Effect of pharmacological manipulation of nucleus subpretectalis/interstitiopretecto-subpretectalis (SP/IPS) on figure-ground discrimination in pigeons
Hannah E.
1
Moses ,
Erin N.
1Drake
Background
 Collothalamic visual pathway is a
major source of visual information
(90%; Shimizu & Watanabe, 2012)
 N. rotundus (Rt) is the largest
midbrain nucleus in birds
 Rt receives inhibitory input from
nucleus subpretectalis/interstitiopretecto-subpretectalis (SP/IPS)
1
Scully ,
Martin
2
Acerbo ,
and Olga F.
1
Lazareva
University, 2Iowa State University
SP connectivity
Results: CNQX
Excitatory connections from optic
tectum
 Affected by CNQX
7 out of 9 birds injected
o Complete absence of any behavioral responses during first 30 min for
only in a few birds
 Relatively short-lasting
effect
Inhibitory connections within SP and
from SP to Rt
Affected by both bicuculline and
muscimol
 Non-dose-dependent
on background trials
 Dose-dependent effect
on figure trials
Earlier study (Acerbo et al., 2012) demonstrated higher activity of Rt and SP/IPS
after figure-ground discrimination, but not after color or shape discrimination
We also found significant impairment of figure-ground discrimination after lesion
of SP/IPS complex (Scully, Acerbo, & Lazareva, in prep.)
Goal: Investigate the modulatory role of SP in figure-ground discrimination by
Results: Bicuculline
7 out of 9 birds injected
o Complete absence of any behavioral responses during first 30 min or
even 90 min for some of the birds
conducting pharmacological blockade of specific neurotransmitter receptors
Method
 Very large individual
differences (e.g.,
background trials range
from +0.05 to -0.21)
Dose-dependent effect
on figure trials
 Non-dose-dependent
effect on figure-trials
(modified from Lazareva et al., 2006)
Stimuli
 Target presented in one of four locations,
equally often on figure or ground region (see
left)
Large individual
differences (e.g.,
background trials ranges
from +0.11 to -0.28)
Subjects
 9 pigeons, kept at 85% of free-feeding weight
Preliminary results
 All three drugs produced a deleterious effect on figure-ground discrimination
 Both muscimol and CNQX produce a dose-dependent impairment on figure trials
but not on background trials
 Bicuculline produces a dose-dependent effect on background trials
 The effect of CNQX suggests that excitatory input from optic tectum is critical for
accurate performance on figure trials but not on background trials
 The increased inhibitory activity in SP produced by muscimol impairs discrimination
on figure trials, possibly due to imbalance of modulation of Rt by SP
Procedure
 Trained until 80% correct or better
on both figure and background
trials
Surgery
Bilateral implantation of
cannuli into SP (n = 9)
Four-day recovery
Results: Muscimol
8 out of 9 birds injected
o Complete absence of any behavioral responses during first 30 min for
most of the birds
o Concentrated on 90-mi data
 Non-dose-dependent
effect on background
trials
 Dose-dependent effect
on figure trials
Intracranial injections
 Alternating injections of drug and baseline (artificial cerebrospinal fluid)
Bicuculline (GABA antagonist), muscimol (GABA agonist), CNQX
(glutamate antagonist)
Two doses for each drug (12.75 and 25.5 ng for bicuculline, 0.5 and 1 ng
for muscimol, 0.3 and 0.6 ng for CNQX)
Order and dose of drugs randomized across birds
 Has to maintain high levels of performance to proceed to next drug injection
 It is possible that the decreased inhibitory activity in SP primarily affects background
trials
 Large individual differences may be due to the precise location of the cannula
 Future work will include determining the exact location of the cannuli via histological
analysis
Acknowledgments
This research was supported by the A&S Drake University Faculty Development Research grant to OFL. We thank all
members of CoPAL research team for their help with running experiments.
References
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