Individuals With Amnesia are not Stuck in Time: Evidence From Risky Decision-Making, Intertemporal Choice, and Scaffolded Narratives

This dissertation investigates the supposition that individuals with amnesia are cognitively stuck in time. In Experiment 1, I used a Galton-Crovitz cueing paradigm to test etiologically diverse amnesic cases on their ability to richly recollect autobiographical episodic memories and imagine future experiences. In Experiment 2, I use two behavioural economics tasks (a risky decision-making task and an intertemporal choice task) to examine whether amnesic cases judgment and decision-making reflects proneness to risky choices or steep disregard for the future. In Experiment 3, I examine the flexibility of amnesics intertemporal choice by testing whether cueing them with personal future events increases their value of future rewards as it does in healthy controls. In Experiment 4, I attempt to decrease the severity of amnesic cases episodic memory and prospection impairment by using structured and personally meaningful cues rather than the single cue words featured in the Galton-Crovitz paradigm. I replicated existing research showing that those with MTL damage have impaired ability to (re)construct rich and detailed narratives of past and future experiences, and I extended this finding for the first time to a lateral dorsal thalamic stroke case (Experiment 1). Despite this impairment in mental time travel, the same amnesic cases made financial decisions that a) systematically considered and valued the future and b) showed normal sensitivity to risk (Experiment 2). The normalcy of intertemporal choice in amnesia extends beyond basic rates of future reward discounting in intertemporal choice. In controls, cues to imagine future experiences can modulate decision-making by increasing the value one places on future rewards. Here, most amnesic cases also retain this modulatory effect, despite having impaired ability to generate detailed representations of future experiences (Experiment 3). Finally, I found that the severity of episodic prospection impairment in MTL amnesia is cue-dependent and likely overestimated in current research: specific, personally meaningful cues lead to an appreciable reduction of episodic prospection impairment over single cue words for those with mild-moderate amnesia (Experiment 4). Collectively, results challenge assumptions that amnesic populations are cognitively confined to the present and call for refinement to simple accounts of limited temporality in individuals with amnesia.