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Long-term potentiation (LTP) phenomenon is widely accepted as a cellular model of memory consolidation. Object recognition (OR) is a particularly useful way of studying declarative memory in rodents because it makes use of their innate preference for novel over familiar objects. In this study, mice had electrodes implanted in the hippocampal Schaffer collaterals-pyramidal CA1 pathway and were trained for OR. Field EPSPs evoked at the CA3-CA1 synapse were recorded at the moment of training and at different times thereafter. LTP-like synaptic enhancement was found 6 h post-training. A testing session was conducted 24 h after training, in the presence of one familiar and one novel object. Hippocampal synaptic facilitation was observed during exploration of familiar and novel objects. A short depotentiation period was observed early after the test and was followed by a later phase of synaptic efficacy enhancement. Here, we show that OR memory consolidation is accompanied by transient potentiation in the hippocampal CA3-CA1 synapses, while reconsolidation of this memory requires a short-lasting phase of depotentiation that could account for its well described vulnerability. The late synaptic enhancement phase, on the other hand, would be a consequence of memory restabilization. hippocampus | long-term potentiation | memory consolidation and reconsolidation | synaptic plasticity www.pnas.org/cgi/doi/10.1073/pnas.0915059107

The biased-competition theory accounts for attentional effects at the single-neuron level: It predicts that the neuronal response to simultaneously-presented stimuli is a weighted average of the response to isolated stimuli, and that attention biases the weights in favor of the attended stimulus. Perception, however, relies not on single neurons but on larger neuronal populations. The responses of such populations are in part reflected in large-scale multivoxel fMRI activation patterns. Because the pooling of neuronal responses into blood-oxygen-level-dependent signals is non-linear, fMRI effects of attention need not mirror those observed at the neuronal level. Thus, to bridge the gap between neuronal responses and human perception, it is fundamental to understand attentional influences in large-scale multivariate representations of simultaneously-presented objects. Here, we ask how responses to simultaneous stimuli are combined in multivoxel fMRI patterns, and how attention affects the paired response. Objects from four categories were presented singly, or in pairs such that each category was attended, unattended, or attention was divided between the two. In a multidimensional voxel space, the response to simultaneously-presented categories was well described as a weighted average. The weights were biased toward the preferred category in category-selective regions. Consistent with single-unit reports, attention shifted the weights by [approximately equal to]30% in favor of the attended stimulus. These findings extend the biased-competition framework to the realm of large-scale multivoxel brain activations. pattern classification | fMRI | response combination | ventral temporal cortex doi/ 10.1073/pnas.0907330106

Efficient execution of perceptual-motor tasks requires rapid voluntary reconfiguration of cognitive task sets as circumstances unfold. Such acts of cognitive control, which are thought to rely on a network of cortical regions in prefrontal and posterior parietal cortex, include voluntary shifts of attention among perceptual inputs or among memory representations, or switches between categorization or stimulus-response mapping rules. A critical unanswered question is whether task set shifts in these different domains are controlled by a common, domain-independent mechanism or by separate, domain-specific mechanisms. Recent studies have implicated a common region of medial superior parietal lobule (mSPL) as a domain-independent source of cognitive control during shifts between perceptual, mnemonic, and rule representations. Here, we use fMRI and event-related multivoxel pattern classification to show that spatial patterns of brain activity within mSPL reliably express which of several domains of cognitive control is at play on a moment-by-moment basis. Critically, these spatio-temporal brain patterns are stable over time within subjects tested several months apart and across a variety of tasks, including shifting visuospatial attention, switching categorization rules, and shifting attention in working memory. fMRI | pattern classification | task switching | working memory doi/ 10.1073/pnas.0903593106

We investigated the hazard perception ability of older drivers. A sample of 118 older drivers (65 years and older) completed a video-based hazard perception test and an assessment battery designed to measure aspects of cognitive ability, vision, and simple reaction time that might plausibly be linked to hazard perception ability. We found that hazard perception response times increased significantly with age but that this age-related increase could be accounted for by measures of contrast sensitivity and useful field of view. We found that contrast sensitivity, useful field of view, and simple reaction time could account for the variance in hazard perception, independent of one another and of individual differences in age. Key Words: Contrast sensitivity--Hazard perception--Useful field of view.

We review the organization of the neural networks that underlie haptic object processing and compare that organization with the visual system. Haptic object processing is separated into at least two neural pathways, one for geometric properties or shape, and one for material properties, including texture. Like vision, haptic processing pathways are organized into a hierarchy of processing stages, with different stages represented by different brain areas. In addition, the haptic pathway for shape processing may be further subdivided into different streams for action and perception. These streams may be analogous to the action and perception streams of the visual system and represent two points of neural convergence for vision and haptics. Nous examinons l'organisation des reseaux neuronaux qui sous-tendent le traitement haptique des objets et comparons cette structure au systeme visuel. Le traitement haptique des objets est separe en au moins deux circuits neuronaux: un pour les proprietes geometriques ou formes, et l'autre pour les proprietes physiques, dont la texture. Comine dans le cas de la vision, les circuits de traitement haptique sont organises en une hierarchie de stades de traitement, les differents stades etant representes par des aires differentes du cerveau. De plus, le circuit haptique implique dans le traitement des formes peut etre encore subdivise en differentes voies pour l'analyse et la perception. Ces voies peuvent etre analogues aux voies d'action et de perception du systeme visuel, et representent deux points de convergence neuronale pour les modalites visuelle et haptique.

The surface myoelectric signal (MES) has been used as an input to controllers for powered prostheses for many years. As a result of recent technological advances it is reasonable to assume that there will soon be implantable myoelectric sensors which will enable the internal MES to be used as input to these controllers. An internal MES measurement should have less muscular crosstalk allowing for more independent control sites. However, it remains unclear if this benefit outweighs the loss of the more global information contained in the surface MES. This paper compares the classification accuracy of six pattern recognition-based myoelectric controllers which use multi-channel surface MES as inputs to the same controllers which use multi-channel intramuscular MES as inputs. An experiment was designed during which surface and intramuscular MES were collected simultaneously for 10 different classes of isometric contraction. There was no significant difference in classification accuracy as a result of using the intramuscular MES measurement technique when compared to the surface MES measurement technique. Impressive classification accuracy (97 %) could be achieved by optimally selecting only three channels of surface MES. Index Terms--Classification, EMG, intramuscular, myoelectric, pattern recognition, prostheses.

Grasping requires coding of the object's intrinsic properties (size and shape), and the transformation of these properties into a pattern of distal (finger and wrist) movements. Computational models address this behavior through the interaction of perceptual and motor schemas. In monkeys, the transformation of an object's intrinsic properties into specific grips takes place in a circuit that is formed by the inferior parietal lobule and the inferior premotor area (area F5). Neurons in both these areas code size, shape and orientation of objects, and specific types of grip that are necessary to grasp them. Grasping movements are coded more globally in the inferior parietal lobule, whereas they are more segmented in area F5. In humans, neuropsychological studies of patients with lesions to the parietal lobule confirm that primitive shape characteristics of an object for grasping are analyzed in the parietal lobe, and also demonstrate that this 'pragmatic' analysis of objects is separated from the 'semantic' analysis performed in the temporal lobe.

Cellular responses in the V2 secondary visual cortex to simple as well as complex visual stimuli have been welt studied. However, the role of area V2 in visual memory remains unexplored. We found that layer 6 neurons of V2 are crucial for the processing of object-recognition memory (ORM). Using the protein regulator of G protein signaling--14 (RGS-14) as a tool we found that the expression of this protein into layer 6 neurons of rat-brain area V2 promoted the conversion of a normal short-term ORM that normally lasts for 45 minutes into tong-term memory detectable even after many months. Furthermore, elimination of the same-layer neurons by means of injection of a selective cytotoxin resulted in the complete loss of normal as welt as protein-mediated enhanced ORM.

Tactile perception refers to the understanding, or 'reading', of a shape by touching it, without seeing it. This type of perception may be influenced by spacial abilities residing in the brain, which may be mediated by the use of the left versus right hand to touch the object. In one study, children were asked to feel shapes that did not resemble any letter or other symbol; they were then asked to identify each shape from a visual array. Boys who were right-handed performed better when they felt the object with their left hands, suggesting that the right hemisphere of the brain is superior at spacial perception (messages from the left hand are processed primarily by the right brain). In this study, several aspects of tactile perception were evaluated in right-handed male college students. There were two experiments; in the first, 36 men were presented with random shapes and were asked to determine when a shape was the same as a previously learned target shape. They were only allowed to press on the objects, which were made of hard plastic, and were not allowed to make any other movements including tracing the outline of the shape. Under various experimental conditions, the subjects did better when using their left hands. In the second experiment, 18 of the original subjects were told to use mental imagery to enhance their performance. The use of imagery improved performance with the right hand, removing the previous advantage experienced when using the left hand. This shows that the difference in tactile perception between the two hands is easily overridden by employing higher-order cognitive processes. (Consumer Summary produced by Reliance Medical Information, Inc.)