The Brain in Space

1

The Brain in Space

Gilles Clément, Ph.D

CNRS "Cerveau et Cognition" Laboratory

Toulouse, France

Kluwer Academic Publishers • Copyright © 2003 • All rights reserved

Fundamentals of Space Medicine — Chapter 3

The Brain in Space

2Key Concepts

• How the central nervous system evaluates our position and motion. The sense of motion

• How we use gravity to control our posture and equilibrium

• Why eye movements are helpful for evaluating the functioning of the vestibular system

• The effects of spaceflight on posture, equilibrium, eye movements, and spatial orientation (perception of "up" and "down")

• The possible causes, symptoms, and treatment for space motion sickness

The Brain in Space

3

Distance and

Speed

Gon

ick

& H

uffm

an (

1991

)

The Brain in Space

4

Velocity

Gon

ick

& H

uffm

an (

1991

)

The Brain in Space

5AccelerationG

onic

k &

Huf

fman

(19

91)

The Brain in Space

6AccelerationsG

onic

k &

Huf

fman

(19

91)

d = 1/2 gt2

The Brain in Space

7The Sense of Motion

VestibularOrgans Vision

Proprioception

Muscles

Tendons and Joints

Skin

The Brain in Space

8The Neuro-Vestibular SystemG

illin

gham

& W

olfe

(19

86)

The Brain in Space

9

Movementof Support

Surface

EyeMovements

BodyPosture

MotionSickness

Spatial OrientationStatic or

MovingVisualStimuli

AngularAcceleration

LinearAcceleration

Retina

Ocular Muscles

CerebralCortex

Oculomotor Nuclei

Cerebellum

AutonomicCenters

VestibularNuclei

SemicircularCanals

Otoliths

Somatic Musculature

Central Nervous System

Peripheral Nervous System

Inputs/Outputs of the Vestibular System

The Brain in Space

10Inner Ear — Semi-Circular Canals

The Brain in Space

11Inner Ear — Otoliths

The Brain in Space

12Stimulation of the Otolith Organs

Tilt Translation

Einstein’s equivalence principle states that all linear accelerometers must measure

linear acceleration and gravity

The Brain in Space

13Stimulation of the Otolith Organs

In 0-G, the otolith organs of the vestibular system are stimulated by head translation movements only, not by head tilt

Tilt Translation

The Brain in Space

14

Rest(Semi-Flexed) Posture in 0-G

Pho

to N

AS

A

The Brain in Space

15

“Upright” Posture

in 0-G

Pho

to N

AS

A

The Brain in Space

16

Out

Visual Orientation

The brain uses shading cues to determine how to interpret the shape of objects

The visual scene content influences the perception of up or down

In InOut

Movie: 16_shadow1

Movie: 16_shadow2

The Brain in Space

17Visual Orientation in Space

The Earth is generally

perceived as being

“below”

Photos NASA

The Brain in Space

18"Ball Catching" Experiment

On Earth, the ball would fall based on the acceleration of gravity, but in space the ball is propelled toward the crewmember at a constant velocity

Documents NASA

Movie: 19_ballcatch

The Brain in Space

19Pointing

Subjects are asked to point to memorized targets with their eyes closed

Changes occur in the accuracy of pointing and in the control of limb position

during drawing

Documents NASA

Movie: 19_pointing

The Brain in Space

20

homogenous visual environment

Pitch movement results in forward tumble

ab

a : Actual movementb : Perceived movement

"Giant Hand" phenomena

Actual path

Perceived path

Postflight Postural Illusions

Documents NASA

The Brain in Space

21Vestibulo-Ocular Reflex

The vestibulo-ocular reflex causes the eyes to rotate in a direction opposite from the head’s rotation

Movie: 21_vortoon

The Brain in Space

22Voluntary Head Rotation

Pho

tos

NA

SA

The Brain in Space

23Passive Motion

Documents ESA and NASA

Angular Rotation (IML1)

Linear Translation (D1)

The Brain in Space

24Principle of Centrifugation

on Earth

G

Tilt

GIF(gravito-

inertial force)

2r

G

r

Movie: 24_centriftoon

The Brain in Space

25Principle of Centrifugation

In microgravityon Earth

2r

r

G

Tilt

Translation

G

Tilt

GIF(gravito-

inertial force)

2r

G

r

The Brain in Space

26Centrifugation in Space (Neurolab)

Documents NASA

Movie: 26_neurolab

Movie: 26_crewvideo

The Brain in Space

27Artificial Gravity on Neurolab

L-9

0L

-60

L-3

0L

-15

L-0

2F

D01

FD

02

FD

03

FD

04

FD

05

FD

06

FD

07

FD

08

FD

09

FD

10

FD

11

FD

12

FD

13

FD

14

FD

15

FD

16

R+

0R

+1

R+

2R

+3

R+

4R

+5

R+

6R

+7

R+

8R

+9

15

30

45

60

75

90

Perc

eiv

ed

Roll

Til

t (d

eg

)

Mission Days

LEO/REO

N=4

From Clément et al. (2001)

The Brain in Space

28Off-Vertical Axis Rotation

Photo NASA

The Brain in Space

29Spatial OrientationP

hoto

NA

SA

The Brain in Space

30Mental Rotation

A well-known person is not

easily recognized

when upside-down

The Brain in Space

31Elvis Presley

The Brain in Space

32Who’s That Girl ?

Distortions in the features of a face are not evident when the face is upside-down

The Brain in Space

33Madonna (1984)

Distortions in the features of a face are not evident when the face is upside-down

The Brain in Space

34Cognitive Tests

These two figures are the same

These two figures are different: they are mirror image isomorphs

Mental Rotation of 3-D Objects Symmetry Detection

1.5 s

3.0 s

The Brain in Space

353-D Perception

• Distance perception is altered

• Volumes and objects are perceived smaller in the vertical dimension (height)

Preflight Inflight

Distance perception is altered in absence of landmark references

Pho

to N

AS

A

The Brain in Space

36Space Motion Sickness (SMS)P

hoto

NA

SA

The Brain in Space

37Space Motion Sickness Categorization

USA USSR/Russia

ASTP: Apollo-Soyuz Test Project

• Mild SMS: – One to several transient symptoms– No operational impact– All symptoms resolved in 36-48 hrs

• Moderate SMS: – Several symptoms of a persistent nature– Minimal operational impact– All symptoms resolved in 72 hrs

• Severe SMS: – Several symptoms of a persistent

nature– Significant performance

decrement– Symptoms persist beyond 72 hrs

The Brain in Space

38Space Motion Sickness Experience

• Shuttle SMS experience on first flight (36 flights):– Total crewmembers 109– Total cases of SMS 77 (71%)

• Mild 36 (33%)• Moderate 29 (27%)• Severe 12 (11%)

• Shuttle SMS experience on second flight compared to first flight:– Total crewmembers 62

• No changes 35 (56%)• Slight improvement 22 (35%)• Worst 5 (9%)

• Shuttle anti-SMS drug use:– 30% of Shuttle crewmembers have received medication

for SMS symptoms relief– Scopolamine (0.35 mg) + Dexedrine (5 mg)– IM Promethazine (50 mg) (Phenergan, antihistaminic)

The Brain in Space

39SMS—What do we know?

• We know :

– About 66% of space travelers will experience symptoms of SMS (mostly "Moderate" or "Mild" ; about 10% "Severe")

– First symptoms occur in minutes

– SMS rarely exceeds 2 days

– The problem is generally brought on by head movements in pitch and roll

– Symptoms are not significantly reduced on a reflight

– The current favorite drug treatment is IM injection of promethazine, rather than the use of scopolamine or other prophylactic medications

The Brain in Space

40SMS—What do we know?

• We dont' know :– A reliable and validated predictor of SMS :

• Susceptibility to SMS is not correlated with susceptibility to motion sickness on Earth

• In-flight prevention devices have not proven to be successful

• Preflight Adaptation Training (PAT) looks promising, but for research only (requires voluntary consent)

Pho

to N

AS

A

The Brain in Space

41Preflight Adaptation Training

Head Roll Head PitchHead tilts whereas visual scene translates

Symptom No PAT PAT Improvement (n=40) (n=18)

(%)Impaired Concentration 23 11.1 51.7Headache 55 27.7 49.6Malaise 38 22.2 41.6StomachAwareness 65 44.4 31.7Vomiting 48 38.9 19.0Nausea 60 55.6 7.3

normal

PAT

% of crewmembers reporting symptom(s) D

ocum

ents

NA

SA

The Brain in Space

42SMS—What do we know?

• We dont' know :

– A reliable and validated predictor of SMS :

• Susceptibility to SMS is not correlated with susceptibility to motion sickness on Earth

• Inflight prevention devices have not proven to be successful

• Preflight Adaptation Training (PAT) promising, but for research only (requires voluntary consent)

– The cause of SMS:

• Possible relationship between orientation illusions and SMS

• Possible influence of otolith organs asymmetry

• Sensori-motor conflict. But, how to validate this theory?

– The side effects of promethazine

The Brain in Space

43

ON A MARCHE SUR LA LUNE by HergéArt © 1954 by Editions Casterman, Paris & Tournai

Library of Congress Catalogue n° R 17608

Summary

The Brain in Space

44Additional Reading

• Clément G (2003) Fundamentals of Space Medicine. Dordrecht: Kluwer Academic Publishers

• Clément G, Reschke MF (1996) Neurosensory and sensory-motor functions. In: Biological and Medical Research in Space. Moore D, Bie P, Oser H (eds) Berlin: Springer, Chapter 4, pp 178-258

• Clément G (1998) Alteration of eye movements and motion perception in microgravity. Brain Research Reviews 28: 161-172

• Crampton GE (1990) Motion and Space Sickness. Boca Raton, FL: CRC Press Inc

• Lathan CE, Clément G (1997) Response of the neurovestibular system to spaceflight. In: Fundamentals of Space Life Sciences. Volume 1. Churchill S (ed) Malabar, FL: Krieger, pp 65-82

• Reschke MF, Harm DL, Parker DE, Sandoz GR, Homick JL, Vanderploeg JM (1994) Neurophysiological aspects: space motion sickness. In: Space Physiology and Medicine. Nicogossian AE, Huntoon CL, Pool SL (eds), Philadelphia: Lea & Febiger, pp 228-260

• Space Neuroscience Research. Brain Research Reviews, Volume 28, Numbers 1 and 2, Special Issue, 1998