Decoding the processing stages of mental arithmetic with magnetoencephalography

Abstract

Elementary arithmetic is highly prevalent in our daily lives. However, despite decades of research, we are only beginning to understand how the brain solves simple calculations. Here, we applied machine learning techniques to magnetoencephalography (MEG) signals in an effort to decompose the successive processing stages and mental transformations underlying elementary arithmetic. Adults subjects verified single-digit addition and subtraction problems such as 3 + 2 = 9 in which each successive symbol was presented sequentially. MEG signals revealed a cascade of partially overlapping brain states. While the first operand could be transiently decoded above chance level, primarily based on its visual properties, the decoding of the second operand was more accurate and lasted longer. Representational similarity analyses suggested that this decoding rested on both visual and magnitude codes. We were also able to decode the operation type (additions vs. subtraction) during practically the entire trial after the presentation of the operation sign. At the decision stage, MEG indicated a fast and highly overlapping temporal dynamics for (1) identifying the proposed result, (2) judging whether it was correct or incorrect, and (3) pressing the response button. Surprisingly, however, the internally computed result could not be decoded. Our results provide a first comprehensive picture of the unfolding processing stages underlying arithmetic calculations at a single-trial level, and suggest that externally and internally generated neural codes may have different neural substrates.

Mental Shopping Calculations: A Transcranial Magnetic Stimulation Study

“…Neuropsychological studies in patients and neuroimaging reports in healthy individuals show that the neural circuits for mental calculations form a complex network of interacting areas. They involve the parietal lobes, e.g., the bilateral intraparietal sulcus, the posterior subdivisions of the superior parietal lobules, and the left angular and supramarginal gyri of the inferior parietal lobule ( Gobel et al, 2001 ; Naccache and Dehaene, 2001 ; Dehaene et al, 2003 , 2004 ; Eger et al, 2003 ; Fias et al, 2003 ; Piazza et al, 2004 ; Pinel et al, 2004 ; Nieder, 2005 ; Sato et al, 2007 ; Andres et al, 2008 ; Brozzoli et al, 2008 ; Domahs et al, 2008 , 2010 ; Kaufmann et al, 2008 ), as well as the temporal lobes, e.g., the posterior inferior temporal gyrus ( Daitch et al, 2016 ; Hermes et al, 2017 ; Yeo et al, 2017 ; Pinheiro-Chagas et al, 2018 , 2019 ) and even the left frontal lobe, with the Broca’s area and its vicinity ( Schmithorst and Brown, 2004 ; Shuman and Kanwisher, 2004 ; Majerus et al, 2010 ). While it is still unknown what subdivision of this network is the most critical for mental arithmetic, there is some agreement that such an area should be located in the posterior parietal cortex (PPC) on the left ( Dehaene et al, 2004 ; Nieder, 2005 ).…”

Neural Decoding of Multi-Modal Imagery Behavior Focusing on Temporal Complexity

“…An important strength of MEG is its high temporal resolution. Some earlier studies have benefited from the temporal resolution to examine the time evolution of neural processes of approximately tens to hundreds of milliseconds ( 91 – 93 ). Reports of some studies using fMRI have described increases in the effective connectivity from the supramodal regions to the visual associative regions during VI ( 48 ) and differences in the effective connectivity among motor-related regions during ME and during MI ( 46 ).…”

Electroencephalograms during Mental Arithmetic Task Performance

“…The dataset was collected to investigate EEG correlates of mental activity during an intensive cognitive task (mental arithmetic task-serial subtraction). This model of research is quite common in the study of the mechanisms of human cognitive activity [17,18].…”