Effects of hyperbaric nitrogen-induced narcosis on response-selection processes

Abstract

Certain underwater circumstances carry risk of inert gas narcosis. Impairment of sensorimotor information processing due to narcosis, induced by normobaric nitrous oxide or high partial nitrogen pressure, has been broadly evidenced, by a lengthening of the reaction time (RT). However, the locus of this effect remains a matter of debate. We examined whether inert gas narcosis affects the response-selection stage of sensorimotor information processing. We compared an air normobaric condition with a hyperbaric condition in which 10 subjects were subjected to 6 absolute atmospheres of 8.33% O₂ Nitrox. In both conditions, subjects performed a between-hand choice-RT task in which we explicitly manipulated the stimulus–response association rule. The effect of this manipulation (which is supposed to affect response-selection processes) was modified by inert gas narcosis. It is concluded, therefore, that response selection processes are among the loci involved in the effect of inert gas narcosis on information processing.

Abstract

Practitioner Summary: Does inert gas narcosis affect the response-selection stage of sensorimotor-information processing? Subjects performed a RT task in which response-selection processes were explicitly manipulated. The well-known ‘compatibility’ effect was modified by inert gas narcosis compared with control condition: response-selection processes are among the loci involved in the effect of inert gas narcosis on information processing.

Keywords::

• inert gas narcosis
• reaction time
• response selection
• nitrogen
• humans

Acknowledgements

This study was made possible, thanks to the crew and the hyperbaric facilities of CEPHISMER in Toulon (Cellule Plongée Humaine Intervention Sous la Mer).

Notes

^1. It is only when no systematic rule can be applied to associate a stimulus to a response (e.g. associate a given colour to a given finger) that the response-selection stage is sensitive to the number of choices. This is because, in this case, response selection must be performed by a memory-list scanning operation (Hasbroucq et al. 1990) and the longer the list of the possible S–R pairs, the longer the response selection.

^2. The joint effect of the factors pressure and mapping being smaller than the sum of the effect of these factors administered separately.

^3. The joint effect of the factors pressure and mapping being larger than the sum of the effect of these factors administered separately.