An apical dendrite
is a dendrite that
emerges from the apex of a pyramidal cell.
Apical dendrites are one of two primary cat-
egories of dendrites, and they distinguish the
pyramidal cells from spiny stellate cells in
the cortices. Pyramidal cells are found in the
entorhinal cortex, and the olfactory cortex.
Dendrite arbors formed by apical dendrites
are the means by which synaptic inputs into a
cell are integrated. The apical dendrites in
these regions contribute significantly
memory, learning, and sensory associations
by modulating the excitatory and inhibitory
signals received by the pyramidal cells.
Two types of dendrites present on pyramidal
cells are apical and basal dendrites. Apical
dendrites can be divided into two categories:
distal and proximal. The longer distal apical
dendrites project from the pyramidal cell
body (soma) opposite from the axon. Distal
apical dendrites form non-local synapses.
Shorter proximal apical dendrites project ra-
dially to local pyramidal cells and interneur-
ons. Pyramidal neurons segregate their in-
puts using proximal and apical dendrites.
Apical dendrites are studied in many
ways. In cellular analysis, the electrical prop-
erties of the dendrite are studied using stim-
ulus responses. A single surface shock of the
cerebral cortex induces a 10-20msec negat-
ive potential, a manifestation of the summed
excitatory post-synaptic potentials (EPSPs)
evoked in the distal portions of the apical
dendrite. This has been called the Dendrit-
ic Potential (DP). This is identical with Adri-
an’s Superficial Response in direct cortical
responses. At higher intensities the DP is
followed by slow positive waves (Adrian’s
Deep Response) or by a prolonged negative
wave lasting for more than 200msec (Chang’s
second component). The highest amplitude
of DPs is found on the cortical surface, with
the polarity shifted from negative to positive
within the superficial layer.
Areas of interest