Up
Previous
Next
Functional excitatory laminar input to distinct pyramidal cell types
in layer 6 of primate V1
Farran Briggs and Edward M. Callaway
Salk Institute
A fundamental goal in neurophysiology is to understand how various
inputs give rise to specific functional properties of neurons. The
first visual cortical area of primates, V1, is an ideal area in which
to address how input sources contribute to cellular function because
it contains distinct anatomically and physiologically defined
populations of neurons separated into layers. We examined the laminar
sources of functional excitatory input onto a population of excitatory
pyramidal neurons in the deepest cortical layer of primate V1, layer
6, using scanning laser photostimulation. We found that different
excitatory laminar input patterns correlated with each of 8
anatomically defined cell types. Class I neurons are defined by
axonal arborizations selective for the magnocellular (M) recipient
layer 4C alpha and/or the parvocellular (P) recipient layer 4C beta. Class I
neurons whose axonal arbors targeted layer 4C alpha received functional
input from M-dominated layer 4B while Class I neurons whose axonal
arbors targeted layer 4C beta received functional input from P-dominated
layer 2/3. All Class I cells received inputs of similar strengths
directly from layers 4C alpha and 4C beta. Class II neurons tend to lack
extensive axonal arborizations within layer 4C. Each of the three
anatomically defined types of Class II neuron tended to receive
excitatory functional input from the same layers targeted by their
local axons. These results indicated a combination of segregation and
integration of M- and P-specific information as it travels through V1.
Distinct functional input patterns for each pyramidal cell type
implies each layer 6 excitatory neuron may perform a unique functional
role.