intro to sensation and perception

Question 1

sensation

Answer 1

registering stimulation of the senses

Question 2

perception

Answer 2

processing and interpreting sensory information - the level in which we do

Question 3

cognition

Answer 3

used perceived information to learn, classify, comprehend.

Question 4

why is studying sensation and perception important?

Answer 4

• Sport - pressure sensors to let you know if there is a false start after 100m/s of the go due to perception.
  
  • Cricket - pink ball to see the ball in the dark
  • Paintings - if they relate more to naturalistic things they are more liked
  • Tasting wine - develops our expertise

Question 5

fundamental concepts

Answer 5

• When we are talking about perception we will start with a change in the world i.e., electromagnetic energy, chemical composition, air pressure waves. Tissue distortion gravity acceleration.
  
  • Sensory organs all have receptors
  • After there has been sensation at a receptor level, they will be passed to different receiving cortexts, that will be sent to different senses.

Question 6

fundamental concepts 2

Answer 6

• electromagnetic energy -> photoreceptors - > primary visual cortex
• chemical composition -> chemoreceptors -> gustatory cortex
• chemical composition -> chemoreceptors -> olfactory cortex
• air pressure waves -> mechanoreceptors -> auditory cortex
• tissue distortion -> mechanoreceptors and thermoreceptors -> somatosensory cortex
• gravity, acceleration -> mechanoreceptors -> temporal cortex

Question 7

fundamental concept 3

Answer 7

Brain:
- higher cortex
- secondary (associative) cortex
- receiving area in cortex e.g., primary visual cortex
Sensory pathways:
- thalamus (not via thalamus for smell): neuron mass in middle of brain
- intermediate neurons
Sense organ:
- receptors - transduction: conversion of environmental energy to nerve signals

Question 8

bottom-up processing

Answer 8

• Perception starts within characteristics of stimuli and basic sensory processes e.g., feature detectors.
  
  • Gibson - “direct perception” (1950s):
  • 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.

Question 9

top-down processing

Answer 9

· The perceive 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).

Question 10

how do we investigate sensation and perception?

Answer 10

· Staining - dead brain tissue and apply stains
· Single-cell recordings (electrophysiology)
· Functional magnetic resonance imaging (fMRI) - tells you what parts of the brain are active in response to particular stimuli
· Lesion studies - useful for understanding different parts of the brain that do particular jobs
· Event-related potential (ERP) from electroencephalogram (EEG)
· Optical imaging/near infra-red spectroscopy (NIRS)
· Psychophysics
· Illusions and introspection
· Computational modelling

Question 11

single-cell recording

Answer 11

· Action potentials of neurons recorded with microelectrode inserted close to cell.
· Cortical recording requires section of skull to be removed.
· Only on humans if medical operation i.e., for epilepsy.
· Useful for identifying cells which are selective for certain features e.g., orientations, direction of motion, faces.
· 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.

Question 12

lesion studies

Answer 12

· Animal lesioning - by knife, by neurotoxins (only destroys nerve cells)
· Disadvantages - ethical issues, studying a faulty system, brain changes in response to damage
· Neuropsychology - damage to brain due to stroke, trauma, road accidents, boxing, etc.
· Disadvantages - damage can be diffuse, individual variation in damage

Question 13

virtual lesions - TMS

Answer 13

· Transcranial magnetic stimulation (TMS)
· Pulses of magnetic energy disrupt activity in a small part of the brain for a short period.
· Can be used to investigate sensation and perception
· E.g., biological motion
- TMS over posterior superior temporal sulcus (STS) disrupts biological motion
- disruption of upright biological motion over posterior STS, but not over motion area of visual cortex

Question 14

psychophysics

Answer 14

· Quantifying the relationship between physical stimuli and the psychological response.
· Absolute/detection threshold - smallest stimuli intensity needed for detection e.g., minimum concentration of a flavour you can taste
· Difference threshold - smallest difference between two stimuli that can be detected - the ‘Just-noticeable difference’ (JND) e.g., the minimum difference between two colours that you can see.

Question 15

Psychophysics study

Answer 15

• finds disrupted biological motion in children with autism

Question 16

visual illusions

Answer 16

· “The spinning dance” by Nobuyuki Kayahara (2003):
- Bi-stable perception, no depth cues leads to visual ambiguity
- Striking to individual differences in perception
· Introspection is a valid way to ask questions about sensation and perception.
· Important to also consider how you might investigate it systematically.