Src-NADH dehydrogenase subunit 2 complex and recognition memory of imprinting in domestic chicks.

Src is a non-receptor tyrosine kinase participating in a range of neuronal processes, including synaptic plasticity. We have recently shown that the amounts of total Src and its two phosphorylated forms, at tyrosine-416 (activated) and tyrosine-527 (inhibited), undergoes time-dependent, region-specific learning-related changes in the domestic chick forebrain after visual imprinting. These changes occur in the intermediate medial mesopallium (IMM), a site of memory formation for visual imprinting, but not the posterior pole of the nidopallium (PPN), a control brain region not involved in imprinting. Src interacts with mitochondrial genome-coded NADH dehydrogenase subunit 2 (NADH2), a component of mitochondrial respiratory complex I. This interaction occurs at brain excitatory synapses bearing NMDA glutamate receptors. The involvement of Src-NADH2 complexes in learning and memory is not yet explored. We show for the first time that, independently of changes in total Src or total NADH2, NADH2 bound to Src immunoprecipitated from the P2 plasma membrane-mitochondrial fraction: (i) is increased in a learning-related manner in the left IMM 1 h after the end of training; (ii), is decreased in the right IMM in a learning-related way 24 h after training. These changes occurred in the IMM but not the PPN. They are attributable to learning occurring during training rather than a predisposition to learn. Learning-related changes in Src-bound NADH2 are thus time- and region-dependent.

Filial imprinting in domestic chicks; cytoplasmic polyadenylation element binding protein 3, predispositions and learning.

Visual imprinting is a learning process, whereby young animals come to prefer a visual stimulus after exposure to it (training). Available evidence indicates that the intermediate medial mesopallium (IMM) in the domestic chick forebrain is a site of memory formation during visual imprinting. We have found previously that cytoplasmic polyadenylation element binding protein 3 in the P2 plasma membrane-mitochondrial fraction (CPEB3-P2) is upregulated in a learning-dependent way in the left IMM 24 h after training. CPEB3 has two forms, soluble and aggregated. Soluble CPEB3 represses translation; the aggregated form (CPEB3-AF) is amyloid-like and can promote translation. Our previous study did not show which of these two forms is increased after imprinting. We have now resolved this matter by measuring, 24 h after training, CPEB3-P2 and CPEB3-AF in the IMM and a control brain region, the posterior pole of nidopallium (PPN). The methods include imprinting training with a visual stimulus, behavioral measurement of preference, preparation of aggregated CPEB3, western immunoblotting, quantitation of proteins, statistical linear modeling. Only in the left IMM were the level of CPEB3-AF and learning strength correlated, increased CPEB3-AF level reflecting a predisposition to learn readily. CPEB3-P2 level also increased with learning strength in the left IMM, but as a result of learning. No correlations were detected in the right IMM or PPN. We propose two separate systems, both modulating synaptic strength through control of local translation. They are represented by CPEB3-AF (associated with a predisposition to learn) and soluble CPEB3 (associated with learning itself).

Chicken cognin interactome and the memory of filial imprinting.

Visual imprinting is a learning process whereby young animals come to prefer a visual stimulus after exposure to it (training). The intermediate medial mesopallium in the domestic chick forebrain is critical for visual imprinting and contributes to molecular regulation of memory formation. Criteria used to infer that a change following training is learning-related have been formulated and published. Cognin (protein disulphide isomerase) is one of several identified plasma membrane and mitochondrial proteins that are upregulated in a learning-related way 24 hours after training. Since virtually nothing is known about the cognin interactome, we have used immunoaffinity chromatography and mass spectrometry to identify proteins that interact with cognin in the cytoplasmic and plasma membrane-mitochondrial fractions. As the learning-related upregulation of cognin has been shown to occur in the plasma membrane-mitochondrial fraction and not in the cytoplasmic fraction, we studied the effect of training on three cognin-interacting partners in the plasma membrane-mitochondrial fraction: the b5 subunit of mitochondrial ATP synthase and the alpha-2 and alpha-3 subunits of sodium-potassium ATPase. Learning-related upregulation was found in the left intermediate medial mesopallium 24 hours after training for the b5 subunit of mitochondrial ATP synthase and the alpha-2 subunit of sodium-potassium ATPase. The hemispheric asymmetry revealed here is consistent with the predominance of many other learning-related effects in the left intermediate medial mesopallium. The alpha-2 subunit of sodium-potassium ATPase is mainly expressed in astrocytes, supporting a role for these glial cells in memory.

Visual Imprinting in Birds: Behavior, Models, and Neural Mechanisms.

Filial imprinting is a process, readily observed in precocial birds, whereby a social attachment is established between a young animal and an object that is typically (although not necessarily) a parent. During a perinatal sensitive period, the young animal learns characteristics of the object (the imprinting stimulus) simply by being exposed to it and will subsequently recognize and selectively approach this stimulus. Imprinting can thus establish a filial bond with an individual adult: a form of social cohesion that may be crucial for survival. Behavioral predispositions can act together with the learning process of imprinting in the formation, maintenance, and modification of the filial bond. Memory of the imprinting stimulus, as well as being necessary for social recognition, is also used adaptively in perceptual classification of sensory signals. Abstract features of an imprinting stimulus, such as similarity or difference between stimulus components, can also be recognized. Studies of domestic chicks have elucidated the neural basis of much of the above behavior. This article discusses (1) principal behavioral characteristics of filial imprinting and related predispositions, (2) theoretical models that have been developed to account for this behavior, and (3) physiological results elucidating the underlying neural mechanisms. Interactions between these different levels of analysis have resulted in advancement of all of them. Taken together, the different approaches have helped define strategies for investigating mechanisms of learning, memory, and perception.

Micro-RNAs, their target proteins, predispositions and the memory of filial imprinting.

Visual imprinting is a learning process whereby young animals come to prefer a visual stimulus after exposure to it (training). The intermediate medial mesopallium (IMM) in the domestic chick forebrain is critical for visual imprinting and contributes to molecular regulation of memory formation. We investigated the role of micro-RNAs (miRNAs) in such regulation. Twenty-four hours after training, miRNA spectra in the left IMM were compared between chicks with high preference scores (strong memory for imprinting stimulus), and chicks with low preference scores (weak memory for imprinting stimulus). Using criteria of significance and expression level, we chose gga-miR-130b-3p for further study and found that down-regulation correlated with learning strength. No effect was detected in posterior nidopallium, a region not involved in imprinting. We studied two targets of gga-miR-130b-3p, cytoplasmic polyadenylation element binding proteins 1 (CPEB-1) and 3 (CPEB-3), in two subcellular fractions (P2 membrane-mitochondrial and cytoplasmic) of IMM and posterior nidopallium. Only in the left IMM was a learning-related effect observed, in membrane CPEB-3. Variances from the regression with preference score and untrained chicks suggest that, in the IMM, gga-miR-130b-3p level reflects a predisposition, i.e. capacity to learn, whereas P2 membrane-mitochondrial CPEB-3 is up-regulated in a learning-specific way.

Mitochondrial fusion and fission proteins and the recognition memory of imprinting in domestic chicks.

Visual imprinting is a learning process through which young, visually naive animals come to recognize a visual stimulus by being exposed to it (training) and subsequently approach the stimulus in preference to others. A large body of evidence indicates that a restricted part of the forebrain, the intermediate medial mesopallium (IMM), is a memory region for visual imprinting in the domestic chick. Previous studies have shown learning-related up-regulation of several mitochondrial proteins in the IMM 24 h after training. Learning-related increases in transcription factors involved in mitochondrial biogenesis were found without significant change in mitochondrial DNA copy number, but the issue of whether mitochondrial fusion or fission processes change with learning was unresolved. The present study enquired whether proteins involved in mitochondrial fusion and fission contribute to memory following imprinting. Tissue was sampled from the left and right IMM, and the left and right posterior pole of the nidopallium (a control brain region not involved in imprinting). The amounts of the following proteins were measured by Western immunoblotting 24 h after training: mitochondrial mitofusin-1 (MTF-1, as indicator of mitochondrial fusion), membrane dynamin-related protein-1 (DRP-1, as indicator of mitochondrial fission) and cytoplasmic DRP-1. Learning-related increases in MTF-1 and DRP-1 were observed bilaterally in the IMM, but not in either side of the posterior pole of the nidopallium. Cytoplasmic DRP-1 was not changed significantly in any region studied. The results implicate increased, balanced levels of mitochondrial fusion and fission in memory formation up to 24 h after training.Supplementary Video Abstract (Supplemental digital content 1, http://links.lww.com/WNR/A446).

A Proteomic Study of Memory After Imprinting in the Domestic Chick.

The intermediate and medial mesopallium (IMM) of the domestic chick forebrain has previously been shown to be a memory system for visual imprinting. Learning-related changes occur in certain plasma membrane and mitochondrial proteins in the IMM. Two-dimensional gel electrophoresis/mass spectrometry has been employed to identify more comprehensively learning-related expression of proteins in the membrane-mitochondrial fraction of the IMM 24 h after training. We inquired whether amounts of these proteins in the IMM and a control region (posterior pole of the nidopallium, PPN) are correlated with a behavioral estimate of memory for the imprinting stimulus. Learning-related increases in amounts of the following proteins were found in the left IMM, but not the right IMM or the left or right PPN: (i) membrane cognin; (ii) a protein resembling the P32 subunit of splicing factor SF2; (iii) voltage-dependent anionic channel-1; (iv) dynamin-1; (v) heterogeneous nuclear ribonucleoprotein A2/B1. Learning-related increases in some transcription factors involved in mitochondrial biogenesis were also found, without significant change in mitochondrial DNA copy number. The results indicate that the molecular processes involved in learning and memory underlying imprinting include protein stabilization, increased mRNA trafficking, synaptic vesicle recycling, and specific changes in the mitochondrial proteome.

Molecular mechanisms of memory in imprinting.

Converging evidence implicates the intermediate and medial mesopallium (IMM) of the domestic chick forebrain in memory for a visual imprinting stimulus. During and after imprinting training, neuronal responsiveness in the IMM to the familiar stimulus exhibits a distinct temporal profile, suggesting several memory phases. We discuss the temporal progression of learning-related biochemical changes in the IMM, relative to the start of this electrophysiological profile. c-fos gene expression increases <15 min after training onset, followed by a learning-related increase in Fos expression, in neurons immunopositive for GABA, taurine and parvalbumin (not calbindin). Approximately simultaneously or shortly after, there are increases in phosphorylation level of glutamate (AMPA) receptor subunits and in releasable neurotransmitter pools of GABA and taurine. Later, the mean area of spine synapse post-synaptic densities, N-methyl-D-aspartate receptor number and phosphorylation level of further synaptic proteins are elevated. After ∼ 15 h, learning-related changes in amounts of several synaptic proteins are observed. The results indicate progression from transient/labile to trophic synaptic modification, culminating in stable recognition memory.

Diagnostic reliability of MMPI-2 computer-based test interpretations.

Reflecting the common use of the MMPI-2 to provide diagnostic considerations, computer-based test interpretations (CBTIs) also typically offer diagnostic suggestions. However, these diagnostic suggestions can sometimes be shown to vary widely across different CBTI programs even for identical MMPI-2 profiles. The present study evaluated the diagnostic reliability of 6 commercially available CBTIs using a 20-item Q-sort task developed for this study. Four raters each sorted diagnostic classifications based on these 6 CBTI reports for 20 MMPI-2 profiles. Two questions were addressed. First, do users of CBTIs understand the diagnostic information contained within the reports similarly? Overall, diagnostic sorts of the CBTIs showed moderate inter-interpreter diagnostic reliability (mean r = .56), with sorts for the 1/2/3 profile showing the highest inter-interpreter diagnostic reliability (mean r = .67). Second, do different CBTIs programs vary with respect to diagnostic suggestions? It was found that diagnostic sorts of the CBTIs had a mean inter-CBTI diagnostic reliability of r = .56, indicating moderate but not strong agreement across CBTIs in terms of diagnostic suggestions. The strongest inter-CBTI diagnostic agreement was found for sorts of the 1/2/3 profile CBTIs (mean r = .71). Limitations and future directions are discussed.

AMPA receptor phosphorylation and recognition memory: learning-related, time-dependent changes in the chick brain following filial imprinting.

There is strong evidence that a restricted part of the chick forebrain, the intermediate medial mesopallium (IMM), stores information acquired through the learning process of visual imprinting. We have previously demonstrated that at 1 h but not 24 h after imprinting training, a learning-specific increase in the amount of membrane Thr286-autophosphorylated α-calcium/calmodulin-dependent protein kinase II (αCaMKII), and in the proportion of total αCaMKII that is phosphorylated, occurs in the IMM but not in a control brain region, the posterior pole of the nidopallium (PPN). αCaMKII directly phosphorylates Ser831 in the GluA1 subunit of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor. In the present study we have inquired whether the learning-related increase in αCaMKII autophosphorylation is followed by changes in the Ser831 phosphorylation of GluA1 (P-GluA1) and in the total amount of this subunit (T-GluA1). Trained chicks together with untrained control chicks were killed either 1 or 24 h after training. Tissue was removed from the IMM together with tissue from the PPN as a control. Amounts of P-GluA1 and T-GluA1 were measured. In the left IMM of the 1 h group the P-GluA1/T-GluA1 ratio increased in a learning-specific way. No learning-related changes were observed in other brain regions at 1 h or in any region 24 h after training. The results indicate that a time- and regionally-dependent, learning-specific increase in GluA1 phosphorylation occurs early in recognition memory formation.

Imprinting.

Imprinting is a type of learning by which an animal restricts its social preferences to an object after exposure to that object. Filial imprinting occurs shortly after birth or hatching and sexual imprinting, around the onset of sexual maturity; both have sensitive periods. This review is concerned mainly with filial imprinting. Filial imprinting in the domestic chick is an effective experimental system for investigating mechanisms underlying learning and memory. Extensive evidence implicates a restricted part of the chick forebrain, the intermediate and medial mesopallium (IMM), as a memory store for visual imprinting. After imprinting to a visual stimulus, neuronal responsiveness in IMM is specifically biased toward the imprinting stimulus. Both this bias and the strength of imprinting measured behaviorally depend on uninterrupted sleep shortly after training. When learning-related changes in IMM are lateralized they occur predominantly or completely on the left side. Ablation experiments indicate that the left IMM is responsible for long-term storage of information about the imprinting stimulus; the right side is also a store but additionally is necessary for extra storage outside IMM, in a region necessary for flexible use of information acquired through imprinting. Auditory imprinting gives rise to biochemical, neuroanatomical, and electrophysiological changes in the medio-rostral nidopallium/mesopallium, anterior to IMM. Auditory imprinting has not been shown to produce learning-related changes in IMM. Imprinting may be facilitated by predispositions. Similar predispositions for faces and biological motion occur in domestic chicks and human infants. WIREs Cogn Sci 2013, 4:375-390. doi: 10.1002/wcs.1231 For further resources related to this article, please visit the WIREs website.

Bribery or just desserts? Evidence on the influence of Congressional reproductive policy voting patterns on PAC contributions from exogenous variation in the sex mix of legislator offspring.

Evidence on the relationship between political contributions and legislators' voting behavior is marred by concerns about endogeneity in the estimation process. Using a legislator's offspring sex mix as a truly exogenous variable, we employ an instrumental variable estimation procedure to predict the effect of voting behavior on political contributions. Following previous research, we find that a legislator's proportion daughters has a significant effect on voting behavior for women's issues, as measured by score in the "Congressional Record on Choice" issued by NARAL Pro-Choice America. In the second stage, we make a unique contribution by demonstrating a significant impact of exogenous voting behavior on PAC contributions, lending further credibility to the hypothesis that Political Action Committees respond to legislators' voting patterns by "rewarding" political candidates that vote in line with the positions of the PAC, rather than affecting those same votes - at least in this high-profile policy domain.

Rapid induction of the immediate early gene c-fos in a chick forebrain system involved in memory.

Previous work has shown that expression of Fos protein in neurons of the intermediate and medial mesopallium (IMM), a memory region in the forebrain of the domestic chick, increases in a learning-related manner after behavioural imprinting. We show here, using in situ hybridisation, that when chicks are trained for 15 min with an imprinting stimulus, expression of c-fos mRNA in the IMM rises to a maximum at or before the end of this training period. The results suggest that the learning-related increase in Fos protein production, which occurs in identifiable neuronal sub-populations in the IMM, reflects events that make an early contribution to learning and/or memory processing.

Different forms of MARCKS protein are involved in memory formation in the learning process of imprinting.

There is strong evidence that a restricted part of the chick forebrain, the IMM (formerly IMHV), stores information acquired through the learning process of visual imprinting. Twenty-four hours after imprinting training, a learning-specific increase in amount of myristoylated, alanine-rich C-kinase substrate (MARCKS) protein is known to occur in the homogenate fraction of IMM. We investigated the two components of this fraction, membrane-bound and cytoplasmic-phosphorylated MARCKS. In IMM, amount of membrane-bound MARCKS, but not of cytoplasmic-phosphorylated MARCKS, increased as chicks learned. No changes were observed for either form of MARCKS in PPN, a control forebrain region. The results indicate that there is a learning-specific increase in membrane-bound, non-phosphorylated MARCKS 24 h after training. This increase might contribute to stabilization of synaptic morphology.

Dynamics of a memory trace: effects of sleep on consolidation.

BACKGROUND: There is evidence that sleep is important for memory consolidation, but the underlying neuronal changes are not well understood. We studied the effect of sleep modulation on memory and on neuronal activity in a memory system of the domestic chick brain after the learning process of imprinting. Neurons in this system become, through imprinting, selectively responsive to a training (imprinting) stimulus and so possess the properties of a memory trace. RESULTS: The proportion of neurons responsive to the training stimulus reaches a maximum the day after training. We demonstrate that sleep is necessary for this maximum to be achieved, that sleep stabilizes the initially unstable, selective responses of neurons to the imprinting stimulus, and that for sleep to be effective, it must occur during a particular period of time after training. During this period, there is a time-dependent increase in EEG activity in the 5-6 Hz band, that is, in the lower range of the theta bandwidth. The effects of sleep disturbance on consolidation cannot be attributed to fatigue or to stress. CONCLUSIONS: We establish that long-term trace consolidation requires sleep within a restricted period shortly after learning. Undisturbed sleep is necessary for the stabilization of long-term memory, measured at the behavioral and neuronal levels, and of long-term but not short-term neuronal responsiveness to the training stimulus.

Ca2+/calmodulin protein kinase II and memory: learning-related changes in a localized region of the domestic chick brain.

The role of calcium/calmodulin-dependent protein kinase II (CaMKII) in the recognition memory of visual imprinting was investigated. Domestic chicks were exposed to a training stimulus and learning strength measured. Trained chicks, together with untrained chicks, were killed either 1 h or 24 h after training. The intermediate and medial hyperstriatum ventrale/mesopallium (IMHV/IMM), a forebrain memory storage site, was removed together with a control brain region, the posterior pole of the neostriatum/nidopallium (PPN). Amounts of membrane total alphaCaMKII (tCaMKII) and Thr286-autophosphorylated alphaCaMKII (apCAMKII) were measured. For the IMHV/IMM 1 h group, apCaMKII amount and apCAMKII/tCaMKII increased as chicks learned. The magnitude of the molecular changes were positively correlated with learning strength. No learning-related effects were observed in PPN, or in either region at 24 h. These results suggest that CaMKII is involved in the formation of memory but not in its maintenance.