Science 4 April 2008:
Vol. 320. no. 5872, pp. 110 - 113
Entrainment of Neuronal Oscillations as a Mechanism of Attentional Selection
Whereas gamma-band neuronal oscillations clearly appear integral to visual attention, the role of lower-frequency oscillations is still being debated. Mounting evidence indicates that a key functional property of these oscillations is the rhythmic shifting of excitability in local neuronal ensembles. Here, we show that when attended stimuli are in a rhythmic stream, delta-band oscillations in the primary visual cortex entrain to the rhythm of the stream, resulting in increased response gain for task-relevant events and decreased reaction times. Because of hierarchical cross-frequency coupling, delta phase also determines momentary power in higher-frequency activity. These instrumental functions of low-frequency oscillations support a conceptual framework that integrates numerous earlier findings.

Science 4 April 2008:
Episodic-Like Memory in Rats: Is It Based on When or How Long Ago?
Recent experiments with rats suggest that they show episodic-like or what-where-when memory for a preferred food found on a radial maze. Although memory for when a salient event occurred suggests that rats can mentally travel in time to a moment in the past, an alternative possibility is that they remember how long ago the food was found. Three groups of rats were tested for memory of previously encountered food. The different groups could use only the cues of when, how long ago, or when + how long ago. Only the cue of how long ago food was encountered was used successfully. These results suggest that episodic-like memory in rats is qualitatively different from human episodic memory.

Nature 452, 642-645 (3 April 2008)
A neural representation of depth from motion parallax in macaque visual cortex
Perception of depth is a fundamental challenge for the visual system, particularly for observers moving through their environment. The brain makes use of multiple visual cues to reconstruct the three-dimensional structure of a scene. One potent cue, motion parallax, frequently arises during translation of the observer because the images of objects at different distances move across the retina with different velocities. Human psychophysical studies have demonstrated that motion parallax can be a powerful depth cue, and motion parallax seems to be heavily exploited by animal species that lack highly developed binocular vision. However, little is known about the neural mechanisms that underlie this capacity. Here we show, by using a virtual-reality system to translate macaque monkeys (Macaca mulatta) while they viewed motion parallax displays that simulated objects at different depths, that many neurons in the middle temporal area (area MT) signal the sign of depth (near versus far) from motion parallax in the absence of other depth cues. To achieve this, neurons must combine visual motion with extra-retinal (non-visual) signals related to the animal's movement. Our findings suggest a new neural substrate for depth perception and demonstrate a robust interaction of visual and non-visual cues in area MT. Combined with previous studies that implicate area MT
in depth perception based on binocular disparities, our results suggest that area MT contains a more general representation of three-dimensional space that makes use of multiple cues.

JAMA. 2008;299(13):1533
Alzheimer Plaques
The amyloid plaques found in the brain of patients with Alzheimer disease may form much more rapidly than previously thought. Using an advanced microscopic imaging technique called longitudinal in vivo multiphoton microscopy to examine brain tissue in mouse models of the disease, researchers from the MassGeneral Institute for Neurodegenerative Disease in Charlestown, Mass, found that plaques form quickly over a 24-hour period (Meyer-Luehmann M et al. Nature. 2008;451[7179]:720-724). They also observed that within 1 to 2 days of a new plaque's appearance, microglia are activated and recruited to the site.
The findings may help solve a long-standing debate regarding whether plaques precede and induce the neuronal abnormalities seen in dementia or are simply a by-product of other alterations in the brain.

The Lancet Volume 371, Issue 9618, 29 March 2008-4 April 2008, Pages 1126-1135
Contributions of non-human primates to neuroscience research
Non-human primates have a small but important role in basic and translational biomedical research, owing to similarities with human beings in physiology, cognitive capabilities, neuroanatomy, social complexity, reproduction, and development. Although non-human primates have contributed to many areas of biomedical research, we review here their unique contributions to work in neuroscience, and focus on four domains: Alzheimer's disease, neuroAIDS, Parkinson's disease, and stress. Our discussion includes, for example, the role of non-human primates in development of new treatments (eg, stem cells, gene transfer) before phase I clinical trials in patients; basic research on disease pathogenesis; and understanding neurobehavioural outcomes resulting from genotype–environment interactions.

NEJM Volume 358:1518-1521  April 3, 2008  Number 14
Patent Foramen Ovale and Cryptogenic Stroke
It is hard to accept that a study of patent foramen ovale and cryptogenic stroke, reported by Handke et al.
(Nov. 29, 2007, issue), would show that almost half of 596 consecutive patients admitted to a major university medical center for acute brain ischemia had a cryptogenic stroke, especially since 272 cases of stroke had no angiographic studies done (neither magnetic resonance nor digital-subtraction angiography). Without these critically important imaging studies, how can such a large group of cases of stroke be declared cryptogenic?
Table 1 of the article contains data on 276 stroke cases of known cause that are identical to data reported in the authors' earlier article on 503 cases examined by transesophageal echocardiography. However, Table 2 in this 2006 report revealed only 44 cases of patent foramen ovale among the 227 cases of stroke of unknown cause, in contrast to the much higher number of 77 reported in Table 1 of the current report on data from the same population of patients.The size of patent foramen ovale increases with age.
This condition has not been found by others to be a risk factor for stroke in the elderly.