@article {34, title = {Large-Scale, High-Resolution Neurophysiological Maps Underlying fMRI of Macaque Temporal Lobe}, journal = {Journal of Neuroscience}, volume = {33}, year = {2013}, month = {2013}, pages = {15207 - 15219}, abstract = {

Maps obtained by functional magnetic resonance imaging (fMRI) are thought to reflect the underlying spatial layout of neural activity. However, previous studies have not been able to directly compare fMRI maps to high-resolution neurophysiological maps, particularly in higher level visual areas. Here, we used a novel stereo microfocal x-ray system to localize thousands of neural recordings across monkey inferior temporal cortex (IT), construct large-scale maps of neuronal object selectivity at subvoxel resolution, and compare those neurophysiology maps with fMRI maps from the same subjects. While neurophysiology maps contained reliable structure at the sub-millimeter scale, fMRI maps of object selectivity contained information at larger scales (\>2.5 mm) and were only partly correlated with raw neurophysiology maps collected in the same subjects. However, spatial smoothing of neurophysiology maps more than doubled that correlation, while a variety of alternative transforms led to no significant improvement. Furthermore, raw spiking signals, once spatially smoothed, were as predictive of fMRI maps as local field potential signals. Thus, fMRI of the inferior temporal lobe reflects a spatially low-passed version of neurophysiology signals. These findings strongly validate the widespread use of fMRI for detecting large (\>2.5 mm) neuronal domains of object selectivity but show that a complete understanding of even the most pure domains (e.g., faces vs nonface objects) requires investigation at fine scales that can currently only be obtained with invasive neurophysiological methods.

}, issn = {0270-6474}, doi = {10.1523/JNEUROSCI.1248-13.2013}, url = {http://www.jneurosci.org/cgi/doi/10.1523/JNEUROSCI.1248-13.2013}, author = {Issa, E. B. and Papanastassiou, A. M. and DiCarlo, J. J.} } @proceedings {48, title = {Towards large-scale, high resolution maps of object selectivity in inferior temporal cortex}, journal = {Computation and Systems Neuroscience (COSYNE)}, year = {2010}, month = {02/2010}, address = {Salt Lake City, Utah, USA}, abstract = {

Inferior temporal cortex (IT) has been shown to have large-scale (mm to cm) maps of object category selectivity as well as small-scale (sub-millimeter) organization for object features.\  These two scales of spatial organization have yet to be linked because they were measured using different techniques (fMRI, optical imaging, and local electrophysiology), each with their own limitations.\  For example, fMRI has poor spatial resolution while optical imaging has higher resolution at the expense of a narrow field of view of only surface-accessible cortex.\  Given that much of IT lies inside a major cortical sulcus or at the skull base, what is needed is a method that can access the whole of IT with high resolution.\  Microelectrode based mapping has such potential: electrodes can reach almost anywhere in IT (high spatial coverage) and record from single cells (high spatial resolution).\ This potential has not yet been realized because of the difficulty of precisely localizing and co-registering many electrode recordings in vivo.\  Methods such as histological reconstruction of lesion sites or MRI visualization of electrodes are post-hoc and can introduce additional spatial errors.\  Here, we have adopted a microfocal stereo x-ray system for localizing electrodes that can be used at an unlimited number of sites and operates virtually in real-time (Cox et al., J. Neurophys. 2008).\  We have used this system to construct broad scale maps of object category selectivity in IT for comparison to fMRI-based maps.\  We found a weak but significant correspondence between physiology and fMRI maps collected in the same animal, and this correspondence improved substantially when MUA and LFP signals were smoothed (~3-5 mm) to broader scales suggesting the spatial low pass nature of fMRI.\  Transformations other than spatial smoothing such as dividing the LFP into power in different frequency bands did not produce noticeable improvement in map correspondence.

}, doi = {10.3389/conf.fnins.2010.03.00154}, url = {https://www.frontiersin.org/Community/AbstractDetails.aspx?ABS_DOI=10.3389/conf.fnins.2010.03.00154\&eid=770\&sname=computational_and_systems_neur}, author = {Issa, Elias B. and Papanastassiou, A. M. and Andken, BB and DiCarlo, James J.} } @proceedings {66, title = {A systematic exploration of the relationship of fMRI signals and neuronal activity in the primate temporal lobe}, journal = {Society for Neuroscience}, year = {2009}, month = {11/2009}, publisher = {SFN}, address = {Washington, DC, USA}, author = {Papanastassiou, A. M. and Op de Beeck, H. P. and Andken, BB and DiCarlo, James J.} }