Associative learning shapes the neural code for stimulus magnitude in primary auditory cortex. Polley, D. B, Heiser, M. A, Blake, D. T, Schreiner, C. E, & Merzenich, M. M Proc Natl Acad Sci U S A, 101(46):16351-6, 2004.
doi  abstract   bibtex   
Since the dawn of experimental psychology, researchers have sought an understanding of the fundamental relationship between the amplitude of sensory stimuli and the magnitudes of their perceptual representations. Contemporary theories support the view that magnitude is encoded by a linear increase in firing rate established in the primary afferent pathways. In the present study, we have investigated sound intensity coding in the rat primary auditory cortex (AI) and describe its plasticity by following paired stimulus reinforcement and instrumental conditioning paradigms. In trained animals, population-response strengths in AI became more strongly nonlinear with increasing stimulus intensity. Individual AI responses became selective to more restricted ranges of sound intensities and, as a population, represented a broader range of preferred sound levels. These experiments demonstrate that the representation of stimulus magnitude can be powerfully reshaped by associative learning processes and suggest that the code for sound intensity within AI can be derived from intensity-tuned neurons that change, rather than simply increase, their firing rates in proportion to increases in sound intensity.
@Article{Polley2004,
  author   = {Daniel B Polley and Marc A Heiser and David T Blake and Christoph E Schreiner and Michael M Merzenich},
  journal  = {Proc Natl Acad Sci U S A},
  title    = {Associative learning shapes the neural code for stimulus magnitude in primary auditory cortex.},
  year     = {2004},
  number   = {46},
  pages    = {16351-6},
  volume   = {101},
  abstract = {Since the dawn of experimental psychology, researchers have sought
	an understanding of the fundamental relationship between the amplitude
	of sensory stimuli and the magnitudes of their perceptual representations.
	Contemporary theories support the view that magnitude is encoded
	by a linear increase in firing rate established in the primary afferent
	pathways. In the present study, we have investigated sound intensity
	coding in the rat primary auditory cortex (AI) and describe its plasticity
	by following paired stimulus reinforcement and instrumental conditioning
	paradigms. In trained animals, population-response strengths in AI
	became more strongly nonlinear with increasing stimulus intensity.
	Individual AI responses became selective to more restricted ranges
	of sound intensities and, as a population, represented a broader
	range of preferred sound levels. These experiments demonstrate that
	the representation of stimulus magnitude can be powerfully reshaped
	by associative learning processes and suggest that the code for sound
	intensity within AI can be derived from intensity-tuned neurons that
	change, rather than simply increase, their firing rates in proportion
	to increases in sound intensity.},
  doi      = {10.1073/pnas.0407586101},
  keywords = {Acoustic Stimulation, Animals, Association Learning, Auditory Cortex, Auditory Threshold, Conditioning (Psychology), Electrophysiology, Loudness Perception, Neuronal Plasticity, Rats, Sprague-Dawley, Reinforcement (Psychology), Research Support, Non-U.S. Gov't, U.S. Gov't, P.H.S., Reward, 15534214},
}

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