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. 2003 Sep 16;100(19):11070-5.
doi: 10.1073/pnas.1334187100. Epub 2003 Aug 26.

Reward-dependent plasticity in the primary auditory cortex of adult monkeys trained to discriminate temporally modulated signals

Ralph E Beitel  1 , Christoph E Schreiner, Steven W Cheung, Xiaoqin Wang, Michael M Merzenich
Affiliations

Reward-dependent plasticity in the primary auditory cortex of adult monkeys trained to discriminate temporally modulated signals

Ralph E Beitel et al. Proc Natl Acad Sci U S A. .

Abstract

Adult owl monkeys were trained to detect an increase in the envelope frequency of a sinusoidally modulated 1-kHz tone. Detection was positively correlated with the magnitude of the change in the envelope frequency. Surprisingly, neuronal responses recorded in the primary auditory cortex of trained monkeys were globally suppressed by the modulated tone. However, the contrast in neuronal responsiveness to small increases versus large increases in envelope frequencies was actually enhanced in the trained animals. The results suggest behaviorally contingent inhibitory and excitatory processes that are modulated by the probability that a particular signal predicts a reward.

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Figures

Fig. 1.
Fig. 1.
(Left) Mean p(HIT) and average RT versus SAMc for two trained monkeys. Error bars: SD (sessions). Arrows indicate SAMs (4 and 10 Hz) and 50% detection thresholds. (A–D) Compound PSTHs (spikes per bin) normalized for number of recording sites (N). Bin width: 2 ms. Neuronal CFs are within an octave band centered at 1 kHz. Carrier frequency: 1 kHz. PSTHs represent the population responses evoked by standard (SAMs;0–500 ms) and comparison (SAMc; 500–1,000 ms) modulation frequencies. Numbers to the right of PSTHs indicate SAMc frequencies (Hz). (A and B) Data for trained monkeys OM2178 (SAMs = 4 Hz) and OM2184 (SAMs = 10 Hz). (C and D) Data for naïve monkeys.
Fig. 3.
Fig. 3.
Single and compound eMTFs (spikes per cycle) normalized to maximum firing rate. (A) Examples of eMTFs recorded at five sites in naïve monkeys (Upper) and five sites in OM2178 (Lower). (B) Percentage of recording locations with notched eMTFs in trained and naïve monkeys. (C and D) Compound eMTFs for trained (solid curves) and naïve monkeys (dashed curves). p(HIT) functions (open symbols) and arrows are reproduced from Fig. 1.
Fig. 2.
Fig. 2.
Compound pMTFs (number of phase-locked spikes) normalized for the number of recording sites. pMTFs are based on the neuronal data in Fig. 1. The key corresponds to A–D in Fig. 1. The shaded area depicts the range of SAMc frequencies used in behavioral training.
Fig. 4.
Fig. 4.
Frequency histograms of BMFs for neurons recorded in naïve and trained monkeys. Arrows indicate median BMFs.
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References

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