The effects of varying levels of hemispheric activation on episodic memory

Laterality. 2018 Jul;23(4):409-421. doi: 10.1080/1357650X.2017.1369985. Epub 2017 Aug 30.


Bilateral saccadic eye movements enhance episodic memory retrieval; however, this usually only occurs for consistent-handed, not inconsistent-handed, individuals. It was hypothesized that inconsistent-handers begin closer to the peak of a Yerkes-Dodson-type inverted-U curve and increasing activation pushes them along the curve eventually decreasing performance, while consistent-handers start at a lower baseline and therefore increasing activation increases their performance. The current study tested this hypothesis by using hand clenching (grip strength) to increase activation at 5 different levels for both consistent- and inconsistent-handers. A total of 316 participants were presented with a list of 36 words after which they squeezed a hand dynamometer to induce cortical activation, and then recalled as many of the words as they could. Results showed that, as predicted, both inconsistent- and consistent-handers demonstrated an inverted-U pattern of memory performance as the strength of squeeze increased with inconsistent-handers peaking at a lower level of grip strength than consistent-handers. These results may help explain past findings, not only with episodic memory but also a variety of other cognitive tasks. They may also have interesting theoretical and real-world implications, which are discussed.

Keywords: Handedness; episodic memory; grip strength; interhemispheric interaction; laterality.

MeSH terms

  • Brain / physiology
  • Female
  • Functional Laterality / physiology*
  • Hand / physiology*
  • Hand Strength / physiology
  • Humans
  • Male
  • Memory, Episodic*
  • Mental Recall / physiology
  • Motor Activity / physiology*
  • Multivariate Analysis
  • Muscle Strength Dynamometer
  • Neuropsychological Tests
  • Pattern Recognition, Visual / physiology
  • Random Allocation
  • Reading
  • Regression Analysis