Neuromodulation of Cortical Plasticity
Sensory experience
alters the functional organization of cortical networks. Previous studies using
behavioral training motivated by aversive or rewarding stimuli have
demonstrated that cortical plasticity is specific to salient inputs in the
sensory environment. Sensory experience associated with electrical activation
of the nucleus basalis (NB) generates similar input specific plasticity. By
directly engaging plasticity mechanisms and avoiding extensive behavioral
training, NB stimulation makes it possible to efficiently explore how specific
sensory features contribute to cortical plasticity. Our recent experiments have
documented that cortical networks employ a variety of distinct strategies to
improve the representation of the sensory environment. Different combinations
of receptive field, temporal, and spectrotemporal
plasticity were generated in primary auditory cortex neurons depending on the
pitch, modulation rate and order of sounds paired with NB stimulation. Simple
tones led to map expansion, while modulated tones altered the maximum cortical
following rate. Exposure to complex acoustic sequences led to the development
of combination sensitive responses. This remodeling of cortical response
characteristics may reflect changes in intrinsic cellular mechanisms, synaptic
efficacy, and local neuronal connectivity. The intricate relationship between
the pattern of sensory activation and cortical plasticity suggests that
network-level rules alter the functional organization of cortex to generate the
most behaviorally useful representation of the sensory environment.
Current treatment
of neurological disease is limited to pharmacological, surgical, or behavioral
intervention. Our ability to influence
cortical plasticity by manipulating the sensory environment suggests that it
may be possible to similarly manipulate plasticity mechanisms in human patients
and aid recovery from brain damage.
·
Preference for FM Sweep Direction and Rate
·
Experience-Dependent Changes in Cortical
Synchronization