Research Interests:
Research Interests: Addendum and Apomorphine
Research Interests: Philosophy and Gynecology
Research Interests:
Associative learning involves learning a connection between two events (two stimuli or a stimulus and a response) after their presentation so that the posterior occurrence of one of them activates the representation of the other. In the... more
Associative learning involves learning a connection between two events (two stimuli or a stimulus and a response) after their presentation so that the posterior occurrence of one of them activates the representation of the other. In the present dissertation, two associative learning paradigms are used in order to study the role of the glutamatergic and dopaminergic systems on learning. Apomorphine-induced learning and a simultaneous visual discrimination task are used to assess the participation of both systems mentioned above.Chapter I includes a brief introduction to learning (especially classical conditioning), the use of drugs and of contextual cues as stimuli in this domain. It also treats discrimination learning and colour preferences in birds and in animals in general. The two paradigms used in this work are briefly described in the context of dopamine and glutamate involvement. A brief introduction to dopaminergic and glutamatergic systems introduces the associative learning...
Research Interests:
Research Interests:
7 Chapter I A general introduction 13 Learning and memory 14 Classical conditioning 15 The context as a CS 16 Drug action as a US 16 Discrimination learning 17 Dopamine in learning 18 The Wickens' learning model 20 The hypothesis 22... more
7 Chapter I A general introduction 13 Learning and memory 14 Classical conditioning 15 The context as a CS 16 Drug action as a US 16 Discrimination learning 17 Dopamine in learning 18 The Wickens' learning model 20 The hypothesis 22 Chapter II The glutamatergic and dopaminergic systems. The glutamatergic system Glutamate based transmission 25 Glutamate synthesis 26 Glutamate receptors 26 Glutamate pathways 29 LTP and glutamate NMDA receptors 33 Pharmacology of NMDA receptors 34 The dopaminergic system Dopaminergic based transmission 36 Dopamine receptors 38 Dopamine in the CNS 41 Pharmacology of the dopaminergic system 43 Apomorphine 44 Dopamine in the spinal cord of pigeon 46 Experiment 1 49 Methods 49 Results 50 TH-immunoreactive cells 52 DA-immunoreactive cells 52 DARPP-32-immunoreactive cells 54 Discussion 55 Pre-synaptic membrane 55 Post-synaptic membrane 58 Dopaminergic functionality in the pigeon' spinal cord 59 Chapter III Conditioning induced by apomorphine Introduc...
Research Interests:
Figure-ground segregation is a fundamental visual ability that allows an organism to separate an object from its background. Our earlier research has shown that nucleus rotundus (Rt), a thalamic nucleus processing visual information in... more
Figure-ground segregation is a fundamental visual ability that allows an organism to separate an object from its background. Our earlier research has shown that nucleus rotundus (Rt), a thalamic nucleus processing visual information in pigeons, together with its inhibitory complex, nucleus subpretectalis/interstitio-pretecto-subpretectalis (SP/IPS), are critically involved in figure-ground discrimination (Acerbo et al., 2012; Scully et al., 2014). Here, we further investigated the role of SP/IPS by conducting bilateral microinjections of GABAergic receptor antagonist and agonists (bicuculline and muscimol, respectively) and non-NMDA glutamate receptor antagonist (CNQX) after the pigeons mastered figure-ground discrimination task. We used two doses of each drug (bicuculline: 0.1 mM and 0.05 mM; muscimol: 4.4 mM and 8.8 mM; CNQX: 2.15 mM and 4.6 mM) in a within-subject design, and alternated drug injections with baseline (ACSF). The order of injections was randomized across birds to r...
Research Interests:
Research Interests:
Research Interests:
Research Interests:
A typical nonverbal transitive inference task (TI) consists of several overlapping discriminations (A+ B-, B+ C-, C+ D-, D+ E-, where letters indicate stimuli and pluses and minuses denote reinforcement and nonreinforcement). A choice of... more
A typical nonverbal transitive inference task (TI) consists of several overlapping discriminations (A+ B-, B+ C-, C+ D-, D+ E-, where letters indicate stimuli and pluses and minuses denote reinforcement and nonreinforcement). A choice of stimulus B in a novel pair BD is interpreted as indicative of a TI (if B > C and C > D, then B > D). Although hippocampus has been implicated in nonverbal TI, it is not clear whether it simply maintains memory of associative values or stores an ordered representation of stimuli. We investigated the effect of hippocampal lesion on TI in pigeons while controlling reinforcement history so that reliance on associative values would lead to a choice of a stimulus D in the pair BD instead of a choice of a stimulus B expected by inferential mechanisms. Prior to the lesion, some of the pigeons (relational group; n = 4) have selected B over D indicating TI, while other birds (associative group; n = 6) chose D over B suggesting reliance on associative values. Hippocampal lesion had no effect on postlesion performance in associative group. In contrast, the relational group that preferred stimulus B in a pair BD before lesion showed a near-chance performance after the lesion. Our results demonstrate that hippocampus may be involved in creating a representation of an ordered series of the stimuli instead of maintaining reinforcement history of each stimulus. In addition, we provide a behavioral procedure suitable for dissociating different behavioral strategies used to solving TI task. Finally, we show for the first time the involvement of avian hippocampus in the task that is not explicitly spatial in nature. These results further confirm the notion that avian hippocampus is functionally analogous to mammalian hippocampus despite the significant differences in their anatomy.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests: Psychology, Perception, Cognition, Medicine, Nucleus Accumbens, and 15 moreDopamine, Glutamate, Discrimination Learning, Animals, Metabotropic Glutamate Receptors, Animal Model, Antagonist, Columbidae, Glycine, Alanine, Pigeon, Glutamate Receptor, Dopamine antagonists, NMDA receptor, and Pharmacology and pharmaceutical sciences
Research Interests: Figure Ground and Nucleus
Research Interests:
Research Interests:
Research Interests: Physics and Figure Ground
Research Interests:
Research Interests:
Research Interests:
Earlier, we reported that nucleus rotundus (Rt) together with its inhibitory complex, nucleus subpretectalis/interstitio-pretecto-subpretectalis (SP/IPS), had significantly higher activity in pigeons performing figure–ground... more
Earlier, we reported that nucleus rotundus (Rt) together with its inhibitory complex, nucleus subpretectalis/interstitio-pretecto-subpretectalis (SP/IPS), had significantly higher activity in pigeons performing figure–ground discrimination than in the control group that did not perform any visual discriminations. In contrast, color discrimination produced significantly higher activity than control in the Rt but not in the SP/IPS. Finally, shape discrimination produced significantly lower activity than control in both the Rt and the SP/IPS. In this study, we trained pigeons to simultaneously perform three visual discriminations (figure–ground, color, and shape) using the same stimulus displays. When birds learned to perform all three tasks concurrently at high levels of accuracy, we conducted bilateral chemical lesions of the SP/IPS. After a period of recovery, the birds were retrained on the same tasks to evaluate the effect of lesions on maintenance of these discriminations. We fou...