Abstract
Brain signal recordings with epidural microarrays constitute a low-invasive approach for recording distributed neuronal signals. Epidural field potentials (EFPs) may serve as a safe and highly beneficial signal source for a variety of research questions arising from both basic and applied neuroscience. A wider use of these signals, however, is constrained by a lack of data on their specific information content. Here, we make use of the high spatial resolution and the columnar organization of macaque primary visual cortex (V1) to investigate whether and to what extent EFP signals preserve information about various visual stimulus features. Two monkeys were presented with different feature combinations of location, size, shape, and color, yielding a total of 375 stimulus conditions. Visual features were chosen to access different spatial levels of functional organization. We found that, besides being highly specific for locational information, EFPs were significantly modulated by small differences in size, shape, and color, allowing for high stimulus classification rates even at the single-trial level. The results support the notion that EFPs constitute a low-invasive, highly beneficial signal source for longer-term recordings for medical and basic research by showing that they convey detailed and reliable information about constituent features of activating stimuli.
Highlights
Brain signal recordings with epidural microarrays constitute a low-invasive approach for recording distributed neuronal signals
Objects were shown at several close-by locations; they consisted, of differently colored letter stimuli, such that decoding performance relied on differences in stimulus size, orientation statistics, and color
We address the question whether and to what extent stimulus location and stimulus size is represented in Epidural field potentials (EFPs) if differences in location and size are kept within, or even below, the range of epidural receptive field (ERF) diameters
Summary
Brain signal recordings with epidural microarrays constitute a low-invasive approach for recording distributed neuronal signals. Hypercolumns span about one to two degrees of the parafoveal visual field[13], the area represented by an ERF is likely to cover, at least partly, several hypercolumns While this suggests that the EFP at a given electrode is integrating over multiple sets of orientation columns and color blobs, parts of a stimulus may activate distinct neuronal subsets and may shape the integrated response in a specific manner. The results of the study show that, albeit the EFP is a mass signal that integrates over presumably tens of thousands of neurons, it preserves detailed information about spatial but nonspatial stimulus features, which can be decoded with high classification rates on the single-trial level This renders the EFP a highly informative yet minimally invasive brain signal for chronic, long-term applications in both clinical settings and basic research
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