Why do important things leap into sight? The realities of the top-down control system in the sense of sight
Top-down processing and bottom-up processing in the sense of sight
From when we get up until when we go to sleep, we spend our days looking at many things.
They could be unimportant advertisements or the characters in this article that you are reading, but what is the mechanism for this kind of visual recognition?
Various studies have reported that visual recognition can be top-down or bottom-up.
Top-down visual recognition is visual recognition when you look for something yourself, such as when you look for someone you are meeting at the station.
On the other hand, bottom-up visual recognition refers to cases where snakes or large spiders, or an attractive person suddenly appears and you look at them without being conscious of it. It is also called stimulus-driven visual recognition.
Top-down and bottom-up visual recognition are reported to have their respective brain activity, but the paper I discuss today shows specifically what top-down visual processing is.
Top-down visual information processing: frontal eye field → intraparietal sulcus → high-order visual cortex
Visual information processing is generally considered to have two broad pathways.
The first is the dorsal visual pathway (yellow-green), which processes spatial recognition, i.e., where something visible is located, and the second is the ventral visual pathway (purple), which relates to semantic recognition, i.e., what something visible is.
The research I discuss today measures brain activity using an fMRI while the patient performs visual recognition tasks to investigate the relationships between brain regions relating to visual processing when top-down attention is operating.
The subject brain regions are the frontal eye field, which relates to movement of the eyeball, the intraparietal sulcus, which is a high-order recognition area relating to the integration of various information, and V4 (quaternary visual cortex) and VP (ventral region of the tertiary visual cortex), which are high-order regions in the ventral visual pathway relating to semantic processing, and V1 (primary visual cortex) and V2 (secondary visual cortex), which are low-order visual regions.
The results showed that top-down visual recognition has the relationship:
frontal eye field (FEF) → intraparietal sulcus → high-order regions of ventral pathway (V4, VP),
and the stronger this relationship, the higher the success rate in the task.
There are examples in brain damage and developmental disorders where the patients are not good at deliberately directing attention, but I wondered whether these kinds of phenomena are related to the lack of a smooth connection somewhere in the above pathway.
Reference URL: Top-Down Control of Human Visual Cortex by Frontal and Parietal Cortex in Anticipatory Visual Spatial Attention
