BA17

BA17, or Brodmann area 17, is a region of the cerebral cortex defined by Korbinian Brodmann's cytoarchitectural map. In humans, it corresponds to the primary visual cortex and is commonly referred to as V1. BA17 is located in the occipital lobe along and around the calcarine sulcus, with boundaries that vary slightly among individuals. It is often called the striate cortex because the stria of Gennari, a myelinated band in layer IV, is visible in histological sections.

Histology and structure: BA17 is a granular, six-layered cortex. A prominent layer IV (often labeled 4C) receives the majority of input from the lateral geniculate nucleus of the thalamus. The laminar organization supports the initial processing of visual information, including edge and orientation discrimination, within a retinotopic layout.

Function and connectivity: BA17 serves as the primary recipient of visual data, performing early processing to produce basic representations such as edges, contrasts, and basic spatial organization. Retinotopy is preserved across BA17, with high acuity mapped to central vision. Information is transmitted from BA17 to adjacent visual areas (notably BA18, the secondary visual cortex) and onward to higher-order regions involved in form, motion, and color perception, as well as to parietal and temporal pathways for further processing and action guidance.

Clinical significance: Lesions restricted to BA17 can cause contralateral visual field deficits, such as homonymous hemianopia or quadrantanopia, depending on lesion size and location. Extensive damage may result in cortical blindness. Macular sparing can occur in some cases due to differing blood supply in the occipital cortex.

History: The area was defined as part of Brodmann's map in 1909, and in humans it roughly corresponds to the primary visual cortex.