Abstract
Animals exploit visual information to identify objects, form stimulus-reward associations, and prepare appropriate behavioral responses. The nidopallium caudolaterale (NCL), an associative region of the avian endbrain, contains neurons exhibiting prominent response modulation during presentation of reward-predicting visual stimuli, but it is unclear whether neural activity represents valuation signals, stimulus properties, or sensorimotor contingencies. To test the hypothesis that NCL neurons represent stimulus value, we subjected pigeons to a Pavlovian sign-tracking paradigm in which visual cues predicted rewards differing in magnitude (large vs. small) and delay to presentation (short vs. long). Subjects’ strength of conditioned responding to visual cues reliably differentiated between predicted reward types and thus indexed valuation. The majority of NCL neurons discriminated between visual cues, with discriminability peaking shortly after stimulus onset and being maintained at lower levels throughout the stimulus presentation period. However, while some cells’ firing rates correlated with reward value, such neurons were not more frequent than expected by chance. Instead, neurons formed discernible clusters which differed in their preferred visual cue. We propose that this activity pattern constitutes a prerequisite for using visual information in more complex situations e.g. requiring value-based choices.
Highlights
Delayed alternation performance[11], response selection[12], and reversal learning[13], while sparing sensorimotor functions[14]
Previous studies have hinted at the possibility that NCL neurons represent the reward value of conditioned visual stimuli[17,19,20], based on the observed reward-related neural modulation during post-choice, pre-reward delay phases as well as during reward consumption itself[20,22,29]
We asked whether NCL neurons signal the ‘integrated value’ of visual cues, i.e. subjective value integrated across two different dimensions of reward – magnitude and delay to presentation
Summary
Delayed alternation performance[11], response selection[12], and reversal learning[13], while sparing sensorimotor functions[14]. Previous studies have hinted at the possibility that NCL neurons represent the reward value of conditioned visual stimuli[17,19,20], based on the observed reward-related neural modulation during post-choice, pre-reward delay phases as well as during reward consumption itself[20,22,29]. We aimed to factor out sensorimotor contingencies confounded with cue value as a modulator of stimulus-related response modulation[20] To this end, we subjected birds to a sign-tracking paradigm in which distinct visual cues predicted different outcomes, namely rewards of large or small magnitude, available after a short or long delay, or non-reward. Because the animals’ pecking rate at the visual stimuli scales monotonically with the desirability of the predicted reward, we used this measure to index subjects’ CS valuation[30]
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