What part of the brain controls depth perception?

In this post we are going to answer the question ‘’What part of the brain controls depth perception?’’ We will explain what depth perception is and how the brain is able to perceive and control it.

What part of the brain controls depth perception?

The primary visual cortex controls depth perception.

Our retina captures images in two dimensions and from this, we can organize three-dimensional perceptions. Viewing objects in three dimensions are called depth perception, and it allows us to calculate how far away objects are. With the naked eye, we estimate the distance of an oncoming car or the height of a house.

This ability is, in part, innate. Eleanor Gibson and Richard Walk discovered this ability in 1960 with the use of a miniature visual cliff with a chasm covered by strong glass. Gibson’s inspiration for the experiment came when she was having lunch on the edge of the Grand Canyon. That day she wondered if a baby, looking down, would sense danger and back away.

It allows us to calculate how far the objects are

When they returned to the Cornell University laboratory, Gibson and Walk placed 6- to 14-month-old babies on the edge of a “canyon” where they were in no danger, that is, a visual cliff. Their mothers tried to persuade them to crawl on the glass.

Most refuse to do so, showing that babies can perceive depth. Children are likely to learn to perceive depth at this stage in life. However, some newborn animals that have virtually no visual experience, such as small cats, day-old goats, and newborn chicks, respond in the same way.

Under normal circumstances, all species, when they begin to walk, have the perceptual capacity they need.

Furthermore, during the first month of life, infants try to avoid objects that are approaching directly towards them, while not being intimidated by anything that approaches them at an angle that does not directly reach them (Ball and Tronick, 1971).

At 3 months they already use the Gestalt principles of perception, looking more closely at the objects grouped differently (Quinn et al., 2002).

Biological maturity predisposes us to be cautious in the face of heights and experience increases it. Babies’ caution against heights increases when they begin to crawl, regardless of the age at which they begin to crawl. Babies who begin to walk become more cautious of heights.

How do we perceive depth?

To perceive depth and determine distance, our eyes use three methods:

Size of the known object on your retina

Previous experience allows us to know the size of the objects. This is helpful for the brain in calculating distance based on the size of the object on the retina.

Moving parallax

The best example of this is standing face to face with another person and moving your head from side to side. The person we are looking at moves quickly, while objects at a greater distance do not move. This helps our brain to calculate how far or close objects are from us.

Stereoscopic vision

Our eyes are about two inches apart.

In this way, each eye receives a different image of an object on its retina, especially when the observed object is at a short distance.

When you’re far away, stereoscopic vision doesn’t work as well, as objects appear more similar when they’re further away from your eyes.

Types of depth perception

There are different types of depth perception, known as depth signals. The depth signals are divided into:

• Binoculars (both eyes).
• Monoculars (one eye).
• Inferred (the combination of binocular and monocular signals).

All require the contribution of one or both eyes to the brain to achieve a correct perception of depth. Perceiving distances and sizes well depends on what type of signal each person has.

Stereoscopic viewing of images occurs when a person sees clearly with both eyes. Those who only see with one eye do not have this ability and must use other indicators to determine depth.

Other binocular signals are: 

• Retinal Disparity: Each eye receives a slightly different image as each eye perceives the object from a different angle.
• Fusion: it happens when the brain, through the retinal images of the two eyes, forms an object. Blending occurs when objects appear the same.

In people with only one eye, monocular signals make it possible to perceive the depth and size of objects.

Relative size is when we know that two objects are the same size, but their actual size is unknown. This allows to estimate and perceive the relative depth of the two objects.

Other monocular signs are:

• Interposition: these signals occur when there is an overlap of objects.
• Linear perspective: when objects of known distance are perceived smaller and smaller, they are interpreted as objects that are further away.
• Aerial perspective: the contrast of objects, as well as their relative color, gives clues about the distance at which it is. The object is perceived as distant, when the scattering of light blurs its contours.
• Light and Shadow: Light and shadow also provide information about the depth and dimensions of an object.
• Monocular motion parallax: When we move our head from one side to the other, objects move at different speeds when they are at different distances.

Visual cortex: what is it and where is it?

The part of the cortex primarily dedicated to processing visual stimulation from the photoreceptors of the retina is known as the visual cortex. It is one of the most represented senses at the level of the cortex, processing most of the occipital lobe and a small part of the parietal lobes.

Visual information passes ipsilaterally from the eyes to the lateral geniculate nucleus of the thalamus and the superior colliculus, finally reaching the cerebral cortex for processing.

Once there, the different information captured by the receivers are worked on and integrated to give them meaning and allow us the real perception of fundamental aspects such as distance, color, shape, depth or movement, and finally to give them a joint meaning.

However, the total integration of visual information (that is, the last step of its processing) does not take place in the visual cortex, but in networks of neurons distributed throughout the rest of the cerebral cortex.

Main areas or parts of the visual cortex

The visual cortex is not made up of a single uniform structure, but rather includes different areas and brain pathways. In this sense, we can find the primary visual cortex (or V1) and the extrastriate cortex, which in turn is subdivided into different areas (V2, V3, V4, V5, V6).

1. Primary visual cortex

The primary visual cortex, also called the striate cortex, is the first cortical area that receives visual information and performs the first processing of it.

It is made up of both simple cells (which respond only to stimulations with a specific position in the visual field and analyze very specific fields) and complex (which capture broader visual campuses), and is organized into a total of six layers. The most relevant of all of them is number 4, since it receives the information from the geniculate nucleus.

In addition to the above, it must be taken into account that this cortex is organized into hypercolumns, composed of functional columns of cells that capture similar elements of visual information.

These columns capture a first impression of the orientation and ocular dominance, depth and movement (what happens in the columns called interblob) or a first impression of the color (in the columns or blob regions also known as spots or drops).

In addition to the above, which the primary visual cortex begins to process itself, it should be noted that in this brain region there is a retinotopic representation of the eye, a topographic map of vision similar to that of Penfield’s homunculus in terms of the somatosensory and motor system it means.

2. Extra-striated or associative cortex

In addition to the primary visual cortex, we can find various associative brain areas of great importance in the processing of different characteristics and elements of visual information.

Technically there are around thirty areas, but the most relevant are those coded from V2 (remember that the primary visual cortex would correspond to V1) to V8.

Some of the information obtained in the processing of the secondary areas will later be re-analyzed in the primary area to be re-analyzed.

Their functions are diverse and they handle different information. For example, the area V2 receives from the regions the color information and from the interblob information regarding spatial orientation and movement.

The information passes through this area before going to any other, forming part of all visual pathways. Area V3 contains a representation of the lower visual field and has directional selectivity, while the ventral posterior area has a representation of the upper visual field determined with selectivity by color and orientation.

The V4 participates in the processing of information in the form of stimuli and in their recognition.

The V5 area (also called the medial temporal area) is mainly involved in the detection and processing of the movement of stimuli and depth, being the main region in charge of the perception of these aspects. The V8 has color perception functions.

To better understand how visual perception works, however, it is advisable to analyze the passage of information in different ways.

FAQS: What part of the brain controls depth perception?

Where does depth perception occur in the brain?

In the medial temporal region of the cerebral cortex, visual system neurons which exhibit depth specificity are prevalent. Electrical activity of these cells can bias the depth calculations of an observer, meaning that they play a significant role in the perception of depth.

What is responsible for depth perception?

The focus of both eyes on a particular object, the relative variations in the form and scale of the images on each retina, the relative size of the objects in comparison to each other, and other signs such as texture and constancy are the basis of deep perception.

What causes lack of depth perception?

Refractive defects

This problem prevents you from having a clear or sharp vision.

Strabismus.

Strabismus is a visual problem that causes the eyes to be misaligned, pointing in different directions.

Amblyopia

It occurs when vision does not develop properly during childhood. It is also known as the lazy eye.

What part of the brain interprets visual form color depth and motion?

The ganglion cells send their signals to thalamus lateral geniculate nucleus (LGN) cells that respond uniquely to the particular type of information (color, shape, or motion), and so on to the primary visual cortex and other cortical areas.

How do you fix bad depth perception?

The most common way to treat depth perception problems is vision therapy. Through this therapy the brain is trained to fuse the image of each eye, or ignore the image of the eye that is not working properly.

In this post we are going to answer the question ‘’What part of the brain controls depth perception?’’ We will explain what depth perception is and how the brain is able to perceive and control it.

If you have any questions or comments please let us know!

References

Lui, J.H.; Hansen, D.V.; Kriegstein, A.R. (2011). Development and evolution of the human neocortex. Cell. 146(1): pp. 18 – 36.

Possin, K.L. (2010). Visual spatial cognition in neurodegenerative disease. Neurocase 16 (6).

Richman, D.P.; Stewart, R.M.; Hutchinson, J.W.; Caviness, V.S. (1975). Mechanical model of brain convolutional development. Science. 189(4196): 18 – 21