1. Combined-Eye-and-Head-Movements as Indicators of
Mild Brain Trauma
Molly Olmsted*, Alex Schnabel*, and Thomas A. Knight, PhD
Biology Department, Whitman College
Walla Walla, WA 99362
Background
• When you change your line of sight in space, you are making a gaze shift. Gaze shifts can be ac-
complished by rapid eye movements (saccades) alone, or in combination with rapid head move-
ments (i.e., combined eye-head gaze shifts, CEHG).
• CEHG shifts depend critically on multiple regions of the brain – the brain stem, subcortical mo-
tor regions, and the frontal and parietal cortex – with cortical regions most susceptible to mild
traumatic brain injury (mTBI; i.e., concussion). Injury to these regions may manifest in gaze shift
deficits (Scudder, 2002).
• Concussions are a major public health concern – especially in the student athlete population –
and early detection is critical to avoiding long-term negative effects (Jordan, 2013; Malpass, 20130.
• Recent research has demonstrated that subjects with concussion exhibit deficits (decreased accu-
racy, increased directional errors, increased latency) in saccadic eye movements that involve high-
er cortical areas (Heitger et al., 2004; Stahl, 1999).
Objectives and Hypotheses
• The goal of this experiment was to record CEHG shifts in varsity athletes at risk for minor head
trauma to determine if injury impacted gaze shift velocity, accuracy, head contribution, and laten-
cy. Additionally for any student athlete that went uninjured, we investigated whether CEHG func-
tion changed across the season. Ultimately, we hope to demonstrate that CEHG shifts are reliable
indicators of brain health due to their multi-region neural circuitry.
• Hypothesis 1: CEHG shift velocity, accuracy, and latency worsen, and composition (i.e., relative
proportion of eye and head contributions to CEHG) changes following concussion.
• Hypothesis 2: CEHG shift velocity, accuracy, and latency worsen, and composition (i.e., relative
proportion of eye and head contributions to CEHG) changes in athletes across the season in the
absence of concussion
Introduction
• 10 student subjects (8 female varsity, 1 male and 1 female author) participated (2 varsity athletes
and author at low risk for head injury)
• Subjects’ eye and head movements were measured using the EyeSeeCam (a videooculography
(VOG) device, or eye tracker) during three visually guided tasks with increasing levels of difficulty,
primarily across large-amplitude CEHG shifts:.
-Saccade: a visual target jumped from one horizontal location to another and subjects shifted
gaze to acquire it.
-Memory-Guided: while fixating a central target, a peripheral target appeared and then dis-
appeared, and after central fixation offset, subjects shifted gaze to memorized target location.
-Anti-Saccade: a central target jumped to a peripheral location, and subjects shifted gaze an
equal distance in the opposite direction of the new target.
• At least two sessions for each of seven student-athletes were recorded: mid- and post-season for
four, and pre- and post-season for three.
• Gaze was calculated offline (E+H) position, velocity, and timing metrics were collected for com-
parisons of gaze eye and head movements and contributions (comparisons with target timing and
location will be possible at later time).
Methods
• Results 1: Does CEHG shift velocity, accuracy, and latency worsen, and head composition (i.e.,
relative proportion of eye and head contributions to CEHG) increase following concussion?
-No participants who sustained concussion had baseline recordings prior to impact.
• Results 2: Does CEHG shift velocity, accuracy, and latency worsen, and head composition (i.e.,
relative proportion of eye and head contributions to CEHG) increase in athletes across the season
in the absence of concussion?
-Three student athletes with pre-season baseline measurements and who reported no concus
sion – exhibited very few changes in CEHG behavior pre- to post-season. Some CEHGs had
decreased peak velocity or increased head contribution, but no pattern emerged.
Results
• There may be some alterations in CEHG behavior (and therefore brain function) for some unin-
jured athletes at specific task and CEHG amplitudes, but it is as likely that these changes are nor-
mal intrasubject variability.
• Preliminary results suggest that concussion is related to alterations in CEHG shift behavior and
that these alterations may last for > 60 days. Alterations seem to exist in saccade task CEHG be-
havior where previous studies found no changes in eye movement alone.
• Additional analyses will include comparisons of accuracy and latency, and compare neurocogni-
tive test (ImPACT) results with CEHG shift measurements.
Conclusion
Works Cited:
• Griggs, W. S. 2013. Eliminating intersubject variability of large amplitude gaze metrics by reducing the visual field. Whitman College Biochemistry,
Biophysics and Molecular Biology Program Thesis.
• Heitger, M. H., Anderson, T. J., Jones, R. D., Dalrymple,-Alford, J. C., Frampton, C. M., Ardagh, M. W. 2004. Eye movement and visuomotor arm
movement deficits following mild closed head injury. Brain127:575–90.
• Jordan, B. D. 2013. The clinical spectrum of sport-related traumatic brain injury. Nature Reviews Neurology, 9(4), 222-230.
• Malpass, K. 2013. Read all about it! Why TBI is big news. Nature Reviews Neurology, 9(4), 179-179.
• Scudder, C. A., Kaneko, C. R. S., Fuchs, A. F. 2002. The brainstem burst generator for saccadic eye movements: a modern synthesis, Exp Brain Res,
142: 439-462.
• Stahl, J.S. 1999. Amplitude of human head movements associated with horizontal saccades. Exp Brain Res 126: 41-54.
Acknowledgements: We would like to thank Thomas Knight and Whitney Griggs ‘13 for their help on and contributions to our study. We would also
like to thank all of our participants without the hard work and patience of whom our study would not have been possible. And finally the Whitman
College Athletic Trainers who assisted in subject aquisition.
* equivilent authors
References and Acknowlegements
Saccade Task
Memory Guided Task
Anti-Saccade Task
n=
n=
n=
n=
n=
n=
15 8 27 25 20 43
15 8 27 25 20 43
• For one subject who had not recorded a pre-season baseline and who had sustained concussions,
qualitative comparisons show changes in CEGH behavior compared to the three above.
• These changes include multi-step CEHG shifts during the saccade task, increased direction er-
rors and multistep CEHG shifts during the antisaccade task; surprisingly no alterations were ob-
served for the memory-guided task.
Results
Saccade Task Memory Guided Task Anti-Saccade Task
43 51 51 64 21 32
43 51 51 64 12 33
20 32 27 25 6 9
20 33 27 25 5 10
†
† statistically significant
†
†
†
†
0
2
4
6
8
10
12
14
Pre-­‐
Season
Post-­‐
Season
Pre-­‐
Season
Post-­‐
Season
Pre-­‐
Season
Post-­‐
season
Number
of
Direc-onal
Erros
Axis
Title
Direc-onal
Errors
per
Task
0
20
40
60
80
100
Pre-­‐
Season
Post-­‐
Season
Pre-­‐
Season
Post-­‐
Season
Pre-­‐
Season
Post-­‐
season
Number
of
Correc,ves
Saccade
Correc,ve
Gaze
Shi6s
per
Task
• Directional errors result from a subject initially shifting gaze in the opposite direction from the
stimulus and corrective gaze shifts include any additional shifts made unstimulated by subject.
• While corrective gaze shifts showed no correlation when comparing pre- and post- season record-
ings, directional errors were more common in post-season recordings than in pre-season recordings.
Saccade Memory-Guided AntiSaccade Saccade Memory-Guided AntiSaccade