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Visual Stimulus-Specific Adaptation in the Avian Imc and Its Effect on Target Decoding Performance
by
,
Jiangtao Wang
1,
Keli Yu
1,
Ruohan Li
1,
Liuyang Ma
2,
Lipeng Zhang
1,
Minjie Zhu
1 and
Zhizhong Wang
1,* 1
School of Electrical and Information Engineering, Zhengzhou University, Zhengzhou 450001, China
2
The 27th Research Institute of China Electronics Technology Group Corporation, Zhengzhou 450047, China
*
Author to whom correspondence should be addressed.
Animals 2026, 16(17), 2655; https://doi.org/10.3390/ani16172655
Submission received: 28 May 2026
/
Revised: 11 August 2026
/
Accepted: 21 August 2026
/
Published: 24 August 2026
(This article belongs to the Section Birds)
Simple Summary
Stimulus-specific adaptation (SSA) is a neural mechanism that selectively reduces responses to repeated, predictable stimuli while preserving sensitivity to novel, unexpected ones, thereby optimizing sensory processing. Although extensively studied in mammals, SSA in the avian visual system remains poorly understood. This study investigated visual SSA in the nucleus isthmi pars magnocellularis (Imc), a key inhibitory structure in the pigeon midbrain attention network. We simultaneously recorded spike firing rates and local field potentials (LFPs) while presenting moving dot stimuli in alternating directions. Our results suggest that Imc neurons exhibit SSA: responses to repeated stimuli progressively declined but recovered upon direction change, with gamma-band LFP energy showing stronger adaptation than spike firing rates. Using machine learning decoders, we found that before adaptation, spike rates effectively encoded motion direction. However, SSA may impair the encoding of directional information across all signal types, reducing decoding accuracy to near chance levels. These findings indicate that gamma-band LFP primarily reflects stimulus salience, while spikes encode both identity and salience. This study advances our understanding of how evolutionarily conserved adaptation mechanisms balance sensitivity to novelty and suppression of redundancy in the avian brain.
Abstract
SSA serves as a fundamental mechanism for optimizing sensory processing by selectively reducing neural responses to prevalent stimuli. While well-characterized in mammals, its evolutionary conservation and functional impact in avian species, particularly on neural coding and decoding, remain largely unexplored. Here, we investigated visual SSA in the avian nucleus Imc by simultaneously analyzing LFP spectral power and single-unit spiking activity in pigeons. During exposure to constant-order moving dot stimuli, repeated presentations induced sustained suppression of both low-gamma-band (31–70 Hz) and high-gamma (71–120 Hz) LFP power, which recovered upon novel stimulus introduction. A similar adaptive pattern was observed in spike firing rates. Stimulus-specific indices revealed that over 80% of Imc neurons exhibited SSA in gamma-band LFP energy, compared to 65.6% based on spike rates. To quantify the functional consequence, we employed machine learning decoders to assess the discrimination of moving targets. Prior to adaptation, decoding based on the spike rate achieved up to 81.8% accuracy, outperforming LFP-based decoding. Critically, SSA may impair the encoding of directional information in sustained responses, reducing the decoding accuracy of classifiers using spike rates, LFP features, or their combinations to near-baseline levels. These findings indicate that gamma-band LFP energy in the Imc primarily reflects stimulus salience, whereas spike rates concurrently encode both identity and salience. This study elucidates the differential roles SSA and its effect on multiplexed neural codes, advancing the understanding of invariant visual representation in the avian brain.
