Precise neural stimulation in the retina using focused ultrasound.

Focused ultrasound is a promising noninvasive technology for neural stimulation. Here we use the isolated salamander retina to characterize the effect of ultrasound on an intact neural circuit and compared these effects with those of visual stimulation of the same retinal ganglion cells. Ultrasound stimuli at an acoustic frequency of 43 MHz and a focal spot diameter of 90 μm delivered from a piezoelectric transducer evoked stable responses with a temporal precision equal to strong visual responses but with shorter latency.

The effect of fixation instability on the multifocal VEP.

In multifocal visually evoked potentials (mfVEP), we find reversals in waveform near the horizontal meridian due to convolutions in the cortex. This renders the mfVEP very sensitive to small changes in gaze position. In this study we tested the effects of very small amounts of fixation instability on the mfVEP topography under controlled conditions using four normal subjects.

Functional connectivity of disparity-tuned neurons in the visual cortex.

Different mechanisms have been proposed concerning how disparity-tuned neurons might be connected to produce the signals for depth perception. Here we present neurophysiological evidence providing insight on this issue. We have recorded simultaneously from pairs of disparity-tuned neurons in the cat's striate cortex.

Temporal dynamics of binocular disparity processing in the central visual pathway.

To solve the stereo correspondence problem (i.e., find the matching features of a visual scene in both eyes), it is advantageous to combine information across spatial scales.

Stereoscopic depth processing in the visual cortex: a coarse-to-fine mechanism.

For binocular animals viewing a three-dimensional scene, the left and right eyes receive slightly different information, and the brain uses this 'binocular disparity' to interpret stereoscopic depth. An important theoretical conjecture in this mechanism is that coarse processing precedes and constrains finely detailed processing. We present three types of neurophysiological data from the cat's visual cortex that are consistent with a temporal coarse-to-fine tuning of disparity information.