Function
Area 19 is a histologically delineated band anterolaterally abutting visual area 18. Single-cell electrophysiological recordings from area 19 in the cat suggest sensitivity to motion-delineated forms; recordings from primates have yielded varying results, indicating that this area may be a heterogeneous collection of visual areas, with multiple incomplete representations of the visual scene.
In humans, this band putatively contains regions of the visual areas designated V3, V4, V5 (also known as the middle temporal area, or MT) and V6 (also known as dorsomedial area) in the primate. Functional magnetic resonance imaging shows the existence of various retinotopic maps within area 19. In general, the diverse fields that comprise area 19 have reciprocal connections with areas 17 and 18, as well as posterior parietal and inferior temporal association areas.
Area 19 has been noted to receive inputs from the retina via the superior colliculus and pulvinar, and may contribute to the phenomenon of blindsight. In patients blind from a young age, the area has been found to be activated by somatosensory stimuli.
Because of these findings, it is thought that area 19 is the differentiation point of the two visual streams, of the 'what' and 'where' visual pathways. The dorsal region may contain motion-sensitive neurons, and ventral areas may be specialised for object recognition.
Read more about this topic: Brodmann Area 19
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