Cognitive impairment during 5 m water immersion

Abstract

Experimental data document that human cognition remains intact down to 6 m water immersion. This, however, is difficult to reconcile with introspective observations from experienced divers, who report cognitive impairments. We hypothesized that the discrepancy might be related to the fact that previous experiments assessed abstract cognitive skills, such as mental arithmetic, which might be less sensitive to immersion than performance-related cognitive skills, such as planning of behavior that is adequate for a given situation. Moreover, previous studies did not control for the effects of water viscosity on subjects' response times. To address these issues, the present study evaluated performance-related cognitive skills based on subjects' isometric responses. Forty-eight subjects were tested in 5 m under water and on dry land using multiple choice reaction tasks, a tracking task, and a combination of both. Sustained attention was also registered, and subjective workload was assessed by questionnaire. We found that a subject's cognitive performance was degraded under water by 9%, independent of task type and equally under single- and dual-task conditions. Sustained attention was reduced under water by 11% and tracking by 48%. The observed deficits were not correlated, which suggests multiple independent effects of immersion. Our findings support the hypothesis that performance-related cognitive skills are affected already by shallow-water immersion. Since no such deficits were observed in a companion study just below the water's surface, the present findings are probably due to increased ambient pressure.

Executive Functions of Divers Are Selectively Impaired at 20-Meter Water Depth

“…Generally, our findings agree with observations that cognitive performance deteriorates in water depth shallower than the usually accepted nitrogen narcosis threshold of 4 ATA (Poulton et al, 1964; Petri, 2003; Dalecki et al, 2012, 2013). Because those observations with respect to our study were either detected with specific tests measured with a computer in the pressure chamber (Petri, 2003) or with a computer in shallow water immersion (i.e., 5 m) (Dalecki et al, 2012, 2013), the necessity for investigating cognitive functions in real water immersion in combination with sensitive and specific computer-based tests is confirmed.…”

“…Because those observations with respect to our study were either detected with specific tests measured with a computer in the pressure chamber (Petri, 2003) or with a computer in shallow water immersion (i.e., 5 m) (Dalecki et al, 2012, 2013), the necessity for investigating cognitive functions in real water immersion in combination with sensitive and specific computer-based tests is confirmed. However, it should also be noted that only two out of the three tested cognitive domains were influenced by 20-m, which suggests that central parts of the cognitive control system retained their full functionality.…”

“…Baddeley, 2000; Freiberger et al, 2016; Lafere et al, 2016), little attention has been paid to shallower water depths (Petri, 2003), i.e., pressure less or equal than 4–5 absolute atmosphere pressure (ATA; 1 ATA corresponds to 760 mmHg or to 1.01325 bar), which is commonly thought as the critical threshold to clearly identify nitrogen narcosis (Braubakk and Neuman, 2003; Clark, 2015). More specifically, detrimental effects on cognition and psychomotor performance, measured by a computer, as well as by means of objective measures of brain cortical arousal, have been detected already at 1.5–5 ATA in the hyperbaric chamber and in real-water immersion (Poulton et al, 1964; Petri, 2003; Balestra et al, 2012; Dalecki et al, 2012, 2013; Freiberger et al, 2016; Lafere et al, 2016; Germonpré et al, 2017), and changes in brain cortical arousal were even reported to be present 30-min after surfacing (Balestra et al, 2012; Lafere et al, 2016; Germonpré et al, 2017) Other reports suggest that a considerable amount of human performance decrements during diving might be attributed to open-water situations (Nevo and Breitstein, 1999; Baddeley, 2000). However, shallow-water immersion in controlled test conditions (i.e., not in open water) affects human cognitive processing (e.g., psychomotor speed and mental rotation ability) even when psychological factors (e.g., anxiety and mood) are eliminated as possible biasing factors (Dalecki et al, 2012, 2013).…”

Sensorimotor performance and haptic support in simulated weightlessness

“…Nitrogen narcosis is known to degrade cognitive function, but this effect occurs in depths beneath 15-30 m (Abraini 1997). Yet, response slowing during reaction tasks has been documented even for shallow water immersion in 5 m depth (Dalecki et al 2012a) and have been attributed to the higher ambient pressure. In the current study, however, there was no general slowing of responses, they solely occurred when higher resistive forces were activated, and subjective ratings of workload also did not indicate a general impairment during water immersion.…”

Motor imagery: lessons learned in movement science might be applicable for spaceflight

“…Mental practice could be applied to prepare astronauts not only for the sudden onset of gravity upon landing, but also to the sudden absence of gravity after launch. Presently, this preparation is limited to parabolic flights—which offer only brief periods of weightlessness that alternate with periods of hypergravity, and to water immersion—which introduces confounding factors such as viscosity, slight nitrogen narcosis (Dalecki et al, 2012 ) and persistence of normal vestibular inputs. Mental practice could offer an expedient alternative or supplement to those established methods.…”