Impairment from gas narcosis when breathing air and enriched air nitrox underwater.

BACKGROUND: Nitrogen (N2) in air causes cognitive impairment from gas narcosis when breathed at increased ambient pressures. This impairment might be reduced by using enriched air nitrox (EANx) mixtures, which have a higher oxygen and lower N2 content compared to air. This study aimed to investigate if divers differed in memory ability and self-assessment when breathing air and EANx30. METHODS: The effect of depth (shallow vs. deep) and breathing gas (air vs. EANx30) on memory ability and subjective ratings of impairment was compared in 20 divers. RESULTS: Memory performance was significantly worse in deep water (Air: M = 22.1%, SD = 21.7%; EANx30: M = 22.1%, SD = 17.2%) compared to shallow water (Air: M = 29.2%, SD = 18.3%; EANx30: M = 33.3%, SD = 18.2%), but this impairment did not differ significantly between air and EANx30. Subjective ratings of impairment increased significantly from shallow water (Air: M = 5.2, SD = 5.9; EANx30: M = 3.0, SD = 4.4) to deep water (Air: M = 36.8, SD = 25.3; EANx30: M = 24.8, SD = 16.1) when breathing both air and EANx30. However, ratings were significantly lower when breathing EANx30 compared to air when in the deep water. DISCUSSION: It was concluded EANx30 does not reduce narcotic impairment over air. Additionally, divers were able to make a correct global self-assessment they were impaired by narcosis, but were unable to make a finer assessment, leading them to erroneously believe that EANx30 was less narcotic than air.

Differentiating the contribution of pharmacological from alcohol expectancy effects to changes in subjective response and priming over successive drinks.

BACKGROUND: Alcohol consumption can prime motivation to continue drinking and may contribute to excessive drinking. Most alcohol administration research assesses the effect of a single alcohol dose on outcome measures; however, this differs from typical drinking occasions in which several drinks are consumed over time. This research tracks priming measures (alcohol urge, latency to first sip, and consumption time) and subjective effects (intoxication, stimulation, and sedation) across consumption of 5 drinks, over a period of 2.5 hours. Alcohol, placebo, and no-alcohol (i.e., soft drink) conditions are compared with isolate the effects of alcohol expectancies and differentiate these from alcohol's pharmacological effects. METHODS: Alcohol urge and subjective state were measured before and after an initial drink was consumed (preload: alcohol, placebo, or no-alcohol). Four additional drinking phases followed whereby participants had access to 2 drinks (alcohol/no-alcohol, or placebo/no-alcohol). Experimental priming (urge, latency to first sip, consumption time) and subjective effect (intoxication, stimulation, and sedation) outcomes were recorded after each drink. RESULTS: The pattern of alcohol urge following placebo drinks differed compared with alcohol and no-alcohol consumption, Fs(1, 90) > 4.10, ps < 0.003. There was a linear decrease in urge in the no-alcohol condition, while in the alcohol condition urge increased after the first few drinks before decreasing. Urge ratings showed the opposite pattern in the placebo condition (a decrease followed by an increase). Alcohol produced the highest ratings of lightheadedness, F(5, 440) = 2.8, p < 0.02, but both alcohol and placebo produced increased sedated feelings, Fs ≥ 19.05, ps ≤ 0.001. After placebo, urge was positively related to liking and enjoying the "alcoholic" drinks and feeling more stimulated (rs ≥ 0.31, ps ≤ 0.01). CONCLUSIONS: In social drinkers, different factors may affect priming during different stages of a drinking episode. For example, the pharmacological effects of alcohol appear involved in priming during the initial stages of drinking. When alcohol expectancies are activated, blocking access to alcohol can increase urge, supporting Tiffany's cognitive processing model of craving.

Inert gas narcosis and the encoding and retrieval of long-term memory.

BACKGROUND: Prior research has indicated that inert gas narcosis (IGN) causes decrements in free recall memory performance and that these result from disruption of either encoding or self-guided search in the retrieval process. In a recent study we provided evidence, using a Levels of Processing approach, for the hypothesis that IGN affects the encoding of new information. The current study sought to replicate these results with an improved methodology. METHODS: The effect of ambient pressure (111.5-212.8 kPa/1-11 msw vs. 456-516.8 kPa/35-41 msw) and level of processing (shallow vs. deep) on free recall memory performance was measured in 34 divers in the context of an underwater field experiment. RESULTS: Free recall was significantly worse at high ambient pressure compared to low ambient pressure in the deep processing condition (low pressure: M = 5.6; SD = 2.7; high pressure: M = 3.3; SD = 1.4), but not in the shallow processing condition (low pressure: M = 3.9; SD = 1.7; high pressure: M = 3.1; SD = 1.8), indicating IGN impaired memory ability in the deep processing condition. In the shallow water, deep processing improved recall over shallow processing but, significantly, this effect was eliminated in the deep water. DISCUSSION: In contrast to our earlier study this supported the hypothesis that IGN affects the self-guided search of information and not encoding. It is suggested that IGN may affect both encoding and self-guided search and further research is recommended.

The levels of processing effect under nitrogen narcosis.

Previous research has consistently demonstrated that inert gas (nitrogen) narcosis affects free recall but not recognition memory in the depth range of 30 to 50 meters of sea water (msw), possibly as a result of narcosis preventing processing when learned material is encoded. The aim of the current research was to test this hypothesis by applying a levels of processing approach to the measurement of free recall under narcosis. Experiment 1 investigated the effect of depth (0-2 msw vs. 37-39 msw) and level of processing (shallow vs. deep) on free recall memory performance in 67 divers. When age was included as a covariate, recall was significantly worse in deep water (i.e., under narcosis), compared to shallow water, and was significantly higher in the deep processing compared to shallow processing conditions in both depth conditions. Experiment 2 demonstrated that this effect was not simply due to the different underwater environments used for the depth conditions in Experiment 1. It was concluded memory performance can be altered by processing under narcosis and supports the contention that narcosis affects the encoding stage of memory as opposed to self-guided search (retrieval).

Measuring manual dexterity and anxiety in divers using a novel task at 35-41 m.

BACKGROUND: Nitrogen narcosis has a detrimental impact on the manual dexterity of divers and prior research has suggested that this impairment may be magnified by anxiety. Preliminary findings of the effects of depth (i.e., narcosis) and subjective anxiety on a novel test of manual dexterity are presented. METHODS: There were 45 subjects who were given a test of manual dexterity once in shallow water (1-10 m/3-33 ft) and once in deep water (35-41 m/115-135 ft). Subjective anxiety was concurrently measured in 33 subjects who were split into 'non-anxious' and 'anxious' groups for each depth condition. RESULTS: Subjects took significantly longer (seconds) to complete the manual dexterity task in the deep (mean = 52.8; SD = 12.1) water compared to the shallow water (mean = 46.9; SD = 8.4). In addition, anxious subjects took significantly longer to complete the task in the deep water (mean = 48.6; SD = 6.8) compared to non-anxious subjects (mean = 53.2; SD = 9.9), but this was not the case in the shallow water. DISCUSSION: This selective effect of anxiety in deep water was taken as evidence that anxiety may magnify narcotic impairments underwater. It was concluded that the test of manual dexterity was sensitive to the effects of depth and will be a useful tool in future research.

Anxiety and psychomotor performance in divers on the surface and underwater at 40 m.

INTRODUCTION: Performance impairments attributed to the effects of nitrogen narcosis have been reported to be significantly larger in studies conducted underwater compared to in hyperbaric chambers. One suggestion is that the larger impairment results from higher levels of anxiety in the underwater environment. The current study aimed to investigate the impact of anxiety and narcosis, in isolation and in combination, on a measure of psychomotor performance. METHODS: The effects of self-reported anxiety (anxious vs. not anxious) and depth (surface vs. underwater) on performance on the digit letter substitution test (DLST) were measured in 125 divers. RESULTS: Change from baseline scores indicated that divers performed significantly worse on the DLST underwater (mean = 3.35; SD = 4.2) compared to the surface (mean = 0.45-0.73; SD = 4.0-4.2). This decrement was increased when divers reported they were also anxious (mean = 7.11; SD = 6.1). There was no difference on DLST performance at the surface between divers reporting they were anxious and those reporting they were not anxious. DISCUSSION: The greater decrement in performance at depth in divers reporting anxiety compared to those not reporting anxiety and the lack of this effect on the surface suggested that anxiety may magnify performance deficits presumed to be caused by narcosis.

Monitoring drinking behaviour and motivation to drink over successive doses of alcohol.

The objective of this study was to compare alcohol urge, drinking behaviour and mood across two beverage conditions (alcohol/soft drink), over multiple drinks. Forty-five (22 men) participants completed two conditions (alcohol/soft-drink). Baseline alcohol urge and mood was measured before an initial drink consumed (0.2 g/kg alcohol or lemonade). Four drinking phases, which provided alcohol and lemonade, followed. Alcohol urge, mood and liking/enjoyment of beverages were measured. Participants' typical drinking habits were recorded, allowing comparisons across drinking factors. Alcohol urge was greater in the alcohol condition (P<0.03), which positively correlated with liking and drinking enjoyment of the alcohol beverage (P<0.04). Binge drinking and weekly alcohol consumption positively related to alcohol urge during the first half of the alcohol condition (P<0.02). Feeling stimulated was positively related to alcohol urge (P<0.01). Sip latency was quickest for alcohol in the alcohol condition (P<0.001) and did not increase over time as in the soft-drink condition (P<0.001). This study presents a paradigm in which alcohol motivation can be assessed within more typical drinking occasion parameters. Urge related to alcohol's positive reinforcing effects. As more alcohol was consumed, a disassociation of liking and wanting alcohol occurred, indicating that different processes may underlie behaviour during different periods of a drinking occasion.

Distortion of Prospective Time Production Underwater.

BACKGROUND: The few prior studies of time perception underwater have reached contradictory conclusions as to how, and if, time perception becomes distorted when submerged. The current paper expands upon this limited data by describing two studies of prospective time production in scuba divers. METHODS: Study 1 (N = 32) compared performance on a 30-s interval time production task in deep water (35 m-42 m/∼115-138 ft) with a shallow water control (3-12 m/∼10-39 ft). Using the same task, study 2 (N = 31) tested performance at the surface and at a range of depths underwater (1 m/3 ft; 11 m/36 ft; 20 m/66 ft; 30 m/98 ft; 40 m/131 ft). RESULTS: Study 1 revealed time production to be significantly longer in deep water compared to shallow water. In study 2 time production at the surface was not significantly different from that at 1 m, but productions at 11-40 m were significantly longer than at both 1 m and on the surface. Time productions between 11-40 m did not differ significantly. DISCUSSION: It was concluded that divers judge less time to have passed underwater than is objectively the case from a depth of 11 m, but that this effect does not deteriorate significantly once past 11 m. The cause of this distortion of time perception underwater was suggested to be the action of gas narcosis.Hobbs MB, Kneller W. Distortion of prospective time production underwater. Aerosp Med Hum Perform. 2017; 88(7):677-681.

Dissociation of wanting and liking for alcohol in humans: a test of the incentive-sensitisation theory.

RATIONALE: Incentive sensitisation theory (IST) claims that the mechanism of reward is comprised of separate neurobiological systems of wanting and liking, that dependent drug use occurs as a result of sensitisation of the system controlling wanting, and that the two systems can be dissociated. OBJECTIVE: To test the IST prediction that wanting and liking for alcohol can be dissociated in humans. METHODS: Measures of wanting and liking for alcohol were obtained in three experiments. Experiment 1 examined whether liking for alcohol was associated with levels of wanting, as indexed by self-reported weekly alcohol intake. Experiments 2 and 3 also assessed the association between liking and wanting but in these experiments wanting was also indexed by alcohol consumption in the laboratory. Experiment 2 increased wanting for alcohol using an alcohol priming dose to determine whether liking would be similarly affected. Experiment 3 reduced liking for alcohol by adulterating drinks with Tween to see whether wanting would also be reduced. RESULTS: Little evidence for an association between liking and wanting for alcohol was found in Experiments 1-3 but, collapsing across all experiments, a weak positive correlation between liking and wanting was found. However, in Experiment 2, wanting was increased by the alcohol priming dose whereas liking was not and in Experiment 3 liking was reduced without a concurrent reduction in wanting. CONCLUSIONS: Although correlations between wanting and liking can be observed these results support the contention of the IST that wanting and liking for alcohol can be dissociated in human participants.

Inert gas narcosis disrupts encoding but not retrieval of long term memory.

Exposure to increased ambient pressure causes inert gas narcosis of which one symptom is long-term memory (LTM) impairment. Narcosis is posited to impair LTM by disrupting information encoding, retrieval (self-guided search), or both. The effect of narcosis on the encoding and retrieval of LTM was investigated by testing the effect of learning-recall pressure and levels of processing (LoP) on the free-recall of word lists in divers underwater. All participants (n=60) took part in four conditions in which words were learnt and then recalled at either low pressure (1.4-1.9atm/4-9msw) or high pressure (4.4-5.0atm/34-40msw), as manipulated by changes in depth underwater: low-low (LL), low-high(LH), high-high (HH), and high-low (HL). In addition, participants were assigned to either a deep or shallow processing condition, using LoP methodology. Free-recall memory ability was significantly impaired only when words were initially learned at high pressure (HH & HL conditions). When words were learned at low pressure and then recalled at low pressure (LL condition) or high pressure (LH condition) free-recall was not impaired. Although numerically superior in several conditions, deeper processing failed to significantly improve free-recall ability in any of the learning-recall conditions. This pattern of results support the hypothesis that narcosis disrupts encoding of information into LTM, while retrieval appears to be unaffected. These findings are discussed in relation to similar effects reported by some memory impairing drugs and the practical implications for workers in pressurised environments.

Memory and metacognition in dangerous situations: investigating cognitive impairment from gas narcosis in undersea divers.

OBJECTIVE: The current study tested whether undersea divers are able to accurately judge their level of memory impairment from inert gas narcosis. BACKGROUND: Inert gas narcosis causes a number of cognitive impairments, including a decrement in memory ability. Undersea divers may be unable to accurately judge their level of impairment, affecting safety and work performance. METHOD: In two underwater field experiments, performance decrements on tests of memory at 33 to 42 m were compared with self-ratings of impairment and resolution. The effect of depth (shallow [I-II m] vs. deep [33-42 m]) was measured on free-recall (Experiment I; n = 41) and cued-recall (Experiment 2; n = 39) performance, a visual-analogue self-assessment rating of narcotic impairment, and the accuracy of judgements-of-learning JOLs). RESULTS: Both free- and cued-recall were significantly reduced in deep, compared to shallow, conditions. This decrement was accompanied by an increase in self-assessed impairment. In contrast, resolution (based on JOLs) remained unaffected by depth. The dissociation of memory accuracy and resolution, coupled with a shift in a self-assessment of impairment, indicated that divers were able to accurately judge their decrease in memory performance at depth. CONCLUSION: These findings suggest that impaired self-assessment and resolution may not actually be a symptom of narcosis in the depth range of 33 to 42 m underwater and that the divers in this study were better equipped to manage narcosis than prior literature suggested. The results are discussed in relation to implications for diver safety and work performance.