An Analysis of the Brain Systems Involved with Producing Letters by Hand

Abstract

Complex visual–motor behaviors dominate human–environment interactions. Letter production, writing individual letters by hand, is an example of a complex visual–motor behavior composed of numerous behavioral components, including the required motor movements and the percepts that those motor movements create. By manipulating and isolating components of letter production, we provide experimental evidence that this complex visual–motor behavior is supported by a widespread neural system that is composed of smaller subsystems related to different sensorimotor components. Adult participants hand-printed letters with and without “ink” on an MR-safe digital writing tablet, perceived static and dynamic representations of their own handwritten letters, and perceived typeface letters during fMRI scanning. Our results can be summarized by three main findings: (1) Frontoparietal systems were associated with the motor component of letter production, whereas temporo-parietal systems were more associated with the visual component. (2) The more anterior regions of the left intraparietal sulcus were more associated with the motor component, whereas the more posterior regions were more associated with the visual component, with an area of visual–motor overlap in the posterior intraparietal sulcus. (3) The left posterior intraparietal sulcus and right fusiform gyrus responded similarly to both visual and motor components, and both regions also responded more during the perception of one's own handwritten letters compared with perceiving typed letters. These findings suggest that the neural systems recruited during complex visual–motor behaviors are composed of a set of interrelated sensorimotor subsystems that support the full behavior in different ways and, furthermore, that some of these subsystems can be rerecruited during passive perception in the absence of the full visual–motor behavior.

Relating visual production and recognition of objects in human visual cortex

“…Drawing is a complex visuomotor behavior, involving the concurrent recruitment of both occipitotemporal and parietal lobes (Vinci-Booher et al, 2018). In agreement with prior work, we found consistent engagement in voxels within V1, V2, LOC, and parietal cortex during drawing production relative to rest, as measured by a univariate contrast (see Methods).…”

“…Moreover, our findings are congruent with a growing body of evidence showing a large degree of functional overlap in the network of regions during the perception and production of abstract symbols (James, 2017; James & Gauthier, 2006), as well as overlap between regions recruited during production of symbols and object drawings (Planton et al, 2017). This convergence suggests that common functional principles (Lake, Salakhutdinov, & Tenenbaum, 2015), if not identical neural mechanisms, may underlie fluent perception and production of symbols and drawable objects, in particular the recruitment of representations in visual cortex and computations in parietal cortex that are thought to transform perceptual representations into actions (Vinci-Booher et al, 2018).…”

“…Motivated by prior work investigating visually-guided action (Vinci-Booher et al, 2018; Goodale & Milner, 1992), we also sought to analyze how sensory information represented in occipital cortex is related to downstream parietal cortex, which is associated with action planning and execution. Accordingly, a parietal lobe ROI mask was also generated for each participant based on their Freesurfer segmentation.…”

“…However, given that visual production inherently entails the coordination between posterior perceptual and downstream action-oriented systems, we developed an approach to explore how sensory information is transmitted between regions. Specifically, because prior work has indicated that parietal cortex is also engaged during visual production (Vinci-Booher et al, 2018), we measured how activation patterns in visual cortex are related to activation patterns in parietal cortex during drawing production.…”

“…To what extent are these core visual processing mechanisms also recruited to produce a recognizable drawing of those objects? Initial insights bearing on this question have come from human neuroimaging studies investigating the production of handwritten symbols (though not drawings of real-world objects), revealing general engagement of visual regions during both letter production and recognition (Vinci-Booher, Cheng, & James, 2018; James & Gauthier, 2006). However, the format and content of the representations active in these regions during visual production is not yet well understood.…”