Ventral stream

The primate visual system consists of about thirty areas of the cerebral cortex called the visual cortex. The visual cortex is divided into the ventral stream and the dorsal stream. The ventral stream is associated with object recognition and form representation. It has strong connections to the medial temporal lobe (which stores long-term memories), the limbic system (which controls emotions), and the dorsal stream (which deals with object locations and motion).

From caudal to rostral, the ventral stream consists of visual areas V1 (primary visual cortex), V2, V4, and the areas of the inferior temporal cortex: PIT (posterior inferotemporal), CIT (central inferotemporal), and AIT (anterior inferotemporal). Each visual area contains a full representation of visual space. That is, it contains neurons whose receptive fields together represent the entire visual field. Visual information enters the ventral stream through the primary visual cortex and travels through the rest of the areas in sequence.

Moving along the stream from V1 to AIT, receptive fields increase their size, latency, and the complexity of their tuning.

All the areas in the ventral stream are influenced by extraretinal factors in addition to the nature of the stimulus in their receptive field. These factors include attention, working memory, and stimulus salience. Thus the ventral stream does not merely provide a description of the elements in the visual world&mdash;it also plays a crucial role in judging the significance of these elements.