Motivation to pursue a goal is a fundamental driving force behind mundane but important behaviors. For example, I do laundry when I am motivated to achieve the goal of having clean clothes. Consequently, impaired motivation in patients with schizophrenia seriously impacts functional behaviors such as maintaining a job or relationship, and basic activities of daily living. Furthermore, impaired motivation can exacerbate cognitive deficits by rendering incentives to try to perform well less effective.
In a recent paper in Behavioral Neuroscience, Avlar and colleagues (2015) (PDF, 207KB)opens in new window investigated the relationship between motivation and cognitive deficits in a transgenetic line of mice that were created to model overexpression of dopamine receptors found in patients with schizophrenia. Mice had to press one of two response levers in response to short or long tones of varying duration to receive a reward (e.g., press left for short tones, right for long tones).
Transgenetic mice were impaired in this task relative to control mice in terms of both accuracy (ability to respond to exact cue durations) and precision (variability in temporal judgments), and were particularly impaired in classifying long tones.
Next, Avlar and colleagues investigated whether enhancing motivation molecularly, behaviorally, or pharmacologically could reduce these temporal judgment deficits.
First, motivation was manipulated molecularly by normalizing dopamine receptor expression. This led to accuracy that was comparable to control mice, but precision did not recover completely.
Second, motivation was manipulated behaviorally by varying reward magnitude. Doubling the reward magnitude for long tones led to improvements in accuracy and precision for control mice, but not transgenetic mice, who only showed improvements in precision. However, when reward was equalized for short and long tones in a final test phase after the doubled reward phase, transgenetic mice were even more impaired. This suggests that, like patients with schizophrenia, transgenetic mice were more sensitive to decreases versus increases in reward.
Finally, motivation was manipulated pharmacologically by administering a drug that is known to produce global changes in motivation. This drug led to improvements in both accuracy and precision in transgenetic mice.
Thus, the pharmacological intervention was most effective at reducing temporal judgment deficits in transgenetic mice, suggesting that cognitive deficits in patients with schizophrenia may be alleviated using pharmacological strategies that increase motivation. Moreover, the authors speculate that the relationships between motivation and cognitive performance observed in their experiments were due to the impact of motivation on working memory updating and/or capacity.
Because working memory is an integral part of functional behaviors across a broad range of activities, pharmacological interventions that target general motivation could have a profound effect on quality of life in patient populations.
Citation:
Avlar, B., Kahn, J. B., Jensen, G., Kandel, E. R., Simpson, E. H., & Balsam, P. D. (2015). Improving temporal cognition by enhancing motivation. Behavioral Neuroscience, 129(5), 576–588. https://dx.doi.org/10.1037/bne0000083
Note: This article is in the Neuroscience & Cognition topic area. View more articles in the Neuroscience & Cognition topic area.