September 2011
Volume 11, Issue 11
Free
Vision Sciences Society Annual Meeting Abstract  |   September 2011
Working memory representations of visual motion direction are encoded in the firing patterns of neurons in dorsolateral prefrontal cortex, but not in area MT
Author Affiliations
  • Diego Mendoza
    Department of Physiology, McGill University, Canada
  • Julio Martinez-Trujillo
    Department of Physiology, McGill University, Canada
Journal of Vision September 2011, Vol.11, 1241. doi:10.1167/11.11.1241
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      Diego Mendoza, Julio Martinez-Trujillo; Working memory representations of visual motion direction are encoded in the firing patterns of neurons in dorsolateral prefrontal cortex, but not in area MT. Journal of Vision 2011;11(11):1241. doi: 10.1167/11.11.1241.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

It is thought that primate dorsolateral prefrontal cortex (dlPFC) neurons play a role in the maintenance of visual information in working memory (Goldman-Rakic, 1995). It has been recently suggested that this process also involves the recruitment of neurons in early visual cortex that are selective for the stimulus features to be remembered. Supporting this hypothesis, recent fMRI studies have reported that the contents of visual working memory can be decoded from patterns of BOLD signals in visual areas (Harrison and Tong, 2009). However, because fMRI does not directly measure the neurons' spiking activity, it remains controversial whether this effect is attributable to variations in the firing patterns of neurons, or in the amplitude of other signals such as local field potentials. Here, we investigate this issue by recording the spiking activity of single neurons simultaneously from the dlPFC (n = 53) and early visual area MT (n = 33) of two rhesus monkeys during a working memory task requiring them to remember the motion direction of a sample random dot pattern and match it to the direction of one of two test patterns serially presented inside the neurons' receptive field. During the memory period, the activity of most dlPFC remained above or below baseline, and approximately 1/6 of the neurons showed sustained tuning to the remembered direction. In all of the recorded MT neurons, activity remained at baseline levels and direction tuning was not present throughout the memory period. Our results show that working memory representations of motion direction are encoded in the firing patterns of neurons in dlPFC but not in MT. They further suggest that the reported patterns of BOLD activation in visual cortex reflecting the contents of working memory may originate from changes in other signals such as local field potentials rather than spiking activity.

Canadian Institute of Health Research & EJLB Foundation. 
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