Light Color Changes The Density and Height of Synapses in an Area of the Brain Essential For Learning

Abstract

The effects of pre and post-passive avoidance training, and exposure to different wavelengths of light on numerical synapse density and the mean projected synapse height in the intermediate and medial part of the hyperstriatum ventrale (IMHV) of the chick brain were investigated. Synaptic counts and the mean projected synapse height measurements were done using a 3-dimensional stereological probe, the disector, which requires no assumptions about size, shape, and orientation of synapses. It was found that there was a significant increase in the density of synapses in the left IMHV of chicks in white, yellow and red light illuminations respectively. However, the mean projected height of synapses in these chicks was significantly increased in the right IMHV under white, yellow, green but not red light illumination conditions. These results suggest that numerical and structural modification of synapses may depend on wavelengths of white, yellow, red and green lights.

Keywords

• Learning, synapses, asymmetry, stereology, wavelength specificity, intermediate and medial hyperstriatum ventrale, chick.

References

1. Bradley, P.M., Burns, B.D., Kaplan, S., Webb, A.C. 1994. Effects of light hatching on synapse number and size in the intermediate and medial part of the hyperstriatum ventrale of the domestic chick. Dev. Brain Res. 80, 295-298.
2. Calverley, R.K.S., Jones, D.G. 1990. Contributions of dendritic spines and perforated synapses to synaptic plasticity. Brain Res. Rev. 15, 215-249.
3. Cherkin, A.,1969. Kinetics of memory consolidation: role of amnesic treatment parameters. Proc. Natl. Acad. Sci. 63, 1094-1101.
4. Crowe, S.F., Zhao, W-Q, Sedman, G.L., 1994. 2-Deoxygalactose interferes with an intermediate processing stage of memory. Behav. Neural. Bio. 61, 206-213.
5. DeGroot, D.M.G.1988. Comparison of the methods for the estimation of the thickness of ultra thin tissue sections. J. Microsc. 151, 23-42.
6. Dubbeldam, J.L. 1991. The avian and mammalian forebrain correspondences and differences. Neuronal.behav. plasticity. New York: Oxford University Press. 67-91.
7. Doubell, T.P., Stewart, M.G. 1993. Short-term changes in the numerical density of synapses in the intermediate and medial hyperstriatum ventrale following one-trial passive avoidance training in the chick. J. Neurosci.13, 230-2236
8. Galal, K.M., Bradley, P.M., Drummond, P. 1990. The effect of dark rearing on dendritic development in two regions of the forebrain of the chick. Dev. Brain Res. 53,135-138.

9. Gasten, K.E., Gasten, M.G. 1984. Unilateral memory after binocular discrimination training: left hemisphere dominance in the chick. Brain Res. 303, 190-193.
10. Gundersen, H.J.G. 1977. Notes on the estimation of the numerical density of arbitrary profiles: the edge effect. J. Microsc. 111, 219-223.
11. Horn, G. 1991. Technique for removing IMHV from the chick brain, and Imprinting and recognition memory; a review of neural mechanisms. Neural. Behav. Plasticity. New York: Oxford Univ Press.44-48 and 219-261.
12. Horn, G., Bradley, P., McCabe, M.J. 1985. Changes in the structure of synapses associated with learning. J. Neurosci. 5, 3161-3168.
13. Hunter, A., Stewart, M.G. 1993. Long-term increases in the numerical density of synapses in the chick lobus parolfactorius after passive avoidance training. Brain Res. 605, 251-255.
14. Hunter, A. 1991. Synaptic plasticity in the chick lobus parolfactorius during development and following memory formation. PhD thesis, The Open University UK.
15. Mayhew, T.M., Gundersen, H.J.G. 1996. ‘If you assume, you can make an ass out of and me’: a decade of disector for stereological counting of particles in space. J. Anat. 188, 1-15.
16. Patterson, T.A., Gilbert, D.B., Rose, S.P.R. 1990. Pre- and post-training lesions of the intermediate medial hyperstriatum ventrale and passive avoidance learning in the chick. Exp. Brain Res. 80,189-195.
17. Patel, S.N., Stewart, M.G. 1988. Changes in the number and structure of dentritic spines 25 hours after passive avoidance training in the domestic chick. Brain Res. 449, 34-46.
18. Rogres, L.J. 1996. Behavioral structural and neurochemical asymmetries in the avain brain: a model system for studing visual development and processing. Neurosci. Biobehav. Rev. 20, 487-503.
19. Rose, S.P.R. 1991. How chicks make memories: the cellular cascade from C-fos to dentritic remodeling. Trends Neurosci. 14, 390-397.
20. Rogers, L.J. 1986. Lateralizastion of learning in chicks. Adv. Study Behav. 16, 147-189.
21. Stewart, M.G., Rose, S.P.R., King, T.S., Gabbott, P.L.A., Bourne, R. 1984. Hemisphere asymmetry of synapses in chick medial hyperstriatum ventrale following passive avoidance training: a stereological study. Dev. Brain Res. 12, 261- 269.
22. Stewart, M.G. 1991. Changes in dentritic and synaptic structure in chick forebrain consequent on passive avoidance learning. Neural. behavioral plasticity. New York: Oxford Univ Press; 305-328.
23. Stewart, M.G., Lowdnes, M., Hunter, A. 1992. Memory storage in chicks involves an increase in dendritic spine number and synaptic density. Brain Dysfunction 5, 50-64.
24. Sterio, D.C. 1984. The unbiased estimation of number and sizes of arbitrary particles using the disector. J. Microsc. 134, 127-136.
25. West, M.J. 1999. Stereological methods for estimating the total number of neurons and synapses: issues of precision and bias. Trends Neurosci. 22, 51-61. for excellent reviewing. We would also like to thank Prof.
26. Dr. Mehmet Kaya, Ms. Gunseli Tuygun and Mr. Nevruz
27. Dural for providing laboratory facilities and assistance;
28. Ondokuz Mayıs University Research Fund supported (T144) this work.