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Abstract:
Under certain conditions, lesions of the adult central nervous system can induce reorganization of cortical sensory representations in the brain. This capacity of cortical circuitry for reorganization can potentially contribute in accelerating recovery after nervous system injury, such as stroke.
In the visual system, extrastriate cortex has been shown to reorganize in an adult human subject with an extensive lesion of the primary visual cortex (Baseler et al., J Neurosci 1999). However, the extent and time course of the process of reorganization after focal area V1 lesions remains incompletely characterized. Here we use functional magnetic resonance imaging (fMRI) to characterize how the topography of early macaque visual areas changes following V1 lesions.
After creating a ~1.2 cm x 1.2 cm lesion in area V1 by aspiration, we used 4.7 T fMRI in the anesthetised macaque preparation (Logothetis et al. Nat Neurosci 1999) to monitor changes in the topographic maps of early visual areas (V2, V3) as a function of time. The stimuli we used to map the topography of visual areas were a standard ring/wedge retinotopic stimulation paradigm (Brewer et al. J Neurosci, 2002) as well as a ~20 degree x 27 degree rotating checkerboard stimulus alternating with uniform background illumination. Both stimuli have been previously shown to activate reliably early visual areas (Smirnakis et al., Nature, 2005).
Preliminary results revealed a localized cortical region within area V2/V3 whose visual modulation was strongly diminished following the V1 lesion. By monitoring how the strength of the visual modulation inside this region evolves in time we will quantify the degree of reorganization seen in area V2/V3.
