On balance: weighing harms and benefits in fundamental neurological research using nonhuman primates

One of the most controversial areas of animal research is the use of nonhuman primates for fundamental research. At the centre of the controversy is the question of whether the benefits of research outweigh the harms. We argue that the evaluation of harms and benefits is highly problematic. We describe some common procedures in neurological research using nonhuman primates and the difficulties in evaluating the harm involved. Even if the harm could be quantified, it is unlikely that it could be meaningfully aggregated over different procedures, let alone different animals. A similar problem arises for evaluating benefits. It is not clear how benefits could be quantified, and even if they could be, values for different aspects of expected benefits cannot be simply added up. Sorting harms and benefits in three or four categories cannot avoid the charge of arbitrariness and runs the risk of imposing its structure on the moral decision. The metaphor of weighing or balancing harms and benefits is inappropriate for the moral decision about whether to use nonhuman primates for research. Arguing that the harms and benefits in this context are incommensurable, we suggest describing the moral consideration of harms and benefits as a coherent trade-off. Such a decision does not require commensurability. It must be well-informed about the suffering involved and the potential benefits, it must be consistent with the legal, regulatory and institutional framework within which it is made, and it must cohere with other judgments in relevant areas.

Ethograms indicate stable well-being during prolonged training phases in rhesus monkeys used in neurophysiological research

Awake, behaving rhesus monkeys are widely used in neurophysiological research. Neural signals are typically measured from monkeys trained with operant conditioning techniques to perform a variety of behavioral tasks in exchange for rewards. Over the past years, monkeys' psychological well-being during experimentation has become an increasingly important concern. We suggest objective criteria to explore whether training sessions during which the monkeys work under controlled water intake over many days might affect their behavior. With that aim, we analyzed a broad range of species-specific behaviors over several months ('ethogram') and used these ethograms as a proxy for the monkeys' well-being. Our results show that monkeys' behavior during training sessions is unaffected by the duration of training-free days in-between. Independently of the number of training-free days (two or nine days) with ad libitum food and water supply, the monkeys were equally active and alert in their home group cages during training phases. This indicates that the monkeys were well habituated to prolonged working schedules and that their well-being was stably ensured during the training sessions.

Stimulation of the nucleus accumbens as behavioral reward in awake behaving monkeys

It has been known that monkeys will repeatedly press a bar for electrical stimulation in several different brain structures. We explored the possibility of using electrical stimulation in one such structure, the nucleus accumbens, as a substitute for liquid reward in animals performing a complex task, namely visual search. The animals had full access to water in the cage at all times on days when stimulation was used to motivate them. Electrical stimulation was delivered bilaterally at mirror locations in and around the accumbens, and the animals' motivation to work for electrical stimulation was quantified by the number of trials they performed correctly per unit of time. Acute mapping revealed that stimulation over a large area successfully supported behavioral performance during the task. Performance improved with increasing currents until it reached an asymptotic, theoretically maximal level. Moreover, stimulation with chronically implanted electrodes showed that an animal's motivation to work for electrical stimulation was at least equivalent to, and often better than, when it worked for liquid reward while on water control. These results suggest that electrical stimulation in the accumbens is a viable method of reward in complex tasks. Because this method of reward does not necessitate control over water or food intake, it may offer an alternative to the traditional liquid or food rewards in monkeys, depending on the goals and requirements of the particular research project.