Noradrenaline and dopamine neurons integrate reward value and effort cost: a direct electrophysiological comparison in behaving monkeys
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1
ICM - Brain & Spine Institute, France
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2
Université Paris Descartes-Sorbonne, France
Neuromodulation is essential for numerous aspects of behavior, but the specific contribution of each neuromodulator to motivation remains unclear. Here, we take advantage of a dual effect of effort: the perspective of a physical effort reduces the action value as it represents a cost, but it also boosts the mobilization of physiological energy necessary to perform the action. We hypothesize that these 2 aspects differentially involve dopamine (DA) and noradrenaline (NA).
We record single unit activity from 60 NA neurons from locus coeruleus (LC) and 47 DA neurons from substantia nigra pars compacta (SNc) of two rhesus macaques who must produce a given effort (3 force levels) in order to obtain a given reward (3 reward sizes). Force level and reward size are visually cued. Abandon rates increase as reward is lower and as effort is higher, indicating that reward value is discounted by the amount of effort required to obtain it.
Both NA and DA neurons show a significant increase (p<.01) in firing rates 100-400 ms after cue onset (DA: n=38/47, 83%; NA: n=50/60, 85%) and -100-400 ms around effort onset (DA: n=34/47, 74%; NA: n=47/60, 80%). Cue-response is positively modulated by expected reward in both populations (DA: 24%, n=11/47, NA: 20%, n=12/60. Population-level analyses reveal a correlation between action value and cue-response in DA neurons (r=.15, p<.01), but not in NA neurons. Conversely, during the action itself, we found that response magnitudes of NA neurons positively correlate with the amount of exerted force (r=.17, p<.01) and with pupil dilation (r=.13, p<.01), while DA neurons do not.
We conclude that NA and DA neurons share many similarities in reward and effort encoding, but the extent to which our experimental factors affect such activities differs: DA neurons are more sensitive to reward and action value, whereas NA neurons are more sensitive to effort.
Keywords:
Dopamine,
Electrophysiology,
Motivation,
noradrenaline,
effort,
non-human primates
Conference:
XII International Conference on Cognitive Neuroscience (ICON-XII), Brisbane, Queensland, Australia, 27 Jul - 31 Jul, 2014.
Presentation Type:
Poster
Topic:
Cognition and Executive Processes
Citation:
Varazzani
C,
San-Galli
A and
Bouret
S
(2015). Noradrenaline and dopamine neurons integrate reward value and effort cost: a direct electrophysiological comparison in behaving monkeys.
Conference Abstract:
XII International Conference on Cognitive Neuroscience (ICON-XII).
doi: 10.3389/conf.fnhum.2015.217.00382
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Received:
19 Feb 2015;
Published Online:
24 Apr 2015.
*
Correspondence:
Mrs. Chiara Varazzani, ICM - Brain & Spine Institute, Paris, France, chiaravara@gmail.com