ISSN 0869-6632 (Print)
ISSN 2542-1905 (Online)


cognitive neuroscience

Revealing the neural network underlying covert picture-naming paradigm using magnetoencephalography

The ability to name trivial everyday objects is a key cognitive function that is tested after head injuries or brain surgeries. Although quite a lot of long-standing knowledge on this topic has accumulated over the past few decades and many theoretical models have been created, the underlying neural substrate and brain functioning are still not fully aligned. As far as we know, there have been no studies on this topic using magnetoencephalography (MEG), which allows recording electrophysiological activity with a high temporal resolution.

Dynamics of an artificial recurrent neural network for the problem of modeling a cognitive function

The purpose of this work is to build an artificial recurrent neural network whose activity models a cognitive function relating to the comparison of two vibrotactile stimuli coming with a delay and to analyze dynamic mechanisms underlying its work. Methods of the work are machine learning, analysis of spatiotemporal dynamics and phase space. Results. Activity of the trained recurrent neural network models a cognitive function of the comparison of two stimuli with a delay. Model neurons exhibit mixed selectivity during the course of the task.

Revealing the neural network underlying covert picture-naming paradigm using magnetoencephalography

We have conducted a series of MEG experiments based on the covert picture-naming task with fourteen non-native English speakers, who made up three groups with different kinds of language training and proficiencies. We found two stages of brain response, corresponding to sensory and semantic processing, which differed in spatio-temporal cortical activation. The active regions found in our two-stage response are consistent with the active regions found in other studies based on techniques such as fMRI, ECoG, and direct electrical stimulation. The sensory processing stage remained uniform across the three differently proficient groups, whereas the semantic processing stage showed inconsistencies. A new understanding of the mechanisms of covertly naming pictures and their neuronal substrate has been obtained. The complete mechanism of the semantic processing stage seems to be much more complex and requires further work. It seems that there are bidirectional connections between the three-focal network formed by fusiform gyrus, Broca's area, and Wernicke's area, and their causal relationships need to be investigated in the future. The connections of this network with the intraparietal sulcus also need to be investigated. In addition, a robust method to identify evoked response peaks needs to be developed in future. Finally, this work highlights the importance of fusiform gyrus, which is at risk of resection in mesial temporal lobe epilepsies.