Sensation/Perception Flashcards
What are the four types of sensation?
- superficial
- deep
- visceral
- special
What are the superficial sensations?
touch, pain, temperature, two point discrimination
What are the deep sensations?
proprioception, deep muscle pain, vibration
What is psychophysics?
- a field that deals with physical stimuli and the mental phenomena related to their perception
- it relates stimulus intensity to perception in what are known as “power curves”
Sensation is proportional to the ___ of the stimulus.
power/intensity
What is a generator potential?
- the transmembrane potential difference produced by activation of a sensory receptor
- generator potentials sum to reach the threshold for action potential generation
What is the “neural code”?
the firing pattern of populations of neurons used to represent sensory input
Stimulus intensity is usually encoded by what characteristic of the neural code?
the number or rate of action potentials as well as the number of neurons activated
What is “contrast enhancement” with regards to coding of sensory inputs?
parallel processing of cells of different thresholds refines acuity
How are temporal aspects of a stimulus encoded in firing patterns of sensory receptors?
adaptation to persistent stimuli varies across different receptor subtypes, so slowly and rapidly adapting mechanoreceptors will have different firing patterns
What is adaptation?
a decrease in neural response to a maintained stimulus
How is spatial information about a stimulus encoded?
through the function of receptive fields and the location of the sensory receptors currently firing
What is a receptive field?
- usually defined as the area of skin where stimulation produces activation of a neuron
- but can be defined at different levels like the thalamus and cortex
Which sorts of receptive fields have higher acuity?
smaller ones
What is the “labelled lines” theory of sensory coding?
essentially that somatotopy is retained and there is a specific pathway for conduction of info about a somatopic location or for a specific modality
How does “pattern theory” differ from the “labelled lines theory”?
- pattern theory is related to certain sensory systems like color perception in which information is integrated across multiple primary afferents, so it is the pattern of activation of whole neuronal populations that form the basis of perception
- e.g. three color receptors combine to respond to the spectrum of visible light
Convergence of primary afferents is an important processing step in what way?
- individual inputs may have different strength in stimulating the subsequent neuron
- interneurons may modify the interactions between receptors (surround inhibition)
What is surround inhibition?
central signals are facilitated and eccentric signals are inhibited (by interneurons or that central signal) in order to sharpen the contrast between them
What are two possible reasons a secondary receptive field may be rather large?
- the primary receptive field was larger
- many neurons converge on the same secondary neuron
Convergence can have what effect on receptive field size?
the more neurons that converge on a single secondary neuron, the larger the secondary receptive field, and the lower the acuity
Convergence is an important concept with regards to ___ pain.
- referred pain
How is convergence an important concept with regards to referred pain?
referred pain is the result of visceral input onto secondary neurons that also receive sensory info from cutaneous nerves
What is the first step in percept construction from sensory information?
convergence