Complex cells are also neurons in V1 that respond optimally to a stimulus with a particular orientation. But, unlike simple cells, they respond to a variety of stimuli across different locations. For example, a complex cell will respond to a dark bar on a light background and a light bar on a dark background. In contrast, a simple cell only responds to one but not the other. Moreover, complex cells do not have peak location sensitivity as simple cells do. That is, they will respond equally well to an optimal orientation regardless of where it is within the cell’s receptive field. Complex cells also respond best to moving stimuli.
In this activity, you can simulate recording from a complex cell. You can try to use a dot to map the receptive field and bars to try to determine the optimal stimulus.
To see the illustration in full screen, which is recommended, press the Full Screen button, which appears at the top of the page.
On the Illustration tab, you can stimulate a region of the retina and see the effect on the single cell you are recording from.
Below is a list of the ways that you can alter the model. The settings include the following:
Screen Area: The black area on the screen to the left is a screen that the
eye of your animal is seeing. The receptive field of the
cell you are recording from is responding to some part of this screen.
Click on or touch the screen to move the dot around, and see how the cell responds by looking at
to the right.
Stimulus Type: Choose the stimulus you are using. You can chose a Dot, a White Bar, a Black Bar, or a Moving Bar.
If the stimulus is any of the bars, you can change the bar:
Tilt: Change the orientation of the bar.
Change Direction: Reverse the direction of the bar movement.
The adding of marks using the controls mentioned below only works when the stimulus is a dot:
Excite Resp (+): If the firing rate goes above the horizontal blue line, the cell is said to be excited. You can place a green plus mark at that location by pressing this button.
Inhib Resp (-): If the firing rate goes below the horizontal blue line, the cell is said to be inhibited. You can place a red minus sign at that location by pressing this button.
Remove Last Mark: press to remove the last mark, and then sequentially the previous marks, if you added any marks by mistake.
Show Cell: You can show the shape of this receptive field.
When the receptive field is visible, the following two controls work:
Increase Angle: Rotate the prefered orientation of the receptive field in a counterclockwise direction.
Decrease Angle: Rotate the prefered orientation of the receptive field in a clockwise direction.
Pressing this button restores the settings to their default values. It also gets you a new cell, which might have a different receptive field.