[Paleopsych] Functional MR Imaging of Visual Processing: Developmental Aspects and Brain Plasticity.

[Steve Hovland]

http://www.research-projects.unizh.ch/med/unit41900/area173/p248.htm	
with applications to propaganda?  skh	
	
	
	
	

a) Visual processing in neonates, infants and children: Subcortical 
structures appear to play an important role in processing visual in 
neonates and infants. In the present study, subcortical activity has been 
observed in a minority of infants, children and adults alike, suggesting 
that the subcortical structures play an important role in visual perception 
from birth until adulthood. b) Development of functional subsystems in the 
human visual cortex: We are investigating the development of both the 
primary visual cortex (striate cortex or V1) and the extra-striate cortical 
visual areas V4 and MT/V5. In the former we are following the emergence of 
the topographical representation and in the latter our research efforts are 
centred on the emergence of specialisation of function. Awake children, 
aged 8 years and older and anaesthetised infants and young children, ran  
ging from birth to 6 years are investigated in conjunction with a 
diagnostic MR imaging session. In addition, we are investigating the effect 
of different levels of anaesthesia on the fMRI signal in children. This 
study will provide us with an insight into the differential effect of 
development and depth of anaesthesia on the observed fMRI signal. c) 
Neuronal plasticity of the human visual cortex: We are investigating the 
difference in neuronal plasticity in the developing and the mature CNS by 
generating topographical activity maps of the primary visual cortex. Any 
reparative process following insult should be visible in the topography of 
V1 as observed by our topographical activity mapping. d) Cue integration 
and higher visual processing: The visual system appears to be organised 
into a dorsal pathway, dealing with motion and spatial information and the 
ventral pathway dealing with form and colour information. Our pilot 
experiments with FMRI reveal the cortical visual areas involved in the 
processing of such stimuli. e) Influence of sedative / anaesthesia (in 
particular the anaesthetic depths) on the cerebral response: Investigation 
of the influence on neural metabolism and on changes of the blood flow, 
which modulate the functional MRI (BOLD) signal. f) Visual perception 
involves the grouping of individual elements into coherent patterns that 
reduce the descriptive complexity of a visual scene. We investigate the 
cognitive basis of this perceptual simplification in younger children. g) 
Emphasis of the project in the last year was to investigate the hypothesis 
that the hemodynamic response to cortical activity does not show a 
pseudo-linear behaviour but corresponds to a two-stage model (on-off).	
	
	
	
	
	
Publications	
Martin E, Joeri P, Loenneker T, Ekatodramis D, Vitacco D, Hennig J, Marcar 
V. Visual Processing in Infants and Children studied using functional MRI. 
Pediatr Res, 8:1-6, 1999. 	
	
Martin E, Joeri P, Loenneker Th, Thiel T, Ekatodramis D, Huisman T, Hennig 
J, Marcar VL. The effect of pentobarbital on visual processing in man. 
Human Brain Mapping, 10(2), 2000. 	
	
Valentine L. Marcar, Andrea Straessle, Franck Girard, Thomas Loenneker and 
Ernst Martin. When more means less: a paradox BOLD response in human visual 
cortex. MRI, 22 (4): 441-597, 2004. 	
	
Index Terms	
functional MRI, visual processing, infants, children, brain development 	
	

Contacts		
Dr. V. Marcar (Project Leader)	Valentin.Marcar at kispi.unizh.ch 
<mailto:Valentin.Marcar at kispi.unizh.ch>	
Prof. E. Martin-Fiori (Project Leader)	ernst.martin at kispi.unizh.ch 
<mailto:ernst.martin at kispi.unizh.ch>	
Dr. Th. Loenneker	thomas.loenneker at kispi.unizh.ch 
<mailto:thomas.loenneker at kispi.unizh.ch>	
Th. Dietrich	thomas.dietrich at kispi.unizh.ch 
<mailto:thomas.dietrich at kispi.unizh.ch>