Chapter 1-Psychophysics and Sensory Biology Flashcards
Proximal Stimulus
What we Perceive
Distal Stimulus
Actual object in the world
Sensation
Detection of environmental stimulus
Perception
Providing an interpretation of that stimulus
Bottom-up processing
Starting with features and building to something complex
Top-down processing
Using context to interpret features
Psychophysics
Study of quantifiable relationships between physical events and sensations and perceptions
-Gustav Fechner
Absolute Threshold
Minimum Intensity that is stimulation necessary for a person to detect a stimulus 50% of the time
-Subthreshold- Intensities below the AT
-Suprathreshold-Intensities above the AT
Difference Threshold (JND)
Smallest ‘detectable difference’ between two different intensities (Minimum change in stimulus intensity that is just noticeable
Method of Limits
-Used for Absolute Thresholds
-Switch between ascending series and descending series
-Ascending Series-Subthreshold until “Yes I detect it”
-Descending Series-Suprathreshold until “No I don’t detect it”
Method of Adjustment
The participant controls intensity until the stimulus is just detectable or ‘just noticeably different’
Magnitude Estimation
Participant assigns scaled values to stimuli according to perceived magnitude relative to a reference intensity
Method of Constant Stimuli
Stimuli range from rarely to always perceivable are randomly presented
-Can be used to measure response bias
-Can be used to measure sensitivity
Signal Detection Theory
Difference between ability to perceive signal and willingness to report
-Quantifies the response of an observer to the presentation of a signal in the presence of “noise”
(Noise is not physical noise)
Weber’s Law
Greater stimulus values have larger JND
Smaller stimulus values have smaller JND
Fechner’s Law
Need larger physical changes to produce the same changes in perception
S.S Stevens Power law
Sensation is related to stimulus intensity by an exponent
-Best quantification of perception to physical stimulation
Transduction
Converting an environmental signal to a signal we can perceive
-Occurs in the sensory organs
Doctrine of Specific Nerve Energies (Johannes Mueller)
-12 pairs of cranial nerves originate in the brain stem
-Reach sense organs and muscles
-Show that it is not HOW a nerve is stimulated but WHICH nerve is stimulated
Basic Sensory Biology
Different areas of the cerebral cortex are associated with specific sensory and motor tasks
Contralateral v. Ipsilateral Processing
Contra-Opposite Sides
(Most senses initially processed in contralateral hemisphere except for smell)
Ipsi-Same Side
Cortical Magnification
Small areas of the body are processed on large areas of the cortex
Synapse
Gap between neurons that permits info transfer via neurotransmitters (Chemicals in neuronal communication)
Neuron Firing
Neurons fire in an all or none fashion in a process called the action potential
Single Cell Recording
-Microelectrode inserted near regions of interest
-Neurons fire more with increased stimulation
