psyc304 week 4 discussion
psyc304 week 4 discussion
First, watch the video below discussing the primary visual cortex. Then discuss a minimum of two functions of visual cortical cells. Include in your discussion how the human brain uses these properties in perceiving objects in our everyday activities. In addition, discuss three things (situations, age etc.) that can impede the normal functioning of these properties.
Support your answer and use specific examples. You may refer to your assigned Week 3 readings in the syllabus or draw on scholarly online resources. The latter must be academic in nature (e.g. from the APUS online library) and not from pop culture and/or commercial websites, blogs, opinion sites, etc.
Minimum 300 words answer
This week we focus on the primary visual cortex. The primary visual cortex is the cortical region of the brain that receives, integrates and processes visual information relayed from the retinas. The visual cortex is divided into five areas (V1 to V5) and is based on function and structure. Visual information from the retinas passes through the thalamus, where it synapses in a nucleus called the lateral geniculate. This information then leaves the lateral geniculate and travels to V1, which centers around the calcarine sulcus. The right cortical areas process information from the left eye and the left cortical areas process information from the right eye. Three types of cells make up the primary visual cortex, which are the simple, complex and hypocomplex cells. Simple cells are the most specific and they respond to lines of width, orientation, angle and position within the visual field. Complex cells respond to the proper stimulus in any position within their receptive field. Some complex cells respond particularly to lines or edges moving in a particular direction across the receptive field. Hypocomplex cells are responsive to lines of a specific length. The human brain uses the properties of the visual cortical cells to perceive things in our everyday life. If there is damage to the fovea, a blind spot can occur. This occurs because no cortical cells are activated within the blind spot because no input from the retina has occurred. Akinetopsia can also occur, preventing someone from seeing visual motion. If a visual motion is skewed, oneâ€™s perception of an object can be altered. Age can alter oneâ€™s normal functioning of cortical cells by the speed of moving objects. As humans age, the speed and motion of cortical cells can decline (Mendelson, Wells 2001). If oneâ€™s attention and ability to focus and filter is off due to damage to cortical cells, oneâ€™s perception can be altered as well. The fovea allows us to filter out unwanted information. If this part of the visual cortex is damaged, perception can be changed. Balintâ€™s Syndrome occurs when one is unable to focus and shift attention when presented with multiple stimuli (APUS 2019). Without the cortical cells in the primary visual cortex, daily tasks that we take for granted can be impeded.
Mendelson, Wells. Elsevier. 2000. â€œAge-related changes in the visual cortexâ€. Retrieved from https://doi.org/10.1016/S0042-6989(01)00307-8.
American Public University System. 2019. PSYC304| Lesson 4: Visual Attention; Object Perceptionâ€. Retrieved from https://apus.brightspace.com/shared/elf/psyc304/lesson4/index.html
Classmates and Professor,
In this week’s video presented in our forum discussion, we listened to a lecture about the primary visual cortex and the cells within the cortex. In the video, we learned the primary visual cortex is the primary cortical region of the brain; this is near the back of the head located mostly on the medial side. In this region of the brain, we receive, integrate, and process the various types of visual information that our retinas are relaying to us. There are a few different names for the primary visual cortex; it can be commonly referred to as V1, A17, and the striate cortex.
The cells that are within the primary visual cortex are called simple cells, complex cells, and hypercomplex cells. Simple cells can primarily found in the 4c layers of grey matter within the V1. These cells primary function is to respond to objects with a particular orientation within our field of vision; this means edges and bars. The complex cell is much like the simple cell responding to objects in a specific orientation. Still, these cells have a degree of spatial orientation â€” complex cells fire over a more substantial portion of the retina, creating a sensitivity to motion. Hypercomplex cells are much like complex cells, except their vast receptive field may combine complex cell signals. Hypercomplex cells can help use perceive corners and curves in our given environment.
The primary functions of the V1 are detecting objects in motion, specific angles, position, orientation, and width within our visual environment. This means on a daily basis we use these cells to help us walk without running into objects, grab things from certain locations, walk upstairs, grab a specific item out of a box, or even drive a car.
One function that can impede this functioning properly is damage to the V1. Damage to the V1 can cause various things to happen. A common one would be running into corners and edges of furniture. Age is also a factor, as humans tend to age, our sensory functions start depleting, loss of vision can tend to happen. The speed of objects can also be affected. This is a complaint us younger folks have when we see an old person driving.
After reviewing the video regarding the primary visual cortex, I was amazed at the complexity of the structure and pathways that a visual stimulus travels from the nerves of the retina (ganglion cell axons), to the LGN or the lateral geniculate nucleus as well as the superior colliculus. We were asked to discuss a minimum of two functions of visual cortical cells as and human brain uses these properties in perceiving objects in our everyday activities. The cortical cells are made up three different neurons; the simple cell, the complex cell, and hypercomplex cells. Each of these cells all have unique characteristics in how they perform in vision.
The simple cells are responding to certain lines we see that are a particular width, orientation, angle, and position in the field of vision. (https://www.psych.athabascau.ca/, 2020). These cells can be monocular a binocular and are orientation selective. According to the two scientist who found these cells, Hubel and Weisel, these cells responded to elongated stimuli that resembled bars. (http://www.isle.hanover.edu/, 2019)
Complex Cells are orientation selective and almost all are binocular. (https://www.cns.nyu.edu/, 2020). These cells are different than simple cells in that they respond to the stimulus in any direction and lie over a larger area. Our video stated that these cells fire during movement. These cells will fire to a dark bar on a light background and light bar on a dark background when tested.
The Hypercomplex cells are unique as they respond to a specific length of lines. This cell is also called the end stop cell. These cells will respond that is in a 45-degree angle that is traveling up. Making that line longer in both directions would make the response weaker. (https://www.cns.nyu.edu/, 2020).
The primary visual cortex or V1, is responsible for how we see thing in space. The cells in V1 are arranged like a point to point map that exist between the retina and the V1. This arrangement is organized retinotopically. (https://www.ncbi.nlm.nih.gov/, 2008). This map allows the V1 to position a 2D image, horizontal and vertical point-of-view, of object. The 3D image that is mapped in V1 happens from the brain comparing both the signals and triangulating the image.
Three things that can impede the V1 from doing its job could first be observed in damage to the V1. Damage will cause visual awareness problems and blindness. This can also affect visual imagery in dreams. Age will affect the V1 as with the brain aging, the cells that let us determine speed and motion becomes hindered. Lastly, a blindspot or an area of visual space, can occur from damage to the fovea. Strokes in the brain have produced this in people. (https://www.ncbi.nlm.nih.gov/, 2012).
Minimum 200 words answer to each