  A salient feature of prefrontal cortex organization is the vast diversity of
cell types that support the temporal integration of events required for
sculpting future responses. A major obstacle in understanding the routing of
information among prefrontal neuronal subtypes is the inability to manipulate
the electrical activity of genetically defined cell types over behaviorally
relevant timescales and activity patterns. To address these constraints, we
present here a simple approach for selective activation of prefrontal
excitatory neurons in both in vitro and in vivo preparations. Rat prelimbic
pyramidal neurons were genetically targeted to express a light-activated
nonselective cation channel, channelrhodopsin-2, or a light-driven inward
chloride pump, halorhodopsin, which enabled them to be rapidly and reversibly
activated or inhibited by pulses of light. These light responsive tools provide
a spatially and temporally precise means of studying how different cell types
contribute to information processing in cortical circuits. Our customized
optrodes and optical commutators for in vivo recording allow for efficient
light delivery and recording and can be requested at
www.neuro-cloud.net/nature-precedings/baratta.
