Figure 1.

Monosynaptic connectivity of the MT area of the visual cortex and unilateral early-life ablative lesion approach. A, Wiring diagram detailing monosynaptic reciprocal connectivity of area MT and proposed behavioral function. B, Lateral view of the left hemisphere of the marmoset cortical surface highlighting anatomic positioning of areas in A. C, T2-weighted MRI of a marmoset brain at the level of the parafoveal MT, which was targeted for ablation at P14. MT was demarcated based on the dorsal shift in layer 4 (left, inset, red asterisk). In the anterior/posterior plane, the core of MT was denoted as when the most caudal aspect of the corpus callosum becomes visible (arrow). Further T2-weighted scans were conducted at 6 weeks and 1 year postinjury to confirm lesion location and also DTI for fractional anisoptropy analysis (Fig. 5, DTI results). Scale bar, 5 mm. D, Histologic analysis with myelin silver staining for ex vivo demarcation of MT and localization of the lesion in all five cases. Anterior/posterior positioning of the lesion is referenced against the coordinates outlined in the Paxinos marmoset brain atlas (Paxinos et al., 2012). Scale bar, 2 mm. E, Summary of the extent and retinotopic relationship of MT lesion in each lesioned lesion animal. Squares represent the horizontal meridian. Circles represent the vertical meridian. Dashed lines and associated numbers represent the eccentricity from the fovea in degrees. Solid lines represent area boundaries. Each 2D representation was created by reconstructing area MT and the lesion from histologic sections in D. Scale bar, 2 mm. Details of the experimentation each animal underwent are shown in Table 1. FEF, frontal eye fields; PE, area PE; MIP, medial intraparietal area; AIP, anterior intraparietal area; V1, primary visual cortex.