The Effect of Fraternal Birth Order on Motor Coordination: Developing a Model

for Autism, Attention Deficit/Hyperactivity Disorder, and

Dyslexia

Allison S. Shaw1,2,3, Dave Putz1, and S. Marc Breedlove1

1 Neuroscience Program, Michigan State University, East Lansing, MI2 College of Communication Arts and Sciences, Michigan State

University, East Lansing, MI 3Ronald E. McNair Post-Baccalaureate Achievement

Program/Summer Research Opportunity Program, Office of Supportive Services, Michigan State University, East Lansing, MI

Neurodevelopmental Disorders Disorders that appears early in childhood Most common are autism, dyslexia, and

attention deficit/hyperactivity disorder Suggested that they have a maternal

antibody basisDalton et al. (2003) and Vincent et al.(2002)

posit that these disorders may be caused by antibodies that transfer through the placenta to the fetus and affect development

Maternal Immune Transfer

This transfer has become known as the Maternal Immune Hypothesis and has been suggested as the cause for many other traits as well.

Fraternal Birth Order

Blanchard & Bogaert (1996) suggest that fraternal birth order may effect fetuses in utero by a similar maternal transfer

They posit that maternal immune response signals androgen release

Fetal antigens

Mother’s immune system

antibodiesandrogen

Maternal Immune Hypothesis

Fraternal Birth Order Fraternal Birth Order

The birth order of male siblings born Numerous human traits are related to fraternal

birth order Females overlooked

Females are not affected by fraternal birth order Female birth order does not affect traits

Seem to be an additive affect

Fraternal Birth Order and Neurodevelopmental Disorders Autism and Dyslexia have a fraternal birth order

effect (Cohen-Baron, unpub. & Caspi, unpub.) Males with Attention Deficit/Hyperactivity

Disorder have been shown to be hypermasculinized in specific traits due to prenatal androgens, as suggested by the maternal immune hypothesis (McFadden, unpub.)

Motor Coordination

Impaired motor coordination Ranging from inability to control movement

to deficiencies in fine motor movement Static rod is a rodent paradigm used to

assess motor coordination

This is the first study to control the birth order of mice in order to develop a model that will examine the etiology of Autism, Dyslexia, and Attention Deficit/Hyperactivity Disorder

Methodology Participants

110 mice 61 males

25 older brothers 36 older sisters

49 females 20 older brothers 29 older sisters

First litter fetuses were separated using Green Fluorescent Protein (GFP) transgene

Green Fluorescent Protein (GFP) transgenic mice

Green Fluorescent Protein (GFP) transgenic mice (cont’d)

Methodology (cont’d) Procedures

5 wooden dowel rods Length: 69.5mm Diameters: 31.1, 25.6, 19.5, 15.4, 9.4mm

Mice taken in groups of 10 All mice in group run on Rod 1 (31.1mm

diameter) Placed at end of rod facing away from ledge Clock started when experimenter released mouse

Procedures were repeated for Rods 2-5.

Methodology (cont’d)

InstrumentationRecorded into The Observer

Time to rotate 180 Time to reach line 10cm from ledge

If the mouse fell off, default time was given (180secs.)

Maximum time-180secs.

Results-Rotation Times

Effect F Hypothesis df Error df Sig.

Weight 2.42 5 101 0.041

Older Siblings 1.24 5 101 0.296

Sex 0.22 5 101 0.959

Older Siblings * Sex 1.45 5 101 0.212

No significant effects of sex and older siblings on Static Rod rotation times

Results-Transit Times

Effect F Hypothesis df Error df Sig.

Weight 0.76 5 101 0.583

Older Siblings 0.38 5 101 0.862

Sex 1.04 5 101 0.399

Older Siblings * Sex 2.02 5 101 0.082

There exists a small effect of sex and older sibling on Static Rod transit times

Transit Times as a Function of Sex and Older Siblings

Older Sisters Older Brothers

145

150

155

160

165 MalesFemales

Rod 1*

Older Sisters Older Brothers

136

138

140

142

144

146

148

150

Rod 2

Older Sisters Older Brothers

154

156

158

160

162

164

166

Rod 3

Older Sisters Older Brothers

155

160

165

170

175

180

Rod 4*

Older Sisters Older Brothers

165

170

175

180

185

Rod 5

seconds seconds

seconds seconds seconds

Rod 1 *

seconds

*p< .056

**p< .034

seconds

Rod 4

Tentative Conclusions

Birth Order differentially affects motor coordination depending on sex

Females may not be affected by fraternal birth order, but instead by their male litter mates

Future Direction

Continue behavioral testing: object recognition and novelty, gap detection, social recognition, etc.

Modify model in order to better control for variability

Use male/female sets of twins to investigate androgen response

Acknowledgements

Breedlove/Jordan Lab McNair/SROP staff McNair/SROP Natural

Science Methods Class

McNair/SROP colleagues

This research project was funded by NIH grant MH58703