A Linear Physiological Visual-Vestibular A Linear Physiological Visual-Vestibular Interaction Model for the Prediction of Interaction Model for the Prediction of Motion Sickness Incidence:Motion Sickness Incidence:Adaptation and Habituation IssuesAdaptation and Habituation Issues

ByBy

Lt P. Matsagas, M.Sc., Hellenic Navy, andLt P. Matsagas, M.Sc., Hellenic Navy, and

M.E. McCauley, Ph.D., Naval Postgraduate M.E. McCauley, Ph.D., Naval Postgraduate SchoolSchool

Human Systems IntegrationSymposium 2005"Enhancing Combat EffectivenessThrough Warfighter Performance"

Motion SicknessMotion Sickness

Motion sickness is a general term that Motion sickness is a general term that describes the discomfort and associated describes the discomfort and associated emesis (vomiting) induced by many kinds of emesis (vomiting) induced by many kinds of motions. motions.

Motion sickness effects are evident in Motion sickness effects are evident in numerous provocative motion environments, numerous provocative motion environments, such as ships, aircraft, automobiles, and air-such as ships, aircraft, automobiles, and air-cushioned vehicles. cushioned vehicles.

Cause of motion Cause of motion sicknesssickness

Neural mismatch theoryNeural mismatch theory

Current sensory input

Neural store

Vestibular systemVision

ProprioceptionError signal

Effects on Effects on performanceperformance The consequences on human performance The consequences on human performance

and operational efficiency are:and operational efficiency are:– Ataxia (Ataxia (lack of muscular coordinationlack of muscular coordination))– Decreased spontaneityDecreased spontaneity– CarelessnessCarelessness– IncoordinationIncoordination– Reductions in subject motivationReductions in subject motivation– Mood changesMood changes– Sleepiness, drowsiness (through sopite Sleepiness, drowsiness (through sopite

syndrome)syndrome)

Motion Sickness Motion Sickness Incidence (MSI)Incidence (MSI) A historically common index of motion A historically common index of motion

sickness severity is the Motion sickness severity is the Motion Sickness Incidence (MSI), which is the Sickness Incidence (MSI), which is the percentage of people who vomit when percentage of people who vomit when exposed to a nauseogenic exposed to a nauseogenic environment. environment.

HFR model (1974)HFR model (1974)

Proposed modelProposed model

Conceptually based on existing theoriesConceptually based on existing theories Combined with observer theory conceptsCombined with observer theory concepts MSI estimation based on:MSI estimation based on:

– Gravity estimation errorGravity estimation error– Residual optical flowResidual optical flow

Model input parametersModel input parameters– Vertical acceleration frequency and amplitudeVertical acceleration frequency and amplitude

Model OverviewModel Overview

Predicted MSIPredicted MSI

Model ValidationModel Validation

Model ValidationModel ValidationComparison plotComparison plot

MSI accumulationMSI accumulation

Adaptation to Adaptation to nauseogenic motionnauseogenic motion

MSI HabituationMSI Habituation

MSI Habituation and MSI Habituation and RetentionRetention

Model significanceModel significance

ParametricParametric Easily extended to various Easily extended to various

combinations of sensory cuescombinations of sensory cues Validated but not “tuned”Validated but not “tuned” PrecisePrecise EtiologicEtiologic Linear and time invariantLinear and time invariant

Why is the model Why is the model useful?useful? Current stateCurrent state

– True motion detectionTrue motion detection– Seated subject Seated subject – No voluntary motionsNo voluntary motions

Future stateFuture state– True and apparent motion detectionTrue and apparent motion detection– ProprioceptionProprioception– Refinement of Neural Store modelRefinement of Neural Store model– Parametric input of other human physiology Parametric input of other human physiology

parametersparameters

Future ResearchFuture Research

Include motion in 6 degrees of Include motion in 6 degrees of freedomfreedom

Implementation of “all” physiological Implementation of “all” physiological systemssystems

Central Nervous System (CNS) non-Central Nervous System (CNS) non-linear characteristics linear characteristics

Questions?Questions?

Adaptation Adaptation mechanism detailmechanism detail

++

ExponentialIncrease

ExponentialDecrease

+

+

Perceived Linear Acceleration

Perceived Gravity Adaptation

signal

Neural Store

Σ

Future ResearchFuture Research

Current StateCurrent State Future StateFuture State

InputsInputs True motionTrue motion True motionTrue motion Visually detected motionVisually detected motion

Human systems Human systems involvedinvolved

VestibularVestibular Central VisionCentral Vision

Vestibular Vestibular Central VisionCentral Vision Peripheral VisionPeripheral Vision ProprioceptionProprioception

Neural StoreNeural Store One average motionOne average motion Multiple motion Multiple motion characteristicscharacteristics

Cue errors Cue errors contributing to contributing to MSIMSI

Gravity vector Gravity vector estimationestimation Retinal SlipRetinal Slip

Gravity vector estimationGravity vector estimation Retinal SlipRetinal Slip Difference between true Difference between true motion and vectionmotion and vection

Current effortsCurrent efforts

Modeling ofModeling of

InputsInputs True motionTrue motion Visually detected motionVisually detected motion

Human systems Human systems involvedinvolved

Vestibular Vestibular Central VisionCentral Vision Peripheral VisionPeripheral Vision ProprioceptionProprioception

Neural StoreNeural Store Multiple motion characteristicsMultiple motion characteristics

Cue errors Cue errors contributing to MSIcontributing to MSI

Gravity vector estimationGravity vector estimation Retinal SlipRetinal Slip Difference between true motion Difference between true motion and vectionand vection