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SUMMARY:Imprinting primes learning: thyroid hormone a determining factor f
 or the critical period - Professor Koichi J. Homma\, Department of Molecul
 ar Pathology\, Teikyo University\, Tokyo\, Japan
DTSTART:20110706T113000Z
DTEND:20110706T123000Z
UID:TALK32018@talks.cam.ac.uk
CONTACT:Dr Brian McCabe
DESCRIPTION:Filial imprinting predisposes an animal to form an attachment 
 to animals within a critical period. The critical period for imprinting in
  chicks (Gallus gallus domesticus) is restricted to the first few days aft
 er hatching.\n   As the first topic in my talk\, I will introduce our stra
 tegy using a combination with molecular methods in analysing the function 
 of microtubule-associated protein 2 (MAP2) as an example in imprinting. We
  developed an in-vivo RNAi-mediated gene-silencing system and suppressed t
 he up-regulation of MAP2 in vivo accompanying filial imprinting. As a resu
 lt\, filial imprinting in chicks was greatly impaired. The data suggest th
 at the regulation of MAP2 expression is required for imprinting and may mo
 dify microtubule stability\, thereby leading to cytoskeletal reorganizatio
 n during imprinting.\n   As the second and main topic\, I will show that t
 hyroid hormone signalling is a determinant for the critical period and tha
 t imprinting itself primes learning. We found that the concentration of th
 yroid hormone in brain peaked around hatching\, and imprinting caused an a
 dditional increase in the concentration through enhanced conversion in bra
 in\, enabling imprinting specifically via non-genomic action\, i.e.\, impr
 inting fuels instantaneous imprinting with thyroid hormone. Four days afte
 r hatching\, thyroid hormone levels fell to background level. We found\, h
 owever\, that injecting thyroid hormone on day 4 could open a once closed 
 critical period and enable imprinting once again. If thyroid hormone was a
 pplied on day 1 without imprinting\, chicks became imprintable on day 4．
 Furthermore\, reinforced learning (as well as imprinting) was facilitated 
 by the thyroid hormone fuelling on day 1. Our data indicate that thyroid h
 ormone is a determining factor for the critical period of imprinting and i
 s able to confer memory priming. In other words\, imprinting is not a spec
 ial type of learning that serves a particular function at a particular age
 . Rather\, imprinting appears to play a crucial role in the development of
  learning in juveniles through the self-fuelling action of thyroid hormone
 .\n
LOCATION:Sub-Department of Animal Behaviour\, Madingley\, CB23 8AA
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