Current Opinion in Neurobiology

Odor representations in mammalian cortical circuits.

Publication Date: 2010 Mar 4 PMID: 20207132
Authors: Isaacson, J. S.
Journal: Curr Opin Neurobiol

Spatial and temporal activity patterns of olfactory bulb projection neurons underlie the initial representations of odors in the brain. However, olfactory perception ultimately requires the integration of olfactory bulb output in higher cortical brain regions. Recent studies reveal that odor representations are sparse and highly distributed in the rodent primary olfactory (piriform) cortex. Furthermore, odor-evoked inhibition is far more widespread and broadly tuned than excitation in piriform cortex pyramidal cells. Other recent studies highlight how olfactory sensory inputs are integrated within pyramidal cell dendrites and that feedback projections from piriform cortex to olfactory bulb interneurons are a source of synaptic plasticity.

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How do you (estimate you will) like them apples? Integration as a defining trait of orbitofrontal function.

Publication Date: 2010 Mar 3 PMID: 20206497
Authors: Schoenbaum, G. - Esber, G. R.
Journal: Curr Opin Neurobiol

The past 15 years have seen a rapid increase in our understanding of orbitofrontal function. Today this region is the focus of an enormous amount of research, including work on such complex phenomena as regret, ambiguity, and willingness to pay. The orbitofrontal cortex is also credited as a major player in a host of neuropsychiatric diseases. This transformation arguably began with the application of concepts derived from animal learning theory. We will review data from studies emphasizing these approaches to argue that the orbitofrontal cortex forms a crucial part of a network of structures that signals information about expected outcomes. Further we will suggest that, within this network, the orbitofrontal cortex provides the critical ability to integrate information in real-time to make what amounts to actionable predictions or estimates about future outcomes. As we will show, the influence of these estimates can be demonstrated experimentally in appropriate behavioral settings, and their operation can also readily explain the role of orbitofrontal cortex in much more complex phenomena such as those cited above.

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Multisensory systems integration for high-performance motor control in flies.

Publication Date: 2010 Mar 2 PMID: 20202821
Authors: Frye, M. A.
Journal: Curr Opin Neurobiol

Engineered tracking systems 'fuse' data from disparate sensor platforms, such as radar and video, to synthesize information that is more reliable than any single input. The mammalian brain registers visual and auditory inputs to directionally localize an interesting environmental feature. For a fly, sensory perception is challenged by the extreme performance demands of high speed flight. Yet even a fruit fly can robustly track a fragmented odor plume through varying visual environments, outperforming any human engineered robot. Flies integrate disparate modalities, such as vision and olfaction, which are neither related by spatiotemporal spectra nor processed by registered neural tissue maps. Thus, the fly is motivating new conceptual frameworks for how low-level multisensory circuits and functional algorithms produce high-performance motor control.

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Computational models of cognitive control.

Publication Date: 2010 Feb 23 PMID: 20185294
Authors: O'Reilly, R. C. - Herd, S. A. - Pauli, W. M.
Journal: Curr Opin Neurobiol

Cognitive control refers to the ability to perform task-relevant processing in the face of other distractions or other forms of interference, in the absence of strong environmental support. It depends on the integrity of the prefrontal cortex and associated biological structures (e.g., the basal ganglia). Computational models have played an influential role in developing our understanding of this system, and we review current developments in three major areas: dynamic gating of prefrontal representations, hierarchies in the prefrontal cortex, and reward, motivation, and goal-related processing in prefrontal cortex. Models in these and other areas are advancing the field further forward.

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Brain oscillations and memory.

Publication Date: 2010 Feb 22 PMID: 20181475
Authors: Duzel, E. - Penny, W. D. - Burgess, N.
Journal: Curr Opin Neurobiol

Oscillatory fluctuations of local field potentials (LFPs) in the theta (4-8Hz) and gamma (25-140Hz) band are held to play a mechanistic role in various aspects of memory including the representation and off-line maintenance of events and sequences of events, the assessment of novelty, the induction of plasticity during encoding, as well as the consolidation and the retrieval of stored memories. Recent findings indicate that theta and gamma related mechanisms identified in rodent studies have significant parallels in the neurophysiology of human and non-human primate memory. This correspondence between species opens new perspectives for a mechanistic investigation of human memory function.

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Interactions between orbital prefrontal cortex and amygdala: advanced cognition, learned responses and instinctive behaviors.

Publication Date: 2010 Feb 22 PMID: 20181474
Authors: Murray, E. A. - Wise, S. P.
Journal: Curr Opin Neurobiol

Recent research indicates that the orbital prefrontal cortex (PFo) represents stimulus valuations and that the amygdala updates these valuations. An exploration of how PFo and the amygdala interact could improve the understanding of both. PFo and the amygdala function cooperatively when monkeys choose objects associated with recently revalued foods. In other tasks, they function in opposition. PFo uses positive feedback to promote learning in object-reward reversal tasks, and PFo also promotes extinction learning. Amygdala function interferes with both kinds of learning. The amygdala underlies fearful responses to a rubber snake from the first exposure on, but PFo is necessary only after the initial exposure. The amygdala mediates an arousal response in anticipation of rewards, whereas PFo sometimes suppresses such arousal. A role for PFo in advanced cognition, for the amygdala in instinctive behavior, and for cortex-subcortex interactions in prioritizing behaviors provides one account for these findings.

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Learning and cognitive flexibility: frontostriatal function and monoaminergic modulation.

Publication Date: 2010 Feb 16 PMID: 20167474
Authors: Kehagia, A. A. - Murray, G. K. - Robbins, T. W.
Journal: Curr Opin Neurobiol

Learning in a constant environment, and adapting flexibly to a changing one, through changes in reinforcement contingencies or valence-free cues, depends on overlapping circuitry that interconnects the prefrontal cortex (PFC) with the striatum and is subject to several forms of neurochemical modulation. We present evidence from recent studies in animals employing electrophysiological, pharmacological and lesion techniques, and neuroimaging, neuropsychological and pharmacological investigations of healthy humans and clinical patients. Dopamine (DA) neurotransmission in the medial striatum and PFC is critical for basic reinforcement learning and the integration of negative feedback during reversal learning, whilst orbitofrontal 5-hydroxytryptamine (5-HT) likely mediates this type of low level flexibility, perhaps by reducing interference from salient stimuli. The role of prefrontal noradrenaline (NA) in higher order flexibility indexed through attentional set-shifting has recently received significant empirical support, and similar avenues appear promising in the field of task switching.

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Developmental neurobiology of cognitive control and motivational systems.

Publication Date: 2010 Feb 16 PMID: 20167473
Authors: Somerville, L. H. - Casey, B.
Journal: Curr Opin Neurobiol

One form of cognitive control is the ability to resist temptation in favor of long-term goal-oriented behavior. Historically, the development of cognitive control capacity has been described by a linear function from infancy to adulthood. However, the context in which control is required impacts behavioral regulation abilities, such that emotionally charged or rewarding contexts can diminish control. More recently, studies have begun to examine the development of cognitive control in contexts that vary in motivation. These studies suggest specific windows of development in which cognitive control capacity is more vulnerable to incentive-based modulation. In this review we highlight the most recent work on neurobiological changes supporting motivational and cognitive development, underscoring the importance of functional organization and development of the underlying circuitry implicated in these processes, and provide a theoretical perspective that moves away from discussing singular functional regions toward considering functional circuitry.

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