Abstract
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.
Highlights
Naïve domestic chicks come to recognize a visual stimulus by being exposed to it and subsequently approach that stimulus in preference to other stimuli
Cognin Antibodies generated against cognin both in P2 and cytoplasmic fractions reacted with a protein of apparent molecular weight 55–56 kDa, which according to the blocking reaction to immunizing peptide and molecular weight was identified as cognin (Figure 2A)
Cognin resides in two different sub-cellular compartments: (1) endoplasmic reticulum, from which it is suggested to escape to the cell surface after cleavage from its endoplasmic reticulum retention signal and (2) cell surface membrane fraction (Pariser et al, 2000; Capitani and Sallese, 2009)
Summary
Naïve domestic chicks come to recognize a visual stimulus by being exposed to it and subsequently approach that stimulus in preference to other stimuli. This learning process is known as visual imprinting and involves the formation of a memory of the imprinting stimulus (for review, see e.g., Bolhuis, 1991). The available evidence (cf Horn, 1985, 2004; McCabe, 2013) indicates that storage of information about the imprinting stimulus occurs in the IMM. This region was formerly known as the intermediate and medial hyperstriatum ventrale (IMHV) (Reiner et al, 2004). This region was formerly known as the intermediate and medial hyperstriatum ventrale (IMHV) (Reiner et al, 2004). (ii) The visual experience of the recently-hatched chick is minimal and can be controlled, giving a low baseline against which
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