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Christopher Tyler, Lora Likova, Spero Nicholas; Reconsideration of the functionality of human Frontal Eye Fields.. Journal of Vision 2013;13(9):925. doi: 10.1167/13.9.925.
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© ARVO (1962-2015); The Authors (2016-present)
Introduction. The Frontal Eye Fields (FEF) are conventionally designated as a region of frontal cortex activated in conjunction with eye movement tasks. However, most studies of their function employ a wide array of working memory (WM), spatial attention, visual search tasks and cognitive tasks such as mathematical calculation. Here we ask what form of neural coding could underlie the processing of such a wide variety of mental processes, and whether they can be meaningfully associated with an oculomotor function. Methods. Functional MRI of human observers at 3T in a whole-brain paradigm morphed to the MNI brain coordinates was used to contrast a) the activation in a simple, attentionally non-demanding, repetitive left-right saccade task involving only two eye muscles per eye with b) activation in an advanced calculation (working memory) task of adding, subtracting, multiplying or dividing three-digit numbers with controlled fixation. Results. 1. Both task activations overlapped only in the dorsal FEF. 2. Surprisingly, activation in the ventral FEF, also a well-known saccadic area, was virtually eliminated in the simple saccade task. 3. The calculation WM activated the full extent of the premotor cortex, commonly activated in WM tasks. 4. The saccadic task bilaterally activated a small well-focused region of the primary motor cortex (M1) centered within the face region. Conclusion. Although part of premotor cortex is commonly designated as the dorsal ‘FEF’ for eye movement control, its ubiquitous activation in non-oculomotor WM and other cognitive tasks implies a much broader role beyond oculomotor functions. The ventral ‘FEF’ activation we found in the calculation task partially overlaps with Broca’s area, and may support a subvocal component of the WM operation. Finally, the local patch of M1 activation is suggested as the specific eye muscle control region (from the ~650 muscles controlled by the ‘homunculus’ of the full M1 strip).
Meeting abstract presented at VSS 2013
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