In 1952 he started at the
New York University Medical School. By graduation he was firmly interested in the biological basis of the mind. During this time he met his future wife,
Denise Bystryn. Kandel was first exposed to research in
Harry Grundfest's laboratory, for six months in 1955-56, at Columbia University. Grundfest was known for using the
oscilloscope to demonstrate that
conduction velocity during an
action potential depends on
axon diameter. The researchers Kandel interacted with were contemplating the technical challenges of
intracellular recordings of the electrical activity of the relatively small
neurons of the vertebrate brain. After starting his neurobiological work in the difficult thicket of the
electrophysiology of the
cerebral cortex, Kandel was impressed by the progress that had been made by
Stephen Kuffler using a much more experimentally accessible system: neurons isolated from
marine invertebrates. After becoming aware of Kuffler's work in 1955, Kandel graduated from medical school and learned from Stanley Crain how to make micro
electrodes that could be used for intracellular recordings of
crayfish giant
axons.
Karl Lashley, a well-known American neuropsychologist, had tried but failed to identify an anatomical locus for memory storage in the cortex of the brain. When Kandel joined the Laboratory of Neurophysiology at the US
National Institutes of Health in 1957,
William Beecher Scoville and
Brenda Milner had recently described the patient
HM, who had lost the ability to form new memories after removal of his
hippocampus. Kandel took on the task of performing electrophysiological recordings from hippocampal
pyramidal neurons. Working with
Alden Spencer, he found electrophysiological evidence for action potentials in the
dendritic trees of hippocampal neurons. The team also noticed the spontaneous pacemaker-like activity of these neurons, as well as a robust recurrent inhibition in the hippocampus. They provided the first intracellular records of the electrical activity that underlies the
epileptic spike (the intracellular
paroxysmal depolarizing shift) and the epileptic runs of spikes (the intracellular sustained depolarization). But, with respect to memory, there was nothing in the general electrophysiological properties of hippocampal neurons that suggested why the hippocampus was special for explicit memory storage. Kandel began to realize that memory storage must rely on modifications in the
synaptic connections between neurons and that the complex connectivity of the hippocampus did not provide the best system for study of the detailed function of synapses. Kandel was aware that comparative studies of behavior, such as those by
Konrad Lorenz,
Niko Tinbergen, and
Karl von Frisch had revealed that simple forms of learning were found even in very simple animals. Kandel felt it would be productive to select a simple
animal model that would facilitate electrophysiological analysis of the synaptic changes involved in learning and memory storage. He believed that, ultimately, the results would be found to be applicable to humans. This decision was not without risk: many senior biologists and psychologists believed that nothing useful could be learned about human memory by studying invertebrate physiology. In 1962, after completing his residency in psychiatry, Kandel went to Paris to learn about the marine mollusk
Aplysia californica from
Ladislav Tauc. Kandel had realized that simple forms of learning such as habituation, sensitization, classical conditioning, and operant conditioning could readily be studied with
ganglia isolated from
Aplysia. "While recording the behavior of a single cell in a ganglion, one nerve axon pathway to the ganglion could be stimulated weakly electrically as a conditioned [tactile] stimulus, while another pathway was stimulated as an unconditioned [pain] stimulus, following the exact protocol used for classical conditioning with natural stimuli in intact animals." Electrophysiological changes resulting from the combined stimuli could then be traced to specific synapses. In 1965 Kandel published his initial results, including a form of presynaptic
potentiation that seemed to correspond to a simple form of learning. ==Faculty member at New York University Medical School==