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Experience-dependent plasticity in S1 caused by noncoincident inputs.
David T Blake1, Fabrizio Strata, Richard Kempter
1Coleman Laboratory and Keck Center for Integrative Neuroscience, University of California, San Francisco, USA. dblake@phy.ucsf.edu
Journal of Neurophysiology
|August 18, 2005
Summary
Co-representation of digits in the brain, previously thought to require synchronous inputs, can develop with asynchronous stimuli over 100 ms. This neuroplasticity suggests increased cortical excitability during new task learning.
Area of Science:
- Neuroscience
- Sensory processing
- Cortical plasticity
Background:
- Prior research indicated coincident sensory inputs are co-represented in the somatic sensory cortex.
- The precise temporal requirements for this co-representation, particularly for multi-digit stimuli, remained unclear.
Purpose of the Study:
- To test the hypothesis that co-representation of digits necessitates synchronous inputs.
- To investigate the developmental timeline of two-digit receptive fields in the primate somatosensory cortex.
Main Methods:
- Adult primates were trained to detect temporal differences in paired taps delivered to adjacent digits.
- Cortical implants were used to observe the development of receptive fields over four weeks.
- Stimulus onset asynchronies (SOAs) were varied, with a focus on SOAs >= 100 ms.
Main Results:
- Two-digit receptive fields emerged within four weeks of training with SOAs >= 100 ms.
- Responsive receptive fields more than doubled in size, while non-responsive sites showed no significant change.
- Further training did not enhance the expression of two-digit receptive fields.
- Cortical responses were not interval-length dependent, but differences in ongoing cortical rates were observed post-stimulus.
- Emergent responses showed longer latencies, suggesting cortical plasticity.
- New response correlations developed in parallel with new receptive fields.
Conclusions:
- Co-representation can be induced by stimuli presented across a broader time window than predicted by spike-timing-dependent plasticity.
- Learning new sensory tasks is associated with increased cortical excitability.