Abstract
The human lateral occipital complex (LOC) is more strongly activated by images of objects compared to scrambled controls, but detailed information at the neuronal level is currently lacking. We recorded with microelectrode arrays in the LOC of 2 patients and obtained highly selective single-unit, multi-unit, and high-gamma responses to images of objects. Contrary to predictions derived from functional imaging studies, all neuronal properties indicated that the posterior subsector of LOC we recorded from occupies an unexpectedly high position in the hierarchy of visual areas. Notably, the response latencies of LOC neurons were long, the shape selectivity was spatially clustered, LOC receptive fields (RFs) were large and bilateral, and a number of LOC neurons exhibited three-dimensional (3D)-structure selectivity (a preference for convex or concave stimuli), which are all properties typical of end-stage ventral stream areas. Thus, our results challenge prevailing ideas about the position of the more posterior subsector of LOC in the hierarchy of visual areas.
Highlights
Our understanding of the human brain is hampered by the limitations imposed upon neuroscience research in humans
In 2 patients who were evaluated for refractory epilepsy, we ran an lateral occipital complex (LOC)-localizer functional magnetic resonance imaging (fMRI) experiment, in which blocks of nonscrambled shapes and outlines were interleaved with control blocks of scrambled stimuli (Fig 1 center [17])
We verified the anatomical location of the array using a computed tomography (CT) scan obtained after array implantation, which was coregistered onto the anatomical MRI
Summary
Our understanding of the human brain is hampered by the limitations imposed upon neuroscience research in humans. Noninvasive measurements of brain activity (Electroencephalography [EEG], functional magnetic resonance imaging [fMRI]) often provide only coarse information regarding neural activity, due to their limited spatial or temporal resolution. Genuine insight into the function of a brain area requires detailed measurements of the electrical activity of individual neurons and small populations of neurons at high spatiotemporal resolution. Intracortical electrophysiological recordings in humans are scarce, the human visual cortex is virtually unexplored at the level of the individual neurons and small populations of neurons.
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