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
Free Fulltext: Science-Direct

MRIcro free viewing software

http://www.sph.sc.edu/comd/rorden/mricro.html
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.

Fulltext: http://download.neuron.org/pdfs/0896-6273/PIIS0896627307005387.pdf

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
http://www.researchchannel.org/prog/displayevent.aspx?rID=16250&fID=345

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

Fulltext: http://www.jneurosci.org/cgi/content/full/27/32/8533

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.

Hardware/Software Hacking: Joining the Real and the Virtual

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

Research Channel

http://www.researchchannel.org For Scientific lecture fans! Who download the entire Internet! ;-)
Specifically see Science section, with some lectures on Neurosciences.

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.