Both response effort and current intensity affect self-stimulation train duration thresholds

Area of Science:

• Neuroscience
• Behavioral Neuroscience
• Psychology

Background:

• Self-stimulation thresholds are commonly used to assess brain stimulation reward (BSR).
• These measures assume independence from performance factors, an assumption rarely tested.
• The influence of performance variables on BSR thresholds requires explicit investigation.

Purpose of the Study:

• To investigate the combined effects of response effort and current intensity on self-stimulation thresholds.
• To determine if performance variables significantly alter BSR threshold measurements.
• To assess the relative contribution of reward intensity versus performance effort on threshold determination.

Main Methods:

• Factorial combination of three stimulation current levels and three lever weightings (response effort).
• Determination of train duration thresholds, defined as 50% of maximum response rates, for each condition.
• Analysis of how changes in current intensity and response effort impact self-stimulation thresholds.

Main Results:

• Both current intensity and response effort significantly shifted train duration thresholds.
• The magnitude of shifts caused by current intensity and response effort were approximately equal.
• Self-stimulation response functions were similarly affected by reward and performance manipulations.

Conclusions:

• Caution is advised when interpreting self-stimulation threshold data for BSR measurement.
• Performance factors, such as response effort, can significantly confound BSR threshold interpretations.
• Thresholds may not solely reflect reward value but also the cost of performance.