Prospective memory and working memory: Asymmetrical effects during frontal lobe TMS stimulation

• Published in: Neuropsychologia Vol. 48; no. 11; pp. 3282 - 3290
• Main Authors: Basso, Demis, Ferrari, Marcella, Palladino, Paola
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01.09.2010; Elsevier
• Subjects: Adult; Adult and adolescent clinical studies; Biological and medical sciences; Cognitive ability; Data Interpretation, Statistical; Decision Making - physiology; Female; Humans; Male; Medical sciences; Memory - physiology; Memory, Short-Term - physiology; Organic mental disorders. Neuropsychology; Prefrontal cortex; Prefrontal Cortex - physiology; Prospective memory; Psychology. Psychoanalysis. Psychiatry; Psychomotor Performance - physiology; Psychopathology. Psychiatry; Reaction Time - physiology; Resource demands; TMS; Transcranial Magnetic Stimulation; Working memory; Young Adult; Resource demands; Prospective memory; Working memory; Prefrontal cortex; TMS; Human; Frontal lobe; Transcranial magnetic stimulation; Asymmetry; Central nervous system; Cognition; Encephalon
• ISSN: 0028-3932; 1873-3514
• DOI: 10.1016/j.neuropsychologia.2010.07.011

[Display omitted] ▶ Prospective memory needs working memory resources only at high demand. ▶ PM and WM are only partially based on a common neural substrate. ▶ PM is not only related to the frontopolar cortex, but also to dorsolateral PFC. ▶ TMS resulted as a technique suitable to study high-level cognitive processes. The role of working memory (WM) for the realization of an intended action (prospective memory, PM) has been debated in recent neuropsychological literature. The present study aimed to assess whether WM and PM share resources or are, alternatively, two distinct mechanisms. A verbal task was used, which manipulated the cognitive demand of both WM and PM dimensions on an event-based prospective task. Transcranial magnetic stimulation (TMS) was also employed to clarify the causal contribution of frontal areas previously related to WM, to the PM process. The prospective task required the participant to respond whenever a word appeared which had been presented before the beginning of the task. Two ongoing tasks were administered: an updating WM task (in two conditions of medium and high WM demands) and a lexical decision task (representing a low WM demand). In the first two experiments, higher PM demand affected WM only at higher loads, but the PM load effect was independent of WM, showing asymmetrical behavioural effects. In the third experiment, single pulse TMS was applied to left and right dorsolateral prefrontal cortices. When applied to the experimental sites, stimulation increased error rates of the PM task, while the effect was only marginal in the WM task. The effect was bilateral, since there was no difference between left and right stimulation sites. These findings demonstrated, from both behavioural and neurofunctional perspectives, that WM and PM processes are not based on the same memory system, but PM may require WM resources at high demand.