Journal of Visualized Experiments

http://www.myjove.com/ 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

NeuroMorpho.org

NeuroMorpho.org 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.

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 ( http://www.sfn.org 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 Rhazas	M. 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 Iran	A. 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 evidence	M. 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	K. MIRPOUR1, *H. ESTEKY
6	(375.7/V9) Behavioral effects of caloric restriction in a model of temporal lobe epilepsy in rats	N. PARINEJAD1, S. KESHAVARZI2, *M. RAZA
7	(96.11/VV10) Decreased locomotor and ingestive behaviors accompany increased neuroinflammation in aged BALB/cBy mice	S. J. BONASERA1, V. MOJTAHEDZADEH5, E. H. GOULDING2, K. A. SCHENK3, W. XU4, R. BARBEAU4, L. H. TECOTT
8	(189.1/TT3) Muscle cocontraction following motor learning	M. DARAINY1,2, D. OSTRY
9	(253.4/L10) Network Eigen Kinetic Analysis (NEKA): A novel data-driven approach to modeling the uptake of dopamine in the brain	A. H. ASSADI1, M. E. KLOC2, H. TORABI-DASHTI3, Q. LIU4, C. DAVIDSON4, T. H. LEE
10	(674.15/E6) Purification of neurons from neural stem cells	H. AZARI1, G. OSBORNE2, B. SCHEFFLER3, D. STEINDLER3, *B. A. REYNOLDS
11	(362.12/M5) Type-5 metabotropic glutamate receptor-dependent LTP of excitatory synapses on fast-spiking GABAergic neurons in mouse visual cortex	A. SARIHI1, B. JIANG1,3, A.-R. KOMAKI4, K. SOHYA1, K. OBATA1, Y. YANAGAWA5, *T. TSUMOTO2
12	(683.13/H1) Na,K-ATPase alpha2 isoform heterozygous knockout mice show increased susceptibility to cortical spreading depression and altered neuronal excitability	C. REIFFURTH1, M. ZAHEDI KHORASANI2, M. ALAM1, A. E. MOSELEY3, J. B. LINGREL3, A. FRIEDMAN4, J. P. DREIER

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

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.

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
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