Neural Correlates Of The Production Effect: Insights From Univariate And Multivariate Analyses Of fMRI Data

Abstract

The production effect is a simple phenomenon in human memory: words that are read aloud are more likely to be remembered on a subsequent memory test (e.g., a recognition task) compared to words read silently. This effect, along with its proposed underlying mechanisms, has received much attention from cognitive research relying near-exclusively on data from behavioural paradigms. To date, the neural underpinnings of this effect remain largely unexplored. In this dissertation I present a comprehensive functional magnetic resonance imaging (fMRI)-based investigation of the production effect in recognition memory. In three fMRI experiments, participants read a series of words either aloud or silently and (in two experiments) were later tested on their recognition memory for all the studied words. Potential neural correlates of the production effects ought to be evidenced by contrasts of brain activity between aloud and silent reading conditions; therefore, across three empirical chapters, I present evidence of differences in encoding and retrieval processes between these two reading conditions. In Chapter 2 I show that aloud reading (during both encoding and subsequent recognition) elicits preferential activity in brain areas associated with speech production and perception. In Chapter 3, I use representational similarity analysis (RSA) to demonstrate that reading aloud is associated with increased sensitivity to multiple properties of presented words; primarily phonological and articulatory features. In Chapter 4, I use pattern similarity analysis (PSA) to show that recognising aloud versus silent words depends on dissociable roles of neural reactivation (reinstatement of stimulus-specific activity patterns from encoding) and neural transformation (systematic changes to activity patterns). Taken together, these findings are broadly consistent with dominant theoretical accounts of the production effect whereby aloud words benefit from distinctive sensorimotor processing. However, some results are also compatible with alternative accounts which emphasise semantic and attentional components. Moreover, evidence for dissociable processes between aloud and silent reading challenges long-standing assumptions of prior research in this area. Overall this work provides novel insights, at the neural level, into encoding and retrieval processes which contribute to the behavioural production effect.