Can SSRIs enhance human visual cortex plasticity?
Alice
Lagas1, 2*,
Joanna
Black2,
Cathy
M.
Stinear1, 3,
Winston
D.
Byblow1, 4,
Geraint
Phillips2,
Bruce
R.
Russel1, 5,
Robert
R.
Kydd1, 3 and
Benjamin
Thompson1, 2
-
1
University of Auckland, Centre for Brain Research, New Zealand
-
2
University of Auckland, Optometry and Vision Science, New Zealand
-
3
University of Auckland, School of Medicine, New Zealand
-
4
University of Auckland, Sport and Exercise Science, New Zealand
-
5
University of Auckland, Psychological Medicine, New Zealand
Background: Selective serotonin reuptake inhibitors (SSRIs) have been shown to enhance visual cortex plasticity in adult animals, an effect that was blocked by the benzodiazepine triazolam. The aim of this study was to assess whether SSRIs increase visual cortex plasticity in humans.
Methods: In experiment 1, male participants (n = 20) with normal vision were randomized to a 3-week course of fluoxetine (20mg per day) or placebo. During the final 5 days of drug administration, participants were trained extensively on a motion discrimination task at a fixed motion direction. The amount of learning was assessed for the trained motion direction and an untrained direction with and without a single dose of the benzodiazepine triazolam (0.0625 mg). Adult patients with amblyopia (n = 7) took part in experiment 2, which employed a cross-over design whereby placebo and citalopram (20mg per day) were each combined with two weeks of occlusion therapy (2 hours per day). Visual functions, including visual acuity, were measured fortnightly on five occasions.
Results: In experiment 1 there was no effect of fluoxetine on learning. However, triazolam significantly impaired performance for the untrained but not the trained motion direction (F = 3.3, p = 0.04). In experiment 2, 3 patients experienced VA improvements of over 0.1 LogMAR when treated with citalopram but not with placebo.
Conclusion: SSRI administration did not affect visual cortex plasticity in normal observers. However, separate learning mechanisms were unveiled; as only the untrained task was susceptible to neuronal hyperpolarization, caused by allosteric modulation of the GABA binding site by triazolam. Citalopram may allow for visual acuity improvements in some patients with amblyopia, however longer treatment durations may be required to improve visual functions such as acuity and stereopsis in a larger number of patients.
Keywords:
Amblyopia,
Perceptual Learning,
Selective Serotonin Reuptake Inhibitors,
intracortical inhibition,
visual plasticity
Conference:
XII International Conference on Cognitive Neuroscience (ICON-XII), Brisbane, Queensland, Australia, 27 Jul - 31 Jul, 2014.
Presentation Type:
Poster
Topic:
Sensation and Perception
Citation:
Lagas
A,
Black
J,
Stinear
CM,
Byblow
WD,
Phillips
G,
Russel
BR,
Kydd
RR and
Thompson
B
(2015). Can SSRIs enhance human visual cortex plasticity?.
Conference Abstract:
XII International Conference on Cognitive Neuroscience (ICON-XII).
doi: 10.3389/conf.fnhum.2015.217.00246
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Received:
19 Feb 2015;
Published Online:
24 Apr 2015.
*
Correspondence:
Miss. Alice Lagas, University of Auckland, Centre for Brain Research, Auckland, New Zealand, a.lagas@auckland.ac.nz