Optogenetics (PulsePal)
Overview
The ConductMaze optogenetics module interfaces with the Sanworks PulsePal v2 pulse generator to deliver precisely timed optical stimulation synchronized to behavioral events. PulsePal is a USB-connected 4-channel parametric pulse generator that drives laser diodes or LED fiber-optic systems with microsecond temporal precision. ConductMaze communicates with PulsePal through the IExternalAdapter interface, sending trigger commands that initiate pre-programmed pulse trains on any combination of the four output channels.
Stimulation parameters — pulse frequency, pulse width, train duration, inter-train interval, and voltage amplitude — are configured in ConductMaze's protocol editor and downloaded to PulsePal at session start. During the experiment, ConductMaze triggers stimulation in response to behavioral events: a lever press can initiate a 20 Hz, 5 ms pulse train for 1 second; entering a spatial zone can activate continuous stimulation; completing a trial can trigger a brief identification pulse. Each trigger event is logged with its exact timestamp, behavioral context, and stimulation channel for post-hoc analysis.
The system supports both event-triggered (reactive) and schedule-triggered (proactive) stimulation paradigms. In event-triggered mode, the animal's behavior determines when light is delivered — ideal for studying the causal role of neural circuits in specific behavioral actions. In schedule-triggered mode, stimulation follows a predetermined temporal pattern independent of behavior — suitable for studying how circuit activation modulates overall behavioral output. Both modes can be combined within a single session for within-subject comparison.
Trial Flow
Configure PulsePal
Set pulse frequency, width, train duration, voltage on each of 4 output channels
USB Connect
ConductMaze establishes USB serial connection to PulsePal v2
Upload Parameters
Download stimulation program to PulsePal hardware registers
Start Behavioral Session
Begin protocol with stimulation triggers armed
Behavioral Trigger
Animal performs triggering action (lever press, zone entry, trial phase)
Evaluate Trigger Rule
Check if event matches stimulation trigger criteria and refractory period has elapsed
Fire PulsePal
SendMessage command triggers pulse train on designated output channel(s)
Log Stimulation
Record trigger time, channel, parameters, and behavioral context
Session End
Disarm triggers, disconnect PulsePal, export stimulation log
Parameters
| Parameter | Type | Default | Description |
|---|---|---|---|
| Pulse Frequency | float | 20 | Stimulation frequency in Hz (1–1000 Hz range) |
| Pulse Width | seconds | 0.005 | Duration of each light pulse in seconds (typically 5–20 ms) |
| Train Duration | seconds | 1.0 | Duration of each stimulation train |
| Inter-Train Interval | seconds | 5.0 | Minimum time between consecutive stimulation trains (refractory period) |
| Voltage Amplitude | float | 5.0 | Output voltage amplitude in volts (0–10 V, drives laser/LED driver) |
| Active Channels | enum | Channel 1 | PulsePal output channels to activate (Channel 1–4, or multiple) |
| Trigger Mode | enum | Event-Triggered | Stimulation mode: Event-Triggered (by behavior), Schedule-Triggered (by time), or Both |
| Trigger Event | enum | Lever Press | Behavioral event that triggers stimulation (Lever Press, Zone Entry, CS Onset, Trial Start, Custom) |
Metrics
| Metric | Unit | Description |
|---|---|---|
| Total Stimulations | count | Total number of pulse trains delivered during the session |
| Total Light-On Time | seconds | Cumulative duration of optical stimulation across all trains |
| Mean Trigger Latency | ms | Average delay between behavioral trigger event and PulsePal output onset |
| Stimulations per Phase | count | Number of stimulation trains delivered in each protocol phase (baseline, stimulation, recovery) |
| Behavioral Effect Index | ratio | Ratio of behavioral output during stimulation vs non-stimulation periods |
| Refractory Violations | count | Number of trigger events that occurred during refractory period and were suppressed |
Sample Data
| Trial | Event_Time_s | Trigger_Event | Channel | Freq_Hz | Train_Dur_s | Stim_Delivered |
|---|
Representative data for illustration purposes. Actual values will vary by species, strain, and experimental conditions.
Applications
- 1Circuit-specific reinforcement — activate VTA dopamine neurons on lever press to study the sufficiency of circuit activation for reward learning
- 2Anxiety circuit dissection — inhibit BLA→CeA projections during elevated plus maze open arm exploration to test anxiolytic effects
- 3Memory consolidation — deliver hippocampal stimulation during the post-training consolidation window in fear conditioning
- 4Real-time place preference — create an optogenetic real-time place preference by triggering stimulation in one CPP compartment
- 5Motor circuit mapping — activate motor cortex during rotarod or skilled reaching to study circuit contributions to coordinated movement
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