Visual perception

To start, for my project I have decided to compose a report on how our minds perceive the world around us. How initial contact with the world is processed by the brain, as well as the origins of perception. Through my research I have tried to bridge together concepts from neuropsychology, with the biology/anatomy of the brain. My aim was to look at individual concepts/areas of research  in depth, and link them together to give a more holistic view of the cognitive process of perception.

I hope this information can be valuable to anyone studying psychology, or simply with anyone with the slightest interest in the subject, who wants to know more of the neuroscience behind how our brains are able to carry out an autonomic process, such as having the ability to detect changes in facial expression. I have tried to break down my research as much as I could so that it can be easily understood. Enjoy!


The retina is a light sensitive, specialised tissue lining the inner surface of the human eye (consisting of a layered structure, made up at least five neurons: photoreceptors, horizontal cells, bipolar cells, amacrine cells and ganglion cells.) Using an ophthalmoscope looking into the human eye, the optic nerve will be seen in the centre of the retina, with the appearance of a small white circle measuring about 2 x 1.5 mm across. Ganglion cells are known as the output cells of the retina, which are contained within the optic nerve. The axons of these neurons transmit electrical impulses to the brain, relaying information of the objects we see, while the photoreceptors are located on the outer of the retina, closest to the lens of the eye. As light travels through the human retina, the activation of the rods and cones (type of photoreceptor) takes place. The pigment contained within these photoreceptors absorb photons (a particle of energy associated with light), stimulating an electrical impulse in order to activate the succeeding neurons forming the retina.
But how exactly is this electrical impulse initiated?
To break it down: 

  • The pigment molecule present in rod cells is called rhodopsin.
  • When light reacts with this molecule, it is broken down into two: opsin (an enzyme), and retinal.
  • The enzyme formed works by keeping the rod cell constantly hyper-polarised (by  closing the Sodium ion channels).
  • As we’ve already learnt, this hyper polarisation allows an action potential to be generated, which travels through the optic nerve to our brain. In this way, our brains are able to form an image of the object we are viewing.
  • This is why after staring at a bright light, it takes a while for this light to disappear from our vision, as not all of the rhodopsin has been restored.

Screen Shot 2014-08-06 at 22.07.14

 


Sensory memory, also known to psychologists as the working memory model, may be defined as a system with ability to momentarily hold multiple pieces of information within the brain, which can then be manipulated. The role of working memory is concerned with the initial contact between the individual and their external environment. It’s function mainly is in processing environmental stimuli, and is associated with vital cognitive functions such as language comprehension, as well the perception of familiar faces (a human instinct). Such information is recognised by the brain, processed and decoded, existing in our memories for extremely brief moments.

The neural basis of facial perception is an area of great interest to neuroscientists and psychologists, providing a key focus for extensive research. This area of study can provide scientists with information of the specificity of  our visual recognition system , as well as the structural arrangement of the brain; not to mention the importance to humans of forming the ability to recognise faces, being able to determine someones identity, as well as to learn about their mood, sex, and age. The fusiform gyrus (also known as the occipitotemporal gyrus) forms part of the  temporal lobe, and is thought to be associated with both face, and body recognition (despite the many conflicting ideas of the functionalities of this region), and sits just above the brain’s cerebellum, pons and medulla.

These identified “core” regions of the occipital and temporal lobes have been found to play a  vital role in how our brain distinguishes between different faces, of which the neural activity has been found to have a much higher response to known faces than to faces that are otherwise “unknown” to us, confirming the specific response of our brains to specific faces. The cognitive processing of human faces has also generated much research, revealing that our fusiform gyrus forms a “holistic” view of faces, taking in details such as the distance between facial features, as opposed to focusing on individual features separately, which then allows us to form a general overview of someone’s face. Not only will enhancing our understanding of how our brains distinguish between faces reveal details of the highly complex cognitive processes involved, but will also aid the development of sophisticated technologies needed for various security procedures (as seen in airports for example). Additionally, such research will be able to shed light on disorders such as “face blindness”, otherwise known as prosopagnosia, or other such related disorders, known to occur following serious brain injury, or a stroke (when the bloody supply to the occipitotemporal gyrus is completely cut off).

The amygdala specifically, lies deep within the brain’s temporal lobe, forming a dense network of neurons, of which have been found to be important in regulating our emotions. However, it has emerged from recent study that there may be cross communication between the amygdala and the fusiform gyrus during facial recognition (receiving electrical input from regions such as the hypothalamus, hippocampus and olfactory bulbs). What this tells us about the brain is that these components do not have simply one function. The way we see things occurs as a result of rapid cross communication between these components.
BrainDevelopment143

This research has helped me confirm that the way we perceive the world is pretty incredible. Thinking of each and every thing we recognise from our environment at each given moment confirms the complexity of the perceptual process. However, with this in mind, this complexity requires technological advances to enable scientists to locate, and map the origin of where perception comes from. While studies suggest the significance of the fusiform gyrus in facial recognition, more research is needed to confirm this. As for working memory, the neural basis, and genetic component is not yet known, while numerous theories exist.


Sources:

 Author:   Soderquist, David R.
Title:   Sensory Processes
URL: http://web.b.ebscohost.com.revproxy.brown.edu/ehost/ebookviewer/ebook/ZTAwMHhuYV9fNDc0NjEzX19BTg2?sid=19d47c53-6d07-4bed-bf9b-9b16e599231e@sessionmgr111&vid=1&format=EB&rid=1http://faculty.stcc.edu/AandP/AP/AP2pages/Units14to17/unit15/retina.htm

 http://vpnl.stanford.edu/papers/GrillSpectorWeiner_NRN_2014.pdf
http://neuroscience.uth.tmc.edu/s2/chapter14.html
 http://neuroscience.uth.tmc.edu/s2/chapter15.html
http://webvision.med.utah.edu/book/part-i-foundations/simple-anatomy-of-the-retina http://web.mit.edu/bcs/nklab/media/pdfs/KanwisherMoscovitch2000.pdf   http://psy2.ucsd.edu/~dmacleod/221/cortex%20papers/haxbyface.pdf http://neuroscience.uth.tmc.edu/s4/chapter06.html

http://rstb.royalsocietypublishing.org/content/362/1481/761.full#ref-43
http://www.ncbi.nlm.nih.gov/pubmed/21497657

http://brainmind.com/BrainLecture5.html
http://webvision.med.utah.edu/book/part-i-foundations/simple-anatomy-of-the-retina/

 

2 responses to “Visual perception”

  1. Aiswarya Nagasubramony says:

    Wow, you integrated a lot of information into this post. I appreciate the diagrams that you have included, as it helps me understand some of the concepts better. Great job!

  2. Carlos Aizenman says:

    Great breakdown on the inner working of the visual system!

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