Introduction to sensation and perception Flashcards
What is the definition of sensation, perception and cognition?
Sensation: registering stimulation of the senses
Perception: processing and interpreting sensory information
Cognition: using perceived information to learn, classify, comprehend
List some examples of why studying sensation and perception is important
1) Sprinters starting a running race- on blocks pressure sensors will inform judges of the race if someone has falsely started. But the false start rule also includes any pressure on the blocks after 100m/s of the gun. We know theres a physical limit to how quickly you hear a sound and react to the sound of the gun
2) cricket- pink ball introduced to enhance visibility of the ball to get away from safety and performance issues
3) artwork (aesthetic perception)- if you analyse the picture for their statistical properties, those features are similar to those that exist in the natural world. Art work is resembling nature.
4) Developing expertise by tasting/ judging wine
5) airport console- if you’re trying to search through image of belongings, this is much more difficult than just trying to look for one category of things.
6) AI- Computers are getting better at summarising images- this is because we understand what the brain is doing
7) sensory differences- effects of people who don’t have certain senses. Whats parts of the brain are involved in the process.
8) product that emits high frequency sound- keep teenagers away from your shop- their ears are more sensitive to them compared to older people
9) find out about how the brain works- how does in take in and filter information
Fundamental concepts:
List types of energy linked to sense organs which contain different receptors.
- Electromagnetic energy (light)
Eye - Photoreceptors (vision)
Primary visual cortex - Chemical composition
Chemoreceptors (detect chemicals)
Smell - olfactory cortex
Taste- gustatory cortex - Air pressure waves
Hearing- mechanoreceptors
Auditory cortex - tissue distortion
Touch- mechanoreceptors and thermoreceptors
Somatosensory cortex - gravity acceleration
Mechanoreceptors
Temporal cortex
Fundamental concepts:
Where is information passed and receiving areas
After theres been sensation at the receptor level information is passed eventually by different pathways to receiving areas of the cortex. There are different receiving areas for different receptors.
Sensitive to all of these and the sense organs contain different types of receptors
List the pathway where information travels
Information comes in from the bottom:
1) starts at the environmental stimulus
2) Up to the receptors- converted to nerve signals (transduction= conversion of environmental energy to nerve signals)
3) Goes via the thalamus (except smell) (thalamus- neuron mass in middle of brain)
4) Receiving area in cortex (eg. primary visual cortex)
5) Secondary (associative) cortex
6) Higher cortex
7) more recently- feedback mechanisms
- There is ……… from different parts of the brain towards more sensory parts of the brain.
- What do these help modulate
- What is there tension between?
- Feedback Projections
- These help modulate our experience and keep them more stable. It goes into sensory pathways.
- Tension between environmental stimulus and top down influence is a critical tension
Bottom-up processing:
- What does perception start with?
- What can you do with enough feature detectors?
- Describe Gibson- “Direct Perception” (1950s)
- Perception starts with the physical characteristics of stimuli and basic sensory processes (e.g., feature detectors- idea that there are parts of your sensory system that detect features).
- You can put them together into a sense of what the world is like.
- The information coming from sensory receptors is enough for perception to be rich and detailed – complex mechanisms are not necessary.
The environment contains sufficient cues to provide context to aid perception – e.g. texture can indicate depth.
Top-down processing:
- What does the perceiver do?
- What does Gregory (1966) describe it as?
- What helps you figure out what something is when only given small information?
- The perceiver constructs their understanding of external stimuli based on their past experience and knowledge.
- “Perception is not determined simply by stimulus patterns; rather it is a dynamic searching for the best interpretation of the available data.” (Gregory, 1966). (Thinking of brain is computer and taking in data then constructing what it thinks really is out there in the world)
- More context
When shown a video of a mask rotating but it appears to rotate the other way - how does our brain perceive this?
All of our experience with faces is that they point outwards so the hollow mask is ambiguous- don’t have 3D cues so our brain knows that faces comes outwards so it affects the way you see the object.
What are the methods used to investigate sensation and perception?
- Staining
- Single-cell recordings (electrophysiology)
- Functional Magnetic Resonance Imaging fMRI
- Lesion studies
- Event-related potential (ERP) from electro-encephalogram (EEG)
- Optical Imaging / Near infra-red spectroscopy (NIRS)
- Psychophysics
- Illusions & introspection
- Computational modelling
Explain the methods of:
1. Staining
2. Single-cell recordings (electrophysiology)
3. Functional Magnetic Resonance Imaging fMRI
- Staining: take dead brain tissue and apply stains which enables you to see the structure of the brain
- Single-cell recordings (electrophysiology): insert electrodes into the brain and measure from individual neurons. So you’re able to see whether neurons are sensitive to that type of visual stimulus.
- Functional Magnetic Resonance Imaging fMRI: tells you what parts of the brain are active in response to particular stimuli
Explain the methods of:
4. Lesion studies
5. Event-related potential (ERP) from electro-encephalogram (EEG)
6. Optical Imaging / Near infra-red spectroscopy (NIRS)
- Lesion studies: understanding parts of the brain that do particular jobs. Eg. phineas gage- part of the brain gets destroyed (lesioned)- whats the effect- if a part of the brain is missing it can help you tell what that part of the brain was doing related to that particular function.
- Event-related potential (ERP) from electro-encephalogram (EEG): Records the electrical activity across the scalp. Measures the time course. Early components- sensory process, Later components- cognitive process.
- Optical Imaging / Near infra-red spectroscopy (NIRS): Optoids- light sensors. And an LED which shines bright near the infra red. This light goes through the scalp and skull . Then you can measure the change in reflected light and the amount of blood flow over the surface of the brain. This is an alternative way to see the activity of the brain.
Explain the methods of:
7. Psychophysics
8. Illusions & introspection
9. Computational modelling
- Psychophysics: Give a pp something to do in front of a computer- manipulate physical stimulus then measure psychological response by asking people to respond in a certain way.
- Illusions & introspection: not seeing whats real so can ask why our brain has constructed things that way for us.
- Computational modelling: Build a computer that operates in the same way as a brain might work. Give the computer a task and see if a human reacts in a similar way.
Single-cell recording:
- What are Action Potentials of neuron recorded with?
- what does cortical recording require?
- useful for?
- Action potentials of neurons recorded with micro electrode inserted close to cell.
- Cortical recording requires section of skull to be removed.
- Only on humans if medical operation (e.g., for epilepsy).
- Useful for identifying cells which are selective for certain features (e.g., orientations, direction of motion, faces).
Single-cell recording:
What can single neurons be selective for?
Quiroga et al. (2005)
Tasks and results
Single neurons can be selective for a stimulus as specific as one particular person.
- Epilepsy patients implanted with depth electrodes, recording from single cells
- Presented with photos, text name and spoken name of multiple people
- Selective neurons in medial temporal lobe represent individuals in multiple sensory modalities
