Martin Sereno - Academia.edu (original) (raw)

Papers by Martin Sereno

The human language system interacts with cognitive and sensorimotor regions during natural langua... more The human language system interacts with cognitive and sensorimotor regions during natural language processing. However, where, when, and how these processes occur remain unclear. Existing noninvasive subtraction-based neuroimaging techniques cannot simultaneously achieve the spatial and temporal resolutions required to visualize ongoing information flows across the whole brain. Here we have developed phase-encoded designs to fully exploit the temporal information latent in functional magnetic resonance imaging (fMRI) data, as well as overcoming scanner noise and head-motion challenges during overt language tasks. We captured neural information flows as coherent waves traveling over the cortical surface during listening, reciting, and oral cross-language interpreting. The timing, location, direction, and surge of traveling waves, visualized as ‘brainstorms’ on brain ‘weather’ maps, reveal the functional and effective connectivity of the brain in action. These maps uncover the functi...

Frontiers in Systems Neuroscience

We first briefly summarize data from microelectrode studies on visual maps in non-human primates ... more We first briefly summarize data from microelectrode studies on visual maps in non-human primates and other mammals, and characterize differences among the features of the approximately topological maps in the three main sensory modalities. We then explore the almost 50% of human neocortex that contains straightforward topological visual, auditory, and somatomotor maps by presenting a new parcellation as well as a movie atlas of cortical area maps on the FreeSurfer average surface, fsaverage. Third, we review data on moveable map phenomena as well as a recent study showing that cortical activity during sensorimotor actions may involve spatially locally coherent traveling wave and bump activity. Finally, by analogy with remapping phenomena and sensorimotor activity, we speculate briefly on the testable possibility that coherent localized spatial activity patterns might be able to ‘escape’ from topologically mapped cortex during ‘serial assembly of content’ operations such as scene and...

Human Brain Mapping, 2020

Electrophysiological signals from the cerebellum have traditionally been viewed as inaccessible t... more Electrophysiological signals from the cerebellum have traditionally been viewed as inaccessible to magnetoencephalography (MEG) and electroencephalography (EEG). Here, we challenge this position by investigating the ability of MEG and EEG to detect cerebellar activity using a model that employs a high‐resolution tessellation of the cerebellar cortex. The tessellation was constructed from repetitive high‐field (9.4T) structural magnetic resonance imaging (MRI) of an ex vivo human cerebellum. A boundary‐element forward model was then used to simulate the M/EEG signals resulting from neural activity in the cerebellar cortex. Despite significant signal cancelation due to the highly convoluted cerebellar cortex, we found that the cerebellar signal was on average only 30–60% weaker than the cortical signal. We also made detailed M/EEG sensitivity maps and found that MEG and EEG have highly complementary sensitivity distributions over the cerebellar cortex. Based on previous fMRI studies c...

Journal of Theoretical Biology, 1991

The intricate phenomena of biology on one hand, and language and culture on the other, have inspi... more The intricate phenomena of biology on one hand, and language and culture on the other, have inspired many writers to draw analogies between these two evolutionary systems. These analogies can be divided into four principal types: species/language, organism/concept, genes/culture, and cell/person. I argue that the last analogy-between cells and persons-is the most profound in several respects, and, more importantly, can be used to generate a number of empirical predictions. In the first half of the paper, the four analogies are each evaluated after briefly describing criteria for a good predictive analogy. In the second half of the paper, the cell/person analogy and predictions deriving from it are explored in detail.

Philosophical transactions of the Royal Society of London. Series B, Biological sciences, Jan 19, 2014

Natural language--spoken and signed--is a multichannel phenomenon, involving facial and body expr... more Natural language--spoken and signed--is a multichannel phenomenon, involving facial and body expression, and voice and visual intonation that is often used in the service of a social urge to communicate meaning. Given that iconicity seems easier and less abstract than making arbitrary connections between sound and meaning, iconicity and gesture have often been invoked in the origin of language alongside the urge to convey meaning. To get a fresh perspective, we critically distinguish the origin of a system capable of evolution from the subsequent evolution that system becomes capable of. Human language arose on a substrate of a system already capable of Darwinian evolution; the genetically supported uniquely human ability to learn a language reflects a key contact point between Darwinian evolution and language. Though implemented in brains generated by DNA symbols coding for protein meaning, the second higher-level symbol-using system of language now operates in a world mostly decou...

Proceedings of the National Academy of Sciences USA, 2020

The surface of the human cerebellar cortex is much more tightly folded than the cerebral cortex. ... more The surface of the human cerebellar cortex is much more tightly folded than the cerebral cortex. It was computationally recon- structed for the first time to the level of all individual folia from multicontrast high-resolution postmortem MRI scans. Its total shrinkage-corrected surface area (1,590 cm2) was larger than expected or previously reported, equal to 78% of the total surface area of the human neocortex. The unfolded and flattened surface comprised a narrow strip 10 cm wide but almost 1 m long. By applying the same methods to the neocortex and cerebellum of the macaque monkey, we found that its cerebellum was relatively much smaller, approximately 33% of the total surface area of its neocortex. This suggests a prominent role for the cerebellum in the evolution of distinctively human behaviors and cognition.

Proceedings of the National Academy of Sciences, 2020

Significance The cerebellum has long been recognized as a partner of the cerebral cortex, and bot... more Significance The cerebellum has long been recognized as a partner of the cerebral cortex, and both have expanded greatly in human evolution. The thin cerebellar cortex is even more tightly folded than the cerebral cortex. By scanning a human cerebellum specimen at ultra-high magnetic fields, we were able to computationally reconstruct its surface down to the level of the smallest folds, revealing that the cerebellar cortex has almost 80% of the surface area of the cerebral cortex. By performing the same procedure on a monkey brain, we found that the surface area of the human cerebellum has expanded even more than that of the human cerebral cortex, suggesting a role in characteristically human behaviors, such as toolmaking and language.

The Journal of neuroscience : the official journal of the Society for Neuroscience, Jan 4, 2018

Sensory perception relies on the precise neuronal encoding of modality-specific environmental fea... more Sensory perception relies on the precise neuronal encoding of modality-specific environmental features in primary sensory cortices. Some studies have reported the penetration of signals from other modalities even into early sensory areas. So far, no comprehensive account of maps induced by "foreign sources" exists. We addressed this question using surface-based topographic mapping techniques applied to ultra-high resolution fMRI neuroimaging data, measured in female participants. We show that fine-grained finger maps in human primary somatosensory cortex, area 3b, are somatotopically activated not only during tactile mechanical stimulation, but also when viewing the same fingers being touched. Visually-induced maps were weak in amplitude, but overlapped with the stronger tactile maps tangential to the cortical sheet when finger touches were observed in both first- and third-person perspectives. However, visually-induced maps did not overlap tactile maps when the observed f...

Auditory selective attention is vital in natural soundscapes. But it is unclear how attentional f... more Auditory selective attention is vital in natural soundscapes. But it is unclear how attentional focus on the primary dimension of auditory representation-acousticfrequency-mightmodulatebasicauditoryfunctionaltopographyduringactivelistening.Incontrasttovisualselectiveattention,which issupportedbymotor-mediatedoptimizationofinputacrosssaccadesandpupildilation,theprimateauditorysystemhasfewermeansofdifferentially sampling the world. This makes spectrally-directed endogenous attention a particularly crucial aspect of auditory attention. Using a novel functional paradigmcombinedwithquantitativeMRI,weestablishinmaleandfemalelistenersthathumanfrequency-band-selectiveattentiondrivesactivationin both myeloarchitectonically estimated auditory core, and across the majority of tonotopically mapped nonprimary auditory cortex. The attentionally driven best-frequency maps show strong concordance with sensory-driven maps in the same subjects across much of the temporal plane, with poor concordance in areas outside traditional auditory cortex. There is significantly greater activation across most of auditory cortex when best frequency is attended, versus ignored; the same regions do not show this enhancement when attending to the least-preferred frequency band. Finally, the results demonstratethatthereisspatialcorrespondencebetweenthedegreeofmyelinationandthestrengthofthetonotopicsignalacrossanumberofregions in auditory cortex. Strong frequency preferences across tonotopically mapped auditory cortex spatially correlate with R 1-estimated myeloarchitecture, indicating shared functional and anatomical organization that may underlie intrinsic auditory regionalization.

Mathematics and visualization, 2017

Cortical parcellations provide valuable localisation resources for other neuroimaging modalities ... more Cortical parcellations provide valuable localisation resources for other neuroimaging modalities such as fMRI as well as insight into the structure-function relationship of the brain. The venerable but now dated ex vivo Brodmann map is currently being superseded by in vivo techniques that can better take into account intersubject variability. One popular in vivo method focusses on myeloarchitecture by measuring T1. This, however, probes only one aspect of cortical microstructure and is less useful in regions of low myelination. In contrast, diffusion MRI (dMRI) is sensitive to several additional microstructural features and can potentially provide a richer set of information regarding the architecture of grey matter microcircuitry. The following study used 3T HARDI data of multiple subjects to produce an entirely unsupervised, hemisphere-wide, group-average, parcellation. A qualitative assessment of the resulting coritcal parcellation demonstrates several spatially coherent clusters in areas corresponding to well known functional anatomical areas. In addition, it exhibits some cluster boundaries that correlate with independently derived myelin mapping data for the same set of subjects, whilst also providing distinct clusters in areas (e.g., within MT+) where myelination is a less informative measurement.

NeuroImage: Clinical, 2022

The Journal of Neuroscience, Nov 14, 2012

In contrast to vision, where retinotopic mapping alone can define areal borders, primary auditory... more In contrast to vision, where retinotopic mapping alone can define areal borders, primary auditory areas such as A1 are best delineated by combining in vivo tonotopic mapping with postmortem cyto-or myeloarchitectonics from the same individual. We combined highresolution (800 m) quantitative T 1 mapping with phase-encoded tonotopic methods to map primary auditory areas (A1 and R) within the "auditory core" of human volunteers. We first quantitatively characterize the highly myelinated auditory core in terms of shape, area, cortical depth profile, and position, with our data showing considerable correspondence to postmortem myeloarchitectonic studies, both in cross-participant averages and in individuals. The core region contains two "mirror-image" tonotopic maps oriented along the same axis as observed in macaque and owl monkey. We suggest that these two maps within the core are the human analogs of primate auditory areas A1 and R. The core occupies a much smaller portion of tonotopically organized cortex on the superior temporal plane and gyrus than is generally supposed. The multimodal approach to defining the auditory core will facilitate investigations of structure-function relationships, comparative neuroanatomical studies, and promises new biomarkers for diagnosis and clinical studies.

Current Opinion in Neurobiology, 2014

Parietal cortex has long been known to be a site of sensorimotor integration. Recent findings in ... more Parietal cortex has long been known to be a site of sensorimotor integration. Recent findings in humans have shown that it is divided up into a number of small areas somewhat specialized for eye movements, reaching, and hand movements, but also face-related movements (avoidance, eating), lower body movements, and movements coordinating multiple body parts. The majority of these areas contain rough sensory (receptotopic) maps, including a substantial multisensory representation of the lower body and lower visual field immediately medial to face VIP. There is strong evidence for retinotopic remapping in LIP and face-centered remapping in VIP, and weaker evidence for hand-centered remapping. The larger size of the functionally distinct inferior parietal default mode network in humans compared to monkeys results in a superior and medial displacement of middle parietal areas (e.g., the saccade-related LIP's). Multisensory superior parietal areas located anterior to the angular gyrus such as AIP and VIP are less medially displaced relative to macaque monkeys, so that human LIP paradoxically ends up medial to human VIP.

NeuroImage, 2019

The reach-to-eat task involves a sequence of action components including looking, reaching, grasp... more The reach-to-eat task involves a sequence of action components including looking, reaching, grasping, and feeding. While cortical representations of individual action components have been mapped in human functional magnetic resonance imaging (fMRI) studies, little is known about the continuous spatiotemporal dynamics among these representations during the reach-to-eat task. In a periodic event-related fMRI experiment, subjects were scanned while they reached toward a food image, grasped the virtual food, and brought it to their mouth within each 16-s cycle. Fourier-based analysis of fMRI time series revealed periodic signals and noise distributed across the brain. Independent component analysis was used to remove periodic or aperiodic motion artifacts. Timefrequency analysis was used to analyze the temporal characteristics of periodic signals in each voxel. Circular statistics was then used to estimate mean phase angles of periodic signals and select voxels based on the distribution of phase angles. By sorting mean phase angles across regions, we were able to show the real-time spatiotemporal brain dynamics as continuous traveling waves over the cortical surface. The activation sequence consisted of approximately the following stages: (1) stimulus related activations in occipital and temporal cortices; (2) movement planning related activations in dorsal premotor and superior parietal cortices; (3) reaching related activations in primary sensorimotor cortex and supplementary motor area; (4) grasping related activations in postcentral gyrus and sulcus; (5) feeding related activations in orofacial areas. These results suggest that phase-encoded design and analysis can be used to unravel sequential activations among brain regions during a simulated reach-to-eat task.

Magnetic Resonance Materials in Physics Biology and Medicine, Mar 12, 2021

Objective To investigate whether varied or repeated b-values provide better diffusion MRI data fo... more Objective To investigate whether varied or repeated b-values provide better diffusion MRI data for discriminating cortical areas with a data-driven approach. Methods Data were acquired from three volunteers at 1.5T with b-values of 800, 1400, 2000 s/mm 2 along 64 diffusionencoding directions. The diffusion signal was sampled from gray matter in seven regions of interest (ROIs). Rotational invariants of the local diffusion profile were extracted as features that characterize local tissue properties. Random forest classification experiments assessed whether classification accuracy improved when data with multiple b-values were used over repeated acquisition of the same (1400 s/mm 2) b-value to compare all possible pairs of the seven ROIs. Three data sets from the Human Connectome Project were subjected to similar processing and analysis pipelines in eight ROIs. Results Three different b-values showed an average improvement in correct classification rates of 5.6% and 4.6%, respectively, in the local and HCP data over repeated measurements of the same b-value. The improvement in correct classification rate reached as high as 16% for individual binary classification experiments between two ROIs. Often using only two of the available three b-values were adequate to make such an improvement in classification rates. Conclusion Acquisitions with varying b-values are more suitable for discriminating cortical areas.

Co-chair We see and hear so freely that to the casual observer it is not obvious that perception ... more Co-chair We see and hear so freely that to the casual observer it is not obvious that perception would be such a difficult problem for modern science to understand. David Marr suggested that an understanding of perception requires analyzing the problems it solves along with the assumptions necessary for a solution. In this thesis I maintain that generative probabilistic models are a powerful tool to implement Marr's approach. In generative models one has to explitly encode the assumptions and goals of perceptual problems, whereas specific knowledge of the world is gleaned from the sensory data by learning within the model. This thesis explores the use of generative models for understanding perception in audiovisual systems as well as in the individual modalities. The cocktail-party problem of single-channel sound separation is addressed using competing sound models, including a novel factorial model that unites pitch tracking and formant-based models. A convolutional hidden Markov model for video tracking performs exact inference in maps of object location, using a novel technique to make this inference tractable for extremely large hypothesis spaces. A model of non-rigid 3D tracking is presented in which some simple assumptions unify template matching and optic flow under the same framework. Finally, an audiovisual model brings together aspects of each of these models to exploit xvi cross-modal information for speech enhancement. Along the way, key benefits of generative modeling, such as the flexibility of inference, the "explaining-away" phenomenon, and the "problem-level" formulation of the models, are introduced and discussed in light of the research presented.

NeuroImage, 2006

Though the function of prefrontal cortex has been extensively investigated, little is known about... more Though the function of prefrontal cortex has been extensively investigated, little is known about the internal organization of individual prefrontal areas. Functional magnetic resonance imaging was used to show that some frontal and prefrontal cortical areas represent visual space in orderly, reproducible, topographic maps. The map-containing areas partly overlap dorsolateral prefrontal areas engaged by working memory tasks. These maps may be useful for attending to task-relevant objects at various spatial locations, an aspect of the executive control of attention.

The Journal of Neuroscience, Sep 15, 1997

Using functional magnetic resonance imaging (fMRI) and cortical unfolding techniques, we analyzed... more Using functional magnetic resonance imaging (fMRI) and cortical unfolding techniques, we analyzed the retinotopy, motion sensitivity, and functional organization of human area V3A. These data were compared with data from additional human cortical visual areas, including V1, V2, V3/VP, V4v, and MT (V5). Human V3A has a retinotopy that is similar to that reported previously in macaque: (1) it has a distinctive, continuous map of the contralateral hemifield immediately anterior to area V3, including a unique retinotopic representation of the upper visual field in superior occipital cortex; (2) in some cases the V3A foveal representation is displaced from and superior to the confluent foveal representations of V1, V2, V3, and VP; and (3) inferred receptive fields are significantly larger in human V3A, compared with those in more posterior areas such as V1. However, in other aspects human V3A appears quite different from its macaque counterpart: human V3A is relatively motionselective, whereas human V3 is less so. In macaque, the situation is qualitatively reversed: V3 is reported to be prominently motion-selective, whereas V3A is less so. As in human and macaque MT, the contrast sensitivity appears quite high in human areas V3 and V3A.

Cogn. Sci. Online, 2005

Despite the paucity of direct evidence about the origin of human language, the great intrinsic in... more Despite the paucity of direct evidence about the origin of human language, the great intrinsic interest in this question has made it difficult for writers to resist speculating about it (Harnad et al., eds., 1976; Merlin, 1991; Deacon, 1997; Jablonski & Aiello, eds., 1998; King, ed., ...