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, ranging 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).

Martin E, Thiel T, Joeri P, Loenneker T, Ekatodramis D, Huisman T, Hennig J, Marcar VL. Effect of pentobarbital on visual processing in man. Hum Brain Mapp 2000;10(3):132-139.

Marcar VL, Loenneker T, Straessle A, Girard F, Martin E. How much luxury is there in 'luxury perfusion'? an analysis of the BOLD response in the visual areas V1 and V2. Magn Reson Imaging 2004;22(7):921-928.

Marcar VL, Loenneker T, Straessle A, Girard F, Martin E. What the little differences between men and women tells us about the BOLD response. Magn Reson Imaging 2004;22(7):913-919.

Marcar VL, Loenneker T, Strassle AE, Schwarz U, Martin E. What effect does measuring children under anesthesia have on the blood oxygenation level-dependent signal? A functional magnetic resonance imaging study of visual cortex. Pediatr Res 2004;56(1):104-110.

Marcar VL, Straessle A, Girard F, Loenneker T, Martin E. When more means less: a paradox BOLD response in human visual cortex. Magn Reson Imaging 2004;22(4):441-450.

Marcar VL, Loenneker T, Straessle A, Jaggy S, Kucian K, Martin E. An fMRI study of the cerebral macro network involved in cue invariant form perception and how it is influenced by stimulus complexity. NeuroImage 2004;23:947–955

Marcar VL, Strässle A, Loenneker T, Schwarz U, Martin E. The influence of cortical maturation on the BOLD response: An fMRI study of visual cortex in children. Pediatr Res 2004;56(6):967-974.

Marcar VL, Loenneker T. The BOLD response: A new look at an old riddle. NeuroReport 2004;15(13):1997-2000

Marcar VL, Schwarz U, Martin E, Loenneker T. How depth of anesthesia influences the BOLD signal from visual cortex of children. AJNR 2005; accepted for publication