Brief Communications in 2008

Neuronal response selectivity and perceptual discrimination can be affected by acoustic experience during development. Here the authors show that intensive discrimination training in adult animals can restore normal cortical response patterns.

Attention is thought to select nonspatial features later than spatial location. This study uses ERPs to show that color-based attention effects manifest themselves as early as 100 ms, similar to spatial attention effects.

Prosopagnosics have impaired face recognition, but make relatively normal responses to face stimuli in core brain regions for face recognition. The authors now report that it is the connectivity among these regions that is being disrupted in the disorder.

The striatum receives projections to a number of cortical and subcortical areas. The authors report here that fiber tracts from prefrontal cortex are correlated with individual differences in reward dependence and that tracts from the hippocampus, amygdala and ventral striatum are correlated with individual differences in novelty seeking.

Activation of GABA_A receptors can depolarize specific neuronal compartments, causing excitation. The authors report that hippocampal interneurons hyperpolarize pyramidal cells, irrespective of the location of their synapses, along the entire somato-dendritic axis.

No two roses smell exactly alike, but our brain accurately bundles these variations into a single percept 'rose'. The authors now report that although olfactory bulb neurons decorrelate odor mixtures that are quite similar, piriform cortex neuronal responses show pattern completion and predict olfactory perception.

fMRI studies suggest that nucleus accumbens (NAc) activation increases in response to stimuli of different hedonic valence, whereas physiological evidence suggests that NAc neurons show increases in activity for rewarding stimuli and pauses for aversive stimuli. Using cyclic voltammetry, the authors find that patterns of dopamine release and metabolic activity differentiate between rewarding and aversive stimuli.

Dopamine is known to contribute to the amygdala-mediated aversive response, where increased dopamine release can augment amygdala function. Combining fMRI and PET imaging techniques, Kienast et al. present findings that suggest a functional link between anxiety temperament, dopamine storage capacity and emotional processing in the amygdala.

Following brief stimulation, macroscopic NMDA receptor currents decay with biphasic kinetics believed to reflect glutamate dissociation and receptor desensitization. The authors show that the fast and slow decay components arise from the deactivation of receptor populations that gate with short and long openings.

Memories are dynamic and the reactivation of memories via re-exposure to training stimuli can cause the destabilization of a memory trace. This paper shows that the subsequent reconsolidation of this memory can modify the strength of contextual fear memory during learning.

Auditory cortex neurons fire with high temporal precision to the fine timing of acoustic stimuli. Here, the authors show that stimulation in this area in rat brains, even when differing by as little as 3 ms, can be used to guide decisions.

Previous work suggests that post-learning rapid eye movement (REM) sleep is crucial for memory consolidation, but this study shows that suppressing REM sleep via serotonin/norepinephrine reuptake inhibitors instead enhances memory consolidation of a motor skill task.

The authors report that the action potential voltage threshold is actually higher in the axon than elsewhere in the neuron, but as the current threshold at the axon is lower than elsewhere, the action potential threshold is indeed lowest in the axon.

Under some in vitro conditions, neurons of the deep cerebellar nuclei show a phenomenon called rebound potentiation, where, following a strong hyperpolarization, their membrane potential briefly rebounds to a more depolarized level causing a transient increase in firing rate. The authors, however, found that under more physiological conditions in vitro or in vivo, deep cerebellar nuclei neurons rarely showed rebound potentiation. This finding necessitates a re-evaluation of some cerebellar models, where rebound potentiation was postulated to be involved in plasticity and/or information processing.

Shmuelof and Zohary report that actions seen from an allocentric point of view evoke more activation in the ipsilateral anterior parietal cortex than those seen from an egocentric point of view, even in the absence of active imitation, supporting the idea that there is a mirror-image representation of action in this brain region.

Subcortical auditory neurons show adaptation-dependent coding of sound intensity. Recordings in awake marmoset reveal two populations of intensity-sensitive neurons at the cortical level: one that has a dynamic range that adapts to the statistics of the environment and another that does not, preserving sensitivity to the lowest intensities.

There are many mechanisms for LTD, but it remains unknown which one underlies experience-dependent plasticity during development. Wright and colleagues now report that LTD in response to developmental deprivation depends on the GluR1 subunit in barrel cortex layers 2/3 and 4.

In addition to the changes in synaptic efficacy, modifications in the intrinsic excitability of neurons are seen after learning. Using in vitro operant conditioning of feeding in Aplysia, Mozzachiodi et al. demonstrate that a long-term increase in the neuronal excitability can contribute to the storage of long-term memory.

Synaptic plasticity is believed to underlie the formation of long-term memories, but the mechanisms are not well understood. Elkobi and colleagues now report that induction of PSD-95, a synaptic protein, parallels taste learning, and attenuation of PSD-95 expression in taste cortex blocks learning of novel tastes, but not recollection of familiar ones.

It was previously known that a lack of FMRP can lead to a broad increase in protein synthesis. In this manuscript, the authors demonstrate a direct association between enhanced protein synthesis and the cognitive deficits observed in animal models lacking FMRP.