Saccadic Eye Movements: A New Diagnostic Tool with Eye-Opening

Possibilities for FAS Research

James N. Reynolds

Department of Pharmacology & Toxicology,Centre for Neuroscience Studies,

Queen’s University,Kingston, Ontario, Canada

Saccadic Eye Movements: Integration of activity across multiple neural circuits

• Executive Control: ability to control behaviour flexibly– Responding automatically to a stimulus in one

set of circumstances– Suppressing the automatic response in favour

of an alternative in a different situation

Saccadic Eye Movements: Developmental regulation of the ability to perform the anti-

saccade task

• Young children (< 8 years of age) have difficulty suppressing the automatic pro-saccade– Not due to difficulty understanding the task

• Suppression ability develops gradually in school age children– Adult performance levels at around 18 years of age

• Attributed to protracted maturation of the frontal lobes into the second decade of life

• Improved inhibitory control over the saccade-generating circuitry (plasticity)

Multiple Brain Areas Involved in ControllingSaccadic Eye Movements

Posterior parietal cortexDorsolateralPrefrontal cortex

SupplementaryEye Field

Frontal Eye Field

Cerebellum

Visual Cortex

BrainstemReticular Formation

Basal Ganglia

Superior Colliculus

Visual Cortex

LGN

Retina

ThalamusCN

SNr

STN

GPe

Basal Ganglia

Parietal Cortex (LIP)

DLPFC

SEF

FEF

Frontal Cortex

RF Saccade

Cerebellum

SCsSCi

Neural Circuitry Controlling Saccade Production

Pro-Saccade Task Anti-Saccade Task

Stimulus-response compatibility Stimulus-response incompatibility

Respond automatically Voluntary response: extra stages of processing

1) suppress automatic response

2) transform (invert) target vector

Pro-Saccade Task Anti-Saccade Task

FPT

FPT

Gap Condition

Overlap Condition

Munoz and Everling, Nature Reviews in Neuroscience 5 (2004) 218-228

Saccadic Eye Movements: Clinical Findings in

Neurodevelopmental/Neurodegenerative Disorders • Attention Deficit Hyperactivity Disorder

– increased error rate in anti-saccade task– no change in reaction time for correct anti-saccades

• Schizophrenia– increased error rate in anti-saccade task– prolonged reaction times for correct anti-saccades

• Parkinson’s Disease– increased error rate in anti-saccade task*– prolonged reaction time for correct anti-saccades

Fetal Alcohol Spectrum Disorders

• Neuropathological and/or functional deficits reported in brain structures involved in saccadic eye movements– Prefrontal cortex, caudate putamen, thalamus, cerebellum

• Neurobehavioural deficits in executive function– e.g., planning, response inhibition, abstract thinking, flexibility

• Hypothesis: Individuals diagnosed with FASD will have specific abnormalities that can be measured with eye movement testing

Pilot Study

• 10-15 Children with a diagnosis of FAS– 8-12 years of age, male and female

• Education History

• Medical History

• Family History

• Conners’ Rating Scales

• Pro-saccade, Anti-saccade task

Preliminary ResultsPerformance of female FAS participants and age-matched controls

Anti-Saccade Latency

1 2

300

400

500

Subject

Co

rre

ct

La

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cy

(ms

)

Anti-Saccade Choice

1 20

102030405060

Subject

Pe

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nt

Inc

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