Vision Lunch 2010

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[edit] 2010 Schedule

[edit] Jan

6 Catie Chang, Stanford Radiology: Time-frequency dynamics of resting-state brain connectivity measured with fMRI

Abstract: Studies of resting-state functional connectivity typically apply a single ICA or correlation analysis across all time frames in the scan. However, evidence from both task-based fMRI studies and animal electrophysiology suggests that functional connectivity may exhibit dynamic changes within time scales of seconds to minutes. In this talk, we will discuss an exploration of the dynamic behavior of resting-state connectivity using time-frequency analysis and sliding-window correlations.


13 Jia Liu: Heritability of the specific cognitive ability of face perception
Abstract: What makes one person socially insightful but mathematically challenged, and another musically gifted yet devoid of a sense of direction? Individual differences in general cognitive ability are thought to be mediated by “generalist genes” that affect many cognitive abilities similarly without specific genetic influences on particular cognitive abilities. In contrast, we present here evidence for cognitive “specialist genes”: monozygotic twins are more similar than dizygotic twins in the specific cognitive ability of face perception. Each of three measures of face-specific processing was heritable, i.e., more correlated in monozygotic than dizygotic twins: face-specific recognition ability, the face inversion effect, and the composite face effect. Crucially, this effect is due to the heritability of face processing in particular, not a more general aspect of cognition such as IQ or global attention. Thus, individual differences in at least one specific mental talent are independently heritable. This finding raises the question of what other specific cognitive abilities are independently heritable, and may elucidate the mechanisms by which heritable disorders like dyslexia and autism can have highly uneven cognitive profiles, in which some mental processes can be selectively impaired while others remain unaffected or even selectively enhanced.

20 Journal article: Davie and Bob
Cortical Connections to Area TE in Monkey: Hybrid Modular and Distributed Organization

Borra E, Ichinohe N, Sato T, Tanifuji M, Rockland KS.

To investigate the fine anatomical organization of cortical inputs to visual association area TE, 2-3 small injections of retrograde tracers were made in macaque monkeys. Injections were made as a terminal procedure, after optical imaging and electrophysiological recording, and targeted to patches physiologically identified as object-selective. Retrogradely labeled neurons occurred in several unimodal visual areas, the superior temporal sulcus, intraparietal sulcus (IPS), and prefrontal cortex (PFC), consistent with previous studies. Despite the small injection size (<0.5 mm wide), the projection foci in visual areas, but not in IPS or PFC, were spatially widespread (4-6 mm in extent), and predominantly consisted of neurons labeled by only one of the injections. This can be seen as a quasi-modular organization. In addition, within each projection focus, there were scattered neurons projecting to one of the other injections, together with some double-labeled (DL) neurons, in a more distributed pattern. Finally, projection foci included smaller "hotspots," consisting of intermixed neurons, single-labeled by the different injections, and DL neurons. DL neurons are likely the result of axons having extended, spatially separated terminal arbors, as demonstrated by anterograde experiments. These results suggest a complex, hybrid connectivity architecture, with both modular and distributed components.

conflict: Jan 27, 12-1, Student Lunch with Cog-Neuro candidate Marina Bedny. This may be a conflict for cog/neuro graduate students.
27 Open


[edit] Feb

3 Journal article: Aviv and Andreas
Spatial attention does not strongly modulate neuronal responses in early human visual cortex.

Daniel Yoshor, Geoffrey M. Ghose, William H. Bosking, Ping Sun, and John H. R. Maunsell

Attention can dramatically enhance behavioral performance based on a visual stimulus, but the degree to which attention modulates activity in early visual cortex is unclear. Whereas single-unit studies of spatial attention in monkeys have repeatedly revealed relatively modest attentional modulations in V1, human functional magnetic resonance imaging studies demonstrate a large attentional enhance- ment of the blood oxygen level-dependent (BOLD) signal in V1. To explore this discrepancy, we used intracranial electrodes to directly measure the effect of spatial attention on the responses of neurons near the human occipital pole. We found that spatial attention does not robustly modulate stimulus-driven local field potentials in early human visual cortex, but instead produces modest modulations that are consistent with those seen in monkey neurophysiology experiments. This finding suggests that the neuronal activity that underlies visual attention in humans is similar to that found in other primates and that behavioral state may alter the linear relationship between neuronal activity and BOLD.


conflict: Feb 10, 12-1, Student Lunch with Cog-Neuro candidate John Serences. This may be a conflict for cog/neuro graduate students.

10 Journal article: reading fMRI group (Alison, Reno, Andreas, Michael, Jason?)
Why do children make mirror errors in reading? Neural correlates of mirror invariance in the visual word form area.

Dehaene S, Nakamura K, Jobert A, Kuroki C, Ogawa S, Cohen L.

Young children often make mirror errors when learning to read and write, for instance writing their first name from right to left in English. This competence vanishes in most adult readers, who typically cannot read mirror words but retain a strong competence for mirror recognition of images. We used fast behavioral and fMRI repetition priming to probe the brain mechanisms underlying mirror generalization and its absence for words in adult readers. In two groups of French and Japanese readers, we show that the left fusiform visual word form area, a major site of learning during reading acquisition, simultaneously shows a maximal effect of mirror priming for pictures and an absence of mirror priming for words. Thus, learning to read recruits an area which possesses a property of mirror invariance, seemingly present in all primates, which is deleterious for letter recognition and may explain children's transient mirror errors.

24 DiCarlo JJ, Cox DD (2007) Untangling invariant object recognition. Trends Cogn Sci 11:333-341


[edit] March

3 Discussion: Anticipatory BOLD signals, or misinterpretation?

Anticipatory haemodynamic signals in sensory cortex not predicted by local neuronal activity.
Yevgeniy B. Sirotin & Aniruddha Das
Nature. 2009 Jan 22;457(7228):475-9
http://www.nature.com/nature/journal/v457/n7228/abs/nature07664.html

The blind, the lame, and the poor signals of brain function—A Comment on Sirotin and Das (2009)
Kleinschmidt A, Müller NG.
Neuroimage. 2010 Apr 1;50(2):622-625
http://dx.doi.org/10.1016/j.neuroimage.2009.12.075

News and Views, Neuroscience: Pre-emptive blood flow
David A. Leopold
Nature 457, 387-388 (22 January 2009)
http://www.nature.com/nature/journal/v457/n7228/full/457387a.html


17 Susana Chung, Berkeley, Reading Crowding in patients with central vision loss

24 Felix Biessmann [felix.biessmann@gmail.com] Felix Biessmann will be visiting from Nikos Logothetis' lab. He will tell us what they have been up to: "In short, we developed some algorithm for analysing simultaneous BOLD- Neurophysiology recordings and applied that to data acquired in monkey V1 during visual stimulation http://www.springerlink.com/content/e1425487365v2227 and during spontaneous activity (http://dx.doi.org/10.1016/j.mri.2009.12.016 ). The algorithm finds a multivariate HRF from neurophysiological data to BOLD activation patterns that maximises the cross-correlation between the two modalities."


[edit] April

7 Sahar will present tools for projecting visual field maps into white matter with diffusion tractography

14 Discussion Visual eCOG from Yoshor/Maunsell and crowd

Proc Natl Acad Sci U S A. 2009 Mar 31;106(13):5389-93. Epub 2009 Mar 10. Perceiving electrical stimulation of identified human visual areas. Murphey DK, Maunsell JH, Beauchamp MS, Yoshor D.

Department of Neuroscience, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA. dmkim@post.harvard.edu We studied whether detectable percepts could be produced by electrical stimulation of intracranial electrodes placed over human visual areas identified with fMRI. Identification of areas was confirmed by recording local-field potentials from the electrode, such as face-selective electrical responses from electrodes over the fusiform face area (FFA). The probability of detecting electrical stimulation of a visual area varied with the position of the area in the visual cortical hierarchy. Stimulation of early visual areas including V1, V2, and V3 was almost always detected, whereas stimulation of late visual areas such as FFA was rarely detected. When percepts were elicited from late areas, subjects reported that they were simple shapes and colors, similar to the descriptions of percepts from early areas. There were no reports of elaborate percepts, such as faces, even in areas like FFA, where neurons have complex response properties. For sites eliciting percepts, the detection threshold was determined by varying the stimulation current as subjects performed a forced-choice detection task. Current thresholds were similar for late and early areas. The similarity between both percept quality and threshold across early and late areas suggests the presence of functional microcircuits that link electrical stimulation with perception.


21 Cynthia Henderson

28 Kendrick will discuss FFA paper from Tootell

Cereb Cortex. 2010 Apr 7. [Epub ahead of print] Lower-Level Stimulus Features Strongly Influence Responses in the Fusiform Face Area.

Yue X, Cassidy BS, Devaney KJ, Holt DJ, Tootell RB.

Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA. Abstract

An intriguing region of human visual cortex (the fusiform face area; FFA) responds selectively to faces as a general higher-order stimulus category. However, the potential role of lower-order stimulus properties in FFA remains incompletely understood. To clarify those lower-level influences, we measured FFA responses to independent variation in 4 lower-level stimulus dimensions using standardized face stimuli and functional Magnetic Resonance Imaging (fMRI). These dimensions were size, position, contrast, and rotation in depth (viewpoint). We found that FFA responses were strongly influenced by variations in each of these image dimensions; that is, FFA responses were not "invariant" to any of them. Moreover, all FFA response functions were highly correlated with V1 responses (r = 0.95-0.99). As in V1, FFA responses could be accurately modeled as a combination of responses to 1) local contrast plus 2) the cortical magnification factor. In some measurements (e.g., face size or a combinations of multiple cues), the lower-level variations dominated the range of FFA responses. Manipulation of lower-level stimulus parameters could even change the category preference of FFA from "face selective" to "object selective." Altogether, these results emphasize that a significant portion of the FFA response reflects lower-level visual responses.


[edit] May

5 Dani Bassett from UCSB

(Wandell visitor)

Dani will speak about her analyses of different types of diffusion imaging, including the numerical stability of DTI, HARDI and DSI data. She joins us from the Kavli Institute at UCSB, where she is an advanced graduate student.

12 VSS - Jason to practice HBM presentation

19 VSS Rehash
20 (Note: Thursday) Bosco Tjan: Neural mechanism of crowding

26 In which Jason and Brian present Catani and ffytche on The rises and falls of disconnection syndromes Brain, 2005 Catani and ffytche

[edit] June

9 Double-header:

(1) DISCUSSION: The Functional Anatomy of a Perceptual Decision in the Human Brain
Andrew S. Kayser * , Bradley R. Buchsbaum * , Drew T. Erickson and Mark D'Esposito

ABSTRACT
Our ability to make rapid decisions based on sensory information belies the complexity of the underlying computations. Recently, "accumulator" models of decision making have been shown to explain the activity of parietal neurons as macaques make judgments concerning visual motion. Unraveling the operation of a decision-making circuit, however, involves understanding both the responses of individual components in the neural circuitry and the relationships between them.

In this functional magnetic resonance imaging study of the decision process in humans, we demonstrate that an accumulator model predicts responses to visual motion in the intraparietal sulcus (IPS). Significantly, the metrics used to define responses within the IPS also reveal distinct but interacting nodes in a circuit, including early sensory detectors in visual cortex, the visuomotor integration system of the IPS, and centers of cognitive control in the prefrontal cortex, all of which collectively define a perceptual decision-making network.

(2) KNK: Spiral imaging and multi-frequency reconstructions

I'll talk about some code that I have written that substantially improves the spatial quality and contrast-to-noise ratio of functional images acquired using spiral pulse sequences. The code is a wrapper around Gary Glover's reconstruction code and could probably be successfully applied to any functional dataset.

16 Multi-frequency reconstruction tutorial This will focus on how to use the code and how to inspect/interpret the results. Only for those interested in actually using the code. If necessary, a follow-up meeting will also be held at 7pm.


[edit] July

14 Markus Lappe, Westfalien Wilhelms University Munster

Oculomotor shaping of visual space

Vision informs us about the location of objects around us. Neurons in many brain areas have spatially selective receptive fields, which can in principle convey information about the location of visual stimuli. How does the brain deduce from these many possibilities where objects are located? From an ecological perspective, localization is plainly needed for behavior control. Eye movements are the most ubiquitous behavior, and if we want to know anything about an object somewhere in the scene we usually first look at it. Thus, the most pressing need of visual localization of any object is to guide eye movements to that object. It has been proposed that our perceptual experience of the world is really composed of the sensorimotor transformation laws that govern how we interact with the world. This proposal predicts that our perception of the location of an object draws on the knowledge of the motor system about how to target this object with an eye movement. We have used saccadic adaptation to modify the motor response to a target object. A post-saccadic visual error was introduced artificially by stepping the target while the saccade is in flight. Over the course of several such trials, the amplitude of the saccade to the target eventually matches the stepped location of the target, rather than the initial location. The saccadic adaptation procedure, therefore, introduces a dissociation between the physical location of the target as registered by the retina and the motor program that is executed to move gaze onto that target. This dissociation allows us to investigate whether the perceptual localization of a stimulus at the target location follows the physical location of the stimulus or the motor program set-up by the saccadic system. To decide this question we combined a series of adaptation trials with an interspersed localization task. A small localization probe was briefly presented before and after adaptation. The subject indicated the apparent location of the probe with the mouse pointer. I will report results from several experiments that show that modifications of saccadic amplitude by saccadic adaptation can induce associated changes in visual localization, consistent with the view that oculomotor knowledge is used in the perceptual representation of space.


21 Christine Nordahl, MIND Institute, UC Davis (Wandell invitation)

Christine will be joined by Mark Shen. They will talk with us about their measurements of autistic brains using diffusion imaging. This will be both a presentation (update) of their results, as well as a discussion.

Mark has been using TBSS. So perhaps we could use this event as a marker to move our own thinking about TBSS along.

28 Discussion: The Retinotopic Organization of the Human Middle Temporal Area MT/V5 and Its Cortical Neighbors
The Journal of Neuroscience, July 21, 2010, 30(29):9801-9820; doi:10.1523/JNEUROSCI.2069-10.2010
Hauke Kolster, Ronald Peeters, and Guy A. Orban

Although there is general agreement that the human middle temporal (MT)/V5+ complex corresponds to monkey area MT/V5 proper plus a number of neighboring motion-sensitive areas, the identification of human MT/V5 within the complex has proven difficult. Here, we have used functional magnetic resonance imaging and the retinotopic mapping technique, which has very recently disclosed the organization of the visual field maps within the monkey MT/V5 cluster. We observed a retinotopic organization in humans very similar to that documented in monkeys: an MT/V5 cluster that includes areas MT/V5, pMSTv (putative ventral part of the medial superior temporal area), pFST (putative fundus of the superior temporal area), and pV4t (putative V4 transitional zone), and neighbors a more ventral putative human posterior inferior temporal area (phPIT) cluster. The four areas in the MT/V5 cluster and the two areas in the phPIT cluster each represent the complete contralateral hemifield. The complete MT/V5 cluster comprises 70% of the motion localizer activation. Human MT/V5 is located in the region bound by lateral, anterior, and inferior occipital sulci and occupies only one-fifth of the motion complex. It shares the basic functional properties of its monkey homolog: receptive field size relative to other areas, response to moving and static stimuli, as well as sensitivity to three-dimensional structure from motion. Functional properties sharply distinguish the MT/V5 cluster from its immediate neighbors in the phPIT cluster and the LO (lateral occipital) regions. Together with similarities in retinotopic organization and topological neighborhood, the functional properties suggest that MT/V5 in human and macaque cortex are homologous.


[edit] August

4 Discussion Proc Natl Acad Sci U S A. 2010 Jul 13;107(28):12687-91. Epub 2010 Jun 28. Ultrahigh-resolution microstructural diffusion tensor imaging reveals perforant path degradation in aged humans in vivo.

Yassa MA, Muftuler LT, Stark CE.

Center for Neurobiology of Learning and Memory, Department of Neurobiology and Behavior, University of California, Irvine, CA 92697, USA. Abstract

The perforant path (PP) undergoes synaptic changes in the course of aging and dementia. Previous studies attempting to assess the integrity of the PP in humans using diffusion tensor imaging (DTI) were limited by low resolution and the inability to identify PP fibers specifically. Here we present an application of DTI at ultrahigh submillimeter resolution that has allowed us to successfully identify diffusion signals unique to the PP and compare the intensity of these signals in a sample of young adults and older adults. We report direct evidence of age-related PP degradation in humans in vivo. We find no evidence of such loss in a control pathway, the alveus, suggesting that these findings are not evidence for a global decline. We also find no evidence for specific entorhinal gray matter atrophy. The extent of PP degradation correlated with performance on a word-list learning task sensitive to hippocampal deficits. We also show evidence for gray matter diffusion signals consistent with pyramidal dendrite orientation in the hippocampus and cerebral cortex. Ultrahigh-resolution microstructural DTI is a unique biomarker that can be used in combination with traditional structural and functional neuroimaging methods to enhance detection of Alzheimer disease in its earliest stages, test the effectiveness of new therapies, and monitor disease progression.


11 Franco Pestilli Attentional enhancement via selection and pooling of early sensory responses in human visual cortex
Franco Pestilli Department of Neuroscience, Columbia University

To characterize the cortical processes by which attention improves behavioral performance we measured activity in visual cortex with fMRI as humans performed contrast discrimination with focal and distributed attention. When observers performed the task with focal attention they achieved robust improvements in behavioral performance that were accompanied by increases in cortical response. Were performance limited only by the sensitivity of the measured sensory signals this improvement in behavioral performance could only be achieved by assuming an unrealistically high (4-5 fold) reduction in response variability. Instead, behavioral performance was well characterized by applying a max-pooling rule to the measured sensory signals, suggesting that the selection and pooling of sensory signals to reach the decision played the dominant role in enhancing behavioral sensitivity.


25 Aviv Mezer: A new quantitative MRI contrast for measuring white matter myelin
Several MRI techniques have been proposed for quantifying myelin in white matter (WM). Limitations of current methods include either long scan times or complex searches in parameter space. We propose a new approach for measuring WM myelin by quantifying the hydration layer fraction (HLF).

HLF is calculated using a simple formula to combine noise-corrected T1 and PD Maps. The calculation does not require complex parameter estimation, making it less susceptible to model-fitting problems. A further advantage of the HLF method is that it can be measured at high resolution using a simple stock sequences. This makes it a good candidate for clinical assessment of WM impairments; for brain structural research and correlations with behaviors; as well as for brain tissues segmentation.


[edit] September

Sept. 8th: Held for special infrastructure meeting on wiki pages and computer gear

Sept. 10th (FRIDAY!) Andrew Parker (Oxford) - hosted by Bill Newsome
The talk will be at the usual time / place (Jordan Hall 419, 11:30), but it will be on Friday, not Wednesday.


[edit] October

Oct. 13th: Mehdi Senoussi, a visiting student from Ecole Normale Supérieure (Paris), will discuss:

Decoding and reconstructing color from responses in human visual cortex.

in J Neurosci. 2009 Nov 4;29(44):13992-4003. http://www.ncbi.nlm.nih.gov/pubmed/19890009

Brouwer GJ, Heeger DJ.

Department of Psychology and Center for Neural Science, New York University, New York, NY 10003, USA. gbrouwer@cns.nyu.edu

Abstract

How is color represented by spatially distributed patterns of activity in visual cortex? Functional magnetic resonance imaging responses to several stimulus colors were analyzed with multivariate techniques: conventional pattern classification, a forward model of idealized color tuning, and principal component analysis (PCA). Stimulus color was accurately decoded from activity in V1, V2, V3, V4, and VO1 but not LO1, LO2, V3A/B, or MT+. The conventional classifier and forward model yielded similar accuracies, but the forward model (unlike the classifier) also reliably reconstructed novel stimulus colors not used to train (specify parameters of) the model. The mean responses, averaged across voxels in each visual area, were not reliably distinguishable for the different stimulus colors. Hence, each stimulus color was associated with a unique spatially distributed pattern of activity, presumably reflecting the color selectivity of cortical neurons. Using PCA, a color space was derived from the covariation, across voxels, in the responses to different colors. In V4 and VO1, the first two principal component scores (main source of variation) of the responses revealed a progression through perceptual color space, with perceptually similar colors evoking the most similar responses. This was not the case for any of the other visual cortical areas, including V1, although decoding was most accurate in V1. This dissociation implies a transformation from the color representation in V1 to reflect perceptual color space in V4 and VO1.

Oct. 20th: Jack van Horn, UCLA

Beyond the single MRI study: Databases, Meta-analysis, and Exploratory Data mining in Neuroimaging

As neuroscientists, we have all become expert at conducting highly specific studies of the living brain using modern neuroimaging methods. This has given rise to new concepts of cognition, paradigms for probing the function of the living brain, and the diagnostic implications of alterations in brain structure in disease. Yet individual instances of research studies of brain form and function may only provide a blinkered view of the variability that exists between subjects that may provide deeper insights. Databases have arisen seeking to record both the raw datasets and their results in order for workers to explore, combine datatypes, examine commonalities, and/or test novel computational approaches. Moreover, while researchers take great pains to ensure that study factors are well controlled, variations in methods from across studies may influence the size of reported effects. These, too, can be systematically quantified - sometimes with surprising results. In this presentation I will discuss the role of neuroimaging data archives, their hallmarks for success, and their use in explorative data analysis as well as what might be observed from the neuroimaging literature itself. Finally, I will present the use of interactive data exploration tools that can facilitate inspection of large quantities of neuroimaging datasets simultaneously. From this discussion, the audience will appreciate that there is much to be learned from retrospective examination of data contained in large-scale archives of shared neuroimaging data; that meta-analysis of neuroimaging literature often reveals unexpected effects that provide insights into "how" studies are done; and that our shared data has greater collective value than many of the individual studies we often perform.

Oct. 27th: Peter Basser, hosted by CBIS

[edit] November

3 VERIDICAL REPRESENTATION OF FACE VIEWS BY INFEROTEMPORAL NEURONS
Behrad Noudoost M.D., Ph.D., Postdoctoral fellow, Neurobiology Department, Stanford, Howard Hughes Medical Foundation
This work has been done in Iran under support of: School of Cognitive Sciences, Institute for Research in Fundamental Sciences, Niavaran; and Research Center for Brain and Cognitive Sciences, School of Medicine, Shaheed Beheshti University, Tehran, Iran


Abstract
Models of object recognition traditionally fall into two classes based on whether they use a viewer-centered or an object-centered representation. Whereas existence of view-selective neurons in visual cortical areas has been argued as an indication for viewer-centered representation, object-centered representation is also supported by the existence of view-invariant neurons. The question to be answered is that which of these two types of neurons could be a neural correlate of our perception. To answer this question, first we showed that we could alter the perception of face objects in monkeys and humans by face-view adaptation. Then, we studied responses of face-neurons in inferotemporal cortex of monkeys before and after adaptation and found that these neurons change their response consistent with the observed changes in perception. In addition, we found that whereas both view-selective and view-invariant face-neurons exhibit these changes, the latter neurons change their response earlier than view-selective neurons. The findings constraint models of object recognition by showing that viewpoint dependency in object recognition doesn’t necessarily imply viewer-centered representation of objects.


10 SFN prep
Kevin: High-resolution fMRI reveals separate limb-selective activations surrounding hMT+
Alina: Face-selective activation in the posterior superior temporal sulcus is similar across children, adolescents, and adults
Jason: Developmental trajectories of white matter fascicles are associated with children’s reading skills

17 No Vision lunch: SFN

24 No Vision lunch: Thanksgiving

[edit] December

1 Neuroimaging studies of acquired prosopagnosia: towards a non-hierarchical view of face perception in the human brain

Dr. Bruno Rossion
University of Louvain, Belgium

Understanding the functional neuro-anatomy of face recognition in the human brain is a long-standing goal of Cognitive Neuroscience. Up to the early 90’s, lesion studies provided the most important source of knowledge, i.e. allowing to make correlations between the localization of lesions in groups of brain-damaged patients and their face recognition impairments (prosopagnosia). The influence of the cognitive approach in Neuropsychology, with an emphasis on single-case functional investigations, as well as the advent of neuroimaging studies in the healthy brain, have considerably reduced the importance of lesion studies in clarifying the neuro-anatomical aspects of face recognition. In this talk, I will illustrate how neuroimaging investigations of single-cases of acquired prosopagnosic patients can still greatly increase our knowledge in this field, in particular supporting a non-hierarchical view of face perception in the human brain.

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