動物生理学 III①Handout No. 5②

Figure 27-12 The receptive fields of simple cells in the primary visualcortex are different and more varied than those of the neurons in theretina and lateral geniculate nucleus.
A. Cells of the retina and lateral geniculate nucleus fall into twoclasses: on-center and off-center. The receptive fields of these neurons
have a center-surround organization due to antagonistic excitatory 1+1
and inhibitory (-) regions.
B. The receptive fields of simple cells in the primary visual cortex havenarrow elongated zones with either excitatory (+) or inhibitory(-)flanking areas. Despite the variety, the receptive fields of simple cells
share three features: 11) specific retinal position, (2) discrete excitatory
and inhibitory zones, and (3) a specific axis of orientation.
C. Model of the organization of inputs in the receptive field of simple
cells proposed by Hubel and Wiesel. According to this model, a simple
cortical neuron in the primary visual cortex receives convergent
excitatory connections from three or more on-center cells that together
represent light falling along a straight line in the retina. As a result, thereceptive field of the simple cortical cell has an elongated excitatory
region, indicated by the colored outline in the receptive field diagram.
The inhibitory surround of the simple cortical cells is probably provided
by oft-center cells whose receptive fields (not shown) are adjacent tothose of the on-center cells. (Adapted from Hubel and Wiesel 1962)③

Figure 27-13 The receptive field of a complex cell in the primary visual cortex has no clearly
excitatory or inhibitory zones. Orientation of the light stimulus is important, but position within
the receptive field is not. (Adapted from Hubel and Wiesel 1962).
A. In this example the cell responds best to a vertical edge moving across the receptive fieldfrom left to right. This figure shows the patterns of action potentials fired by the cell in responseto two types of variation in the stimulus: differences in orientation and differences in position.
The line above each record indicates the period of illumination. 1. Different orientations of thelight stimulus produce different rates of firing in the cell. A vertical bar of light on the left of thereceptive field produces a strong excitatory response (a) Orientations other than vertical areless effective (b-d). 2. The position of the border of the light within the receptive field affects thetype of response in the cell. If the edge of the light comes from any point on the right within thereceptive field, the stimulus produces an excitatory response (a-d). If the edge comes from theleft, the stimulus produces an inhibitory response (f-i). Illumination of the entire receptive field
produces no response (e).
B. According to Hubel and Wiesel, the receptive fields of complex cells are determined by thepattern of inputs. Each complex cell receives convergent excitatory input from several simple
cortical cells, each of which has a receptive field with the same organization: a central
rectilinear excitation zone (+) and flanking inhibitory regions (-). In this way the receptive field ofa complex cell is built up from the individual fields of the presynaptic cells.

④FIGURE 21.4 Detection of Orientation Columns (Pinwheels) by OpticalImaging. The activity-dependent reflectance of visual cortex wasrecorded by a sensitive camera while an eye was stimulated withoriented bars. (A) Each orientation caused maximal changes in differentregions (an orientation "contour," encoded by a different color). Although
the pattern seems at first disorderly, close inspection reveals centers at
which all orientation contours come together in a pinwheel, as shown in(B). Note that each orientation is represented only once and that thesequence is beautifully precise. Such pinwheel centers occur at regulardistances from each other. (After Bonhoeffer and Grinvald,1991.)

FIGURE 20.8 Ocular Dominance Columns in monkey cortex demonstrated by injection of radioactive proline into one eye. Autoradiographs
photographed with dark-field illumination in which the silver grains appear
white. (A) At the top of the picture the section passes through layer 4 ofthe visual cortex at right angles to the surface, displaying columns cutperpendicularly. In the center, layer 4 has been cut horizontally, showingthat the columns consist of longer slabs. (B) Reconstruction made fromnumerous horizontal sections of layer 4C in another monkey in which theipsilateral eye had been injected. (No single horizontal section canencompass more than a part of layer 4 because of the curvature of thecortex.) In both A and B, the ocular dominance columns appear as stripesof equal width supplied by one eye or the other. (Autoradiographs kindly
provided by S. LeVay.)