Sensation and Perception Notes 2 PDF

Please do not ever post online and do not ever distribute. All rights reserved. Thanks! :) *** Chapter 5: Sensation & Perception LECT 2 C. Visual Information Processing (1 to 4): ❖ Information processing in order of increasing complexity...

Please do not ever post online and do not ever distribute. All rights reserved. Thanks! :) *** Chapter 5: Sensation & Perception LECT 2 C. Visual Information Processing (1 to 4): ❖ Information processing in order of increasing complexity: 1. Retina: Processing of visual information begins at the level of the retina with bipolar cells. Ultimately, the information will reach the thalamus. 2. Thalamus: After further processing, the thalamus (Lateral geniculate nucleus, LGN) will relay it to the visual cortex. 3. Visual cortex (Occipital lobes): Contains feature detectors (highly specialized cells that are maximally responsive to very specific stimuli). Explore and discover (book): what is the difference between a simple cell and a complex cell? 4. Parietal, Temporal Lobes & Limbic System Dorsal stream: “Where” pathway (where is the object located in space/how far away is it?) Ventral stream: “What” pathway (what are we looking at?) Limbic system: Adds the emotional experience to what it is were looking at. D. Colour Vision (D.1 to D.3): How can we/do we see colour? D.1 Young-Helmholtz Theory/Trichromatic Theory Trichromatic theory: When the theory was first proposed, people knew that there are 3 primary light colours. Three primary colours (red, green, blue) can be combined to create the millions of colours that humans see. Therefore, the trichromatic theory posits that there must be 3 different types of cones in our retina (red cones, green cones, blue cones); each cone is maximally responsive to a very specific light colour. Ex. the red cones are maximally responsive to the red colour of light. R G B The brain is constantly monitoring the activity of these 3 types of cones; what type is being activated, in what combination and to what degree? Based on this, the brain will determine the colour it will see. D.2 Opponent-Process Theory: Hering: acknowledged the value of trichromatic theory but felt that on its own it could not sufficiently explain coloured vision. Ex. it doesn’t explain complimentary afterimages. Complimentary Afterimages: Complimentary images are the colours that we see upon staring at a colour and then looking at a white surface. (ex. stare at blue, you’ll see green when you look at white; stare at green, you’ll see blue). Hering proposed that 4 primary light colours: red, green, blue, yellow. He also proposed that in the visual system, there are 3 antagonistic colour systems. Example: RG/BY/BW - The neurons in this system are maximally responsive to both red light and green light. However, they respond to these lights in opposing ways. In this example, when the red light comes in, neurons will respond with excitement. On the other hand, when a green light comes in, the neurons response in an opposing way/with inhibition to the green light. This informs the brain; when the brain notices that the neurons are inhibited, it knows that it’s a green light and so, you will see a green light. The brain constantly monitors to see what’s being excited and what being inhibited in what combinations and uses this to determine what colours we will see. D.3 Bottom Line (To Date): - Both theories are needed to help us understand colour vision. - Trichromatic theory: Cones (Retina) - Opponent process: Ganglion cells (Retina) + neurons in the brain (e.g., Thalamus) IV. Organization & Interpretation: Introduction (A to F): Gestalt Psychology: Does not exist anymore today. Its main research question was: How does the brain organize information connected by our senses? A gestalt is a form. When we look at something, the brain perceives a “gestalt” (a meaningful form/whole), as opposed to fragmented shapes/images. Thus, this theory posits that a whole may exceed the sum of its parts. The perceiving brain doesn’t perceive the world passively. It uses its knowledge, experiences, assumptions, beliefs, expectations, context to create reality. The brain constructs reality. EARN A POINT: Study in the book: Gestalt principles and Depth Perception. Guaranteed there will be questions on the first midterm from this section. Hearing (Audition) (A to E): A. The Stimulus: soundwave(s). Sound wave: Soundwaves travel in the form of vibrations, enter the ear, then are processed/translated by the brain into the psychological experience of hearing. The 3 characteristics of the soundwave: 1. Frequency: How many times a soundwave peaks per second/the distance between the peaks. Frequency is measured in hertz (Hz). Humans can only detect soundwaves of 20 to 20 000 hz. Frequency is a physical characteristic that translates into the psychological experience of pitch. o Pitch is how high or how low a sound is, NOT how loud. 2. Amplitude: Amplitude means the height of the wave. It’s measured in decibel (Db). It’s a physical characteristic that translates into the psychological experience of loudness. 3. Complexity: The complexity of the soundwave gives the human voice its unique characteristic. It’s a physical characteristic that translates into the psychological experience of timbre B. The Ear Pinna: captures the soundwaves and funnels them into the auditory canal. The soundwaves will travel in the auditory canal until they reach the eardrum, causing it to vibrate. Auditory canal: carries the soundwaves to the eardrum. Eardrum (Tympanic membrane): The vibration of the eardrum causes the ossicles to create the oval window. Ossicles: The (3) tiniest bones in your body (learn the names in the book). The vibration of the ossicles will cause the vibration of the oval window. Oval window: A membrane in the ear that will vibrate as a result of the vibration of the ossicles. Cochlear fluid (cochlea): The vibration of the oval window causes the fluid inside the cochlear to form waves (cochlear fluid). Basilar membrane: The waves in the cochlear will cause the basilar membrane to vibrate. Hair cells (cilia): The vibration of the basilar membrane causes hair cells to sway. This activates them and causes them to send the information to the brain via the auditory nerve. Auditory nerve: Carries the information to the brain. The auditory nerve will carry the information to the brain. Below are a couple of stops: Thalamus MGN (medial geniculate nucleus): The information is first sent to the thalamus. Auditory cortex (temporal lobes): Then, the information goes form the thalamus to the auditory cortex. Explore and discover (book): What does tonotopic organization mean? According to the book, some neurons that process auditory information tend to have faster action potentials and larger terminal buttons. Why?  Simple sounds are processed ___________________ whereas complex sounds are processed _____________________ A. How do we Perceive Pitch?: ❖ 2 theories: Research seems to show that that both theories are needed to understand how we perceive pitch. 1. Place Theory: Sound waves of different frequencies will cause the basilar membrane to vibrate in different locations. According to this theory, high frequency soundwaves will cause vibrations at the beginning of the basilar membrane (HF sound waves). Low frequency soundwaves will cause vibration at the end of the basilar membrane (LF sound waves). 2. Frequency Theory: The frequency of the soundwaves influences and effects the range of firing of the hair stems. 1 hertz will create 1 action potential (1 hz = 1 a.p.). B. Locating Sound: ❖ 2 binaural cues on which the brain relies to locate sound: 1. Time of arrival: This is known as inter-oral time differences. The ear closest to the sound source receives the soundwave first. The ear that is furthest will receive it second. This difference in timing informs the brain. 2. Loudness: This is known as inter-oral level differences. The ear closest to the source of the sound will perceive the sound to be louder than the ear that is further away, because as the sound enters the first ear and travels through flesh and bone, it becomes muffled. This difference in loudness informs the brain and that’s how it locates the sound. Both: What if the soundwaves hit both ears at the same time? You may use your other senses to detect where the sound is coming from. Ex. you can use our vision to see who’s speaking, or tilt your head, etc.