Receptive field Flashcards
Receptive Field (RF) of an individual sensory neuron
= region of the sensory space in which a stimulus will modify the firing of that neuron, that can be either a hair on the cochlea, a piece of skin, retina, or other part
Auditory system
RF modeled as spectro-temporal patterns that cause the firing rate of the neuron to modulate with the auditory stimulus
Spectro-temporal RFs can be understood as
transfer function that maps an acoustic stimulus input to a firing rate response output
Somatosensory System
receptive fields are regions of the skin or of internal organs.
Some types of mechanoreceptors have large receptive fields, while others have smaller ones
Tactile-sense-related cortical neurons
large RFs and can discriminate details due to patterns of excitation and inhibition which leads to spatial resolution
Visual system Receptive Field
receptive field = Center + surround
RF = region of the retina, where the action of light alters the firing of the neuron
Hubel and Wiesel
RF of a cell at one level of the visual system are formed from input by cells at a lower level
Small RFs can be combined to form a larger one
Retina ganglion cells
RF increases with intensifying light (in the largest field, light must be more intense at the periphery)
Stimulating a center of an on-center cell’s RF produces ..
..depolarization (= increased firing) of the cell
stimulation of the periphery produces..
..hyperpolarization (decreased firing)
If th center of a off-center cell gets stimulated it leads to
inhibiton
Lateral geniculate nucleus (LGN)
RF similar as in the ganglion cells with an antagonistic center surround system
Visual Cortex
larger RFs and more complex stimulus requirements
Hubel und Wiese classificate visual cortex into:
- simple cells: elongated
e.g., with an excitatory central oval and an inhibitory surrounding;
images need to have a particular orientation to excite cell - complex cells: a correctly oriented bar of light need to move into a particular direction to excite the cell
- hypercomplex cells: bar might also need to be of a particular length
Extrastriate visual areas
cells can have large RFs requiring complex images to excited cell, e.g., faces in the FFA
RFs are also used as a term in artificial neural networks
• Convolutional neural networks
designed to mimic the way in which animal brains are understood to function; it’s a 3-dimensional structure, primarily used in computer vision
o Each input neuron represents one pixel from the original image
o First layer = input layer
o Next layer receives input from some of the input neurons, but not all: receptive field like layout in which each neuron receives connections only from a subset of neurons in the previous layer
o Advantage: recognizing visual patterns
Large receptive fields of somatosensory system allow the cell to..
detect changes over a wider area, but lead to a less precise perception
Receptors with large receptive fields usually have a “hot spot”
Where is it and what does it do?
an area within the receptive field (usually in the center, directly over the receptor) where stimulation produces the most intense response.
