• Macintosh (MacOS/PowerPC) version (1.8MB, BinHex'ed self-extracting archive, needs MacOS 7.6 or later)
• NEW: Windows 95/98/NT version (1.8MB, ZIP file)

Note that, in this version of VNS, you may define only vertically oriented RF profiles in space.  The Y-dimension is tapered according to a Gaussian.  The built-in receptive fields and the ones you draw are defined in the X-T (space-time) domain, and are not a typical X-Y receptive field you might be familiar with from most text books.  As you will learn after you play with the receptive fields, the shape of RFs in the X-T domain is a critical factor that determines the direction selectivity of neurons to moving stimuli.

The graphics below illustrates the VNS screen with all tool trays open.  These tool trays may be opened or closed by clicking on their edges.  Once receptive field (RF) data are loaded or manually drawn, your neuron is ready to be explored by a variety of visual stimuli at your disposal.

The stimulus tray on the right gives you four choices:

• Vertical bar stimulus
• Bar stimulus of variable orientation
• Drifting sinusoidal gratings
• Reverse correlation RF mapping stimulus -- details of the method

Vertical Bar Stimulus

• Drag it manually with the mouse.
• Drag-extending the upper-left dot on the bar allows you to set auto-sweep velocity.
• Clicking on the bottom-left dot inverts the sign of contrast of the bar (black/white).
• Bottom-right dot allows you to set the width and the length of the bar.
• Double-clicking will turn the bar off, allowing you to study ON/OFF responses.

• Drag the red dot in the center in any direction, the bar orientation will be set perpendicular to the current velocity vector.  (The bar orientation is "jittery" but this is hard to avoid due to the low mouse update rate and the fact that mouse coordinates are reported in pixels. The program already does averarging of the past 3 or so velocity vectors.  But see below.)
• Double-click-dragging the red dot will fix the orientation to the current angle.  This will stabilize the bar orientation.

• Grab the scroller bay to move the grating patch.
• Use the slider on the right edge to set the spatial frequency.
• Click-drag within the patch to cause drifting in the direction opposite to dragging.  The more you drag, the faster the pattern moves.

• Dragging the right edge allows you to set the width of the mapped area.
• Dragging the left edge moves the whole mapping area.
• The upper-left tray automatically opens to display the measured RF profile as it develops.  (The RF here is actually being measured twice, once when the original RF data were obtained, and the second time as you are measuring now.)