There have been at least three holographic memory theories. The first was advanced by the optical physicist Pieter van Heerden in the J. of Applied Optics in 1963. He had basically designed a hardware optical memory, but he realized and remarked it might be a strong metaphor for memory in the brain.
A similar theory was advanced independently by Karl Pribram in a series of papers beginning in 1969. He originally focused on the distributed storage aspect of holograms and, demonstrably, the brain.
Finally, about 1987, there appeared the "holonomic" theory, which seems to be a sort of blend of the classical holographic memory theory with quantum physics. It also seems to have religious or mystical overtones.
In the recent, excellent book, Metaphors of Memory
there is a good chapter on this history. The author thinks these ideas -- notably the idea of distributed storage -- were absorbed into Connectionism. To my knowledge the basic idea of holographic memory was not discredited. It was just sort of swamped out by the avalanche of enthusiasm for neural networks.
Then, when the "holonomic" version of the idea surfaced, it painted the whole idea of holographic memory as mystical and (my opinion) sort of silly. It is a shame because the first two versons of the theory were grounded on arguable but plausible everyday science.
In addition to holographic theories of memory there were holographic theories of vision. These were apparently hooted down in the 1970s. It was believed the retina, like shapshot film, loses the spatial phase information borne by incoming light. It followed that vision could not be holographic. But in retrospect the holographic vision theories seem to have been (or contained) attractive ideas, and they were probably dismissed a little too abruptly.
I have included two essays on holographic memory and vision in a Blog I write about radical ideas in neuroscience. Here is a link to the Blog:http://nine-radical.blogspot.com
And here are links to the holography related entries. These include
"Conservation of Spatial Phase
"Gems in a Junkyard
It seems to me the basic idea of storing memory as an interference pattern is realistic and promising. It was originally conceived by Karl Lashley.
Regards, John Harris