Please enable JavaScript.
Coggle requires JavaScript to display documents.
Biopsychology: Visual System - Coggle Diagram
Biopsychology: Visual System
Introduction:
Some animals have special adaptations that allow them to see under very dim illumination, but no animal can see in complete darkness.
The only way one can see objects around us is the light reflected of them
Light is sometimes known as waves of electromagnetic energy between 1nanometers – 1 kilometerwaves of electromagnetic energy.
Humans can only detect electromagnetic energy in the range of 380-780 nanometers
Pupil & Lens
The amount of light entering the retinas is regulated by the donut-shaped bands of contractile tissue, the irises which give our eyes their characteristic color
The adjustment of pupil size in response to changes in illumination represents a compromise between:
Sensitivity: the ability to detect the presence of dimly lit objects
Acuity: the ability to see the details of objects
When the pupils are constricted, the image falling in each retina is sharper & there is a greater depth of focus:
• A greater range of depths is simultaneously kept in focus on the retinas
However, when the level of illumination is too low to adequately activate the receptors, the pupils dilate to let in more light, thereby sacrificing acuity & depth of focus
When we direct our gaze at something near, the tension on the ligament holding each lens in place is tampered by the ciliary muscles, & the lens goes back to its natural cylindrical shape
When we focus on a distant object, the lens is flattened. The process of adjusting the configuration of the lenses to bring images into focus on the retina is called accommodation
Wavelength:
Some animals like rattlesnakes can see wavelengths that we, humans cannot.
Wavelength & intensity are two properties of light that have particular interest:
• Wavelength plays an important role in the perception of color.
• Intensity plays an important role in the perception of brightness.
The wavelength is directly related to the energy of the light—shorter wavelengths are higher energy and longer wavelengths are lower energy.
This is why gamma radiation such as X-ray, ultraviolet and gamma ray light can be harmful but radiowaves are not.
The brightness is the intensity, whereas the color is the wavelength.
So you can make light with any wavelength you want, and make it more or less intense by making it brighter or dimmer.
Predators & Prey
Predators tend to have front-facing eyes because it enables them to accurately perceive how far away prey animals are
Prey animals tend to have side-facing eyes because it give them larger fields of vision & ability to see predators approaching from most direction
Seeing Colour
Color is one of the most obvious qualities of human visual experience. In this module, we deal with the perception of colors
The perception of an object’s colors depend on the wavelengths of light that it reflects into our eye
Classes of visual cortex
Visual cortex is often considered to be of three different classes:
Primary visual cortex
Secondary visual cortex
Visual association cortex
Primary visual cortex (PVC)
Located in:
posterior region of occipital lobes
Receive most of its input from visual relay nuclei of the thalamus
Secondary visual cortex (SVC)
Most SVC areas are located in two region:
Prestiate cortex: band of tissue in occipital lobe that surround the PVC
Inferotemporal cortex: cortex of inferior temporal lobe
Receive most input from the primary visual cortex
Visual association cortex
Located in several areas of the cerebral cortex, but largest area is in the posterior parietal cortex
Receive input from the areas of secondary visual cortex & from the secondary areas of other sensory systems
Phenomenon caused by the damage in visual part of brain:
Prosopagnosia
Is a visual agnosia for faces that can be acquired either during development or as a result of brain injury
Agnosia: a failure of recognition that is not attributable to a sensory deficit or to verbal or intellectual impairment
Visual agnosia is a specific agnosia for visual stimuli
Akinetopsia
The deficiency in the ability to see movement progress in a normal smooth fashion
It is often associated with damage to the middle temporal area of the cortex, which is located near the junction of the temporal, parietal, & occipital lobe
The position of eyes
Every being in this world has two eyes
Why some living things including human have their eye mounted side by side on the front of their heads?
This arrangement sacrifices the ability to see behind so that what is in front can be viewed through both eyes simultaneously