pulses

Both components listen for the same key ('5'), but serve different purposes:

• TriggerComponent advances the experiment state
• Scanner Pulse Recorder records timing data

Time-locking External Equipment

The TriggerComponent supports Send TTL on Receive - when the scanner trigger is received, it can automatically send a TTL pulse to external psychophysiology equipment (EDA, ECG, eye tracker, etc.). This time-locks all equipment with a single trigger:

{
  "states": [
    {
      "id": "wait-for-scanner",
      "focusComponent": {
        "type": "trigger",
        "config": {
          "mode": "receive",
          "expectedKey": "5",
          "sendTTLOnReceive": true
        }
      }
    }
  ],
  "globalComponents": {
    "scanner-pulse-recorder": {
      "type": "scannerpulserecorder",
      "enabled": true,
      "config": {
        "triggerKey": "5"
      }
    }
  }
}

This configuration will:

1. Wait for scanner '5' trigger
2. Send TTL to external equipment via HyperStudy Bridge
3. Record all TR pulses throughout the experiment

Best Practices

Experiment Design

1. Use with TriggerComponent: Place a TriggerComponent as the first state for synchronized start
2. Enable recordPostTrigger: Usually keep this enabled for complete TR tracking
3. Test before scanning: Verify pulse detection works with your hardware setup

Data Analysis

1. Pre-trigger count: Use preTriggerPulseCount to calculate scanner-to-experiment delay
2. Volume alignment: Each pulse corresponds to one TR (brain volume)
3. Multi-participant alignment: Compare timeSinceFirstPulse across participants

Hardware Setup

1. Verify trigger key: Confirm your interface sends '5' (or configure accordingly)
2. Test connection: Use a text editor to verify key presses are received
3. Check for latency: Ensure no significant delay between scanner and computer

Troubleshooting

Issue	Solution
No pulses recorded	Verify trigger key matches interface output; check cable connections
Wrong trigger key	Update triggerKey in config to match your interface
Missing pre-trigger pulses	Ensure Scanner Pulse Recorder is enabled before TriggerComponent
Pulses stop after trigger	Check that recordPostTrigger is true

Related Components

• TriggerComponent: For experiment state synchronization
• Continuous Rating: For real-time subjective ratings during scanning
• Video Component: For synchronized stimulus presentation