|Example responses of pairs of neurons in macaque MT/V5 to frozen noise stochastic dot stimuli|
|EHUD ZOHARY and WILLIAM T. NEWSOME|
Department of Neurobiology, Stanford University School of Medicine
Fairchild Bldg., Room D-209
Stanford, CA 94305
Support: National Eye Institute, McDonnell-Pew Foundation, Howard Hughes Medical Institute
|PREP||awake, fixation, discrimination|
|DATA TYPE||extracellular spike times|
paired single units on one electrode
|CELL TYPE||V5/MT cell|
Four paired single-unit recordings are presented here, which represent limited frozen noise, also known as no-variance, control data. The first two pairs, emu034 and emu035, where tested at multiple coherence levels in the no-variance condition. The second two pairs (rt068 and rt072) were tested on direction series experiments in the no-variance condition, meaning that only the stimulus direction was varied from trial to trial and coherence was constant at 100%. In addition to the no-variance data, the usual variable-seed data is provided for comparison. Direct observation of the raster plots reveals that there is clear stimulus-locked modulation for emu034 and emu035, but very littled modulation for rt068 and rt072. This is not surprising because there tends to be much less stimulus-locked modulation at c=100% than at lower coherence levels (see Bair and Koch, 1996, Neural Comp 8:1185-1202). Keep in mind that the 100% coherence stimulus is a smoothly translating, fixed dot pattern, whereas all lower coherence levels have a spatial pattern that changes over time. Stimulus
The stimulus was the sparse, dynamic random dot pattern described for data set nsa2004.2. Data files with a 'P' in the name contain psychophysical and neuronal responses as a function of coherence, just like data set nsa2004.2. Files with 'D' in the name are direction series experiments in which the coherence was always 100%, only the direction varied, and the task was simple fixation with no psychophysical response.
A full description of the stimulus is provided in the papers cited below in Electrophysiological Methods.
Zohary E, Shadlen MN, Newsome WT (1994) Correlated neuronal discharge rate and its implications for psychophysical performance. Nature 370:140-143.
Britten KH, Shadlen MN, Newsome WT, Movshon JA (1992) The analysis of visual motion: a comparison of neuronal and psychophysical performance. J Neurosci 12:4745-4765.