Biology subjects

Iamshchinina, P.

Publications and source records attributed to Iamshchinina, P..

3 recordsLinked to original sources

bioRxiv2021

Benchmarking GE-BOLD, SE-BOLD, and SS-SI-VASO sequences for depth-dependent separation of feedforward and feedback signals in high-field MRI

Recent advances in high-field fMRI have allowed differentiating feedforward and feedback information in the grey matter of the human brain. For continued progress in this endeavor, it is critical to understand how MRI data acquisition parameters impact the read-out of information from laminar response profiles. Here, we benchmarked three different MR-sequences at 7T - gradient-echo (GE), spin-echo (SE) and vascular space occupancy imaging (VASO) - in differentiating feedforward and feedback signals in human early visual cortex (V1). The experiment (N=4) consisted of two complementary tasks: a perception task that predominantly evokes feedforward signals and a working memory task that relies on feedback signals. In the perception task, participants saw flickering oriented gratings while detecting orthogonal color-changes. In the working memory task, participants memorized the precise orientation of a grating. We used multivariate pattern analysis to read out the perceived (feedforward) and memorized (feedback) grating orientation from neural signals across cortical depth. Analyses across all the MR-sequences revealed perception signals predominantly in the middle cortical compartment of area V1 and working memory signals in the deep compartment. Despite an overall consistency across sequences, SE-EPI was the only sequence where both feedforward and feedback information were differently pronounced across cortical depth in a statistically robust way. We therefore suggest that in the context of a typical cognitive neuroscience experiment as the one benchmarked here, SE-EPI may provide a favorable trade-off between spatial specificity and signal sensitivity. HighlightsHere, we benchmarked three sequences at high-field fMRI -GE-BOLD, SE-BOLD and VASO - in differentiating feedforward and feedback signals across grey matter depth of area V1. We show that: O_LIAll the MR-sequences revealed the feedforward and feedback signals at the middle and deep cortical bins, respectively. C_LIO_LISuch correspondence across the sequences indicates that widely used GE-BOLD is a suitable method for the exploration of signals in cortical depth. C_LIO_LIOnly SE-BOLD yielded statistically reliable differences between the cortical bins carry- ing feedforward and feedback signals. C_LI

neuroscience↗

bioRxiv2021

Resolving the time course of visual and auditory object categorization

Humans can effortlessly categorize objects, both when they are conveyed through visual images and spoken words. To resolve the neural correlates of object categorization, studies have so far primarily focused on the visual modality. It is therefore still unclear how the brain extracts categorical information from auditory signals. In the current study we used EEG (N=47) and time-resolved multivariate pattern analysis to investigate (1) the time course with which object category information emerges in the auditory modality and (2) how the representational transition from individual object identification to category representation compares between the auditory modality and the visual modality. Our results show that (1) that auditory object category representations can be reliably extracted from EEG signals and (2) a similar representational transition occurs in the visual and auditory modalities, where an initial representation at the individual-object level is followed by a subsequent representation of the objects category membership. Altogether, our results suggest an analogous hierarchy of information processing across sensory channels. However, we did not find evidence for a shared supra-modal code, suggesting that the contents of the different sensory hierarchies are ultimately modality-unique.

animal behavior and cognition↗

bioRxiv2021

Perceived and mentally rotated contents are differentially represented in cortical depth of V1

Primary visual cortex (V1) in humans is known to represent both veridically perceived external input and internally-generated contents underlying imagery and mental rotation. However, it is unknown how the brain keeps these contents separate thus avoiding a mixture of the perceived and the imagined which could lead to potentially detrimental consequences. Inspired by neuroanatomical studies showing that feedforward and feedback connections in V1 terminate in different cortical layers, we hypothesized that this anatomical compartmentalization underlies functional segregation of external and internally-generated visual contents, respectively. We used high-resolution layer-specific fMRI to test this hypothesis in a mental rotation task. We found that rotated contents were predominant at outer cortical depth bins (i.e. superficial and deep). At the same time perceived contents were represented stronger at the middle cortical bin. These results identify how through cortical depth compartmentalization V1 functionally segregates rather than confuses external from internally-generated visual contents. These results indicate that feedforward and feedback manifest in distinct subdivisions of the early visual cortex, thereby reflecting a general strategy for implementing multiple cognitive functions within a single brain region.

neuroscience↗