Deficits in Spatial Cognition After TBI Revealed By Virtual Morris Water Maze

R.W. Skelton & S.P. Ross, Psychology, University of

Victoria, Victoria, BC, CANADA

2Premises

Traumatic brain injury (TBI) damages many neural structures and impairs many cognitive functions, including:

Hippocampus, Episodic memory, Spatial memory. Animal research shows Morris water maze

(MWM) useful for measuring deficits in spatial memory and hippocampal function.

Previous study showed that survivors of TBI show deficits in Virtual MWM

Present study uses more advanced 3D environment

And distal cues for orientation

3Methods

Participants TBI: 14 (11M, 3F)

23-67 years old, ½-48 years post-injury (9 MVA) Non-Injured: 12 (7M, 5F), 19 – 52 years old

Virtual MWM Built with Unreal® Editor, shown on desktop

system Large (~40 m) arena (circus ring) with 2 m circular

platform Large square room with windows and world outside

Room and world has “cardinal” orientation (North-South etc)

4Methods

Trials Free time for orientation, mapping and

joystick practice 4 with platform visible (varying locations) 10 with platform invisible (until tread upon) in

fixed location, from varying start locations 1 Probe (no platform)

Measures Distance and Latency (measured with

TRAM®) Dwell time in correct quadrant on Probe trials Spatial Score: z-score average of invisible

platform trial and probe trial data

5Methods

Virtual MWM requires combinations of distal and proximal cues for navigation (not just single cues or landmarks)

Views showing visible platform and outside scenery

Views of the arena, room and visible platform

6Methods Trials start from 4 different positions.

Visible platform

Views of Arena from the 4 start positions.

Invisible platform

7Results: Learning Trials

Participant with no injury quickly learns to find the invisible platform

Participant with brain injury takes longer to learn to find the platform

Sample Data

8

Distance

0

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 Avg 6-14Trial

Pa

th le

ng

th

TBI

Control

Visible platform Invisible platform

Results: Learning Trials

TBI slows acquisition of platform location: Path lengths are longer

Group Data

Sample Individual

Data

TBI

Control

9

0

5

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Lat

ency

(s)

Visible Invisible

Control

TBI

0

2

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Sp

ee

d

Visible Invisible

Control

TBI

Results: Learning Trials

Groups show large differences in ability to locate invisible platform

Groups show only small differences in speed of movement

0

50

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Dis

tan

ce

Visible Invisible

Control

TBI

0

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Eff

ica

cy

Visible Invisible

Control

TBI

Latency

Distance

Speed

Efficacy

10Results: Probe Trials

Those with TBI showed poor searches when platform absent.

Control participant closest to group

meanParticipant with TBI

closest to group mean0

10

20

30

40

50

60

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80%

Co

rrec

t (D

wel

l Tim

e)

CorrectQuadrant

Quadrant/RingDiscrimination

Control

TBI

11Results: Group Differences

0.0 0.5 1.0 1.5 2.0 2.5 3.0

Speed

Latency

Distance

Efficacy

Corr Quad dw%

Quad/Ring discr

Spatial Score

Effect Sizes (Cohen's d)

Large effects

Effect sizes reveal that most measures of spatial navigation show large differences between TBI and Controls

12Conclusions

Virtual MWM reveals deficits in spatial navigation after TBI.

Some measures show bigger effects. Study replicates previous finding.

Impairment after TBI not due to primitive 3D rendering.

Useful for studying TBI deficits and functions of human

hippocampus.