Flicker Fusion and recording from visual areas

Brian Scott scott at psych.toronto.edu
Thu Jan 12 18:22:53 EST 1995

Hello all!

I'm having a bit of trouble with a simple experiment (or so I thought). 
I'm doing some extracellular single and multi-unit recording in visual areas
of Equithesan anesthetised rats, looking for Critical Flicker Fusion
thresholds.  The visual stimulus is a strobe light presented at frequencies
ranging from 1 Hz to 30 Hz.

I'm having trouble actually finding cells which can be driven by the strobe.
I'm doing penetrations all over the occipital area but only seem to find 2
or 3 cells (or small groups of cells) at most after many many penetrations.
I honestly thought the numbers would be much higher than this.  Has anyone
here done anything similar to this and can tell me 1) about how many cells
they find with each penetration and/or 2) what I'm doing wrong?

Another thing which is curious is that many of the cells I do find seem to
be located about 4 mm below the surface of the brain and _not_ in the
cortex.  It looks more like the hippocampus to me and they are often found
in an area where the cells have rhythmic, synchronized and continuous basal
firing rates.  Does this sound normal?



scott at psych.toronto.edu       | "They are in you and in me; they created us,
Brian Scott                   |  body and mind; and their preservation is 
Department of Psychology      |  the ultimate rationale for our existence."
University of Toronto, Canada |         - Richard Dawkins (The Selfish Gene)

More information about the Neur-sci mailing list