Trigger Component

The Trigger component enables hardware synchronization for experiments, particularly useful for neuroimaging studies (fMRI, EEG) and psychophysiology research. It can either send triggers to external equipment or wait to receive triggers from external devices like MRI scanners.

Key Features

• Send Mode: Send keyboard or TTL triggers to external equipment
• Receive Mode: Wait for triggers from external devices (e.g., MRI scanner)
• TTL Output on Receive: Send TTL to external equipment when receiving a trigger
• Synchronized Broadcast: Coordinate triggers across multiple participants
• HyperStudy Bridge Integration: USB TTL output via bridge application

When to Use

Use the Trigger component when you need to:

• Synchronize experiment start with MRI scanner
• Send TTL pulses to psychophysiology equipment (EDA, ECG, eye tracker)
• Coordinate experiment timing across multiple participants
• Time-lock multiple pieces of equipment together

Modes of Operation

Send Mode

In send mode, the component sends a trigger when activated:

• Keyboard: Participant presses a key to send trigger
• TTL: Automatically sends TTL pulse via HyperStudy Bridge

Receive Mode

In receive mode, the component waits for an external trigger:

• Listens for a specific keyboard key (e.g., '5' from MRI scanner)
• Optionally sends TTL to external equipment when trigger is received
• Can coordinate with other participants via synchronized broadcast

Configuration

Basic Settings

Setting	Description	Default
Mode	send or receive	send
Trigger Type	keyboard or ttl (send mode only)	keyboard
Trigger Key	Key to send (send mode, keyboard)	t
Expected Key	Key to wait for (receive mode)	5
Show Instructions	Display instructions to participant	true
Instructions	Custom instruction text	(auto-generated)

TTL Output on Receive

Setting	Description	Default
Send TTL on Receive	Send TTL pulse when trigger is received	false

When enabled, receiving a trigger (e.g., '5' from MRI scanner) will automatically send a TTL pulse via the HyperStudy Bridge. This is useful for time-locking external psychophysiology equipment with the scanner trigger.

Synchronized Broadcast (Multi-participant)

Setting	Description	Default
Enable Synchronized Broadcast	Wait for all participants before proceeding	false
Broadcast Roles	Which roles to include (empty = all)	[]

Appearance

Setting	Description	Default
Background Color	Component background	#1c1c1c
Text Color	Text color	#ffffff

Use Cases

fMRI Experiment Start

Wait for scanner trigger to start experiment:

Mode: receive
Expected Key: 5
Instructions: "Waiting for scanner..."

fMRI with Psychophysiology Time-locking

Wait for scanner and simultaneously trigger external equipment:

Mode: receive
Expected Key: 5
Send TTL on Receive: true
Instructions: "Waiting for scanner..."

When the scanner sends '5', the component will:

1. Log the received trigger
2. Send TTL pulse to external equipment via HyperStudy Bridge
3. Complete and advance to next state

Multi-participant Synchronization

Coordinate experiment start across participants:

Mode: receive
Expected Key: 5
Enable Synchronized Broadcast: true
Broadcast Roles: [] (all roles)

All participants must receive their scanner trigger before any proceed.

Manual TTL Send

Send TTL pulse on participant action:

Mode: send
Trigger Type: ttl
Instructions: "Preparing to send trigger..."

Hardware Requirements

For TTL Output

1. HyperStudy Bridge: Desktop application for USB communication
2. TTL Device: RP2040-based device (e.g., Adafruit) connected via USB
3. Connection: TTL device connected to external equipment

For Scanner Input

1. Scanner Interface: Current Designs 932 or similar fORP device
2. Configuration: Interface set to output '5' key on trigger
3. Connection: Interface connected to participant computer via USB

Data Collection

Events Recorded

Event	Description
trigger (sent)	Trigger was sent (keyboard or TTL)
trigger (received)	Trigger was received from external device
trigger (sent, TTL on receive)	TTL sent in response to received trigger

Example Event Data

{
  "eventType": "trigger",
  "category": "component",
  "componentId": "scanner-trigger",
  "data": {
    "action": "received",
    "triggerType": "keyboard",
    "triggerValue": "5"
  },
  "metadata": {
    "participantId": "participant-123",
    "roomId": "room-456",
    "stateId": "wait-for-scanner"
  },
  "timestamp": "2024-01-15T10:30:00.000Z"
}

Integration with Scanner Pulse Recorder

For fMRI experiments, use the Trigger component together with the Scanner Pulse Recorder:

1. TriggerComponent (focus component): Waits for initial scanner trigger
2. Scanner Pulse Recorder (global component): Counts all TR pulses

This combination provides:

• Synchronized experiment start
• Pre-trigger pulse count (scanner warm-up time)
• Post-trigger pulse tracking (for brain data alignment)

Troubleshooting

Issue	Solution
Trigger not detected	Verify expected key matches interface output
TTL not sending	Check HyperStudy Bridge connection and device
Synchronized broadcast timeout	Ensure all participants' scanners are ready
Bridge disconnected error	Restart HyperStudy Bridge application

Best Practices

1. Test before scanning: Verify trigger detection with your specific hardware
2. Use receive mode for fMRI: Let the scanner control experiment timing
3. Enable TTL on receive: Time-lock all equipment with a single trigger
4. Combine with Scanner Pulse Recorder: Track all TR pulses for data alignment
5. Clear instructions: Help participants understand what's happening

Related Components

• Scanner Pulse Recorder - Continuous TR pulse recording
• Video Component - Synchronized stimulus presentation