Thursday, August 30, 2007

Journal of Visualized Experiments is a web site which is named YouTube for Science.

Specificity and randomness in the visual cortex

Ohki K, Reid RC
Curr Opin Neurobiol. 2007 Aug 24;

Research on the functional anatomy of visual cortical circuits has recently zoomed in from the macroscopic level to the microscopic. High-resolution functional imaging has revealed that the functional architecture of orientation maps in higher mammals is built with single-cell precision. By contrast, orientation selectivity in rodents is dispersed on visual cortex in a salt-and-pepper fashion, despite highly tuned visual responses. Recent studies of synaptic physiology indicate that there are disjoint subnetworks of interconnected cells in the rodent visual cortex. These intermingled subnetworks, described in vitro, may relate to the intermingled ensembles of cells tuned to different orientations, described in vivo. This hypothesis may soon be tested with new anatomic techniques that promise to reveal the detailed wiring diagram of cortical circuits.

PMID: 17720489 is a centrally curated inventory of digitally reconstructed neurons. NeuroMorpho.Org contains contributions from over two-dozen labs and is continuously updated as new morphological reconstructions are collected, published, and shared, with the goal of densely covering all available data.

Tuesday, August 28, 2007

Iranian Affiliations in SFN

It is quite interesting that there are 12 abstracts for this year's society for neuroscience meeting that have Iranian affiliations.
Just go to SFN website ( and go to the abstracts section) or simply follow this link and search for "Iran".
Following are the titles:

1(24.8/MMM8) Concepts of caloric restriction in the therapy of epilepsy by Avicenna and RhazasM. RAZA1, N. PARINEJAD
2(750.22/HHH2) Does classical music influence depression?M. MOHAMMADIAN1, *P. MOHAMMADIAN, M. AMINI, K. HASHEMIAN
3 (29.7/PPP27-PPP28) Annual workshops: taking the excitement of neuroscience to high school pupils in IranA. LAK1,2, *M. OMRANI3,1,2, B. BABADI1,2, S. R. AFRAZ
4(590.25/U14) Effect of Ethosuximide on parkinsonian tremor: insight to pathophysiology from clinical evidenceM. OMRANI1,2,5, N. ALAVI TABARI2,3, M. A. KHOSHNOODI2,5, M. MOTAMEDI
5(554.7) The effect of stimulus presentation duration on response properties of inferior temporal cortex of macaque monkeys
6(375.7/V9) Behavioral effects of caloric restriction in a model of temporal lobe epilepsy in rats
7(96.11/VV10) Decreased locomotor and ingestive behaviors accompany increased neuroinflammation in aged BALB/cBy mice
8(189.1/TT3) Muscle cocontraction following motor learning
9 (253.4/L10) Network Eigen Kinetic Analysis (NEKA): A novel data-driven approach to modeling the uptake of dopamine in the brain
10(674.15/E6) Purification of neurons from neural stem cells
11(362.12/M5) Type-5 metabotropic glutamate receptor-dependent LTP of excitatory synapses on fast-spiking GABAergic neurons in mouse visual cortex
12 (683.13/H1) Na,K-ATPase alpha2 isoform heterozygous knockout mice show increased susceptibility to cortical spreading depression and altered neuronal excitability

Saturday, August 25, 2007

Enhanced affective brain representations of chocolate in cravers vs. non-cravers

Rolls ET, McCabe C.
Eur J Neurosci. 2007 Aug;26(4):1067-1076

To examine the neural circuitry involved in food craving, in making food particularly appetitive and thus in driving wanting and eating, we used fMRI to measure the response to the flavour of chocolate, the sight of chocolate and their combination in cravers vs. non-cravers. Statistical parametric mapping (SPM) analyses showed that the sight of chocolate produced more activation in chocolate cravers than non-cravers in the medial orbitofrontal cortex and ventral striatum. For cravers vs. non-cravers, a combination of a picture of chocolate with chocolate in the mouth produced a greater effect than the sum of the components (i.e. supralinearity) in the medial orbitofrontal cortex and pregenual cingulate cortex. Furthermore, the pleasantness ratings of the chocolate and chocolate-related stimuli had higher positive correlations with the fMRI blood oxygenation level-dependent signals in the pregenual cingulate cortex and medial orbitofrontal cortex in the cravers than in the non-cravers. To our knowledge, this is the first study to show that there are differences between cravers and non-cravers in their responses to the sensory components of a craved food in the orbitofrontal cortex, ventral striatum and pregenual cingulate cortex, and that in some of these regions the differences are related to the subjective pleasantness of the craved foods. Understanding individual differences in brain responses to very pleasant foods helps in the understanding of the mechanisms that drive the liking for specific foods and thus intake of those foods.

PMID: 17714197

Masking disrupts reentrant processing in human visual cortex

Fahrenfort JJ, Scholte HS, Lamme VA
J Cogn Neurosci. 2007 Sep;19(9):1488-97

In masking, a stimulus is rendered invisible through the presentation of a second stimulus shortly after the first. Over the years, authors have typically explained masking by postulating some early disruption process. In these feedforward-type explanations, the mask somehow "catches up" with the target stimulus, disrupting its processing either through lateral or interchannel inhibition. However, studies from recent years indicate that visual perception-and most notably visual awareness itself-may depend strongly on cortico-cortical feedback connections from higher to lower visual areas. This has led some researchers to propose that masking derives its effectiveness from selectively interrupting these reentrant processes. In this experiment, we used electroencephalogram measurements to determine what happens in the human visual cortex during detection of a texture-defined square under nonmasked (seen) and masked (unseen) conditions. Electro-encephalogram derivatives that are typically associated with reentrant processing turn out to be absent in the masked condition. Moreover, extrastriate visual areas are still activated early on by both seen and unseen stimuli, as shown by scalp surface Laplacian current source-density maps. This conclusively shows that feedforward processing is preserved, even when subject performance is at chance as determined by objective measures. From these results, we conclude that masking derives its effectiveness, at least partly, from disrupting reentrant processing, thereby interfering with the neural mechanisms of figure-ground segmentation and visual awareness itself.

PMID: 17714010

Implicit trustworthiness decisions: automatic coding of face properties in the human amygdala

Engell AD, Haxby JV, Todorov A
J Cogn Neurosci. 2007 Sep;19(9):1508-19

Deciding whether an unfamiliar person is trustworthy is one of the most important decisions in social environments. We used functional magnetic resonance imaging to show that the amygdala is involved in implicit evaluations of trustworthiness of faces, consistent with prior findings. The amygdala response increased as perceived trustworthiness decreased in a task that did not demand person evaluation. More importantly, we tested whether this response is due to an individual's idiosyncratic perception or to face properties that are perceived as untrustworthy across individuals. The amygdala response was better predicted by consensus ratings of trustworthiness than by an individual's own judgments. Individual judgments accounted for little residual variance in the amygdala after controlling for the shared variance with consensus ratings. These findings suggest that the amygdala automatically categorizes faces according to face properties commonly perceived to signal untrustworthiness.

PMID: 17714012

Spatio-temporal prediction and inference by V1 neurons

Guo K, Robertson RG, Pulgarin M, Nevado A, Panzeri S, Thiele A, Young MP
Eur J Neurosci. 2007 Aug;26(4):1045-1054

In normal vision, visual scenes are predictable, as they are both spatially and temporally redundant. Evidence suggests that the visual system may use the spatio-temporal regularities of the external world, available in the retinal signal, to extract information from the visual environment and better reconstruct current and future stimuli. We studied this by recording neuronal responses of primary visual cortex (area V1) in anaesthetized and paralysed macaques during the presentation of dynamic sequences of bars, in which spatio-temporal regularities and local information were independently manipulated. Most V1 neurons were significantly modulated by events prior to and distant from stimulation of their classical receptive fields (CRFs); many were more strongly tuned to prior and distant events than they were to CRFs bars; and several showed tuning to prior information without any CRF stimulation. Hence, V1 neurons do not simply analyse local contours, but impute local features to the visual world, on the basis of prior knowledge of a visual world in which useful information can be distributed widely in space and time.

PMID: 17714195

Friday, August 24, 2007

Experience-dependent coding of facial expression in superior temporal sulcus

Nicholas Furl, Nicola J. van Rijsbergen, Alessandro Treves, Karl J. Friston, Raymond J. Dolan
PNAS | August 14, 2007 | vol. 104 | no. 33 | 13485-13489
Sensory information from the external world is inherently ambiguous, necessitating prior experience as a constraint on perception. Prolonged experience (adaptation) induces perception of ambiguous morph faces as a category different from the adapted category, suggesting sensitivity in underlying neural codes to differences between input and recent experience. Using magnetoencephalography, we investigated the neural dynamics of such experience-dependent visual coding by focusing on the timing of responses to morphs after facial expression adaptation. We show that evoked fields arising from the superior temporal sulcus (STS) reflect the degree to which a morph and adapted expression deviate. Furthermore, adaptation effects within STS predict the magnitude of behavioral aftereffects. These findings show that the STS codes expressions relative to recent experience rather than absolutely and may bias perception of expressions. One potential neural mechanism for the late timing of both effects appeals to hierarchical models that ascribe a central role to backward connections in mediating predictive codes.

Tuesday, August 14, 2007

Human cortical representation of oral temperature

Guest S, Grabenhorst F, Essick G, Chen Y, Young M, McGlone F, de Araujo I, Rolls ET.
Physiol Behav. 2007 Jul 13;

The temperature of foods and fluids is a major factor that determines their pleasantness and acceptability. Studies of nonhuman primates have shown that many neurons in cortical taste areas receive and process not only chemosensory inputs, but oral thermosensory (temperature) inputs as well. We investigated whether changes in oral temperature activate these areas in humans, or middle or posterior insular cortex, the areas most frequently identified for the encoding of temperature information from the human hand. In the fMRI study we identified areas of activation in response to innocuous, temperature-controlled (cooled and warmed, 5, 20 and 50 degrees C) liquid introduced into the mouth. The oral temperature stimuli activated the insular taste cortex (identified by glucose taste stimuli), a part of the somatosensory cortex, the orbitofrontal cortex, the anterior cingulate cortex, and the ventral striatum. Brain regions where activations correlated with the pleasantness ratings of the oral temperature stimuli included the orbitofrontal cortex and pregenual cingulate cortex. We conclude that a network of taste- and reward-responsive regions of the human brain is also activated by intra-oral thermal stimulation, and that the pleasant subjective states elicited by oral thermal stimuli are correlated with the activations in the orbitofrontal cortex and pregenual cingulate cortex. Thus the pleasantness of oral temperature is represented in brain regions shown in previous studies to represent the pleasantness of the taste and flavour of food. Bringing together these different oral representations in the same brain regions may enable particular combinations to influence the pleasantness of foods.

PMID: 17689575
Free Fulltext: Science-Direct

Monday, August 13, 2007

MRIcro free viewing software
This software could be used for localizing and comparing lesions across patients and in a patient across the course of disease or treatment. It supports MRI along with other imaging modalities (?).

Action-Related Properties Shape Object Representations in the Ventral Stream

Bradford Z. Mahon, Shawn C. Milleville, Gioia A.L. Negri, Raffaella I. Rumiati, Alfonso Caramazza, Alex Martin
Neuron, Vol 55, 507-520, 02 August 2007

The principles driving the organization of the ventral object-processing stream remain unknown. Here, we show that stimulus-specific repetition suppression (RS) in one region of the ventral stream is biased according to motor-relevant properties of objects. Quantitative analysis confirmed that this result was not confounded with similarity in visual shape. A similar pattern of biases in RS according to motor-relevant properties of objects was observed in dorsal stream regions in the left hemisphere. These findings suggest that neural specificity for “tools” in the ventral stream is driven by similarity metrics computed over motor-relevant information represented in dorsal structures. Support for this view is provided by converging results from functional connectivity analyses of the fMRI data and a separate neuropsychological study. More generally, these data suggest that a basic organizing principle giving rise to “category specificity” in the ventral stream may involve similarity metrics computed over information represented elsewhere in the brain.


Vision and the Brain: Unseen Complexities – Part 2

Why do we need vision? As it turns out, there are two answers to this question. On the one hand, we need vision to give us detailed knowledge of the world beyond ourselves, knowledge that allows us to recognize things from minute to minute and day to day. On the other hand, we also need vision to guide our actions in that world at the very moment they occur. These are two quite different job descriptions, and nature seems to have given us two different visual systems to carry them out. Dr. Goodale discusses how separate but interacting visual systems have evolved for the perception of objects on the one hand and the control of actions directed at those objects on the other, examining how both systems process information but each using the information in different ways.
By: Melvyn Goodale, Ph.D., C.Psych., F.R.S.C., research professor in visual neuroscience, University of Western Ontario

Sunday, August 12, 2007

Context familiarity enhances target processing by inferior temporal cortex neurons.

Mruczek RE, Sheinberg DL
J Neurosci. 2007 Aug 8;27(32):8533-45

Experience-dependent changes in the response properties of ventral visual stream neurons are thought to underlie our ability to rapidly and efficiently recognize visual objects. How these neural changes are related to efficient visual processing during natural vision remains unclear. Here, we demonstrate a neurophysiological correlate of efficient visual search through highly familiar object arrays. Humans and monkeys are faster at locating the same target when it is surrounded by familiar compared with unfamiliar distractors. We show that this behavioral enhancement is driven by an increased sensitivity of target-selective neurons in inferior temporal cortex. This results from an increased "signal" for target representations and decreased "noise" from neighboring familiar distractors. These data highlight the dynamic properties of the inferior temporal cortex neurons and add to a growing body of evidence demonstrating how experience shapes neural processing in the ventral visual stream.

PMID: 17687031


Wednesday, August 8, 2007

The unsolved mystery of vision

Richard H. Masland, Paul R. Martin
Current Biology Vol 17 No 15

Vision looms large in neuroscience — it is the subject of a gigantic literature and four Nobel prizes — but there is a growing realization that there are problems with the textbook explanation of how mammalian vision works. Here we will summarize the evidence behind this disquiet. In effect, we shall present a portrait of a field that is ‘stuck’. Our initial focus, because it is our area of expertise, is on evidence that the early steps of mammalian vision are more diverse and more interesting than is usually imagined, so that our understanding of the later stages is in trouble right from the start. But we will also summarize problems, raised by others, with the later stages themselves.

Tuesday, August 7, 2007

Hardware/Software Hacking: Joining the Real and the Virtual

For the experimental neuroscientists who need to connect their computers to the external world!

Monday, August 6, 2007

Research Channel For Scientific lecture fans! Who download the entire Internet! ;-)
Specifically see Science section, with some lectures on Neurosciences.

Sunday, August 5, 2007

Is That My Brother? Perceptual and Neurobiological Factors in Face Blindness

Face blindness (technically known as prosopagnosia) is a condition in which people with otherwise normal vision cannot discriminate one ... all » face from another. They may not be able to pick out their own husband or children in a crowded room or even themselves in a mirror. One woman reported she once had to crinkle her face in a crowded rest room to discriminate herself from others in the mirror. This problem can occur through injury to particular areas within the brain (either through head trauma, stoke or surgery), but it can also occur developmentally. In the latter case, the brain appears completely normal, yet developmental prosopagnosics (DP) have never learned to accurately discriminate faces.

There is a large scientific body of work on face perception published in the psychological, social and neurobiological literature, and I will highlight some of the more important findings. I will then discuss work from my own laboratory on perceptual processing of faces; emphasizing training methods we have developed to help individuals with DP identify faces, sometimes for the first time in their lives. This discussion will be complemented by inclusion of documented neurobiological and cognitive changes that accompany the emergence of face recognition abilities.

Technology Insight: future neuroprosthetic therapies for disorders of the nervous system

Richard A Normann
Nature Clinical Practice Neurology (2007) 3, 444-452 doi:10.1038/ncpneuro0556

Most disorders of the nervous system result from localized sensory or motor pathologies attributable to disease or trauma. The emerging field of neuroprosthetics is focused on the development of therapeutic interventions that will be able to restore some of this lost neural function by selective electrical stimulation of sensory or motor pathways, or by harnessing activity recorded from remnant neural pathways. A key element in this restoration of function has been the development of a new generation of penetrating microelectrode arrays that provide unprecedented selective access to the neurons of the CNS and PNS. The active tips of these microelectrode arrays penetrate the nervous tissues and abut against small populations of neurons or nerve fibers, thereby providing selective access to these cells. These electrode arrays are not only beginning to provide researchers with the ability to better study the spatiotemporal information processing performed by the nervous system, they can also form the basis for new therapies for disorders of the nervous system. In this Review, three examples of this new generation of microelectrode arrays are described, as are potential therapeutic applications in blindness and spinal cord injury, and for the control of prosthetic limbs.

Free full text:

Saturday, August 4, 2007

Behavioural improvements with thalamic stimulation

N. D. Schiff, J. T. Giacino, K. Kalmar, J. D. Victor, K. Baker, M. Gerber, B. Fritz, B. Eisenberg, J. O’Connor, E. J. Kobylarz, S. Farris, A. Machado, C. McCagg, F. Plum, J. J. Fins, A. R. Rezai
Nature 448, 600-603(2 August 2007) doi:10.1038/nature06041

Widespread loss of cerebral connectivity is assumed to underlie
the failure of brain mechanisms that support communication and
goal-directed behaviour following severe traumatic brain injury.
Disorders of consciousness that persist for longer than 12 months
after severe traumatic brain injury are generally considered to be
immutable; no treatment has been shown to accelerate recovery or
improve functional outcome in such cases1,2. Recent studies have
shown unexpected preservation of large-scale cerebral networks in
patients in the minimally conscious state (MCS)3,4, a condition
that is characterized by intermittent evidence of awareness of self
or the environment5. These findings indicate that there might be
residual functional capacity in some patients that could be supported
by therapeutic interventions. We hypothesize that further
recovery in some patients in the MCS is limited by chronic underactivation
of potentially recruitable large-scale networks. Here, in
a 6-month double-blind alternating crossover study, we show that
bilateral deep brain electrical stimulation (DBS) of the central
thalamus modulates behavioural responsiveness in a patient
who remained in MCS for 6 yr following traumatic brain injury
before the intervention. The frequency of specific cognitively
mediated behaviours (primary outcome measures) and functional
limb control and oral feeding (secondary outcome measures)
increased during periods in which DBS was on as compared with
periods in which it was off. Logistic regression modelling shows a
statistical linkage between the observed functional improvements
and recent stimulation history. We interpret the DBS effects as
compensating for a loss of arousal regulation that is normally
controlled by the frontal lobe in the intact brain. These findings
provide evidence that DBS can promote significant late functional
recovery from severe traumatic brain injury. Our observations,
years after the injury occurred, challenge the existing practice of
early treatment discontinuation for patients with only inconsistent
interactive behaviours and motivate further research to
develop therapeutic interventions.

PMID: 17671503