Table. Reward processing deficits by disease.

	Primary reward processing	Secondary reward processing	Reward-based learning	Reward-related decision making
Healthy Aging	Decline in primary sensory function	Positivity bias (stronger anticipation of monetary gain than loss)	Positivity bias with possible negativity bias in “older old”	---
Mild cognitive impairment	---	---	Improved learning when faced with negative stimuli or possible loss	---
Alzheimer's Disease	Loss of appetite Poor odor discrimination and identification	---	---	Impairment on tasks of decision-making under uncertainty and risk correlating with cognitive deficits
Behavioral variant frontotemporal dementia	Overeating and sweet preference Odor identification deficit due to semantic impairment with intact odor discrimination Decreased pain sensitivity Decreased fear conditioning to loud noise Hyposexuality	---	---	Risky choices on tasks of decision-making under uncertainty and risk
Semantic variant primary progressive aphasia	Food fads and restrictive dieting Odor and flavor identification deficit due to loss of semantic knowledge	---	---	---
Amyotrophic lateral sclerosis	---	---	Intact probabilistic reversal learning	---
Parkinson's Disease	Olfactory impairment with preservation of gustation	Decreased physiological anticipation of monetary gain with intact response to receipt of monetary reward	Enhanced learning from negative outcomes off dopaminergic medication. Enhanced learning from positive outcomes and decreased learning from negative outcomes on dopaminergic medication	Mixed results on Decision-making tasks reflecting differences in disease stage and medication
Huntington's Disease	---	Decreased anticipation of monetary reward or punishment	---	Intact gambling task performance early in illness. Decision-making task deficits later correlate with cognitive impairment.