Asymmetry of Cerebral Blood Flow Velocity with Processing of Facial Images During Head Down Rest
Philip C. Njemanze
Noninvasive Neurocybernetic Flow Lab, Chidicon Medical Center, Owerri, Nigeria.
CONCLUSION
The present study demonstrated that HDT alters cerebral lateralization for object and facial stimuli, with females showing opposite to male tendencies.
METHODS
INTRODUCTION: Facial expression just like language is crucial for communication among individuals. METHODS: Transcranial Doppler (TCD) ultrasonography was used to monitor mean blood flow velocity in both middle cerebral arteries during processing of facial images before (Pre-HDT), during (6 hrs-HDT and 24 hrs-HDT) and after (Post-HDT) at  -6 degrees for 24 hours of head-down tilt (HDT) in 16 (8 male and 8 female) subjects. Laterality index was assessed as side-to-side differences during each stimulus relative to baseline.  RESULTS: For males, in Pre-HDT, both object and faces were differentially right lateralized (p<0.001), but were left lateralized in females. In males, at 6hrs-HDT, both object and faces were left lateralized (p<0.05), but right lateralized in females (p<0.001). At 24hrs-HDT, both males and females were left lateralized (p<0.05). In immediate Post-HDT condition, both males and females remained left lateralized for all tasks (p<0.05).
HDT with TCD Monitoring
Lateralization Pattern 
Male                        Female
Facial Paradigms 1-5 
Statistics: Results were given as meanąSD and/or meanąSE where applicable. A one way analysis of covariance (ANCOVA) for repeated measures was performed.