2007, Piran, Slovenia

Cold physiology
COGNITIVE PERFORMANCE IS ENHANCED DURING COLD-
WATER IMMERSION AND EXERCISE
John W. Castellani, Ingrid V. Sils, Myra Reese, and Catherine O’Brien
Thermal and Mountain Medicine Division
U.S. Army Research Institute of Environmental Medicine
Natick, Massachusetts 01760 USA
Contact person: john.castellani@us.army.mil
INTRODUCTION
Studies suggest that cognitive performance degrades as core temperature falls during resting
studies. However, it is unknown how the rate of cooling affects cognitive performance at a
specific core temperature. The purpose of this study was to determine if the rate of core
temperature cooling affects cognitive function. We hypothesized that cognitive function
would be impaired to a greater degree during cold-water immersion when the rate of rectal
temperature (Tre) cooling was slower compared to trials where core temperature fell faster.
METHODS
Ten men (20 ± 2 yr, 178 ± 7 cm height, 73.4 ± 7.1 kg body weight, VO2peak, 47.2 ± 4.8 ml·kg -
1 ·min -1 , and 15.5 ± 3.9 % body fat) completed 8 different, randomized, trials (which varied in
the rate of cooling) in either 10 or 15°C water, in either chest (C) or waist (W) deep water
while walking at either 0.44 or 0.88 m·s -1 . Subjects also completed a control trial where they
were not immersed. Cognitive function was measured using standard performance tests: 4choice
reaction time, match-to-sample, visual vigilance, grammatical reasoning, and symbol
substitution. Tests were conducted before immersion and during immersion when Tre reached
36.5°C or 2 hours had elapsed. Significance was set at p < 0.05. Data are presented as mean
± SD.
Visual Vigilance. This test of visual vigilance was designed to resemble military tasks
requiring sustained scanning of the visual environment for infrequent, difficult to detect
stimuli such as those during sentry duty. The task required the participant to detect a small,
faint stimulus that randomly appeared for a second at various locations on the computer
screen On the average, presentation of a stimulus occurred once a minute. The participant
was told to respond as quickly as possible when a stimulus was detected. Dependent measures
included correct detections and the response time. Responses made before (or after) stimulus
occurrence were recorded as false alarms. The duration of this test was 20 minutes.
Four-Choice Visual Reaction Time. Volunteers were presented with a series of visual stimuli
at one of four different spatial locations on the computer screen. The volunteer's task was to
indicate the correct spatial location of each stimulus by striking one of four corresponding
keys on the computer keyboard. Dependent measures included the response latency for each
trial, premature errors (responding before the presentation of the stimulus), errors of omission
(response latency >1 sec) and errors of commission (hitting the wrong key). The duration of
this test was approximately 5 minutes.
Delayed Match-to-Sample. This is a subtest of the Walter Reed Performance Assessment
Battery. During this test, a sample pattern of 36 red and green grid squares was presented on
the computer display. The volunteer studied this pattern and then pressed a key on the
keyboard. The sample pattern disappeared and the screen was blank for either 8 or 16
seconds ("delay"). Next, two patterns were presented and the volunteer selected the pattern
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